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How carbohydrate reserves change in conifers during drought and bark beetle attacks are poorly understood. We investigated changes in carbohydrate reserves and carbon-dependent terpene defenses in ponderosa pine trees experimentally subjected to two levels of drought stress (via root trenching) and two types of biotic challenge treatments (pheromone-induced bark beetle attacks or inoculations with crushed beetles that include beetle-associated fungi) for two consecutive years. Our results showed that trenching did not influence carbohydrates whereas both biotic challenges reduced amounts of starch and sugars of trees. However, only the trenched-beetle attacked trees depleted carbohydrates and died within the first year of bark beetle attacks. While live trees contained higher carbohydrates than dying trees, amounts of constitutive and induced terpenes produced did not vary between live and beetle-attacked dying trees, respectively. Based on these results we propose that reallocation of carbohydrates to terpenes during the early stages of beetle attacks is limited in drought-stricken trees, and that the combination of biotic and abiotic stress leads to tree death. The process tree death is subsequently aggravated by beetle girdling of phloem, occlusion of vascular tissue by bark beetle-vectored fungi, and potential exploitation of host carbohydrates by beetle symbionts as nutrients.

We studied the time-course of stem response for six months following complete girdling in branches of Aquilaria sinensis to determine the potential role of interxylary phloem (IP) in this response. It was found that the vascular cambium, as well as its derivative secondary xylem and phloem, regenerated fully through redifferentiation of IP. We confirmed that vascular cambium regenerated within one month after girdling based on observation of new vessels, IP, and secondary phloem fibers. The time-course study showed that IPs made connections with each other, merged, and became larger through the proliferation of IPs parenchyma cells and the cleaving of secondary xylem in a narrow zone 400 to 1000 μm deep inside the girdled edge. This led to the formation of a complete circular sheath of vascular cambium, followed by the regeneration of vascular tissue. It is worth noting that the secondary xylem is regenerated always following the formation of a thick belt of wound xylem.

Primary growth is less sensitive than secondary growth to water and phloem blockage in maritime pine saplings, with variations in radial growth resulting from tracheid production without altering their size. In plants, primary and secondary growth is regulated by internal and external factors. However, apical and cambial meristems may not respond in the same way. In this study, we disentangle the role of carbon and water availability on stem growth (primary and secondary) and on anatomical tracheid features by investigating the effect of stem girdling (phloem blockage vs. no phloem blockage) and water availability (control vs. drought) in three-year-old Pinus pinaster saplings. We found that primary growth was similar among treatments, while secondary growth was affected by both treatments. Tree ring-width increment in saplings subjected to drought corresponded to half of that on control plants, and phloem blockage enhanced ring width under guidelines soil water conditions. These differences in the radial growth resulted mainly from an increase in tracheid production, which also increased with phloem blockage (above the girdling), regardless the water regime. However, the seasonal pattern of tracheid features was mainly explained by individuals and to a less extent by the water regime and girdling. Contrasting seasonal patterns between treatments were found only on cell wall thickness, showing a faster decrease with increasing water constrains in the drought group than in the control one. The absence of treatment effects on primary growth in P. pinaster saplings suggests a trade-off between the priority in plant development and meristem sensitivity to environmental conditions.

In North America, notodontid caterpillars feed predominantly on hardwood trees; some cause significant economic damage with periodic outbreaks. The late instars of several species cut girdles around the petiole, rachis, or stem before feeding on distal leaf blades. Little is known about the benefits or costs of girdling for caterpillars. In this paper, we analyzed the energetic cost of girdling by comparing final instars of a girdling notodontid, Oedemasia leptinoides, with two non-girdling notodontids, Cecrita guttivitta and Lochmaeus manteo. Time allocated to four behaviors (girdling, feeding, walking, and inactive) was measured in the field with 3-h observations each day over three days. We also measured metabolic rates for the four behaviors using flow-through respirometry. The metabolic rate for each behavior was multiplied by the time spent over the 9 h of observation to estimate the total energetic cost of each behavior. In the field, O. leptinoides on black hickory (Carya texana) spent 4.6 ± 0.9% of their time girdling. They cut girdles primarily on the first day and fed on leaves mostly on days 2 and 3. Their metabolic rate during girdling was similar to feeding and walking, but greater than inactivity. Overall, the larvae utilized 6.4 ± 1.2% of their total energy while girdling. Relative to non-girdlers, O. leptinoides larvae spent significantly less time and energy feeding on leaves suggesting a trade-off between girdling and feeding. To our knowledge, this study is the first to quantify the energetic cost of an insect behavior for modifying host plants before feeding.

Girdling can promote anthocyanin accumulation in grape berries. However, the underlying mechanism is unclear. In this study, we explored the effects of girdling on the accumulation of anthocyanins and the transcript levels of key genes in anthocyanin synthesis in spine grape skins. We also determined the effect of girdling on the contents of vitamin C, titratable acids, soluble sugars, and aroma compounds, and the transcript levels of genes related to sugar transport and aroma compound synthesis. The girdling treatment promoted anthocyanin accumulation in spine grape skins by increasing the transcript levels of genes related to anthocyanin synthesis. Girdling also increased the transcript levels of genes related to sugar transport in leaves, petioles, and flesh, promoted the transport of photosynthetic products to berries, and increased the soluble sugar content in berries. The transcript levels of genes related to aroma compound synthesis and the contents of aroma compounds in flesh were also increased by the girdling treatment. Together, our results show that a girdling treatment can increase the contents of anthocyanins, soluble sugars, vitamin C, and aroma compounds, decrease the titratable acid content, and significantly improve the quality of spine grape berries.

The effect of cane girdling on grape skin phenolic composition and concentration was examined on three Hungarian table grape varieties, i.e. noir-skinned 'Esther', rose-skinned 'Lidi', and blanc-skinned 'Fanny'. Girdling was conducted at the BBCH 75 phenological growth stage (pea-sized berries). A significant increase was observed in anthocyanin-glycosides in the treated berry skins irrespective of the cultivar. Other phenolic substances (gallic acid, trans-resveratrol, (+)-catechin, quercetin-3-glucuronide) were less sensitive to the treatment, but noticeable differences were found between the genotypes.

As we know auxins were the first class of plant hormones to be discovered that use to kill weeds, promote growth and fruit quality of particular plant.in this review paper I have compile the summary of Auxin as important hormone required to carry any essential function in plant viz., delaying, early maturation, help in rooting etc. I have categorized crop in accordance with role of auxin with tropical and temperate crops, which I hope could help scientist for further breeding programme, to acknowledge the role with its pros and cons. In mango it mainly influence the girdling effect, fruit repining process, and in grape it helps in the maturation and quality maintenance of berries on the other hand in apple with the appropriate concentration it triggers the production of ethylene which eventually promotes ripening accompany it helps in the translocation of calcium which maintain the fruit quality. In guava auxin is immensely used in the form IAA and IBA which operates as a rooting hormone in this crop to hasten the growth during layering on the other hand in pear and peach its application influence the growth of primary and secondary shoot.

Summary Experimental evidence that nonstomatal limitations to photosynthesis (NSLs) correlate with leaf sugar and/or leaf water status suggests the possibility that stomata adjust to maximise photosynthesis through a trade-off between leaf CO2 supply and NSLs, potentially involving source-sink interactions. However, the mechanisms regulating NSLs and sink strength, as well as their implications for stomatal control, remain uncertain. We used an analytically solvable model to explore optimal stomatal control under alternative hypotheses for source and sink regulation. We assumed that either leaf sugar concentration or leaf water potential regulates NSLs, and that either phloem turgor pressure or phloem sugar concentration regulates sink phloem unloading. All hypotheses lead to realistic stomatal responses to light, CO2 and air humidity, including conservative behaviour for the intercellular-to-atmospheric CO2 concentration ratio. Sugar- and water-regulated NSLs are distinguished by the presence/absence of a stomatal closure response to changing sink strength. Turgor- and sugar-regulated phloem unloading are distinguished by the presence/absence of stomatal closure under drought and avoidance/occurrence of negative phloem turgor. Results from girdling and drought experiments on Pinus sylvestris, Betula pendula, Populus tremula and Picea abies saplings are consistent with optimal stomatal control under sugar-regulated NSLs and turgor-regulated unloading. Our analytical results provide a simple representation of stomatal responses to above- and below-ground environmental factors and sink activity. Experimental evidence that nonstomatal limitations to photosynthesis (NSLs) correlate with leaf sugar and/or leaf water status suggests the possibility that stomata adjust to maximise photosynthesis through a trade-off between leaf CO2 supply and NSLs, potentially involving source-sink interactions. However, the mechanisms regulating NSLs and sink strength, as well as their implications for stomatal control, remain uncertain. We used an analytically solvable model to explore optimal stomatal control under alternative hypotheses for source and sink regulation. We assumed that either leaf sugar concentration or leaf water potential regulates NSLs, and that either phloem turgor pressure or phloem sugar concentration regulates sink phloem unloading. All hypotheses led to realistic stomatal responses to light, CO2 and air humidity, including conservative behaviour for the intercellular-to-atmospheric CO2 concentration ratio. Sugar-regulated and water-regulated NSLs are distinguished by the presence/absence of a stomatal closure response to changing sink strength. Turgor-regulated and sugar-regulated phloem unloading are distinguished by the presence/absence of stomatal closure under drought and avoidance/occurrence of negative phloem turgor. Results from girdling and drought experiments on Pinus sylvestris, Betula pendula, Populus tremula and Picea abies saplings are consistent with optimal stomatal control under sugar-regulated NSLs and turgor-regulated unloading. Our analytical results provide a simple representation of stomatal responses to above-ground and below-ground environmental factors and sink activity.

To investigate the importance of shoot-to-root communication in modulating tissue phytohormone balance as the soil dries, root and leaf hormonal profiles were determined in soybean plants (Glycine max L. Merr. cv. Siverka) exposed to factorial girdling (achieved surgically on Day 0 by excising the phloem with a sharp razor blade thereby disrupting basipetal hormone transport) and soil drying treatments. Plants were randomized into 2 groups: girdled and intact plants, and each girdled group was further separated into two groups: well-watered and soil drying. Thus the experiment was a two (± girdling) x two (± soil drying) factorial experiment. Within 26 h while the soil was still moist, girdling increased root ACC (by 11-fold) and decreased root ABA concentrations (by 28 %), decreased foliar iP, tZ and GA concentrations (by up to 90 %), and increased foliar ABA and JA concentrations (by 1.6- and 4.9-fold respectively) compared to intact plants, but only leaf ABA concentration correlated with partial stomatal closure. Two days of soil drying increased root ABA and JA concentrations in intact plants, and both hormones significantly decreased in roots of girdled plants compared to intact plants. Soil drying increased foliar iP, ABA, JA and SA concentrations by 1.3-, 2.5-, 1.3- and 1.4-fold respectively compared to well-watered intact plants by the end of the experiment, but girdling prevented this foliar iP, ABA, JA accumulation compared to droughted intact plants. Thus, girdling affects the co-ordination of root and leaf phytohormone concentrations such as JA and ABA, which may transiently modulate stomatal closure. However, leaf ABA concentration varied consistently with root ABA concentration across all treatments, and explained more of the variation in stomatal conductance than any other hormone or leaf water potential., PC thanks the SEW-REAP Project (EuropeAid ECRIP ICI+/2014/348- 010) and a Lancaster University Faculty studentship for supporting his PhD research

Dectes texanus is an important coleopteran pest of soybeans and cultivated sunflowers in the Midwestern United States that causes yield losses by girdling stems of their host plants. Although sunflower and giant ragweed are primary hosts of D. texanus, they began colonizing soybeans approximately 50 years ago and no reliable management method has been established to prevent or reduce losses by this pest. To identify genes putatively involved when feeding soybean, we compared gene expression of D. texanus third-instar larvae fed soybean to those fed sunflower, giant ragweed, or artificial diet. Dectes texanus larvae differentially expressed 514 unigenes when fed on soybean compared to those fed the other diet treatments. Enrichment analyses of gene ontology terms from up-regulated unigenes in soybean-fed larvae compared to those fed both primary hosts highlighted unigenes involved in oxidoreductase and polygalacturonase activities. Cytochrome P450s, carboxylesterases, major facilitator superfamily transporters, lipocalins, apolipoproteins, glycoside hydrolases 1 and 28, and lytic monooxygenases were among the most commonly up-regulated unigenes in soybean-fed larvae compared to those fed their primary hosts. These results suggest that D. texanus larvae differentially expressed unigenes involved in biotransformation of allelochemicals, digestion of plant cell walls and transport of small solutes and lipids when feeding in soybean.

Dectes texanus larvae girdles the stems of soybean and cultivated sunflowers causing significant yield losses in North America. The soybean Plant Introduction (PI) 165673 exhibits antibiosis resistance to the larval stage. The objectives of this study were: (1) to determine the inheritance of D. texanus resistance in PI165673, (2) evaluate PI165673 antibiosis resistance before 21 d post infestation, (3) evaluate girdling damage in PI16563 at the end of the season. K07-1544/PI165673 F2 and F2:3 populations were tested for resistance to D. texanus in 2011 and 2012, and PI165673 antibiosis resistance and girdling damage were evaluated in 2014. Segregation for resistance to D. texanus and heritability estimates in the F2 and F2:3 populations indicated that resistance was controlled by two genes with dominant and recessive epistasis. Antibiosis evaluations indicated: (1) PI165673 contained lower number of larvae and eggs relative to the number of oviposition punctures at 15 d post infestation, (2) the proportion of first-instar larvae was higher in PI165673 at 15 d post infestation, (3) larvae reach the sixth-instar stage in PI165673. None of the PI165673 plants were girdled at the end of the season. Identification of additional sources of D. texanus resistance is required to impair larval development in the stem.

With flooding being one of the numerous challenges that ecosystems face throughout the world, plants are therefore obliged to adopt plastic responses in order to cope with this environmental constraint. When flooded, the tomato hypocotyl undergoes profound changes that entail rearrangements in its physiology and metabolism. In this work, we observed that, although soil flooding markedly dampens root respiration, the submerged hypocotyl surprisingly enhances oxygen consumption in spite of hypoxic conditions. Several pieces of evidence indicate that the respiratory pathway is indeed promoted in submerged stems. Besides, underwater hypocotyls are shown to accumulate sugars. Girdling and feeding experiments revealed that leaf-derived sucrose is metabolized and channelled to maintain respiration in underwater hypocotyls. Our data suggest that high respiration is required for sucrose unloading from phloem, since inhibition of hypocotyls respiration significantly prevents sugar build-up. As substrate availability increases, respiration is fuelled even more, leading to a sustained allocation of sugars to flooded hypocotyls.

Made available in DSpace on 2021-06-25T10:19:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 ‘Candidatus Liberibacter asiaticus’ (Las) is an unculturable, phloem-limited, insect-transmitted bacterium associated with the Asiatic form of huanglongbing (HLB), the most destructive citrus disease. In Asia and the Americas, it is transmitted by the Asian citrus psyllid (Diaphorina citri Kuwavama). Despite considerable research, little is known about the processes involved in plant infection and colonization by Las. This study was conducted to determine whether the basal portion (below girdling) of the plant is an important route for Las to move laterally from a point of inoculation on a branch to pathogen-free branches elsewhere in the canopy, and to quantify the influence of actively growing tissues on vertical upward (acropetally) or downward (basipetally) movement of Las. Nongirdled and fully or partially girdled stems of potted plants of ‘Pera’ sweet orange, graft-inoculated above or below girdling, were sampled in distinct regions and assessed by qPCR, 6 months postinoculation. Las invaded all regions of partially and nongirdled plants but remained restricted to the inoculated regions of fully girdled plants, evidence that in planta bacterium movement is limited to the phloem. In fully girdled plants, starch accumulated above the girdling site, probably because of changes in flow of phloem sap. To study the influence of actively growing tissues, inoculated ‘Valencia’ sweet orange plants were kept intact or were top- or root-pruned to force production of new tissues, and sampled at 15-day intervals. Las migrated rapidly and most predominantly toward newly developing root and leaf tissues. The rapid and predominant movement of Las to newly developed shoots and roots would explain failures of canopy heat treatments and pruning to cure HLB-affected trees, and reinforces the need to protect rapidly growing new shoots from feeding by D. citri in order to minimize transmission and spread of the pathogen by the vector within and between orchards. Fundo de Defesa da Citricultura (Fundecitrus) Universidade Estadual Paulista (UNESP) Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) Universidade Estadual Paulista (UNESP)

Carbon (C) cycling processes are particularly dynamic following disturbance, with initial responses often indicative of longer-term change. In northern Michigan, USA, we initiated the Forest Resilience Threshold Experiment (FoRTE) to identify the processes that sustain or lead to the decline of C cycling rates across multiple levels (0, 45, 65 and 85% targeted gross leaf area index loss) of disturbance severity and, in response, to separate disturbance types preferentially targeting large or small diameter trees. Simulating the effects of boring insects, we stem girdled &gt, 3600 trees below diameter at breast height (DBH), immediately and permanently disrupting the phloem. Weekly DBH measurements of girdled and otherwise healthy trees (n &gt, 700) revealed small but significant increases in daily aboveground wood net primary production (ANPPw) in the 65 and 85% disturbance severity treatments that emerged six weeks after girdling. However, we observed minimal change in end-of-season leaf area index and no significant differences in annual ANPPw among disturbance severities or between disturbance types, suggesting continued C fixation by girdled trees sustained stand-scale wood production in the first growing season after disturbance. We hypothesized higher disturbance severities would favor the growth of early successional species but observed no significant difference between early and middle to late successional species&rsquo, contributions to ANPPw across the disturbance severity gradient. We conclude that ANPPw stability immediately following phloem disruption is dependent on the continued, but inevitably temporary, growth of phloem-disrupted trees. Our findings provide insight into the tree-to-ecosystem mechanisms supporting stand-scale wood production stability in the first growing season following a phloem-disrupting disturbance.

The study was conducted in mango to understand the relationship of various metabolites with flower sex ratio (hermaphrodite/male) and fruit set using stem girdling technique. Girdling one year old branches was carried out in two cultivars, Mangifera indica 'Alphonso' and 'Totapuri' to retain 50, 100 and 150 leaves to vary the content of hormones, sugars, total carbohydrates, and amino acids. The increased leaf number was found to increase the total carbohydrates, glucose, fructose, and other sugars. Girdling also significantly increased the concentration of abscisic acid (ABA), salicylic acid (SA), jasmonic acid (JA), indole acetic acid, indole butyric acid but decreased gibberellins and cytokinins. Amino acids also increased in the girdled branches. Girdling improved the flower sex ratio as well as fruit set more efficiently in 'Alphonso' than in 'Totapuri'. Results indicate that the increase in production of hermaphrodite flowers may be more related to the higher production of growth inhibitors, like ABA, SA, and JA along with increased concentration of sugars. Increased auxin concentration also might play an important role in increasing the fruit set.

Premise of the study New growth in the spring requires resource mobilization in the vascular system at a time when xylem and phloem function are often reduced in seasonally cold climates. As a result, the timing of leaf out and/or flowering could depend on when the vascular system resumes normal function in the spring. This study investigated whether flowering time is influenced by vascular phenology in plants that flower precociously before they have leaves. Methods Flower, leaf, and vascular phenology were monitored in pairs of precocious and non-precocious congeners. Differences in resource allocation were quantified by measuring bud dry mass and water content throughout the year, floral hydration was modelled, and a girdling treatment completed on branches in the field. Key results Precocious flowering species invested more in floral buds the year before flowering than did their non-precocious congeners, thus mobilizing less water in the spring, which allowed flowering before new vessel maturation. Conclusions A shift in the timing of resource allocation in precocious flowering plants allowed them to flower before the production of mature vessels and minimized the significance of seasonal changes in vascular function to their flowering phenology. The low investment required to complete floral development in the spring when the plant vascular system is often compromised could explain why flowers can emerge before leaf out.

Although foliar boron (B) fertilization is regarded as an efficient way to remedy B deficiency, the mechanisms of foliar B transport from leaves to roots are still unclear. In this study, performed with 1-year-old “Newhall” navel orange (Citrus sinensis) grafted on trifoliate orange (Poncirus trifoliata) plants, we analyzed the B concentration in leaves and roots, B-sucrose complex in the phloem sap after foliar application of 10B, girdling, and/or shading treatments. Results indicated that 10B concentration was significantly increased in roots after foliar 10B treatment. On the other hand, both girdling the scion stem and shading over the plants with a black plastic net significantly reduced the B and 10B concentration in roots. LC-MS analysis revealed that foliar 10B-treated plants had higher concentration of sucrose and some sugar alcohols in the phloem sap as compared to foliar water-treated plants. Combining with the analysis in the artificial mixture of B and sucrose, a higher peak intensity of the 10B-sucrose complex was found in the phloem sap of foliar 10B-treated plants compared to the control plants. Taken together, it is concluded that foliar B can be long distance transported from leaves to roots via phloem, at least by forming a B-sucrose complex in citrus plants.

Understanding how soil processes, belowground plant and fungal species composition, and nutrient cycles are altered by disturbances is essential for understanding the role forests play in mitigating global climate change. Here we ask: How are root and fungal communities altered in a mid-successional forest during shifts in dominant tree species composition? This study utilizes the Forest Accelerated Succession ExperimenT (FASET) at the University of Michigan Biological Station (UMBS) as a platform for addressing this question. FASET consists of a 39-ha treatment in which all mature early successional aspen (Populus spp.) and paper birch (Betula papyrifera) were killed by stem-girdling in 2008. Four years after girdling, neither overall fungal diversity indices, plant diversity indices, nor root biomass differed between girdled (treated) and non-girdled (reference) stands. However, experimental advancement of succession by removal of aspen and birch resulted in 1) a shift in fungal functional groups, with significantly less ectomycorrhizal fungi, 2) a trend toward less arbuscular mycorrhizal fungi, and 3) a significant increase in the proportion of saprotrophs in girdled stands. In addition to shifts in functional groups between treated and untreated stands, ectomycorrhizal fungi proportions were negatively correlated with NH4+ and total dissolved inorganic nitrogen (DIN) in soil. This research illustrates the propensity for disturbances in forest ecosystems to shift fungal community composition, which has implications for carbon storage and nutrient cycling in soils under future climate scenarios.

Increasing water use patterns were more spatially restricted than increased nitrogen in leaves and litterfall in mid-canopy sweetgum trees of varying proximity to overstory pines undergoing mortality. Ecosystem changes following selective mortality of individual trees can be difficult to predict and depend on the response of surviving trees in the ecosystem. In the southeastern United States, southern pine beetle (Dendroctonus frontalis Zimmermann) selectively attacks and kills southern pines, particularly loblolly pine (Pinus taeda L.) which is prevalent throughout the region. Loss of loblolly pine should alter water and nutrient cycling unless co-occurring species are able to compensate for this lost functioning. The goals of this study were to determine changes in water and nutrient uptake of sweetgum trees (Liquidambar styraciflua L.) adjacent to loblolly pines experiencing mortality from girdling. We found that sweetgums near girdled pines initially used significantly less water, then similar amounts of water, then more water than sweetgums near control pines as pines experienced mortality. Relationships between daily sapflow and the natural log of vapor pressure deficit also differed significantly across years in sweetgums near girdled pines but not sweetgums near control pines. For sweetgum trees in both locations, both leaf and litterfall nitrogen content were significantly higher in the pine mortality year compared with the previous pine girdling year. Together, these results suggest that changes in water use are more spatially restricted to the region near dying pines whereas sweetgums, regardless of location, benefited from the extra available nitrogen in the ecosystem.

Demirsoy, Husnu/0000-0001-6621-6347 WOS: 000440981400006 The sweet cherry tree shows an acrotonic growth habit and grows as a forest wood. Apical dominance is important in sweet cherries and commercial growth is not possible without human intervention. It is thus difficult to obtain a good tree shape and enough shoots and leaves for quality and a plentiful crop in cherry trees. For this reason, many studies have been carried out in cherries to obtain enough lateral shoots and leaves using different methods. These procedures included Perlan application, pruning (heading), bud management (bud selection, bud removal), girdling, notching, and scoring. The present study aimed to encourage leaf and shoot growth by various applications such as Perlan (BA+GA(4)(+7)), bud management, and bud management + Perlan in sweet cherries in 2015-2017. The Perlan, bud management, and bud management + Perlan applications were applied to trees of the Regina/CAB6P combination just before bud break These applications affected the diameter, length and number of primary shoots on the leader, number of 2-year-old shoots bearing fruit, and also the leaf area. Besides this, the applications affected tree volume. In general, the best results in terms of features were from bud management + Perlan. Ondokuz Mayis UniversityOndokuz Mayis University [PYO.ZRT.1904.10.018] The study was supported by a grant from Ondokuz Mayis University (PYO.ZRT.1904.10.018). We thank Sumiagro Turkey Company, license owner of Perlan in Turkey, and its technical manager, Mr Huseyin Buyuk, very much for providing Perlan.

Long-distance movement via vascular tissues is an essential step for systemic infection by plant viruses. We previously reported that pre-treatment of Nicotiana benthamiana with acibenzolar-S-methyl (ASM) both suppressed the accumulation of plantago asiatica mosaic virus (PlAMV) in inoculated leaves and delayed the long-distance movement to uninoculated upper leaves. These two effects occurred independently of each other. However, it remained unclear where and when the viral long-distance movement is inhibited upon ASM treatment. In this study, we found that ASM treatment restricted the loading of GFP-expressing PlAMV (PlAMV-GFP) into vascular tissues in the inoculated leaves. This led to delays in viral translocation to the petiole and the main stem, and to untreated upper leaves. We used cryohistological fluorescence imaging to show that ASM treatment affected the viral localization and reduced its accumulation in the phloem, xylem, and mesophyll tissues. A stem girdling experiment, which blocked viral movement downward through phloem tissues, demonstrated that ASM treatment could inhibit viral systemic infection to upper leaves, which occurred even with viral downward movement restricted. Taken together, our results showed that ASM treatment affects the loading of PlAMV-GFP into the vascular system in the inoculated leaf, and that this plays a key role in the ASM-mediated delay of viral long-distance movement.

There is a strong genetic background control of the content and composition of anthocyanins in grapes, therefore the anthocyanin profile is a suitable parameter for fingerprinting. Anyway, several studies showed how non-genetic factors such as environmental conditions and viticultural practices, can influence the distribution and the concentration of anthocyanins. A statistical analysis performed considering the influence of thinning and girdling alone or in combination on Sugrathirteen ® vines showed how the investigated factors significantly influence various physical-chemical parameters (sugars accumulation, organic acids, etc.) as well as single anthocyanins detected by HPLC. In particular the results show how the treatments were able not only to affect total polyphenols and anthocyanin concentration, but moreover it was possible an analysis of anthocyanins profile variation in relation to the agronomical treatments performed at different timing (berry set and veraison).

Leaf senescence can be induced by numerous factors. In order to explore the relationship between root respiration and leaf senescence, we utilized different types of phloem girdling to control the root respiration of Alhagi sparsifolia and its physiological response. Our results showed that both girdling and inhibition of root respiration led to a decline of stomatal conductance, photosynthesis, transpiration rate, chlorophyll (Chl) a, Chl b, carotenoid (Car) content, Chl a/b, Chl/Car, water potential, and Chl a fluorescence, as well as to an increase of abscisic acid (ABA), proline, and malondialdehyde content in leaves and to upregulation of senescence-associated gene expression. Our present work implied that both inhibition of root respiration and girdling can induce leaf senescence. In comparison with phloem girdling, the leaf senescence caused by inhibition of root respiration was less significant. The reason for girdling-induced senescence was ABA and carbohydrate accumulation. Senescence induced by inhibition of root respiration occurred due to leaf water stress resulting from inhibition of water absorption.

European fruit tree canker, caused by Neonectria ditissima, is an important disease of pome fruit worldwide. Apple cultivars differ in their levels of susceptibility to N. ditissima. In order to design an effective plant resistance test, we examined the effectiveness of two resistance parameters: infection frequency and lesion growth. Both parameters were evaluated in parallel tests using 10 apple cultivars in three experimental years, applying seminatural infection of leaf scars (infection frequency) or inoculation of artificial wounds (lesion growth). We compared six parameters for lesion growth, of which a new parameter, lesion growth rate (LGR), appeared to be the best with respect to reproducibility and statistical significance. LGR is defined as the slope of the regression of lesion size versus time. The slope was estimated for each lesion, employing a common start date and a lesion-specific end date determined by the girdling of the lesion. The two parameters (infection frequency and LGR) were examined in separate experiments and in three successive years, and provided complementary information and resulted in reproducible conclusions on the relative resistance levels to N. ditissima of the tested cultivars. The presented methods can be used to develop strategies for the control of European fruit tree canker (e.g., in the breeding of new apple cultivars with high levels of resistance to N. ditissima).

The early culmination of maximum radial growth (RG) in late spring has been found in several coniferous species in a dry inner Alpine environment. We hypothesized that an early decrease in RG is an adaptation to cope with drought stress, which might require an early switch of carbon (C) allocation to belowground organs. To test this hypothesis, we experimentally subjected six-year-old Norway spruce saplings (tree height: 1.35 m; n = 80 trees) to two levels of soil water availability (watered versus drought conditions) and manipulated tree C status by physically blocking phloem transport at three girdling dates (GD). The influence of C availability and drought on tree growth (radial and shoot growth; root biomass) in response to girdling was analyzed in both treatments. Non-structural carbohydrates (NSCs, soluble sugars and starch) were measured in the stem, root and current leader to evaluate changes in tree C status due to girdling. The main finding was a significant increase in RG of the girdled trees compared to the controls above the girdling zone (UZ). At all girdling dates the RG increase was significantly more intense in the drought-stressed compared with watered trees (c. 3.3 and 1.9-fold higher compared with controls in the drought-stressed and watered trees, respectively), most likely indicating that an early switch of C allocation to belowground occurs as an adaptation to maintain tree water status under drought conditions. Reactivation of the cambium after the cessation of its regular activity was detected in UZ in drought-stressed trees, while below the girdling zone no xylem formation was found and the NSC content was strikingly reduced. Irrespective of water availability, girdling before growth onset significantly reduced the progression of bud break (P < 0.05) and the length of the current leader shoot by −47% (P < 0.01) indicating a reduction in xylem hydraulic conductance, which was corroborated by significantly reduced xylem sap flow (P < 0.001). Based on our findings, we conclude that during the growing season drought stress prioritizes an early switch of C allocation to the root system as an adaptation to maintain adequate tree water status in drought-prone environments.

Summary Heat girdling is a method to estimate the relative contribution of phloem vs xylem water flow to fruit growth. The heat girdling process is assumed to destroy all living tissues, including the phloem, without affecting xylem conductivity. However, to date, the assumption that xylem is not affected by heat girdling remains unproven. In this study, we used in vivo magnetic resonance imaging (MRI) velocimetry to test if heat girdling can cause xylem vessels to embolize or affect xylem water flow characteristics in the peduncle of tomato (Solanum lycopersicum cv Dirk). Anatomical and MRI data indicated that, at the site of girdling, all living tissues were disrupted, but that the functionality of the xylem remained unchanged. MRI velocimetry showed that the volume flow through the secondary xylem was not impeded by heat girdling in either the short or the long term (up to 91 h after girdling). This study provides support for the hypothesis that in the tomato peduncle the integrity and functionality of the xylem remain unaffected by heat girdling. It therefore confirms the validity of the heat girdling technique as a means to estimate relative contributions of xylem and phloem water flow to fruit growth.

During spring, bud growth relies on long-distance transport of remotely stored carbohydrates. A new hypothesis suggests this transport is achieved by the interplay of xylem and phloem. During the spring, carbohydrate demand of developing buds often exceeds locally available storage, thus requiring the translocation of sugars from distant locations like limbs, stems and roots. Both the phloem and xylem have the capacity for such long-distance transport, but their functional contribution is unclear. To address this ambiguity, the spatial and temporal dynamics of carbohydrate availability in extension shoots of Juglans regia L. were analyzed. A significant loss of extension shoot carbohydrates in remote locations was observed while carbohydrate availability near the buds remained unaffected. This pattern of depletion of carbohydrate reserves supports the notion of long-distance translocation. Girdling and dye perfusion experiments were performed to assess the role of phloem and xylem in the transport of carbohydrate and water towards the buds. Girdling caused a decrease in non-structural carbohydrate concentration above the point of girdling and an unexpected concurrent increase in water content associated with impeded xylem transport. Based on experimental observations and modeling, we propose a novel mechanism for maintenance of spring carbohydrate translocation in trees where xylem transports carbohydrates and this transport is maintained with the recirculation of water by phloem Munch flow. Phloem Munch flow acts as a pump for generating water flux in xylem and allows for transport and mobilization of sugars from distal locations prior to leaves photosynthetic independence and in the absence of transpiration.

Aristobia reticulator (Voet) is reported for the first time in India as a stem borer of litchi trees, Litchi chinensis Sonn. (Sapindaceae) in the State of Arunachal Pradesh. Beetles were observed feeding on bark, thereby girdling stems, branches, and soft twigs, while larvae tunneled inside the stem. Of 382 trees examined in the survey, 88.5% were damaged by this pest. The grubs caused maximum damage in saplings and branches. The beetles emerged during June–August from stems by making an exit hole, and thereafter they fed on the bark of tender branches. After pre-mating and pre-oviposition periods of 4.8 and 7.5 days, respectively, females cut a slit into the bark and laid eggs under it. Incubation period ranged from 15 to 26 days. Newly hatched larvae first started feeding subcortically and then entered the sapwood. Larvae continued to move down the branches, feeding and ejecting frass from their tunnels. The mature larva formed a pupal cell under the bark. The mean larval and pupal periods rang...

In arctic ecosystems, climate change has increased plant productivity. As arctic carbon (C) stocks are predominantly located below ground, the effects of greater plant productivity on soil C storage will significantly determine the net sink/source potential of these ecosystems, but vegetation controls on soil CO2 efflux remain poorly resolved.To identify the role of canopy‐forming species in below‐ground C dynamics, we conducted a girdling experiment with plots distributed across 1 km2 of treeline birch (Betula pubescens) forest and willow (Salix lapponum) patches in northern Sweden and quantified the contribution of canopy vegetation to soil CO2 fluxes and below‐ground productivity.Girdling birches reduced total soil CO2 efflux in the peak growing season by 53% ‐double the expected amount, given that trees contribute only half of the total leaf area in the forest. Root and mycorrhizal mycelial production also decreased substantially. At peak season, willow shrubs contributed 38% to soil CO2 efflux in their patches.Our findings indicate that C, recently fixed by trees and tall shrubs, makes a substantial contribution to soil respiration. It is critically important that these processes are taken into consideration in the context of a greening arctic since productivity and ecosystem C sequestration are not synonymous.

Tissue regeneration upon wounding in plants highlights the developmental plasticity of plants. Previous studies have described the morphological and molecular changes of secondary vascular tissue (SVT) regeneration after large-scale bark girdling in trees. However, how phytohormones regulate SVT regeneration is still unknown. Here, we established a novel in vitro SVT regeneration system in the hybrid aspen (Populus tremula x Populus tremuloides) clone T89 to bypass the limitation of using field-grown trees. The effects of phytohormones on SVT regeneration were investigated by applying exogenous hormones and utilizing various transgenic trees. Vascular tissue-specific markers and hormonal response factors were also examined during SVT regeneration. Using this in vitro regeneration system, we demonstrated that auxin and cytokinin differentially regulate phloem and cambium regeneration. Whereas auxin is sufficient to induce regeneration of phloem prior to continuous cambium restoration, cytokinin only promotes the formation of new phloem, not cambium. The positive role of cytokinin on phloem regeneration was further confirmed in cytokinin overexpression trees. Analysis of a DR5 reporter transgenic line further suggested that cytokinin blocks the re-establishment of auxin gradients, which is required for the cambium formation. Investigation on the auxin and cytokinin signalling genes indicated these two hormones interact to regulate SVT regeneration. Taken together, the in vitro SVT regeneration system allows us to make use of various molecular and genetic tools to investigate SVT regeneration. Our results confirmed that complementary auxin and cytokinin domains are required for phloem and cambium reconstruction.

Gummosis can be seen in many diseased plants and is abundant in several groups, including the order Leguminosae and the families Anacardiaceae, Meliaceae, Rosaceae, and Rutaceae. The first sign of brown rot gummosis caused by Phytophthora citrophthora in Citrus trees, is often the secretion of gum. The fungus usually attacks healthy and well-developed trees and can cause rapid death. The main threat is the death of large areas of the bark and girdling of the tree. Early stages of gum duct formation were described by different authors as being either lysigenous or schizogenous. Gum ducts formed lysigenously are the result of the dissolution of cell walls at the cambial zone where xylem mother cells form, as in cherry shoots. Although gumming probably represents a general response to injury and infection, the proven effectiveness of the response as a protective barrier has yet to be documented.

Nectria haematococca Berk. & Broome causing stem girdling of three cultivars of greenhouse pepper, Capsicum annuum (cvs. Kelvin, Cubico, and Grizzly), was found for the first time in a single greenhouse in south Florida in March 1999. Approximately 10% of the plants were affected at first report increasing to over 40% within 3 months. Black lesions occurred at nodes where the plant was pruned or where fruit had been harvested. No mycelium or perithecia were noted in association with the lesions. All tissue above a lesion appeared normal until the lesion girdled the stem, causing the tissue above the lesion to wilt and die. The plant appeared unaffected below the lesion. The pathogen was isolated on half-strength Difco potato-dextrose agar (½ DPDA). Reddish perithecia developed readily in culture. Two single spore isolates of the pathogen obtained from two naturally infected plants (cultivar Kelvin) were used to satisfy Koch's postulates. Five plants of Kelvin were inoculated with each isolate by inserting a 4-mm agar block of the pathogen grown for 5 days on ½ DPDA into the stem. Five plants of the same cultivar were similarly treated with fungus-free ½ DPDA. Plants were grown under greenhouse conditions after inoculation. In four plants, black lesions similar to those seen in the commercial greenhouse developed within 1 week. In one plant, the portions of the plants above the point of inoculation wilted after 5 days. The upper parts of the plants appeared healthy until lesions girdled the stems. The plants treated with fungus-free agar remained healthy. The fungus was re-isolated from the margins of lesions on the inoculated plants. The pathogen has been reported to cause stem lesions and fruit rot of pepper in greenhouses in England (1) and Canada (2). Fruit symptoms were not observed in the Florida greenhouse. Stem symptoms were again reported from the same greenhouse in the following season. References: (1) J. T. Fletcher. Plant Pathol. 43:225–222, 1994. (2) W. R. Jarvis. Can. Plant Dis. Surv. 74:131–134, 1994.

A vine canker was first observed in the San Joaquin Valley, CA, in fall 1989, on exceptionally vigorous 1-year-old cv. Redglobe vines (Vitis vinifera) when vines were trained up the stakes. Since 1989, the same canker symptoms have been observed in Tulare, Kern, Fresno, and Riverside (Coachella Valley, CA) counties on cv. Redglobe, Crimson Seedless, Chardonnay, and Grenache vines. In affected vineyards, the disease resulted in the retraining of 2 to 6.1% of vines the following spring, using a shoot originating from below the canker. In a sample of 54 infected vines collected in 1997, 65% of cankers were found at the branching (crotch) of the vine, 24% along the shoot, or both (11%). All infections started through wounds caused by removing lateral shoots or leaves when the vine was topped to form cordons or possibly through growth cracks that occur on rapidly growing 1-year-old shoots. The first symptoms usually appear in August as red pinhead-size drops of sap on the surface of discolored tissue. By October to November, the canopies of vines girdled by the canker prematurely display fall colors and are very distinct from healthy vines. The trunk is slightly swollen and spongy where the canker occurs. Internal canker tissue is discolored and dead. Black spores are abundant within the canker, on the surface of the canker, or both. Callous tissue is often associated with the canker as the vine attempts to repair the damage with new tissue. Canker length can range from 3.5 to 26.5 cm (average 7.0 cm) and can affect the shoot's cross section from 0.4 cm to completely girdling the shoot (up to 9.0 cm in circumference). Isolations from cankers or black sporulation inside the canker on acidified potato dextrose agar (APDA) consistently yielded Aspergillus niger van Tiegh. Six well-matured current-season canes of cv. Redglobe in an experimental vineyard at Kearney Agricultural Center were inoculated by inserting a 7-mm plug of mycelium from actively growing cultures on APDA in a cut made with a 7-mm cork borer or by brushing spores of the culture over the surface of six canes wounded with a sterile razor. Six canes were inoculated with a 7-mm plug of APDA and used as noninoculated controls. Inoculated sites were sealed with Parafilm to avoid dehydration. Inoculation of grapevines with A. niger resulted in cankers similar to those observed in commercial vineyards 5 months after inoculation. Cankers ranged from 2.4 to 4.2 cm for mycelial-plug inoculation (100% of canes infected) and 2.3 to 7.3 cm for spore-brushing inoculation (67% infected). Noninoculated control canes were not infected. In another experiment, inoculation of 10 canes each with A. niger on 17 May, 10 June, 2 July, 21 July, and 16 August resulted in 50, 60, 90, 90, and 100% canker formation, respectively, 5 to 8 months after inoculation, suggesting summer inoculations were more effective than spring inoculations. Reisolation from infected canes on APDA revealed A. niger. Aspergillus species in section Nigri have been reported to be among the pathogens involved in the bunch rot complex (1,2), but to our knowledge, this is the first report of A. niger causing a serious canker of vigorously growing grape vines. References: (1) W. B. Hewitt. Berry rots and raisin molds. Pages 26–28 in: Compendium of Grape Diseases. R. C. Pearson and A. C. Gohen, eds. The American Phytopathological Society, St. Paul, MN, 1994. (2) W. R. Jarvis and J. A. Traquair. Plant Dis. 68:718, 1984.

To understand the impact of shoot-to-root ABA transport on water potential of, and xylem ABA concentration in, different plant tissues during soil drying, soybean (Glycine max cv. Siverka) plants were subjected to drought and girdling in a factorial experiment. Girdling was achieved by surgically excising the phloem tissue from just above the cotyledonary node. After girdling and withholding water, ABA concentrations were determined in xylem saps extracted from individual leaves, detached shoots and de-topped roots, after measuring stomatal conductance (gs), tissue water potentials, and root ABA concentrations. Soil drying decreased water potential throughout the plant and approximately doubled xylem ABA concentrations, coinciding with stomatal closure. Girdling slightly enhanced water potential, especially in droughted plants. Girdling diminished the soil-drying induced increase in xylem sap ABA concentration, and completely prevented root tissue ABA accumulation. Furthermore, girdling decreased root ABA concentration and increased leaf xylem ABA concentration of well-watered (WW) plants. Stomatal conductance declined linearly with leaf water potential only in intact plants, while gs declined as leaf xylem ABA concentration increased, independently of girdling. Thus shoot to root ABA transport not only determines (soil-drying induced) root ABA accumulation, but also limits ABA accumulation in the shoot to maintain stomatal opening of WW plants.

The defense of conifers against phytophagous insects relies to a large extent on induced chemical defenses. However, it is not clear how induced changes in chemical composition influence the meal properties of phytophagous insects (and thus damage rates). The defense can be induced experimentally with methyl jasmonate (MeJA), which is a substance that is produced naturally when a plant is attacked. Here we used MeJA to investigate how the volatile contents of Scots pine (Pinus sylvestris L.) tissues influence the meal properties of the pine weevil (Hylobius abietis (L.)). Phloem and needles (both weevil target tissues) from MeJA-treated and control seedlings were extracted by n-hexane and analyzed by two-dimensional gas chromatography-mass spectrometry (2D GC-MS). The feeding of pine weevils on MeJA-treated and control seedlings were video-recorded to determine meal properties. Multivariate statistical analyses showed that phloem and needle contents of MeJA-treated seedlings had different volatile compositions compared to control seedlings. Levels of the pine weevil attractant (+)-α-pinene were particularly high in phloem of control seedlings with feeding damage. The antifeedant substance 2-phenylethanol occurred at higher levels in the phloem of MeJA-treated than in control seedlings. Accordingly, pine weevils fed slower and had shorter meals on MeJA-seedlings. The chemical compositions of phloem and needle tissues were clearly different in control seedlings but not in the MeJA-treated seedlings. Consequently, meal durations of mixed meals, i.e. both needles and phloem, were longer than phloem meals on control seedlings, while meal durations on MeJA seedlings did not differ between these meal contents. The meal duration influences the risk of girdling and plant death. Thus our results suggest a mechanism by which MeJA treatment may protect conifer seedlings against pine weevils.

Phytophthora ramorum has caused extensive dieback and mortality of commercially grown Japanese larch (Larix kaempferi) in many parts of the UK, as infected foliage generates spores that then cause bark lesions and girdling cankers on trees. Following inoculation, individual needles of Japanese, European (L. decidua) and hybrid (L. × eurolepis) larch infected with P. ramorum can produce thousands of sporangia. Mean numbers of sporangia ranged from 806 to 1778 per cm2 (hybrid larch and Japanese larch, respectively), surpassing mean sporulation levels on foliar hosts previously associated with P. ramorum outbreaks in Britain, namely Rhododendron ponticum, Castanea sativa and Vaccinium myrtillus. Sporulation on larch even exceeded that of California bay laurel (Umbellularia californica), which drives the sudden oak death epidemic in California. Inoculation of foliage selected at different times of year revealed that foliage age significantly affected sporulation levels, but this varied with host species. However, symptom development and sporulation were often not correlated. Symptoms on larch were frequently insignificant or even absent at certain times of year, with sometimes the only evidence of infection being the emergence of sporangia from needles, without any sign of discolouration or necrosis. Plating infected but symptomless needles onto Phytophthora selective medium also often failed to yield the pathogen. Symptomless infection of larch needles apparently occurs, but is only detectable with microscopy. More generally, it is suggested that diagnosis of Phytophthora infection in conifers is often underestimated due to isolation difficulties and delayed symptom expression.

This study aimed to examine the effects of girdling on tomato (Solanum lycopersicum L.) plant growth and fruit development, and identify appropriate girdling time on tomato. Girdling was carried out on tomato main stems at four different girdling time: 0 days after anthesis of the last truss (0 DAA), 7 DAA, 14 DAA, and 21 DAA, respectively. Tomato plants that were not treated with girdling served as the control. Girdling altered carbohydrate allocation to different organs. With more carbohydrates partitioned to fruits, girdling significantly increased the fruit weight and yield, and advanced the commercial harvest time by approximately 10 days in comparison to the control. Due to a lack of carbohydrate supply, root biomass and carbohydrate concentration reduced in the girdled plants. No evident sink feedback inhibition of photosynthesis was observed in leaves after girdling. Considering plant growth and fruit development, the appropriate girdling time was approximately 2–3 weeks after anthesis of the last truss. Our results have demonstrated that the application of girdling on tomato plants can increase fruit size and accelerate fruit development, which provides an effective approach to regulate carbohydrate partitioning in tomato production.

Tree canker diseases are mainly caused by necrotrophic fungal pathogens, which induce canker lesions, wilting, or dieback in many species. We hypothesized that canker-associated canopy dieback is related to functional failure of the phloem and cambium, carbon starvation and/or hydraulic failure. Using a girdling and inoculation system, we evaluated gas exchange and hydraulic parameters, concentrations of non-structural carbohydrates (NSCs), leaf characteristics, stem phenotyping and symptoms of 6-month-old poplar saplings with Botryosphaeria or Valsa canker disease. Pathogen inoculations inhibited callus formation and phloem regeneration and altered the physiological parameters, water potential, NSC content in stems, and symptoms on leaves and stems, while the girdling-only control did not. Results suggest that the functional and structural integrity of the phloem and cambium play crucial roles in the pathogenesis of canker disease. Botryosphaeria canker decreased photosynthetic rate (−54% to −75%), stomatal conductance (−71% to −80%) and transpiration rate (−58% to −66%), while Valsa canker decreased photosynthetic rate (−53% to −83%), stomatal conductance (−71% to −87%) and transpiration rate (−53% to −76%) at 20, 25, and 30 days after inoculation. Results suggest that the two fungal pathogens induce carbon starvation by inhibiting photosynthesis. The leaf water potential was higher and the change in specific hydraulic conductivity was smaller in the canker region than in the adjacent regions, while the NSC content was lower in the region below cankers than above them, suggesting that the fungal pathogens caused poplar canopy dieback by initially inducing carbon starvation, not hydraulic failure.

Flower induction in iron walnut (Juglans sigillata) is a complex and highly regulated process involving multiple signal pathways to ensure flower bud formation in the subsequent year. However, the underlying molecular mechanism of the induction remains unknown. Girdling is an effective method for inducing flower bud formation in iron walnut. In this study, comparative transcriptome profiles between girdled (G) and ungirdled (unG) materials on the same tree were used to identify the signal pathway involved in flower bud induction by girdling in iron walnut. The results showed that genes related to starch and carbohydrate metabolism, photosynthesis, and hormone signals, including pectinesterase (PAE), trehalose 6-photosphatase (TPP), α-aminolase (α-AL), atpF, and auxin response factor ARF9, participated in the induction process after girdling. Expression pattern of genes related to sugar metabolism revealed that sugar was the initial signal for flower induction and that photosynthesis increased after girdling, influenced by the carbon source–sink relationship. Hormone signalling networks including auxin, abscisic acid (ABA), and brassinolide also contributed to flower bud induction of iron walnut. Auxin played an important role in tissue regeneration and flower induction after girdling. ABA directly participated in flower induction. Gene expression pattern similarities between ABA and sugar metabolism signals indicated that ABA may also be involved in sugar regulation, in turn regulating floral induction. In summary, flower induction after girdling in iron walnut is mainly regulated by a polygenic network centred on sugar and hormone signals.

Under non-inductive environmental conditions longan trees (Dimocarpus longan Lour.) were subjected to potassium chlorate (KClO3) applications, solely or in combination with shoot girdling or defoliation treatments, to induce flowering. Treated trees showed visible flower buds four weeks after treatment, while untreated reference trees remained vegetative. Trees treated with KClO3 solely and in combination with apical shoot defoliation flowered terminally at the shoot apex. KClO3 treatment in combination with girdling caused flowering exclusively at the lateral buds immediately below the girdle. Results from histological and hormone analyses are integrated with longan flowering gene expression data to build a comprehensive time course model for chemical flower induction in longan. The increased cytokinin concentration in shoot apex tissues, likely due to de novo biosynthesis and translocation, corresponds with transient up-regulation of the flower promoting gene Dimocarpus longan FLOWERING LOCUS 1 (DlFT1) in mature leaves after KClO3 treatment. Both occur during the presumed period of flower induction approximately at 10 days after treatment. Subsequently, and with some delay floral homeotic genes Dimocarpus longan APETALA 1 (DlAP1) are up-regulated in the buds indicating flower bud development, which coincides with visible floral meristems in histological specimen. The specific cytokinin accumulation and flowering gene expression pattern suggest a tight orchestration of hormonal and genetic pathways in chemically induced longan.

Chestnut blight cankers caused by the fungal pathogen Cryphonectria parasitica on infected American chestnut trees can be invaded by hypoviruses that infect C. parasitica mycelia. Hypoviruses lower pathogen virulence (i.e. hypovirulence) and decrease the probability of stem girdling. Cankers also are susceptible to invasion by non-C. parasitica fungi; however, the influence of invading fungi on disease severity is unknown. Fungi may antagonize C. parasitica growth and combine with hypovirulence to further reduce the probability of stem girdling. We conducted a survey to investigate how spatial and temporal dynamics of the fungal community within cankers correlate with canker severity and the likelihood of girdling. Cankers from six American chestnut populations were monitored from 2012 to 2016. We found that the spatial distribution of the fungal community within a canker resembled a mosaic that increased in fungal diversity over time. Cankers with increased fungal diversity were not associated with higher stem survivorship over time, compared to cankers with abundant hypovirulence in recovering chestnut populations. Fungal communities also were unstable, and cankers on surviving trees containing hypovirulence consistently were invaded by non-C. parasitica fungi. Our results suggest that canker communities are not stable, and volatility of the fungal community indicates that cankers can change quickly from less severe to more severe cankers through loss of hypovirulence. Non-C. parasitica fungi may facilitate canker expansion through greater inhibition of hypovirulent C. parasitica relative to virulent C. parasitica, which may permit virulent C. parasitica to escape hypovirus infection and resume rapid canker expansion.

Three inoculation methods were evaluated for effectiveness to cause sunflower premature ripening (PR). Evaluations were conducted on a sunflower (Helianthus annuus) cultivar susceptible to PR in replicated, multilocation experiments under greenhouse conditions. Plants were inoculated with Phoma macdonaldii, either with mycelium, conidia, or infected residues at the stem base or with buried residues. Disease severity (DS) was measured by percent girdling necrosis at the stem base and percent final PR; the infection spread was assessed using the area under the disease progress curve (AUDPC). Inoculation with mycelia or 1 × 106 spores/ml caused significantly more DS and PR than lower spore concentrations or infected residues (P < 0.05). Amending soil with residues induced root necrosis but no PR. P. macdonaldii was mainly isolated at the stem base and above but rarely on root systems. Microscopic evaluations showed that hyphae colonized mainly the cortex and vascular stem tissues. The overall results demonstrated a clear role of aerial infection in PR compared with soilborne inoculum, and that inoculation at the stem base with a spore suspension could be used for screening genotypes for resistance to PR.

Wax apple (Syzygium samarangense (Blume) Merr. & L.M. Perry) is a tropical non-climacteric fruit and belongs to Myrtaceae. It has high diversity in cultivars, metabolite content, and its biological activities. In this comprehensive review, research findings had revealed that various metabolites found in the wax apple have biological activities. The said biological activities such as: antioxidant, immunomodulatory, antibacterial, anticancer, anti-glycation, anti-inflammation, anti-hypertriglyceridemic, anti-hyperglycemic, relaxant, and spasmolytic activities. Other potential use for the metabolites also includes the treatments for neurodegenerative abnormality, analgesic, and central nervous system (CNS) depression agent. Furthermore, wax apple physiological and phytochemical characteristics can be enhanced by girdling technique, hydrogen peroxide treatment, plant growth regulators treatment, and fruit bagging treatment. Meanwhile, postharvest technology of wax apple fruit utilizes nitric oxide treatment, oxalic acid treatment, cold treatment, and Aloe vera gel coating. Wax apple has also been evolved as an ointment, anti-acne cream, and nata de guava. However, environmental stress becomes a challenge in the wax apple plantation. Therefore, the development of molecular biology, chemistry, and postharvest technology will solve those challenges. This review concludes that wax apple (S. samarangense) is a tropical fruit that promises to support the nutritional values and human health.

The competence of adult plants of mate (Ilex paraguariensis St. Hil.) to undergo adventitious rooting is essential to their vegetative rescue by cuttings. This study aimed to evaluate the adventitious rooting competence of adult mate plants, and then rescue these plants by making cuttings from epicormic shoots induced in different trunk positions. The percent survival and rooting of cuttings from epicormic shoots induced by girdling in seven adult plants were evaluated. The two stock plants whose cuttings had the highest rooting competence were further pruned and girdled to evaluate the effect of the position of epicormic shoots on their adventitious rooting competence. The potential success of rescuing of the same adult plants was also studied with cuttings of epicormic shoots induced by coppicing. The shoots were sectioned in single-bud cuttings, either treated with 3,000 mg L-1 indolebutyric acid or untreated, and then cultivated in a humid chamber for 60 days, and then the percent survival and rooting of cuttings was evaluated. In conclusion, we found that it is possible to rescue adult mate plants by cuttings from epicormic shoots induced by pruning, girdling, or coppicing. The adventitious rooting competence of cuttings differs among adult mate plants, and depends on the position of the epicormic shoots on the trunk from which epicormic shoots are collected.

Canker pathogens cause necrosis of the phloem, but in many host/pathogen systems, they also cause canopy dieback, which implicates xylem, not phloem dysfunction. We hypothesize that this dieback distal to the canker is caused by water stress resulting from the lack of a phloem-to-xylem connection, which in a healthy plant would allow delivery of nonstructural carbohydrates (NSCs) and water inward to aid in xylem embolism refilling. We tested several components of this hypothesis in the host/pathogen system Corylus avellana L./Anisogramma anomala (Peck) E. Müll (Eastern filbert blight). Cankers were non-girdling and usually ≥0.1 m long. As expected, healthy controls had higher specific conductivity (Ks) than diseased stems, but unexpectedly, had similar moisture content (m.c.), showing that the lower Ks did not result from more embolisms in the diseased stems. Moreover, manipulations that removed cambium and phloem to simulate a canker, or that shaded stems to lower NSCs, did not result in lower Ks or m.c. than controls. The outer millimeter of xylem adjacent to a canker had infrequent tyloses and/or fungal hyphae in many but not all samples, and dye studies showed little xylem water transport in that region, but the incidence of these blockages was insufficient to cause the observed 19% decrease in Ks. Healthy stems had higher m.c. than diseased stems above the canker (or analogous) location and were longer for the same leaf weight, suggestive of water stress in the upper portion of diseased stems. These results suggest that dieback distal to cankers in this system results from the bottleneck in water transport in the region adjacent to a canker, but did not find evidence to support the requirement of a phloem-to-xylem connection for continued water transport.

Caterpillars of the notodontid Oedemasia leptinoides (formerly Schizura) use their mandibles to cut shallow girdles that encircle the petioles and stems of tree hosts. When girdles are complete, the larvae bathe the girdle surface with fluid. We test whether the fluid originates from the labial salivary glands or ventral eversible gland by blocking the openings to the glands and observing whether fluid is still released onto the girdles. Only larvae with functional labial salivary glands anointed girdles with fluid. Analysis of girdle rinses for a prominent salivary enzyme, glucose oxidase, confirmed that larvae apply saliva and documented that application occurs primarily at the end of girdling. We propose that girdling by notodontids, together with related furrowing and leaf-clipping behaviors exhibited by diverse caterpillar groups, serve at least in part to introduce salivary components to exposed vascular tissues; these compounds presumably function to suppress plant defensive responses normally elicited by caterpillar feeding.

Piercing-sucking insects cause mechanical and physiological injury to plants. Ceresa nigripectus Remes Lenicov is a pest of alfalfa in subtropical regions of South America and a carrier of the ArAWB phytoplasma. The aim of this study was to determine the feeding habits of this treehopper and to describe the effects of the feeding injuries on stem vascular tissues in alfalfa. Adults and nymphs of C. nigripectus inserted their stylets repeatedly girdling the stem. One week after feeding, alfalfa stems exhibited numerous feeding canals with salivary deposits, most of which reached the phloem. Two weeks after feeding, cortex and phloem cells next to the salivary sheath collapsed, mature tracheal elements became sparse and appeared with an increased cross-section area, and phenolic compounds increased in cells and cell walls compared to undamaged plants. Three weeks after feeding, an annular callus, formed by abnormal cell division and hypertrophy of preexisting cortex and vascular cambium cells, appeared immediately above the stem girdle. Parenchyma cells from the outer layers of the callus differentiated to form secondary anomalous amphicribal bundles in the wound. The aerial parts above the stem girdle eventually withered and died. Fil: Perez Grosso, Tomas. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Instituto de Patología Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Mercado, Maria Ines. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Tucuman. Facultad de Cs.naturales E Instituto Miguel Lillo. Departamento de Morfología Fisiología y Taxonomia Vegetal. Laboratorio de Anatomia Vegetal; Argentina Fil: Ponesa, G. I.. Universidad Nacional de Tucuman. Facultad de Cs.naturales E Instituto Miguel Lillo. Departamento de Morfología Fisiología y Taxonomia Vegetal. Laboratorio de Anatomia Vegetal; Argentina. Fundación Miguel Lillo; Argentina Fil: Conci, Luis Rogelio. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Instituto de Patología Vegetal; Argentina Fil: Virla, Eduardo Gabriel. Fundación Miguel Lillo. Dirección de Zoología. Instituto de Entomología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Fusarium circinatum can be a cause of mortality in pine seedlings but it is also possible for infected seedlings to remain symptomless. The results of this study documented a biotrophic phase in symptomless Pinus radiata seedlings that can persist for at least 52 weeks. A strain of F. circinatum, transformed to express the green fluorescent protein, was observed to grow intercellularly in the root cortex, with no evidence of damage to surrounding cells. Under experimental conditions, shoot symptoms developed only following collar infection, and root deterioration was seen only in plants that first expressed aboveground symptoms. This sequence of events implies that damage to the root system was a secondary consequence of girdling. If so, root symptoms may not reliably detect seedlings infected by F. circinatum. Supplemental mineral nutrition increased the incidence of infection and symptom development in seedlings but some infected plants remained symptomless, precluding the use of this approach to detect infected seedlings. Overall, our findings suggest that the ecological activities of F. circinatum may not be limited to a necrotrophic association with pine trees. A more comprehensive understanding of the life history of this fungus may yield insights that contribute to more effective management of pitch canker.

In this study, the characteristics of cadmium (Cd) uptake by roots and translocation from roots to leaves of two eggplant species (Solanum melongena and Solanum torvum) under relatively low Cd concentrations were investigated using stable (108)Cd isotope through a number of hydroponic experiments. The uptake and translocation of (108)Cd was compared with those of (70)Zn and (15)N. The results showed more (108)Cd was loaded to the vascular channels and translocated upward to the leaves in S. melongena than in S. torvum, while the (108)Cd concentrations were significantly lower in the roots of S. melongena than in S. torvum. When the phloem and xylem were wounded by grafting treatments, the foliar (108)Cd concentrations were decreased by more than 66% regardless of the rootstock species, whereas the uptake of (108)Cd in the root was not inhibited by grafting. Similar grafting effects were observed for (70)Zn. Hence, wounding phloem and xylem by grafting disturbed the upward transport of (108)Cd and (70)Zn to the eggplant leaves. Similarly, interruption of the phloem by the girdling treatment reduced the concentrations of (108)Cd in the leaves of S. melongena by approximately 51%, though the uptake of (108)Cd by roots was not reduced by the interruption of phloem. In contrast, neither (70)Zn concentrations nor stable N isotope ratio (δ(15)N) values in the roots and leaves of S. melongena were significantly influenced by the interruption of phloem. In conclusion, the phloem played a dominant role in the long-distance transport of Cd from the root to the leaf of S. melongena, whereas the xylem was the main channel for the translocation of Zn and N.

Flow rates were quantified on detached pedicels and conductances calculated. Flow rates and conductances were independent of time and temperature, increased with the pressure applied and slightly decreased during development. Water uptake is thought to contribute to cracking of sweet cherry fruit. Water uptake/loss occurs not only through the fruit surface but also through the xylem and phloem of the pedicel. The objectives here were: (1) to quantify the hydraulic conductance of the pedicel xylem and (2) to identify the factors affecting pedicel xylem conductance. Using a modified pressure probe, water was forced through excised pedicels. The rates of axial flow were quantified gravimetrically by collecting water at the pedicel’s distal end in a pre-weighed Eppendorf tube. Applying pressure to the proximal end of a pedicel induced a constant axial flow of water through it. The introduction of air embolisms to the xylem markedly decreased axial conductance from 1.3 ± 0.1 × 10−10 m3 MPa−1 s−1 to near zero. Steam girdling had no effect on axial conductance indicating the water flows to be through the xylem, not significantly through the phloem in our ex situ arrangement. Compared with a petiole, the pedicel conductance was 50-fold lower. A cross-section of a pedicel near its distal end revealed about 10 vascular bundles that diverged from a complete ring closer to the proximal end. Conductance estimates from the numbers and sizes of xylem vessels using Hagen–Poiseuille’s law exceed those determined experimentally by about three to fourfold. Conductance of pedicels decreased slightly in developing fruit and then remained about constant until maturity. Surprisingly, there was no significant effect of temperature on conductance. The conductance estimates may be used to model xylem water flows through the pedicel.