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Growth and architectural traits in trees are economically and environmentally important and thus of considerable importance to the improvement of forest and fruit trees. These traits are complex and result from the operation of a number of molecular mechanisms. This review will focus on the regulation of crown architecture, secondary woody growth and adventitious rooting. These traits and processes have significant impact on deployment, management, and productivity of tree crops. The majority of the described work comes from experiments in model plants, poplar, apple, peach, and plum because these species allow functional analysis of the involved genes and have significant genomics resources. However, these studies convincingly show conserved mechanisms for elaboration of specific growth and architectural traits. The conservation of these mechanisms suggest that they can be used as a blueprint for the improvement of these traits and processes in phylogenetically diverse tree crops. We will specifically consider the involvement of flowering time, transcription factors and hormone-associated genes. The review will also discuss the impact of recent technological advances as well as the challenges to the dissection of these traits in trees. [ABSTRACT FROM AUTHOR]

Adventitious roots (ARs) emerge from stems, leaves or hypocotyls, being strategic for clonal propagation. ARs may develop spontaneously, upon environmental stress or hormonal treatment. Auxins strongly influence AR development (ARD), depending on concentration and kind. However, the role of different types of auxin is rarely compared at the molecular level. Rooting triggered by light exposure and flooding was examined in intact etiolated Arabidopsis thaliana hypocotyls treated with distinct auxin types. Morphological aspects, rooting-related gene expression profiles, and IAA immunolocalization were recorded. NAA and 2,4-D effects were highly dose-dependent; at higher concentrations NAA inhibited root growth and 2,4-D promoted callus formation. NAA yielded the highest number of roots, but inhibited elongation. IAA increased the number of roots with less interference in elongation, yielding the best overall rooting response. IAA was localized close to the tissues of root origin. Auxin stimulated ARD was marked by increased expression of PIN1 and GH3.3 . NAA treatment induced expression of CYCB1 , GH3.6 and ARF8 . These NAA-specific responses may be associated with the development of numerous shorter roots. In contrast, expression of the auxin action inhibitor IAA28 was induced by IAA. Increased PIN1 expression indicated the relevance of auxin efflux transport for focusing in target cells, whereas GH3.3 suggested tight control of auxin homeostasis. IAA28 increased expression during IAA-induced ARD differs from what was previously reported for lateral root development, pointing to yet another possible difference in the molecular programs of these two developmental processes. [ABSTRACT FROM AUTHOR]

Commercial carnation (Dianthus caryophyllus) cultivars are vegetatively propagated from axillary stem cuttings through adventitious rooting; a process which is affected by complex interactions between nutrient and hormone levels and is strongly genotypedependent. To deepen our understanding of the regulatory events controlling this process, we performed a comparative study of adventitious root (AR) formation in two carnation cultivars with contrasting rooting performance, "2101-02 MFR" and "2003 R 8", as well as in the reference cultivar "Master". We provided molecular evidence that localized auxin response in the stem cutting base was required for efficient adventitious rooting in this species, which was dynamically established by polar auxin transport from the leaves. In turn, the bad-rooting behavior of the "2003 R 8" cultivar was correlated with enhanced synthesis of indole-3-acetic acid conjugated to aspartic acid by GH3 proteins in the stem cutting base. Treatment of stem cuttings with a competitive inhibitor of GH3 enzyme activity significantly improved rooting of "2003 R 8". Our results allowed us to propose a working model where endogenous auxin homeostasis regulated by GH3 proteins accounts for the cultivar dependency of AR formation in carnation stem cuttings. [ABSTRACT FROM AUTHOR]

Propagation of some Olea europaea L. cultivars is strongly limited due to recalcitrant behavior in adventitious root formation by semi-hardwood cuttings. One example is the cultivar ”Galega vulgar”. The formation of adventitious roots is considered a morphological response to stress. Alternative oxidase (AOX) is the terminal oxidase of the alternative pathway of the plant mitochondrial electron transport chain. This enzyme is well known to be induced in response to several biotic and abiotic stress situations. This work aimed to characterize the alternative oxidase 1 (AOX1)-subfamily in olive and to analyze the expression of transcripts during the indole-3-butyric acid (IBA)-induced in vitro adventitious rooting (AR) process. OeAOX1a (acc. no. MF410318) and OeAOX1d (acc. no. MF410319) were identified, as well as different transcript variants for both genes which resulted from alternative polyadenylation events. A correlation between transcript accumulation of both OeAOX1a and OeAOX1d transcripts and the three distinct phases (induction, initiation, and expression) of the AR process in olive was observed. Olive AOX1 genes seem to be associated with the induction and development of adventitious roots in IBA-treated explants. A better understanding of the molecular mechanisms underlying the stimulus needed for the induction of adventitious roots may help to develop more targeted and effective rooting induction protocols in order to improve the rooting ability of difficult-to-root cultivars. [ABSTRACT FROM AUTHOR]

Tamarix aphylla (L.) Karst., a drought resistant halophyte tree, is an agroforestry species which can be used for reclamation of waterlogged saline and marginal lands. Due to very low seed viability and unsuitable conditions for seed germination, the tree is becoming rare in Indian Thar desert. Present study concerns the evaluation of aeroponics technique for vegetative propagation of T. aphylla. Effect of various exogenous auxins (indole-3-acetic acid, indole-3-butyric acid, naphthalene acetic acid) at different concentrations (0.0, 1.0, 2.0, 3.0, 5.0, 10.0 mg l) was examined for induction of adventitious rooting and other morphological features. Among all three auxins tested individually, maximum rooting response (79%) was observed with IBA 2.0 mg l. However, stem cuttings treated with a combination of auxins (2.0 mg l IBA and 1.0 mg l IAA) for 15 min resulted in 87% of rooting response. Among three types of stem cuttings (apical shoot, newly sprouted cuttings, mature stem cuttings), maximum rooting (~ 90%) was observed on mature stem cuttings. Number of roots and root length were significantly higher in aeroponically rooted stem cuttings as compared to stem cuttings rooted in soil conditions. Successfully rooted and sprouted plants were transferred to polybags with 95% survival rate. This is the first report on aeroponic culture of Tamarix aphylla which can be utilized in agroforestry practices, marginal land reclamation and physiological studies. [ABSTRACT FROM AUTHOR]

Khaya anthotheca is a hardwood species from Africa and recently introduced to Brazil. This species yields high-quality wood for diverse applications, but little has been done toward an effective propagation method for large-scale production in nurseries. We evaluated the effects of different concentrations of macro and micronutrients (i.e., 100, 50 and 25% of the concentration of a referenced solution) combined with indole-3-butyric acid (IBA) at 0 and 2 g L on the survival rate of mini-stumps and the survival and adventitious rooting of K. anthotheca mini-cuttings. The mini-stumps were grown from a source of seeds imported from Ghana, West Africa. The mini-stumps survived at a high rate (97%). Consistently high shoot yields were obtained from the mini-stumps (average of 1.8 per mini-stump). High survival percentage of mini-cuttings and adventitious rooting were observed when solutions with 100 and 50% of the nutrients concentration were combined with 2 g L IBA. Histological sections analyzed through optical microscopy indicated the tissues from mini-cutting stems were juvenile, which might have stimulated adventitious rooting. These results have important implications for further work aimed at establishing propagation strategies for K. anthotheca, which are of prime importance for assisting breeding programs of this species. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The development of adventitious roots is affected by several factors, including the age of the cutting donor plant, which negatively affects rooting capacity. Eucalyptus globulus quickly loses rooting capacity of cuttings as the donor plant ages, although the molecular and biochemical mechanisms behind this process are still unclear. To better understand the bases of rooting competence loss in E. globulus, the time required for a significant decline in rhizogenic ability without exogenous auxin was determined in microcuttings derived from donor plants of different ages after sowing. Tip cuttings of donor plants were severed before and after loss of rooting competence of microcuttings to test the hypothesis that auxin and carbohydrate homeostasis regulate rooting competence decline. There were no significant changes in concentration of carbohydrates, flavonoids, or proteins before and after the loss of rooting capacity. Peroxidase (EC 1.11.1.7) total activity increased with loss of rooting competence. Auxin concentration showed the opposite pattern. In good agreement, TAA1, a key gene in auxin biosynthesis, had lower expression after loss of rooting capacity. The same applied to the auxin receptor gene TIR1, suggesting reduced auxin sensitivity. On the other hand, genes associated with auxin response repression (TPL, IAA12) or with the action of cytokinins, the rhizogenesis inhibitor-related ARR1, showed higher expression in plants with lower rooting competence. Taken together, data suggest that age negatively affects E. globulus rooting by a combination of factors. Decreased endogenous auxin concentration, possibly caused by less biosynthesis, lower auxin sensitivity, higher expression of genes inhibiting auxin action, as well as of genes related to the action of cytokinins, appear to play roles in this process.

Osmotic stress is a major form of abiotic stress that adversely affects growth and development of plants and subsequently reduces yield and quality of crops. In this study, the effect of nitric oxide (NO) and calcium (Ca2+) on the process of adventitious rooting in cucumber (Cucumis sativus L.) under simulated osmotic stress was investigated. The results revealed that the effect of exogenous NO and Ca2+ in promoting the development of adventitious roots in cucumber seedlings under simulated osmotic stress was dose-dependent, with a maximal biological response at 10 μM NO donor nitroprusside (SNP) or 200 μM Ca2+. The application of Ca2+ chelators or channel inhibitors and calmodulin (CaM) antagonists significantly reversed NO-induced adventitious rooting, implying that endogenous Ca2+/CaM might be involved in NO-induced adventitious rooting under osmotic stress. Moreover, intracellular Ca amount was also increased by NO in cucumber hypocotyls during the development of adventitious roots under osmotic stress. This increase of endogenous Ca2+ was inhibited by NO specific scavenger 2-(4-carboxyphenyl) -4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt (cPTIO), nitrate reductase inhibitors tungstate (Na2WO4) and sodium azide (NaN3). This gives an indication that Ca2+ might be a downstream signaling molecule in the adventitious root development by NO under osmotic condition. The results also show that NO or Ca2+ play a positive role in improving plant water status and photosynthetic system by increasing chlorophyll content and photochemical activity in leaves. Furthermore, NO and Ca2+ treatment might alleviate the negative effects of osmotic stress by decreasing membrane damage and reactive oxygen species (ROS) production by enhancing the activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX). Therefore, Ca2+/CaM may act as a downstream signaling molecule in NO-induced development of adventitious root under simulated osmotic stress through improving the photosynthetic performance of leaves and activating antioxidative system in plants.

Adventitious root formation is essential for the vegetative propagation of perennial woody plants. During the juvenile-to-adult phase change mediated by the microRNA156 (miR156), the adventitious rooting ability decreases dramatically in many species, including apple rootstocks. However, the mechanism underlying how miR156 affects adventitious root formation is unclear. In the present study, we showed that in the presence of the synthetic auxin indole-3-butyric acid (IBA), semi-lignified leafy cuttings from juvenile phase (Mx-J) and rejuvenated (Mx-R) Malus xiaojinensis trees exhibited significantly higher expression of miR156, PIN-FORMED1 (PIN1), PIN10, and rootless concerning crown and seminal roots-like (RTCS-like) genes, thus resulting in higher adventitious rooting ability than those from adult phase (Mx-A) trees. However, the expression of SQUAMOSA-PROMOTER BINDING PROTEIN-LIKE26 (SPL26) and some auxin response factor (ARF) gene family members were substantially higher in Mx-A than in Mx-R cuttings. The expression of NbRTCS-like but not NbPINs and NbARFs varied with miR156 expression in tobacco (Nicotiana benthamiana) plants transformed with 35S:MdMIR156a6 or 35S:MIM156 constructs. Overexpressing the miR156-resistant MxrSPL genes in tobacco confirmed the involvement of MxSPL20, MxSPL21&22, and MxSPL26 in adventitious root formation. Together, high expression of miR156 was necessary for auxin-induced adventitious root formation via MxSPL26, but independent of MxPINs and MxARFs expression in M. xiaojinensis leafy cuttings.

In Arabidopsis basal hypocotyls of dark-grown seedlings, xylary cells may form from the pericycle as an alternative to adventitious roots. Several hormones may induce xylogenesis, as Jasmonic acid (JA), as well as indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) auxins, which also affect xylary identity. Studies with the ethylene (ET)-perception mutant ein3eil1 and the ET-precursor 1-aminocyclopropane-1-carboxylic acid (ACC), also demonstrate ET involvement in IBA-induced ectopic metaxylem. Moreover, nitric oxide (NO), produced after IBA/IAA-treatments, may affect JA signalling and interact positively/negatively with ET. To date, NO-involvement in ET/JA-mediated xylogenesis has never been investigated. To study this, and unravel JA-effects on xylary identity, xylogenesis was investigated in hypocotyls of seedlings treated with JA methyl-ester (JAMe) with/without ACC, IBA, IAA. Wild-type (wt) and ein3eil1 responses to hormonal treatments were compared, and the NO signal was quantified and its role evaluated by using NO-donors/scavengers. Ectopic-protoxylem increased in the wt only after treatment with JAMe(10 μM), whereas in ein3eil1 with any JAMe concentration. NO was detected in cells leading to either xylogenesis or adventitious rooting, and increased after treatment with JAMe(10 μM) combined or not with IBA(10 μM). Xylary identity changed when JAMe was applied with each auxin. Altogether, the results show that xylogenesis is induced by JA and NO positively regulates this process. In addition, NO also negatively interacts with ET-signalling and modulates auxin-induced xylary identity.

Adventitious rooting plays an important role in the commercial vegetative propagation of trees. Adventitious root formation is a complex biological process, but knowledge of the possible unintended effects induced by both the integration/expression of transgenes and in vitro conditions on the rooting is limited. The long-term stability of transgene expression is important both for original transformants of woody plants and its progeny. In this study, we used field-grown pear rootstock GP217 trees transformed with the reporter ß-glucuronidase (uidA) genes with and without intron and re-transformed with the herbicide resistance bar gene as model systems. We assessed the unintended effects on rooting of pear semi-hardwood cuttings and evaluated the stability of transgene expression in progeny produced by generative (seedlings) and vegetative (grafting, cutting) means up to four years. Our investigation revealed that: (1) The single and repeated transformations of clonal pear rootstocks did not result in unintended effects on adventitious root formation in cuttings; (2) stability of the transgene expression was confirmed on both generative and vegetative progeny, and no silenced transgenic plants were detected; (3) yearly variation in the gene expressions was observed and expression levels were decreased in extremely hot and dry summer; (4) the intron enhanced the expression of uidA gene in pear plants approximately two-fold compared to gene without intron. The current study provides useful information on transgene expression in progeny of fruit trees under natural environmental conditions.

The initiation and induction of root primordia are of great importance for adventitious root (AR) formation in cutting propagation of horticultural and forestry crops. However, the underlying mechanisms orchestrating these early phases of AR formation remain largely unexplored. Here, we investigated the physiological and transcriptomic changes during the early AR phases in mulberry stem hardwood cuttings. The results showed that the concentrations of soluble proteins increased, whereas concentrations of soluble sugars and starch were decreased. Indole-3-acetic acid (IAA) and zeatin had a rapid transit peak at 6 h after planting (hAP) and declined thereafter. The activities of peroxidase and catalase persistently increased and indole-3-acetic acid oxidase was maintained at a higher stable level from 0 hAP, while the activities of polyphenol oxidase fluctuated with soluble phenolics and IAA levels. The comparative transcriptome identified 4276 common genes that were differentially regulated at −6, 0 and 54 hAP. They were separated into five clusters with distinct biological functions such as defense response and photosynthesis. Considerable common genes were assigned to pathways of sugar metabolism, mitogen-activated protein kinase, and circadian rhythm. The gene co-expression network analysis revealed three major co-expressed modules involved in stress responses, hormone signaling, energy metabolism, starch metabolism, and circadian rhythm. These findings demonstrate the positive effect of auxin on AR induction, and uncovered the crucial roles of stress responses, hormone signaling and circadian rhythm in coordinating the physiological changes during the early phases of AR formation in mulberry stem hardwood cuttings.

Calcium and ethylene are essential in plant growth and development. In this study, we investigated the effects of calcium and ethylene on adventitious root formation in cucumber explants under salt stress. The results revealed that 10 μM calcium chloride (CaCl2) or 0.1 μM ethrel (ethylene donor) treatment have a maximum biological effect on promoting the adventitious rooting in cucumber under salt stress. Meanwhile, we investigated that removal of ethylene suppressed calcium ion (Ca2+)-induced the formation of adventitious root under salt stress indicated that ethylene participates in this process. Moreover, the application of Ca2+ promoted the activities of 1-aminocyclopropane-l-carboxylic acid synthase (ACS) and ACC Oxidase (ACO), as well as the production of 1-aminocyclopropane-l-carboxylic acid (ACC) and ethylene under salt stress. Furthermore, we discovered that Ca2+ greatly up-regulated the expression level of CsACS3, CsACO1 and CsACO2 under salt stress. Meanwhile, Ca2+ significantly down-regulated CsETR1, CsETR2, CsERS, and CsCTR1, but positively up-regulated the expression of CsEIN2 and CsEIN3 under salt stress; however, the application of Ca2+ chelators or channel inhibitors could obviously reverse the effects of Ca2+ on the expression of the above genes. These results indicated that Ca2+ played a vital role in promoting the adventitious root development in cucumber under salt stress through regulating endogenous ethylene synthesis and activating the ethylene signal transduction pathway.

Phytohormones and their derivatives are the major players in the signaling network and regulation of plant defense systems against abiotic stress. A new class of carotenoid-derived plant hormones namely strigolactones (SLs) have been found to regulate various developmental processes in plants. Abiotic stresses, drought, excessive watering, extreme temperatures (cold, frost and heat), salinity, pollutants and mineral toxicity adversely affect plant growth and productivity. Plants have shown positive responses under drought, salinity stress and deficiency of macronutrients in the presence of SL. Plants grown in phosphate deficient soil have shown increased strigolactones production which facilitate root growth development and fungal/mycorrhizal symbiosis increasing phosphate intake from the rhizosphere. Under these circumstances, the extent and quantity of SL varies from plant to plant. The synthetic SLs have shown increased nodulation in mutant plants. Some reports are also available on the role of SLs in adventitious rooting. In this review, we have discussed the latest developments associated with the SLs and their potential applications. [ABSTRACT FROM AUTHOR]

Key message: Concerted control of irradiance, temperature, water availability, mineral nutrition and beneficial root-associated microorganisms significantly improves adventitious rooting in eucalypts and poplars, essentially by modulating auxin and carbohydrate metabolism. Abstract: Eucalyptus and Populus are among the most economically relevant tree genera. Clonal propagation allows fast genetic gain obtained using elite genotypes. Adventitious rooting (AR), a complex and multifactorial process, is often the main limiting factor for tree cloning. Herein, practical and basic approaches to optimize clonal propagation of eucalypts and poplars, focusing on the main environmental control factors affecting it, are explored. Auxin homeostasis and function are central to AR. Irradiance quality and quantity, as well as temperature, can effectively modulate auxin availability, transport and activity. The interaction of carbohydrates, irradiance and temperature is also at the core of AR. Root architecture may be effectively modified by different N sources. Several macro and micronutrients impact on central factors of rhizogenesis, including energy metabolism, gene expression and enzymatic activities regulating auxin and other phytohormonal steady-states driving AR. Appropriate mineral nutrition is often determinant for successful AR and survival. Microbial associations with the root system and the rhizosphere, both bacterial and fungal, can have a role in auxin availability to cuttings, as well as improve disease resistance, nutrition and water relations. Significant cost reduction in clonal propagation systems of eucalypt and poplar are attainable with an adequate control of environmental factors, particularly for donor plants. Future studies should extend the molecular and physiological findings of basic research to the commercial propagation systems, and these, by their turn, should be explored to provide further advances in the basic understanding of this crucial developmental process for human economy. [ABSTRACT FROM AUTHOR]

The influence of a four-day dark treatment and a 48 h IBA pulse on in vitro root formation of Prunus avium microshoots was examined. Both treatments led to significantly higher rooting percentages in the majority of the six genotypes. While the IBA pulse led to a disproportional growth of roots compared to shoots, the plantlets under the dark treatment during root induction were healthy and were not visually distinct from the control plants. Further data collected during the commercial production of 17 genotypes verified the improved root induction using the dark treatment and identified the gelling agent Gelcarin (a carrageenan) as an additional factor with positive effects on rooting. In addition, the importance of in vitro rooting for the successful transfer to greenhouse conditions was confirmed. Rooted plantlets (>3 roots) had a significantly higher survival percentage and showed improved growth during acclimatization compared to unrooted microshoots. [ABSTRACT FROM AUTHOR]

The importance of carbohydrate reserves in leaves for rooting performance of ornamental cuttings is well-known. Especially under environmental conditions unfavourable for photosynthesis, sufficient reserves are indispensable for an undisturbed adventitious root formation and to prevent senescence of leaves during rooting. However, due to time and costs, established methods for carbohydrates analysis are not suitable for implementation in global production chains of ornamentals. Near-infrared spectroscopy (NIRS) might be a valuable alternative. To explore the suitability of this technique, NIR spectra were taken from intact cuttings as well as from upper and lower side of detached leaves of chrysanthemum and pelargonium cuttings and partial least squares (PLS) calibration models were developed for glucose, fructose, sucrose and starch in leaves, which were analysed by a stepwise enzymatic-photometric method. Presumably because of a high percentage of cuttings with very low amounts of glucose, fructose and sucrose, calibration models for single soluble sugars and sum of soluble sugars were poor (R CV 2 ≤ 0.5, RPD CV ≤ 1.5), while prediction performance for starch and sum of starch and soluble sugars was quite good (R 2 > 0.8, RPD > 2.0, RER > 10). The high number of cuttings with depleted reserves of soluble sugars seems to have been at least partly caused by transportation of cuttings, before NIR analysis, from stock plant facilities in Africa and Latin America to Central Europe. The quite low levels of leaf carbohydrates on delivery at rooting facilities cannot be detected by NIRS properly. Thus, NIRS seems to be more suitable for monitoring of leaf carbohydrates in stock plants to optimise crop management than for assessment of cutting quality before rooting. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop a shoot regeneration protocol for Tectona grandis by examining the effects of pretreatments, regeneration culture medium, adventitious rooting, and acclimatization. The best organogenic potential was achieved when hypocotyls and cotyledonary segments from seedlings germinated on a medium containing TDZ, were cultured for four weeks on MS medium supplemented with BAP/GA3. With TDZ pretreatment during seed germination, up to 70% of the cotyledonary segments (0.5 TDZ pretreatment and 1.0 BAP + 0.5 GA3 during regeneration, mg L-1) and 60% of the hypocotyl explants (0.1 TDZ pretreatment and 1.0 BAP + 0.5 GA3 during regeneration, mg L-1) resulted in shoot regeneration. Finally, 65% of the regenerated shoots rooted, of which 60% were successfully acclimatized ex vitro. Our protocol increases regeneration efficiency for teak and it can serve as a platform for genetic transformation to improve this important tree species. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Applied Technology for Agricultural Science / Revista Brasileira de Tecnologia Aplicada nas Ciências Agrárias is the property of Brazilian Journal of Applied Technology for Agricultural Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hydrogen gas (H2) and carbon monoxide (CO) are involved in plant growth and developmental processes and may induce plant tolerance to several stresses. However, the independent roles and interaction effect of H2 and CO in adventitious root development under drought conditions have still not received the needed research attention. We hypothesize that there exists crosstalk between H2 and CO during adventitious root development under drought stress. The results of our current study revealed that 50% (v/v) hydrogen-rich water (HRW), 500 µM Hemin (the CO donor) and 30% (w/v) CO aqueous solution apparently promoted the development of adventitious roots in cucumber explants (Cucumis Sativus L.) under drought stress. H2 and CO increased relative water content (RWC), leaf chlorophyll content (chlorophyll a, b, and aCb), and chlorophyll fluorescence parameters [photochemical efficiency of photosystem II (PSII), PSII actual photochemical efficiency and photochemical quench coefficient] under drought condition. When the CO scavenger hemoglobin (Hb) or zinc protoporphyrin IX (ZnPPIX) was added to HRW/CO aqueous solution, the positive effect of HRW/CO aqueous solution on RWC, leaf chlorophyll content, and chlorophyll fluorescence parameters were reversed. Additionally, superoxide dismutases, peroxidase, catalase, and ascorbate peroxidase was significantly increased in the explants treated with HRW and CO aqueous solution under drought stress, thus alleviating oxidative damage, as indicated by decreases in thiobarbituric acid reactive substances (TBARS), hydrogen peroxide (H2O2), and superoxide radical (O2-) levels. H2 and CO also improved the levels of water soluble carbohydrate, total soluble protein, and proline content. However, the above CO/H2-mediated effects were reversed by CO scavenger Hb or CO specific synthetic inhibitor ZnPPIX. Therefore, CO may be involved in H2-induced adventitious rooting under drought stress and alleviate oxidative damage by enhancing RWC, leaf chlorophyll content, chlorophyll fluorescence parameters, metabolic constituent content, activating anti-oxidant enzymes and reducing TBARS, O2-, and H2O2 levels. [ABSTRACT FROM AUTHOR]

We aimed at evaluating morpho-physiological responses of Populus euphratica to flooding with fresh and saline water to assess its potential for conservation of lowland areas prone to suffer soil waterlogging. One-year-old cuttings were subjected to five treatments, including control, and flooding at increasing salinity concentrations (0, 50, 100, and 150 mM NaCl) for 90 days. Plant survival and growth, leaf gas exchange, leaf water potential, and concentration of Na + , K + , Ca 2 + , Mg 2 + in leaves were assessed. Flooding with saline water of 100 or 150 mM NaCl compromised plant survival. Plant death was preceded by strong reductions in photosynthesis, stomatal conductance and leaf water potential, increments in leaf Na + concentration, and restricted adventitious rooting. By contrast, flooding with fresh or slightly saline water (50 mM NaCl) did not endanger survival although it reduced final plant biomass (65–68%). Cuttings flooded with fresh or slightly saline water showed profuse development of adventitious roots and hypertrophied lenticels in stems as typical adaptive responses to hypoxia, and despite having smaller-sized leaves, these were able to continue photosynthesizing at levels of 40–50% of their controls even after 90 days of flooding. So, P. euphratica appears as a promising candidate species to be included in conservation programs for riparian areas experiencing long-term flooding with fresh or slightly saline water of up to 50 mM NaCl. [ABSTRACT FROM AUTHOR]

Qualitative and quantitative hormone analyses have been essential for understanding the metabolic, physiological, and morphological processes that are influenced by plant hormones. Auxins are key hormones in the control of many aspects of plant growth and development and their endogenous levels are considered critical in the process of adventitious root induction. Exogenous auxins are used extensively in the clonal propagation of tree species by cuttings or tissue culture. Understanding of auxin effects has advanced with the development of increasingly accurate methods for auxin quantification. However, auxin analysis has been challenging because auxins typically occur at low concentrations, while compounds that interfere with their detection often occur at high concentrations, in plant tissues. Interference from other compounds has been addressed by extensive purification of plant extracts prior to auxin analysis, although this means that quantification methods have been limited by their expense. This review explores the extraction, purification, and quantification of auxins and the application of these techniques in developing improved methods for the clonal propagation of forestry trees. [ABSTRACT FROM AUTHOR]

Cytokinins are a group of plant hormones stimulating, among others, axillary bud formation and inhibiting rhizogenesis. Adenine, their common component, often expresses cytokinin-like activity in plant development. The aim of the experiment was to determine the effect of adenine on rooting and development of Fuchsia hybrida cuttings. The influence of adenine was also assessed in comparison to benzyladenine, including their cooperation with 1-naphthaleneacetic acid. Anatomical analysis of the rooting process was also undertaken. Application of BA, both alone or together with NAA, strongly inhibited rhizogenesis, but stimulated axillary shoot outgrowth. Adenine exhibited cytokinin-like activity on axillary shoot development in Fuchsia hybrida cuttings, but did not show the inhibitory effect on root development typical for cytokinins. This compound, particularly at higher concentrations, stimulated both axillary shoot development and rooting, which was expressed as an increase in root number and rooting percentage, even after direct application to the base of the cuttings. Anatomical analysis revealed adenine-derived acceleration during elongation of adventitious root primordia.

This investigation was conducted at the Research Farm of Department of Floriculture and Landscaping, Dr Yashwant Singh Parmar University of Horticulture and Forestry, Solan, Himachal Pradesh during the year 2010 and 2011 to ascertain the rooting behavior of cuttings taken from two chrysanthemum (Dendranthema grandiflora) cultivars Purnima and Ajay as affected by integrated nutrient management during the production phase of the plants. Plants grown under open field condition were subjected to 17 different nutritional regimes in a factorial Randomized Block Design (RBD) replicated thrice. After flowering was over, plants were headed back. Regenerated cuttings from headed back plants were studied for various parameters. The results revealed that plants receiving treatment comprising of 22.5 g/m2 each of NPK + Vermicompost (1 kg/m2) + Biofertilizers (Azotobacter + PSB + VAM) produced the maximum number of cuttings/plant (36.45), length of the longest root (8.58 cm), number of roots/plant (28.95), highest rooting percentage (95.52 %) and maximum fresh weight of cuttings at harvest (3.79 g) and after rooting (3.89 g). The same treatment also took the least number of days (25.20 days) for rooting to occur. Plants treated with 15 g/m2 each of NPK + Vermicompost (1 kg/m2) + Biofertilizers recorded the highest nitrogen contents of cuttings at harvest (5.09 %) and after rooting (4.64 %). Among the cultivars, Purnima exhibited maximum number of cuttings/plant (37.86), lesser number of days for rooting (20.97) and maximum nitrogen contents of cuttings at harvest (4.16 %) and after rooting (4.47 %), whereas cultivar Ajay recorded the maximum length of the root (6.38 cm) and number of roots/plant (22.46).

Nothofagus glauca posee una situación privilegiada en asociaciones con especies problemáticas como Nothofagus alessandrii, Beilschmiedia berteroana y Nothofagus leonii, esto multiplica su valor ecológico y paisajístico, por las relaciones en su hábitat nativo. N. glauca se considera clave en determinados hábitats y su pérdida o continua disminución puede afectar directamente a otras especies. La conservación ex situ es una prioridad para el rescate de la especie, por tanto el cultivo de tejidos es, entre otros, uno de los mecanismos alternativos de propagación y conservación de las especies. El objetivo de este estudio fue evaluar el efecto independiente de dos auxinas, ácido naftalenacético (ANA) y ácido 3-indolbutírico (AIB), en el enraizamiento in vitro de microtallos de N. glauca provenientes de subcultivos sucesivos en medio MS como sustrato. Se establecieron seis tratamientos con: 1 mgl-1, 3 mgl-1 y 5 mgl-1 de ANA y AIB, un control libre de hormonas y cuatro réplicas de cada uno. Se evaluó la supervivencia y enraizamiento de los microtallos, longitud de raíz (mm) y número de raíces por explanto. Se obtuvo supervivencia de hasta 100% con la adición de 3 mgl-1 de AIB al medio de cultivo. Se presentaron diferencias significativas entre el tratamiento control y microtallos sometidos a inmersión en hormonas. Se obtuvo 87,5% de enraizamiento adventicio con 1 mgl-1 de AIB y un 75,0% con 3 mgl-1 de ANA. Se concluye que la presencia de auxinas en el medio de cultivo es indispensable para la formación de raíces in vitro y establece la posibilidad de mantener el potencial rizogénico de la especie en condiciones ex vitro.Nothofagus glauca forms essential associations with problematic species such as Nothofagus alessandrii, Beilschmiedia berteroana and Nothofagus leonii. By enhancing its native environment, N. glauca increases its ecological and scenic value. It is considered a keystone species in certain habitats, and its continued decline or loss may directly affect other species. Ex situ conservation is a priority for the recovery of the species; therefore, tissue culture is, among others, one of the alternative mechanisms for effective propagation and conservation of N. glauca. The aim of this study was to evaluate the independent effect of two auxins, 1-naphthalene acetic acid (NAA) and indole 3-butyric acid (IBA) in vitro rooting of microshoots of N. glauca from successive subcultures on MS medium. Six treatments were established containing 1 mgl-1, 3 mgl-1, and 5 mgl-1 of NAA and IBA. Experimental design included a hormone-free control and four replicates of each treatment. We evaluated the survival and rooting of the microshoots, the root length (mm), and the number of roots formed per explant. Survival of microshoots was recorded at 100% when 3 mgl-1 IBA was added to the culture medium. Furthermore, significant differences existed between the control treatment and the microshoots subjected to hormone immersion. 87.5% adventitious root formation was observed with 1 mgl-1 IBA, and 75.0% was observed with 3 mgl-1 of NAA. The results indicate that the presence of auxin in the culture medium is essential for in vitro root formation and provides the ability to maintain the rhizogenic potential of the species in ex vitro conditions.

The establishing of roses in hydroponic systems implies development propagation techniques that are efficient, economical and that produce homogeneous populations in a short time. In this work, were evaluated the effects of different substrates (peat, agrolite and vermiculite, a 1:1 v/v mixture of peat and vermiculite and two 1:1 v/v and 1:3 v/v mixture of gravel and coconut fiber); two levels of light (548 y 274 µmol.m-2 .s-1) and leaf persistence on cutting (0, 5, 10, 15, 20 y 25 days after establishment) on rooting, root and axial bud developments of commercial variety of rose. The vermiculite had the best results, showed the highest number of cuttings alive and rooting percentage (60%). The light levels, leaf persistence as the interaction, were also significant. The highest rooting percentage, longer roots and better axial bud development was found with 548 µmol.m-2 s-1. Regarding leaf persistence on cutting was found that less than 10 days, the cuttings become necrotic and eventually died. There was also an inverse effect on root and bud development when the leaf persists more days, the root length was increased but axial bud decreased. In conclusion, for enhanced cuttings rooting success of rose, is required use vermiculite as substrate, with good light and leaf persists on cutting at least 15 days.

Cedrela odorata (Meliaceae) is considered as one of the most valuable forest tree in the tropics. Clonal propagation of this species provide an alternative method to propagate superior genotypes, being the production of good quality adventitious roots one of the most important steps in micropropagation techniques. The sequence of anatomical changes that takes place during the formation of adventitious roots in shoots of Cedrela odorata cultured in vitro is described in this study. Eigth-week-old shoots, from multiplication cultures, were rooted in Murashige and Skoog´s medium (1962) with half- strength macronutrients and with 0 or 1mg/l indole-3-butyric acid (IBA). Between 12 and 24h after the start of rooting, some cambium, phloem and interfascicular parenchyma cells became dense cytoplasm, nuclei with prominent nucleoli and the first cell divisions were observed, especially in shoots treated with auxin (dedifferentiation phase). After 3-4 days, the number of dedifferentiated cells and mitotic divisions increased considerably, and the formation of groups of some 30-40 meristematic cells (meristemoids) was observed (induction phase). The first primordial roots developed from the 4th-5th day. The vascular tissues of these primordia connected to those of the explant, and roots began to emerge from the base by day 6. Development of the primordial roots was similar in the control shoots and shoots treated with 1mg/l IBA, although there were more roots per explant in the latter. Rev. Biol. Trop. 59 (1): 447-453. Epub 2011 March 01.Cedrela odorata (Meliaceae) es una especie tropical de gran valor económico. La propagación in vitro de esta especie ofrece una vía alternativa para la clonación de genotipos superiores, siendo la formación de un buen sistema radical uno de los pasos claves en la micropropagación. En este trabajo analizamos la secuencia de cambios anatómicos que tienen lugar durante la formación de raíces adventicias en microestaquillas de Cedrela odorata. Para el enraizamiento se utilizó el medio MS con los macronutrientes reducidos a la mitad, suplementado con AIB 0 ó 1mg/l. A partir de las 12-24 horas del comienzo del enraizamiento, se observaron los primeros cambios en las células del cambium, del floema y del parénquima interfascicular (fase de diferenciación). Después de 3-4 días, aparecen grupos de células meristemáticas (fase de inducción). Los primordios se desarrollan después de 4-5 días, siendo visibles al exterior a partir del sexto día (fase de emergencia). El desarrollo de las raíces fue similar en ambos tratamientos, pero la presencia de AIB aumenta el número de raíces.

Berberidopsis corallina es una planta trepadora endémica de Chile catalogada "en peligro de extinción" y que hoy se encuentra en problemas de conservación, debido al escaso número de poblaciones y a su difícil reproducción por semillas. El objetivo del presente trabajo fue evaluar su capacidad de enraizamiento de estacas recolectadas en distintas épocas del año y utilizando diferentes concentraciones de la auxina ácido 3-indolbutírico. Las muestras se obtuvieron de plantas madres que crecen en Trongol Bajo (Curanilahue 37°28' S; 73°20' O, provincia de Arauco) en época de verano, otoño e invierno de 2006. Estacas de 8-10 cm de longitud fueron tratadas bajo inmersión rápida a diferentes concentraciones de ácido 3-indolbutírico (0, 500, 1.500, 3.000, 5.000 ppm). Después de cinco meses de realizado el ensayo se evaluó el efecto del ácido 3-indolbutírico (AIB) y época de muestreo sobre el potencial de enraizamiento adventicio en las estacas. El estudio reveló que existen diferencias significativas en cuanto a la época de recolecta, alcanzándose un mayor porcentaje de enraizamiento en estacas recolectadas en invierno (93%); sin embargo, entre los tratamientos no existen diferencias significativas. El mayor número de raíces se obtuvo en el tratamiento 500 ppm con un valor promedio de 8,1 raíces por estaca en época de otoño. Se concluye que B. corallina puede ser reproducido vegetativamente sin la necesidad de aplicar auxina a la estaca en época de invierno y otoño, en plantas procedentes de Trongol Bajo, permitiendo propagar la especie con la mínima intervención.Berberidopsis corallina is an endangered vine endemic to Chile, which is difficult to conserve due to its small number of remaining populations and its recalcitrance to reproduce by seeds. The objective of this study was to evaluate the rooting ability of cuttings collected at different times and treated with varying concentrations of the auxin indole-3-butyric acid. Semi-ligneous cuttings were collected from plant material found in Trongol Low (Curanilahue 37° 28'S, 73° 20'W, Arauco province) during the summer, autumn and winter of 2006. Cuttings of 8-10 cm in length were rapidly immersed in solutions with different concentrations of indole-3-butyric acid (0, 500, 1,500, 3,000, 5,000 ppm). The effect of indole-3-butyric acid (IBA) and collection time of the cuttings on their adventitious rooting potential were evaluated five months after rapid immersion. Significant differences existed with regard to the time of collection, with a higher percentage of rooting observed in cuttings collected in winter (93%); however, between the treatments there were no significant differences. The highest number of roots was obtained when autumn cuttings were treated with 500 ppm IBA, yielding an average of 8.1 roots per cutting. The authors conclude that B. corallina can be vegetatively reproduced via cuttings without exogenous hormone addition if the cuttings are selected during winter and autumn from plants in Trongol Low, which allows for the efficient propagation of this endangered species.

As informações a respeito da propagação de Cuphea calophylla subsp. mesostemon (Koehne) Lourteig (Lythraceae) são escassas. As técnicas de propagação podem subsidiar o manejo, fornecendo alternativa para produtores de plantas medicinais e evitando a coleta indiscriminada. O presente trabalho teve como objetivo verificar o efeito de diferentes tipos de estaca, tamanhos e área foliar no enraizamento de estacas semilenhosas. As estacas foram obtidas a partir de plantas espontâneas coletadas na Estação Experimental do Canguiri da Universidade Federal do Paraná (UFPR), localizada em Pinhais - PR. Os experimentos com estaquia foram conduzidos em casa-de-vegetação. O delineamento foi inteiramente casualizado com cinco repetições e 24 estacas por parcela, para todos os experimentos. As estacas obtidas de ramos vegetativos apresentaram maior porcentagem de brotação e massa seca de raízes por estaca em relação àquelas obtidas de ramos reprodutivos, especialmente, as estacas obtidas da parte basal dos ramos vegetativos. As estacas preparadas com 10 e 15 cm de comprimento apresentaram maior número de brotos e maior massa seca de raízes por estaca, em relação às preparadas com 5 cm. As estacas com 3 e 4 pares de folhas apresentaram maior altura, incremento de altura, massa seca de raízes e de brotos por estaca, em relação aos tratamentos com 1 e 2 pares de folhas. Os resultados de propagação vegetativa apontam a estaquia como uma técnica viável para a multiplicação da espécie.Information about the propagation of Cuphea calophylla subsp. mesostemon (Koehne) Lourteig (Lythraceae) is scarce. Propagation techniques may support its management, providing an alternative for medicinal plant producers and avoiding indiscriminate harvests. This study aimed to investigate the effect of different types, sizes and leaf areas of semi-woody cuttings on their rooting. Cuttings were obtained from weeds harvested at the Canguiri Experimental Station of the Paraná Federal University (UFPR), Pinhais Municipality, Paraná State, Brazil. Experiments were carried out in a greenhouse. Experimental design was completely randomized, with five replicates and 24 cuttings per plot. Cuttings obtained from vegetative branches had higher sprouting percentage and root dry matter per cutting relative to those obtained from reproductive branches, especially cuttings obtained from the basal region of vegetative branches. Cuttings prepared with 10 and 15 cm length had larger number of sprouts and higher root dry matter per cutting relative to those prepared with 5 cm. Cuttings presenting 3 and 4 leaf pairs had greater height, increase in height, and root and sprout dry matter per cutting relative to those presenting 1 and 2 leaf pairs. The results regarding vegetative propagation indicate cutting as a viable technique for the multiplication of this species.

Portulaca umbraticola Kunth stem cuttings were treated with BA or BA and NAA in different concentrations. BA was applied by spraying or by the quick-dip method. Independent of application type, in almost all of the treatments BA and BA applied with NAA increased the percentage of rooted cuttings, but had no effect on the number of roots, apart from BA in the 0.5 g dm-3 concentration, which doubled the root number. Treatment with BA alone resulted in more intensive axillary shoot development, although only in one concentration (0.2 g dm-3) did BA significantly influence the number and length of lateral shoots. BA applied together with NAA had no effect or inhibited lateral shoot development.

Tree breeding is basically aimed at producing quality products like seeds and clones and the most valuable contribution ofmolecular markers in breeding programs would be to reduce the time of selection or to reduce the number of breedingcycles. This can be achieved either by the early identification of superior progeny or by the identification of parents that willyield superior progeny. The present study highlights the use of microsatellite markers towards development of putativemarkers tagging the adventitious rooting trait in Eucalyptus tereticornis. Further, putative cellulose synthase specific markerswere identified and correlated with pulping character of wood tissues. The validation of these putative markers in largerpopulations can lead to more efficient and broadly applicable early selection procedure for key traits in eucalypt breedingprograms.

Propagation of some Olea europaea L. cultivars is strongly limited due to recalcitrant behavior in adventitious root formation by semi-hardwood cuttings. One example is the cultivar ”Galega vulgar”. The formation of adventitious roots is considered a morphological response to stress. Alternative oxidase (AOX) is the terminal oxidase of the alternative pathway of the plant mitochondrial electron transport chain. This enzyme is well known to be induced in response to several biotic and abiotic stress situations. This work aimed to characterize the alternative oxidase 1 (AOX1)-subfamily in olive and to analyze the expression of transcripts during the indole-3-butyric acid (IBA)-induced in vitro adventitious rooting (AR) process. OeAOX1a (acc. no. MF410318) and OeAOX1d (acc. no. MF410319) were identified, as well as different transcript variants for both genes which resulted from alternative polyadenylation events. A correlation between transcript accumulation of both OeAOX1a and OeAOX1d transcripts and the three distinct phases (induction, initiation, and expression) of the AR process in olive was observed. Olive AOX1 genes seem to be associated with the induction and development of adventitious roots in IBA-treated explants. A better understanding of the molecular mechanisms underlying the stimulus needed for the induction of adventitious roots may help to develop more targeted and effective rooting induction protocols in order to improve the rooting ability of difficult-to-root cultivars.

Plants are sessile organisms that must deal with various threats resulting in tissue damage, such as herbivore feeding, and physical wounding by wind, snow or crushing by animals. During wound healing, phytohormone crosstalk orchestrates cellular regeneration through the establishment of tissue-specific asymmetries. In turn, hormone-regulated transcription factors and their downstream targets coordinate cellular responses, including dedifferentiation, cell cycle reactivation and vascular regeneration. By comparing different examples of wound-induced tissue regeneration in the model plant Arabidopsis thaliana , a number of key regulators of developmental plasticity of plant cells have been identified. We present the relevance of these findings and of the dynamic establishment of differential auxin gradients for cell reprogramming after wounding. [ABSTRACT FROM AUTHOR]

Asexual propagation in Ceratonia siliqua L. (carob), species of economic value, is difficult because of adventitious rooting recalcitrance. In Pinus radiata adventitious rooting of hypocotyl cuttings is enhanced by two urea-derivatives, 1,3-di(benzo[ d]oxazol-5-yl)urea (5-BDPU) and 1,3-di(benzo[ d]oxazol-6-yl)urea (6-BDPU), combined with exogenous indole-3-butyric acid (IBA). The research was aimed to define the role of these urea-derivatives in adventitious root (AR) formation of carob, and to identify morphogenic roles induced in carob, but also in pine, a distantly-related forest species. In carob, 5-BDPU (10 μM) highly promoted AR formation in combination with IBA (1 μM) when applied for 3 days, followed by a transfer onto hormone free medium (HF) up to culture end (4 weeks). IBA alone (1 μM) was more effective than IBA + kinetin (Kin, 10 nM), whereas Kin alone and 5-BDPU alone were not AR-inductive. The histological analysis showed that the cambial cells initiated the ARs, and similar numbers of AR-primordia were visible at day 12, independently of the AR-inductive treatment (i.e., IBA, IBA + 5-BDPU, IBA + Kin). No cutting treated with Kin alone, and rare HF (±5-BDPU)-treated ones, showed AR-primordia at day 12. The number of AR-forming explants increased under IBA + 5-BDPU. By contrast, the cambial cells were stimulated to initiate deuteroxylem instead of ARs under 5-BDPU alone. The histological analysis in pine microcuttings treated with IBA and/or 5-BDPU at the same concentrations confirmed that 5-BDPU applied alone enhanced xylogenesis, highlighting that this urea-derivative exhibits a dual morphogenic role being involved in the switching between adventitious rooting and xylogenesis depending on the presence of exogenous auxin in both species. [ABSTRACT FROM AUTHOR]

Indole-3-butyric acid (IBA) is an endogenous compound that appears to regulate both lateral and adventitious root formation in many plant species and is also the auxin most available commercially for application to promote rooting. IBA is converted to indole-3-acetic acid (IAA) by β-oxidation in the peroxisomes. This process has been observed in a number of plant species and has been shown to be critical for normal root development in response to treatment with IBA. In this study, we investigated this process in hybrid hazelnut ( Corylus americana × C. avellana), American elm ( Ulmus americana), and Cathedral hybrid elm ( U. pumila × U. davidiana var. japonica 'Cathedral'), in which adventitious rooting is a major bottleneck for vegetative propagation, and the efficacy of IBA treatment is highly variable across different cultivars and at different collection times. Using differentially stable isotope-labeled IBA and IAA tracer and internal standard, respectively, and using gas chromatography coupled with selected reaction monitoring mass spectrometry, IBA-derived IAA was measured in shoot tissue treated with stable isotope-labeled IBA. In elm, higher levels of IBA-to-IAA conversion were generally observed in cultivars which formed adventitious roots most easily in softwood stem cutting trials. IBA-to-IAA conversion was observed in hazelnut genotypes with different rooting abilities and suggested a complex relationship exists between IBA conversion and root organogenesis. In both hazelnut and elm, endogenous free IAA levels were not significantly different across the genotypes examined. High rates of root formation is a key trait for establishment of large-scale production systems. Screening for optimal rates of IBA-to-IAA conversion may facilitate selection against genotypes which respond poorly to exogenous IBA and are thus difficult to propagate using hormone treatment. [ABSTRACT FROM AUTHOR]

An adequate nitrogen supply to stock plants is a well-known key factor in adventitious root formation of herbaceous ornamental cuttings. Both slight deficiency and luxury amount of nitrogen in the tissue can impair rooting. Due to a lack of fast, cheap and reliable analytical methods, parameters characterising the nitrogen status of cuttings are not used as quality indicators. Near infrared reflectance spectroscopy (NIRS) might bridge this gap, especially if sample preparation such as drying or grinding is avoided. NIR spectra of intact chrysanthemum and pelargonium cuttings were taken and partial least square regression models were developed for various nitrogen fractions as well as for total nitrogen. Calibration equations with high prediction performance were developed for insoluble, organic and total nitrogen (R 2 > 0.8). Calibration models for various soluble nitrogen fractions were at least suitable for a rough screening (R 2 > 0.6). In a second experiment, calibration models were extended to poinsettia, impatiens and osteospermum cuttings by adding a few samples to the calibration data set. Thus, analysing nitrogen status of ornamental cuttings by NIRS might be a valuable tool for optimisation of stock plant cultivation and assessment of rooting capacity of cuttings. [ABSTRACT FROM AUTHOR]

Tolerance to flooding is crucial when thinking in promissory species for restoration of ecosystems prone to suffer soil water excess. In this study, we tested the flooding tolerance of two-years-old seedlings of Chestnut-leaved oak (Quercus castaneifoliaC.A.Mey.) to determine whether it can be recommended for use in wetland restoration programs. Seedlings ofQ. castaneifoliawere subjected to three treatments: (1) control (C), (2) flooding for 60 days followed by a 42-day recovery period (F + R) and (3) continuous flooding for 102 days (F). Physiological performance, plant morphological changes and biomass accumulation were assessed. Results showed that, although net photosynthetic rates, stomatal conductance and transpirationdecreased withprolonged flooding, when flood waters were removed, plants were able to recover their physiological activity (49–80% compared to controls). By contrast, when plants were continually flooded, their physiological activity decreased as well as the leaves experienced precocious senescence and wilting. Biomass responses paralleled physiological responses: leaf and root biomass were 42–49% higher under F + R treatment than under continuous flooding, and all plants under the F + R survived. Therefore,Q. castaneifoliaappears as a promising species to be further studied when thinking re-vegetation ofriverine areasand othertemporarily flooded wetlands. [ABSTRACT FROM PUBLISHER]

Adventitious root (AR) formation in cuttings is a multiphase developmental process, resulting from wounding at the cutting site and isolation from the resource and signal network of the whole plant. Though, promotive effects of auxins are widely used for clonal plant propagation, the regulation and function of plant hormones and their intricate signaling networks during AR formation in cuttings are poorly understood. In this focused review, we discuss our recent publications on the involvement of polar auxin transport (PAT) and transcriptional regulation of auxin and ethylene action during AR formation in petunia cuttings in a broad context. Integrating new findings on cuttings of other plant species and general models on plant hormone networks, a model on the regulation and function of auxin, ethylene, and jasmonate in AR formation of cuttings is presented. PAT and cutting off from the basipetal auxin drain are considered as initial principles generating early accumulation of IAA in the rooting zone. This is expected to trigger a self-regulatory process of auxin canalization and maximization to responding target cells, there inducing the program of AR formation. Regulation of auxin homeostasis via auxin influx and efflux carriers, GH3 proteins and peroxidases, of flavonoid metabolism, and of auxin signaling via AUX/IAA proteins, TOPLESS, ARFs, and SAUR-like proteins are postulated as key processes determining the different phases of AR formation. NO and H2O2 mediate auxin signaling via the cGMP and MAPK cascades. Transcription factors of the GRAS-, AP2/ERF-, and WOX-families link auxin signaling to cell fate specification. Cyclin-mediated governing of the cell cycle, modifications of sugar metabolism and microtubule and cell wall remodeling are considered as important implementation processes of auxin function. Induced by the initial wounding and other abiotic stress factors, up-regulation of ethylene biosynthesis, and signaling via ERFs and early accumulation of jasmonic acid stimulate AR formation, while both pathways are linked to auxin. Future research on the function of candidate genes should consider their tissue-specific role and regulation by environmental factors. Furthermore, the whole cutting should be regarded as a system of physiological units with diverse functions specifically responding to the environment and determining the rooting response. [ABSTRACT FROM AUTHOR]

Key message: PeCYCD6_1 , a d- type cyclin gene associated with the SHORT-ROOT/SCARECROW network during adventitious root development, was identified and isolated from poplar. Abstract: SHORT-ROOT (SHR) and SCARECROW (SCR) are key regulators of root radial patterning and stele cell specification and maintenance in the Arabidopsis root. In the cortex/endodermis initial daughter cell, SHR and SCR activate the expression of a d-type cyclin, CYCD6;1, which promotes the periclinal division that maintains the separate endodermis and cortex cell layers. Information on the regulatory network is still poorly understood in trees, despite extensive and detailed analysis of the SHR/SCR regulatory network in herbaceous model organism, Here, PeCYCD6_1, a poplar d-type cycle gene was isolated from the Populus clone 'Nanlin895' ( Populus deltoides × Populus euramericana) and characterized. The PeCYCD6_1 gene consisted of six exons putatively encoding a polypeptide of 324 amino acids. Its mRNA levels significantly increased during adventitious root development. The putative PeCYCD6_1 protein contained two conserved domains, the cyclin_N and cyclin_C. Protoplast transient expression assays showed that a PeCYCD6_1-GFP fusion protein localized to the nucleus, and interactions between PeCYCD6_1 and PeSHR1/PeSCR were demonstrated using a biomolecular fluorescence complementation assay. These results indicated that the PeCYCD6_1 gene is involved in the SHR/SCR regulatory network regulating root patterning and growth in Populus. [ABSTRACT FROM AUTHOR]

Olive ( Olea europaea ) is one of the most important fruit species in the Mediterranean basin, where 95% of the world’s olive orchards are planted, and it has become an economically valuable crop worldwide, due to an increasing interest in olive oil for human consumption. New olive orchards are being planted outside the Mediterranean, calling for an effort to identify the genotypes best adapted to the new conditions. However, some olive cultivars remain difficult to propagate, which significantly reduces the capacity to use the full genetic diversity of the species. Improving rooting ability in cuttings from recalcitrant olive cultivars has become a critical topic, which implies fundamental research on the anatomy, physiology, biochemistry and genetics of the adventitious root formation process. Besides, the existence of different rooting behaviors among olive cultivars also makes the species a candidate model plant for these studies. Olive propagation techniques evolved through time from field- or nursery-planted hardwood cuttings, to semi-hardwood cuttings in greenhouses under mist, and, more recently, to in vitro culture techniques. Nevertheless, research about adventitious root formation carried on each propagation method was mostly based on trial and error approaches. Researchers have mainly investigated different factors involved in the process of adventitious rooting by testing their effect in the rooting capacity of different cultivars, leading to a high dispersion and fragmentation of the available information. The goal of this review is to present the most relevant results achieved on adventitious root formation in olive cuttings, aiming to provide an integrated perspective of the current knowledge. [ABSTRACT FROM AUTHOR]

Economically important plant species, such as Eucalyptus globulus , are often rooting recalcitrant. We have previously shown that far-red light enrichment applied to E. globulus donor-plants improved microcutting rooting competence and increased rooting zone/shoot carbohydrate ratio. To better understand this developmental response, the relative expression profiles of genes involved in auxin signaling ( ARF6, ARF8, AGO1 ), biosynthesis ( YUC3 ) and transport ( AUX1 , PIN1 , PIN2 ); sucrose cleavage ( SUS1 , CWINV1 ), transport ( SUC5 ), hexose phosphorylation ( HXK1 , FLN1 ) and starch biosynthesis ( SS3 ) were quantified during adventitious rooting of E. globulus microcuttings derived from donor plants exposed to far-red or white light. Expression of auxin transport-related genes increased in the first days of root induction. Far-red enrichment of donor plants induced ARF6 , ARF8 and AGO1 in microcuttings. The first two gene products could activate GH3 and other rooting related genes, whereas AGO1 deregulation of the repressor ARF17 may relief rooting inhibition. Increased sink strength at the basal stem with sucrose unloading in root tissue mediated by SUC and subsequent hydrolysis by SUS1 were also supported by gene expression profile. Fructose phosphorylation and starch biosynthesis could also contribute to proper carbon allocation at the site of rooting, as evidenced by increased expression of related genes. These data are in good agreement with increased contents of hexoses and starch at the cutting base severed from far-red exposed donor plants. To sum up, pathways integrating auxin and carbohydrate metabolism were activated in microcuttings derived from donor plants exposed to far red light enrichment, thereby improving rooting response in E. globulus . [ABSTRACT FROM AUTHOR]