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In response to the growing demand for specialty cut flowers, floral crops are increasingly produced in semiarid areaswhere soil salinity can impact crop timing, reduce stemlength, and decrease yield. The goal of this studywas to investigate the salinity sensitivity of 'Carmel' and 'Galilee' anemone (Anemone coronaria), and 'Amandine' and 'LaBelle' ranunculus (Ranunculus asiaticus)withrespect to physiological characteristics andmarketable yield. Nine plantswere irrigated weekly for 8weekswith a nutrient (control) solutionwith an electrical conductivity (EC) of 0.5 dS·m-1 or saline solutions prepared by adding sodium chloride and calcium chloride dihydrate to a nutrient solution to obtain an ECof 1.5, 2.5, 3.5, 4.5, or 5.5 dS·m-1. Yield was evaluated by dividing stems intomarketable and cull grades based on length and bloomquality. At the end of the study, the visual quality of the plantswas scored, and gas exchange data were collected using a portable photosynthesis system. Cultivars of each species responded similarly, andmarketable yields were lowacross all treatments, with averagemarketable yields (mean ± SD) of 1.7 ± 0.6 stems/plant for anemone and 1.2 ± 0.1 stems/plant for ranunculus. Visual quality (0-5 scale, with 0 = dead and 5 = excellent) decreased from3 to 1 for anemone and 3 to 2 for ranunculus as ECincreased from0.5 to 4.5 dS·m-1 and0.5to5.5dS·m-1, respectively. Anemone leaf greenness decreased by 48%, stomatal conductance (gS) decreased by 79%, transpiration (E) decreased by 75%, and net photosynthesis (Pn) decreased by 92% when irrigation solution ECincreased from0.5 to 4.5 dS·m-1. The ranunculus growth index decreased by 17%, leaf greenness decreased by 45%, and E decreased by 23% as irrigation solution ECincreased from0.5 to 5.5 dS·m-1. Both anemone and ranunculus can be considered sensitive to salinity, indicating the importance of careful soilmanagement in cut flower production systems in semiarid areas that are at risk for elevated soil salinity. [ABSTRACT FROM AUTHOR]

Broad-spectrum high-pressure sodium (HPS) lamps are the standard for greenhouse supplemental lighting. However, narrow-spectra light-emitting diodes (LEDs) offer potential benefits for enhancing growth, photosynthesis (Pn), and secondary metabolites in culinary herbs. Our objective was to quantify the effect of supplemental light source and spectra on growth, gas exchange, aroma, and flavor of culinary herbs. Basil (Ocimum basilicum 'Nufar'), dill (Anethum graveolens 'Fernleaf'), and parsley (Petroselinum crispum 'Giant of Italy') were transplanted into hydroponic systems in a glass-glazed greenhouse. Plants were provided with a supplemental photosynthetic photon flux (PPF) density of 100 mmol_m-2_s-1 from an HPS lamp or LEDs with a low blue (B) to red (R) light ratio of 7:93 [low blue (LB)] or high B:R at 30:70 [high blue (HB)]. Compared with plants grown under HPS lamps, basil grown under LB and HB LED lighting was shorter, while only HB-grown parsley was shorter; height of dill was unaffected by light source. Basil and parsley shoot fresh weight was lower for HB-treated plants compared with HPS, though dill was unaffected by supplemental light source. Shoot dry mass of basil, dill, and parsley was unaffected by light source. Both LED treatments increased Pn for basil and parsley compared with HPS-grown plants. Stomatal conductance (gS) was higher under LB and HB for basil compared with HPS in the morning and evening, but only HB-treated parsley was higher than HPS lighting in morning. Basil grown under LB, and parsley under both LEDs had lower chlorophyll fluorescence than those under HPS by the evening, but all three species had more chlorophyll b under LB light than HPS. Essential oil and phenolic accumulation were influenced by supplemental light treatment and responses varied among species. Lighting from LEDs resulted in a 2-fold increase in orientin and myristicin for basil and dill, respectively, while HB increased dillapiole concentration by 89% compared with HPS-grown dill. Notably, quercetin concentration was 2.8 times higher in dill grown under HB compared with HPS. Myrcene increased in all three species under either one (basil HB; dill LB) or both (parsley) LED lights compared with HPS. The increased content of aromatic and flavor compounds demonstrates the potential of supplemental lighting systems using specific wavelengths to add value; but the use of supplemental lighting requires an understanding of the additional stress on the photosynthetic mechanisms and the subsequent effect on biomass accumulation. [ABSTRACT FROM AUTHOR]

Uniform annual apple (Malus ×domestica) fruit production is highly dependent on consistent flower formation from year to year, as inconsistent flowering can lead to the biennial bearing observed in some high-value cultivars. The presence of fruit on a spur has been considered the main cause of the expression of biennial bearing and the inhibition of flower initiation, with a number of theories being introduced to explain the phenomenon. In the current experiment, individual spurs of annual bearing cultivars (Gala, Ruby Jon, and Pink Lady) and biennial bearing cultivars (Honeycrisp, Fuji, and Golden Delicious) were thinned to a single fruit or completely defruited at petal fall. Spurs were sampled at the end of the growing season. Effects of fruiting on spur characteristics such as spur and bourse leaf area, stomatal density, leaf gas exchange, and flower formation were determined. Across all cultivars, the presence of fruit on a spur did not affect spur characteristics or flower formation compared with nonfruiting spurs. Similarly, flowering was unaffected by those factors associated with greater spur carbohydrate status, such as bourse leaf area and assimilation rate. Cultivars with greater transpiration and stomatal conductance (gs) rates had lower rates of flower formation. Future studies should focus on xylem flow and expression of genes regulating flowering and plant growth regulators in annual and biennial bearing cultivars. [ABSTRACT FROM AUTHOR]

Bogota, Colombia, South America, Health and Medicine, Biological Factors, Chlorophyll, Metalloporphyrins, Porphyrins, Chlorophyllides Keywords: Bogota; Colombia; South America; Health and Medicine; Biological Factors; Chlorophyll; Chlorophyllides; Metalloporphyrins; Porphyrins EN Bogota Colombia South America Health and Medicine Biological Factors Chlorophyll Chlorophyllides Metalloporphyrins Porphyrins N.PAG N.PAG 1 09/19/23 20230919 NES 230919 2023 SEP 19 (NewsRx) -- By a News Reporter-Staff News Editor at Cannabis & Marijuana News -- Fresh data on Health and Medicine are presented in a new report. [Extracted from the article]

Chitosan has become of interest as a crop biostimulant suitable for use in sustainable agriculture since it is biocompatible, biodegradable, environmentally friendly, and readily available in large quantity. Short-term (35 d after transplanting) effects of chitosan, applied as a soil amendment at 0%, 0.05%, 0.10%, 0.15%, 0.20%, or 0.30% (w/w), on lettuce (Lactuca sativa) growth, chlorophyll fluorescence, and gas exchange were evaluated in a growth chamber study. Chitosan at 0.05%, 0.10%, and 0.15% increased leaf area from 674 to 856, 847, and 856 cm², and leaf fresh weight from 28.6 to 39.4, 39.1, and 39.8 g, respectively. Only chitosan at 0.05% and 0.10% increased leaf dry weight from 3.42 to 4.37 and 4.35 g, respectively, while chitosan at 0.30% decreased leaf number, area, fresh and dry weight. Chitosan at 0.10%, 0.15%, 0.20%, and 0.30% increased leaf chlorophyll index from 29.8 to 34.4, 35.4, 37.5, and 41.4, respectively. Chitosan at 0.20% and 0.30% increased leaf maximum photochemical efficiency and photochemical yield, and chitosan at 0.10%, 0.15% 0.20%, and 0.30% increased leaf electron transport rate. Leaf photosynthesis rate and stomatal conductance (gS) increased from 9.3 to 12.7, 14.0, and 16.6 µmol⋅m-2⋅s-1 carbon dioxide, and from 0.134 to 0.183, 0.196, and 0.231 mol⋅m-2⋅s-1, under chitosan at 0.15%, 0.20%, and 0.30%, respectively. The results indicated that chitosan, at appropriate application rates, enhanced lettuce growth, and might have potential to be used for sustainable production of lettuce. [ABSTRACT FROM AUTHOR]

Mango wilt, caused by the fungus Ceratocystis fimbriata, is an important disease affecting mango production. In view of the beneficial effects of potassium (K) in other profitable crops and the lack of information about the effect of macronutrients on mango wilt development, the present study aimed to evaluate how mango plants supplied with K respond physiologically when infected by C. fimbriata. Mango plants (» 3 years old) from cultivar Ubá were grown in plastic pots containing 58 mg of K.dm-3 (original K level based on the chemical analysis of the substrate) or in plastic pots with substrate amended with a solution of 0.5 M potassium chloride (KCl) to achieve the rate of 240 mg K.dm-3. Disease symptoms were more pronounced in inoculated plants grown at the lower K level. Substantial declines in stomatal conductance, in line with decreases in the internal-to-ambient CO2 concentration ratio and the absence of detectable changes in the chlorophyll a fluorescence parameters, suggest that the decrease in the net carbon assimilation rate is due, at least initially, to stomatal limitations. High concentrations of K and manganese were found in the stem tissues of inoculated plants and supplied with the highest K rate, most likely due to the involvement of these tissues in the local development of defense mechanisms. The results of this study suggest that the supply of K favored the physiological performance of mango plants and their resistance against C. fimbriata infection. [ABSTRACT FROM AUTHOR]

Protein hydrolysates (PHs) are an important group of plant biostimulants that have received increasing attention in recent years because of their positive effects on crop performance and contribution to agroecological sustainability. The aim of the study was to determine the effects of fish-derived PHs on growth, chlorophyll content and fluorescence, and leaf gas exchange of lettuce (Lactuca sativa) grown in a growth chamber. Fish-derived PHs were drench applied (300 inL of 3 mL·L-1) three times a t 0, 14, and 24 days after transplanting (DAT), and lettuce were evaluated 30 DAT. Application of PHs significantly increased the lettuce leaf number per p lant from 22 to 28, stem diameter from 1.37 to 1.68 cm, shoot fresh and dry weight (FW and DW) from 59 to 89 g and 5.5 to 7.7 g, and root dry weight from 0.52 to 0.80 g. It also significantly increased the leaf relative water content (RWC) from 87% to 90% and succulence from 267 to 288 gm-2 water, but had no effect on specific leaf area (SLA). PHs significantly enhanced chlorophyll content, photosynthetic rate, stomatal conductance, and transpiration rate although they did not alter chlorophyll fluorescence. Our study indicated th a t plant biostimulants and fertilizer PHs improved plant performance and might have potential to be used for sustainable production of lettuce. [ABSTRACT FROM AUTHOR]

To determine the effects of timing and extent of regulated deficit irrigation (RDI) on grapevine (Vitis vinifera) canopies, whole-canopy transpiration (TrV) and canopy conductance to water vapor (gc) were calculated from whole-vine gas exchange near key stages of fruit development. The vines were managed under three approaches to RDI: 1) standard industry practice (RDIS), or weekly replacement of 60% to 70% of estimated evapotranspiration (ET) for well-watered grapevines; 2) early additional deficit (RDIE), or one-half of RDIS applied between fruit set and veraison; and 3) late additional deficit (RDIL), or one-half of RDIS applied between veraison and harvest. Compared with RDIS, the additional deficits (RDIE, RDIL) reduced daily cumulative Trv by about 45% (RDIE) and about 48% [RDIL (57% by unit leaf area)]. Diurnal patterns of gc indicated consistent moderate water stress in all RDI regimens (gc ≈50-150 mmol.m-2.s-1). Under RDIE and RDIL, there were transient occurrences of severe water stress, indicated by gc declining below 50 mmol.m-2.s-1. Across the day, vines under RDIE and RDIL had lower gc than RDIC. Under all deficit regimens, TrV exhibited opposing hysteretic loops with solar radiation [photosynthetic photon flux (PPF)] and vapor pressure deficit (VPD), with less sensitivity to VPD in RDIE and RDIL. For a given value of VPD, TrV was higher in the morning than in the afternoon. For a given value of PPF, TrV was higher in the afternoon than in the morning. Single-leaf measurements of transpiration overestimated TrV by an average of 45%. Instantaneous water use efficiency (WUE) declined during midday at the pre- and postveraison measurements for all RDI regimens. Whole-canopy daily integrated WUE (WUEd) did not differ among regimens during the additional deficits because daily cumulative values of whole-vine net carbon exchange (NCEV) and TrV changed proportionally: by about 43% to 46% in RDIE relative to RDIS. The case was less clear-cut for RDIv, where NCEV declined by 33% and TrV by 48% relative to RDIS. However, WUEd did not differ significantly between the two. More substantial water deficits than those are currently practiced in the industry through RDI could be used for potential water savings in semiarid climates. [ABSTRACT FROM AUTHOR]

During photosynthesis, plants absorb carbon dioxide from the air through these windows, and get water and nutrients from the soil through roots. Green plants are amazing wonders of nature! During the day, plants absorb carbon dioxide and release oxygen into the atmosphere through stomata. [Extracted from the article]

Copyright of Bragantia is the property of Instituto Agronomico de Campinas 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.)

Demand for New Mexico's limited water resources coupled with periodic drought has increased the necessity for tree water status monitoring to guide irrigation scheduling of pecan (Carya illinoinensis) orchards. The objectives of this study were to assess the impact of water status developed during the flood irrigation dry-down cycles on photosynthesis (Pn), and gas exchange [stomatal conductance (gs) to H2O (gH2O), transpiration (E), and intercellular CO2 (ci)] and to establish values of midday stem water potential (ψsmd) that are needed to maintain Pn and gas exchange of pecan. We conducted the study simultaneously on two southern New Mexico mature pecan orchards from 2011 through 2013. Flood irrigation as determined by grower practice was used on both orchards and Pn,gH2O, E and ci were assessed at ψsmd of -0.4 to -2.0 MPa. Photosynthesis and gas exchange were higher in pecan trees shortly after irrigation than trees exhibiting water deficit near the end of a flood irrigation dry-down cycle. The decline in Pn was markedly noticeable when ψsmd dropped below -0.9 MPa. We attributed the reduction in P„ mostly to stomatal limitation. The decline in Pn and gH2O exceeded 50% when ψsmd ranged from -1.5 to -2.0 MPa. For those reasons, we recommended that pecan orchards be maintained at ψsmd higher than -0.90 MPa to prevent significant reductions in carbon assimilation and gas exchange. [ABSTRACT FROM AUTHOR]

The article discusses the growth, gas exchange and yield of peanut crops based on the frequency of irrigation in Brazil. Topics covered include the reduction of the water availability in the soil, the use of irrigated agriculture, and the use of a self-compensating dripper for every plant. Also mentioned is the harvesting of the peanut crop.

2 0 | AMERICAN FRUIT GROWER A ND WESTERN FRUIT GROWER | April 2021 BY KATHIE TAYLOR kathie.taylor@gmail.com TABHEAD E X PAN D E D C O VE R A G E POME FRUIT B ITTER PIT CAN be a troublesome issue, especially for "Honeycrisp" apple growers. CAN ABA HELP MITIGATE BITTER PIT IN "HONEYCRISP" APPLES? Einhorn also ran all the apples over an experimental Compac sorting line to characterize bitter pit by calibrating the number of pixels per fruit with manual measures of the actual disorder present on a fruit's surface. [Extracted from the article]

After an outbreak of blotch leafminer (Cameraria caryaefoliella) on field-grown pecan (Carya illinoinensis) trees in 2010, an experiment was conducted to evaluate the consequences of the injury on carbon assimilation and photosynthetic efficiency, and, in particular, to assess if low-to-moderate injury induces a compensatory increase in photosynthesis. Gas exchange and light-adapted fluorescence were measured on non-injured portions of the leaflet lamina adjacent to the injured area as well as on portions of leaflets that included leafminer injury. Results indicate that damage of the photosynthetic apparatus did not extend beyond the injured areas by leafminers. Furthermore, although a strong relationship between the proportion of leafminer injury and area-based net C02 assimilation rate of injured leaflet tissue was found, there was no evidence that pecan leaves were able to compensate for leafminer injury by upregulating C02 assimilation in leaflet tissue that was unaffected. [ABSTRACT FROM AUTHOR]

Excess transpiration relative to water uptake often causes water stress in transplanted vegetable seedlings. Abscisic acid (ABA) can limit transpirational water loss by inducing stomatal closure and inhibiting leaf expansion. We examined the concentration effect of exogenous ABA on growth and physiology of muskmelon (Cucumis melo L.) seedlings during water stress and rehydration. Plants were treated with seven concentrations of ABA (0, 0.24, 0.47, 0.95, 1.89, 3.78, and 7.57 m\i) and subjected to 4-day water withholding. Application of ABA improved the maintenance of leaf water potential and relative water content, while reducing electrolyte leakage. These effects were linear or exponential to ABA concentration and maximized at 7.57 MM. Gas-exchange measurements provided evidence that such stress control is attributed to ABA-induced stomatal closure. First, net C02 assimilation rate and stomatal conductance initially decreased with increasing ABA concentration by up to 95% and 70%, respectively. A follow-up study (1.89 mM ABA) confirmed this result with or without water stress and further revealed a close positive correlation between intercellular C02 concentration and net C02 assimilation rate 1 day after treatment (r1 > 0.83). In contrast, ABA did not affect leaf elongation, indicating that stress alleviation was not mediated by leaf area adjustment. After 18 days of post-stress daily irrigation, dry matter accumulation showed a quadratic concentration-response, increasing up to 1.89 mM by 38% and 44% in shoot and roots, respectively, followed by 16% to 18% decreases at >1.89 mM ABA. These results suggest that excess levels of ABA delay post-stress growth, despite the positive effect on the maintenance of water status and membrane integrity. Another negative side effect was chlorosis, which accelerated linearly with increasing ABA concentration, although it was reversible upon re-watering. The optimal application rate of ABA should minimize these negative effects, while keeping plant water stress to an acceptable level. [ABSTRACT FROM AUTHOR]

Copyright of Bragantia is the property of Instituto Agronomico de Campinas 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.)

Copyright of Bragantia is the property of Instituto Agronomico de Campinas 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.)

This study examined the response of the crassulacean acid metabolism (CAM) vine-cactus fruit crop species Hylocereus undatus to two CO2 regimes [enrichment (1000 μmol·mol-1) vs. ambient control (380 μmol·mol-1)] and to two fertilization regimes [0.5- vs. 0.1-strength Hoagland's solution (designated high and low, respectively)]. CO2 enrichment increased total daily net CO2 uptake, nocturnal acid accumulation, shoot elongation, and total dry mass by 39%, 24%, 14%, and 6% (averaging the two fertilization regimes) versus ambient CO2 treatment, respectively. Plants exposed to high fertilization demonstrated 36%, 21%, 198%, and 79% (averaging the two CO2 regimes) increases versus those receiving the low fertilization regime in total daily net CO2 uptake, nocturnal acid accumulation, stem elongation, and total dry mass, respectively. Plants exposed to high fertilization and elevated CO2 demonstrated 108%, 77%, 264%, and 111% increases versus those receiving the low fertilization regime at the ambient CO2 concentration in total daily net CO2 uptake, nocturnal acid accumulation, stem elongation, and total dry mass, respectively. This response was 25% to 71% higher than the summed effects of the separate responses to each factor, indicating a synergistic effect of elevated CO2 and high fertilization. Thus, it is apparent that H. undatus crops grown under a high-fertilization agromanagement regime may benefit from elevated CO2 to a greater extent than those grown with low fertilization. [ABSTRACT FROM AUTHOR]

Heat stress is a limiting factor of plant productivity throughout the world and kaolin-based particle films (PF) have demonstrated that the reflective nature of the resulting plant surface can increase plant productivity primarily by reducing temperature in fruit, leaf, and canopy. The purpose of this study was to evaluate the environmental mechanisms and related physiological responses of 'Empire' apple (Malus xdomestica) gas exchange at the canopy level to PF treatments to identify those parameters key to plant response and increased plant productivity. Trees received either no treatment or season-long applications of a PF treatment and each treatment either received no supplemental irrigation or full replacement of evapotranspiration. Studies were begun in 1998 and continued to 2007. Fruit number and fruit weight were measured in all years. Whole canopy carbon dioxide assimilation rates (A) were measured in apple for a 4-year period to determine the relationship with incoming light and vapor pressure deficit (VPD) levels. The photosynthetic response to the irrigation and PF treatments varied between years as a result of environmental variation in VPD and photosynthetically active radiation (PAR) levels. There was a unique treatment response for PAR levels greater than 1600 μmol·m-2·s-1 in which the combination of PF and irrigation maintained midday A at maximum levels compared with other treatments although A was reduced by increasing VPD. This response indicated that although VPD limited A, the combination of PF and adequate water could maintain maximum A rates at full sun levels during the midday period and minimize the midday depression of A that is commonly observed and reduces the daily carbon accumulation. The increased carbon accumulation during the midday period was likely partitioned to the fruit. Increased fruit weight resulting from the PF treatment, compared with the control, was positively correlated with the growing season air temperature and VPD indicating that as the environment becomes hotter and/or drier, the magnitude of the PF response increased as a result of the reduced leaf and fruit temperature and the subsequent physiological effect. The PF treatments reduced radiation and heat load on exposed leaves enabling them to better regulate leaf temperature and improved the light distribution inside the canopy resulting in increased carbon gain at the whole plant scale. Fruit hue angle was reduced and red color improved by PF treatments in 5 of 10 years. The use of PF may be an effective substitute for evaporative cooling to reduce solar injury and to improve apple quality through increased fruit weight. The results indicate that benefits of PF treatments would occur in agroecosystems with large VPDs and high temperatures and that use of irrigation would further enhance the benefits at high PAR levels. [ABSTRACT FROM AUTHOR]

Five cultivars (Blitz, Mariachi, Quest, Rapsodie, and Trust) of tomato (Solanum lycopersicum) were grown hydroponically in a greenhouse to determine photosynthetic and transpirational responses to three electrical conductivities (EC) [2.3 (control), 4.8, and 8.4 dS·m-1] of inflow nutrient solution. Leaf photosynthetic light response curves were measured during the early vegetative growth stage for cv Mariachi and Rapsodie and during the reproductive growth stage for all five cultivars. Leaf transpiration rate and leaf conductance were measured for all five cultivars in both stages. During the vegetative growth stage, high EC treatment of 8.4/14.3 dS·m-1 inflow/efflux solution reduced leaf conductance and transpiration rate by 28% and 29%, respectively, compared with low EC treatment (2.3/5.9 dS·m-1), regardless of cultivar. Effects of EC treatments on leaf photosynthetic light response curves were cultivar specific. For 'Mariachi', moderate EC (4.8/8.7 dS·m-1) and high EC treatments in the vegetative growth stage reduced the maximum photosynthetic rate by 49% compared with the low EC treatment. However, for 'Rapsodie', the moderate EC treatment increased the maximum photosynthetic rate during the vegetative stage by 8% and 47% compared with low and high EC treatments, respectively. During reproductive growth stage, EC treatment did not significantly affect the transpiration rate, but high EC treatment reduced the leaf conductance by 15%, regardless of cultivar. Parameters of leaf photosynthetic response curves were affected by cultivar and EC treatment. Compared with the low EC treatment, the moderate EC treatment did not significantly affect the maximum photosynthetic rate of any cultivar except 'Rapsodie', which showed the greatest maximum photosynthetic rate in the moderate EC treatment. The results showed that the plant physiological response under elevated EC was cultivar and growth-stage specific, and increasing the inflow EC to the moderate level of around 4.8 dS·m-1, during the reproductive growth stage would not negatively impact photosynthesis, transpiration, and leaf conductance of tomato plants, for all cultivars tested in the present experiment. [ABSTRACT FROM AUTHOR]

Successful field establishment of vegetable transplants often depends on the ability of young seedlings to tolerate various biotic and abiotic stresses after transplanting. Treatments that limit transpirational water loss could improve plant survival and stand establishment. In this study we evaluated growth and physiological responses of pepper (Capsicum annuum L.) seedlings to foliar application of chemical plant regulators [abscisic acid (ABA) and aminoethoxyvinylglycine (AVG)] or physical film-forming barriers [AntiStress (AS), Transfilm (TF), and Vapor Gard (VG)] during transient 4-day water deficit cycles. During two 4-day water deficit cycles, stomatal conductance (gs) and net CO2 assimilation rate (ACO2) were unaffected by the application of physical materials, but differed for ABA and AVG. Compared with untreated control plants, ABA reduced gs (47% to 69%) and ACO2 (37% to 57%) by the end of the second water deficit cycle, whereas AVG increased gs (27% to 60%) during the first desiccation cycle. Leaf (Ψlf) and stem (Ψst) xylem water potential of plants treated with film-forming materials generally decreased at the same rate as those of untreated plants, whereas application of AVG caused earlier and more pronounced decline of Ψlf. Application of ABA enabled the maintenance of Ψlf and Ψst during two desiccation cycles, and thus prevented an increase of electrolyte leakage and leaf abscission. Growth rates of all plant components were reduced after ABA applications. However, allometric relationships showed similar patterns of dry matter allocation in leaves and shoots among ABA, TF, VG, and untreated control plants. Application of AS reduced allocation of dry matter to leaves, whereas AVG enhanced it at the expense of roots. These data indicate that water deficit tolerance of pepper seedlings only occurred with foliar application of ABA. This effect was associated with improved plant water relations, increased cell membrane stability, reduced leaf abscission, and a transient reduction in plant growth rates. [ABSTRACT FROM AUTHOR]

A study was conducted to characterize the morphological and physiological responses of four herbaceous perennial species subjected to two subsequent drought cycles. Lantana camara L. ‘New Gold’ (lantana), Lobelia cardinalis L. (cardinal flower), Salvia farinacea Benth. ‘Henry Duelberg’ (mealy sage), and Scaevola aemula R. Br. ‘New Wonder’ (fan flower) were subjected to two consecutive 10-day drought cycles. Growth response, leaf gas exchange, and chlorophyll fluorescence were measured during the experiment. The morphology of L. cardinalis and L. camara was not affected by drought, while S. farinacea had reductions in plant height and leaf area and S. aemula had reductions in dry weight. Overall, plant growth and development continued even when substrate water content was reduced to 0.13 mm³.mm-3, which indicated a level of substrate water below container capacity was sufficient for greenhouse production of these species. The drought treatments had little effect on the photochemical efficiency (Fv/Fm) of Photosystem II. An increase in minimal fluorescence (Fo) was observed in S. aemula on the last day of the second cycle. Drought treatment caused increased leaf-level water use efficiency (WUE) at the end of the first cycle in L. cardinalis and S. aemula, but not in L. camara and S. farinacea. Plants of L. camara, S. farinacea, and S. aemula that had received drought during both cycles became more water use efficient by the end of the second cycle, but L. cardinalis did not. [ABSTRACT FROM AUTHOR]

ABSTRACT. Cloudy days cause an abrupt reduction in daily photosynthetic photon flux (PPF), but we have a poor un- derstanding of how plants acclimate to this change. We used a unique 10-chamber, steady-state, gas-exchange system to continuously measure daily photosynthesis and night respiration of populations of a starch accumulator [tomato (Lycopersicon esculentum Mill. cv. Micro-Tina)] and a sucrose accumulator [lettuce (Lacluca saliva L. cv. Grand Rap- ids)] over 42 days. All measurements were done at elevated CO2 (1200 jimobmol-') to avoid any CO2 limitations and included both shoots and roots. We integrated photosynthesis and respiration measurements separately to determine daily net carbon gain and carbon use efficiency (CUE) as the ratio of daily net C gain to total day-time C fixed over the 42-day period. After 16 to 20 days of growth in constant PPF, plants in some chambers were subjected to an abrupt PPF reduction to simulate shade or a series of cloudy days. The immediate effect and the long term acclimation rate were assessed from canopy quantum yield and carbon use efficiency. The effect of shade on carbon use efficiency and acclimation was much slower than predicted by widely used growth models. It took 12 days for tomato populations to recover their original CUE and lettuce CUE never completely acclimated. Tomatoes, the starch accumulator, ac- climated to low light more rapidly than lettuce, the sucrose accumulator. Plant growth models should be modified to include the photosynthesis/respiration imbalance and resulting inefficiency of carbon gain associated with changing PPF conditions on cloudy days. [ABSTRACT FROM AUTHOR]

Mechanical harvesting of citrus trees can cause physical injuries, such as shedding of leaves, exposing roots, and scuffing bark. Although mechanical harvesting usually has not reduced yield, physiological consequences to the tree from these visible injuries have not been investigated. We hypothesized that physical injuries to tree canopies and root systems from a properly operated trunk shaker would not cause short-term physiological effects. Tree water status and leaf gas exchange of mature ‘Hamlin’ and ‘Valencia’ sweet orange [Citrus sinensis (L.) Osb.] trees that were harvested by a trunk shaker were compared to hand-harvested trees. A trunk shaker was operated with adequate duration to remove »90% of mature fruit or with excessive shaking time under various environmental conditions and drought stress treatments throughout the harvest season. Mid-day stem (Ψstem) and leaf (Ψleaf) water potentials along with leaf gas exchange were measured before and after harvest, lyres harvested by the trunk shaker did not develop altered water status under most conditions. Trees harvested with excessive shaking time and/or with limited soil water supply developed low Ψstem resembling Ψ stem of drought-stressed trees. However, water potential of all treatments recovered to values of the well-irrigated, hand-harvested trees after rainfall. In addition, mechanical harvesting did not reduce CO2 assimilation, transpiration, stomatal conductance, water use efficiency, or photosystem H efficiency as measured by chlorophyll fluorescence. Thus, despite visible injuries, a properly operated trunk shaker did not result in any measurable physiological stress. [ABSTRACT FROM AUTHOR]

The effect of increasing daily light integral (DLI; 5.3, 9.5, 14.4, and 19.4 mol·m-1·d-1) on photosynthesis and respiration of wax begonia (Begonia semperflorens-cultorum Hort.) was examined by measuring CO2 exchange rates (CER) for a period of 25 d in a whole-plant gas exchange system. Although plant growth rate (GR, increase in dry weight per day) increased linearly with increasing DLI, plants grown at low DLI (5.3 or 9.5 mol·m-2·d-1) respired more carbohydrates than were fixed in photosynthesis during the early growth period (13 and 4 d, respectively), resulting in a negative daily carbon gain (DCG) and GR. Carbon use efficiency [CUE, the ratio of carbon incorporated into the plant to C fixed in gross photosynthesis (Pg)] of plants grown at low DLI was low, since these plants used most of the C fixed in Pg for maintenance respiration (Rm), leaving few, if any, C for growth and growth respiration (Rg). Maintenance respiration accounted for a smaller fraction of the total respiration with increasing DLI. In addition, the importance of Rm in the carbon balance of the plants decreased over time, resulting in an increase in CUE. At harvest, crop dry weight (DWCROP) increased linearly with increasing DLI, due to the increased photosynthesis and CUE at high PPF. [ABSTRACT FROM AUTHOR]

The productivity of lettuce in a combination of high light, high temperature, and elevated CO2 has not been commonly studied because rapid growth usually causes a calcium deficiency in meristems called tipburn, which greatly reduces quality and marketability. We eliminated tipburn by blowing air directly onto the meristem, which allowed us to increase the photosynthetic photon flux (PPF) to 1000 µmol·m-2·s-1 (57.6 mol·m-2·d-1); two to three times higher than normally used for lettuce. Eliminating tipburn doubled edible yield at the highest PPF level. In addition to high PPF, CO2 was elevated to 1200 µmol·m-2·mo1-1, which increased the temperature optimum from 25 to 30 °C. The higher temperature increased leaf expansion rate, which improved radiation capture and more than doubled yield. Photosynthetic efficiency, measured as canopy quantum yield in a whole-plant gas exchange system, steadily increased up to the highest temperature of 32 °C in high CO2. The highest productivity was 19 g·m-2·d-1 of dry biomass (380 g.d-1 fresh mass) averaged over the 23 days the plants received light Without the limitation of tipburn, the combination of high PPF, high temperature, and elevated CO2 resulted in a 4-fold increase in growth rate over productivity in conventional environments. [ABSTRACT FROM AUTHOR]

The effects of five mulching treatments on leaf gas exchange, leaf water potential (Ψ1), and soil and plant element levels of 5-year-old `Arkin' carambola (Averrhoa carambola L.) grafted on open-pollinated `Golden Star' rootstock were investigated under field conditions from July 1999 to March 2000. Treatments included: non-mulched soil (control; C); 10-cm thick layer of wood mulch (organic mulch; OM); black polyethylene (BP); ground cloth covered with a 10-cm thick layer of wood mulch (GC+OM); and ground cloth covered with a 10-cm thick layer of wood mulch and a transparent polyethylene film (GC+OM+CP). Soil temperatures of the mulched treatments at a 10- cm soil depth, were ito 8°C higher than those of the non-mulched control. Soil moisture tension was similar at a 10- and 45-cm depth soil depth among all treatments. In general, there was no consistent effect of mulch treatments on leaf water potential (P1). However, Ψ1 was more negative for plants in the non-mulched control during winter and `Ψ1 was more negative in the GC+OM+CP treatment than in the other treatments during March 2000. Net CO2 assimilation and transpiration rate were generally not consistently different among treatments, but were greater for mulch treatments than for the non-mulched control during winter. There were no significant differences in soil element content among mulch treatments after 9 months. Similarly, there were no consistent differences in leaf N, P, K, Ca, Mg, Mn, Zn, Fe and Cu content among treatments. [ABSTRACT FROM AUTHOR]

B What Can Two Hours of CO2 Enrichment Per Day Achieve? Most informed persons know that CO2 is a necessary substrate for plant photosynthesis and that enriching the air with higher levels of CO2 typically enhances this key plant growth parameter. Typically, nearly all CO2-enrichment studies apply CO2 enrichment for the full 24 hours of a day. [Extracted from the article]

The article presents a study on the impact of vapor pressure deficit (VPD) to cool season and warm season turfgrasses in the U.S. It highlights the impact of gas exchange at high VPD to the growth performance of turfgrasses. It explores the limitation of transpiration rate that exists in cool season species.

Evaluation of photosynthetic efficiency of yam bean ( I Pachyrhizus erosus i L.) at saturating photon flux density under elevated carbon dioxide. Focusing on net photosynthesis, results indicated that, compared to ambient CO2 levels at 400 ppm, leaf photosynthesis was I reduced i by 54% at a CO2 concentration of 200 ppm, but I increased i by 19%, 21% and 23% at CO2 concentrations of 600, 800 and 1000 ppm, depicting what Ravi I et al i . describe as "the positive response of yam bean to elevated carbon dioxide." Consequently, the authors conclude their short paper by indicating that their assessment of yam bean is that it is "responsive to elevated carbon dioxide and very well suited to thrive under future projected high CO2 environmental conditions.". [Extracted from the article]

Potassium (K) plays vital roles within corn plants for carbohydrate, nutrient, and water flow. A corn plant requires almost as much K as nitrogen (N); however, when looking at soil test values across the Midwest, soil test K values have been falling. Monitor potassium levels as a part of your comprehensive soil testing regime and develop a plan to ensure adequate plant-available potassium during the growing season. [Extracted from the article]

The article discusses various reports published within the issue, including one by Cantin and colleagues on the enhancement of quality and shelf life of friar plums through box liners and another by Wu and Kubota on tomato leaf gas exchange under high electrical conductivity.

The article reports that Lithuanian competition authority fined OAO Gazprom, extractor of natural gas worth 48 million dollars for breaching competition rules in 2012 as it declined to arrange gas exchange to enable Lithuanian power corporation, Lietuvos Energijos Gamyba to purchase gas from a Western European company. It mentions that the Gazprom refuse to negotiate customers to pay for electricity and heat by Russian gas.

The article discusses research studies on benefits that can be gained by drought-stressed crops from foliar fungicides. It cites corn foliar fungicide research trial from 2008-2011 showing great yield response in fungicide application with high disease pressure while a 2007-2011 research program showed higher yields in both Quadris and Headline varieties. It also notes a published study on foliar fungicides indicating changes induced by strobilurin fungicides in photosynthetic gas exchange.

The article discusses a study on the effect of elevated carbon dioxide levels on trees. The study examined the leaf gas exchange characteristics and other properties of the leaves of paper birch and quaking aspen trees, as they were exposed to high levels of carbon dioxide and the highest temperature levels of the Wisconsin heat wave in the summer of 2006. According to the study, the elevated carbon dioxide protected photosynthesis of the tree from moderate heat stress, enabling the trees to transpire more and cool their leaves when needed.

This study examined the interaction between a reflective particle film and water use efficiency (WUE) response of irrigated and non-irrigated apple trees (Malus xdomestica) over a wide range of environmental conditions. The objectives were to measure isotopic discrimination (δ13C and δ18O), specific gas exchange, and WUE response of 'Empire' apple treated with a reflective particle film (PF), with and without supplemental irrigation, compared with an untreated control, with and without supplemental irrigation, over a range of leaf area indices (LAI), seasonal evapotranspiration (ETo), and vapor pressure deficits (VPD) to determine the mechanisms of action affecting WUE in apple. Short-term whole canopy gas exchange studies and isotope discrimination analysis were used to test the hypothesis that WUE was modified by the use of a PF. In whole canopy gas exchange studies, carbon assimilation (A) and transpiration tended to increase, and WUE and canopy conductance tended to decrease, with VPD within each LAI class from 2 to 6. For VPD > 1 kPa, the PF irrigated treatment consistently had the greatest WUE and other treatments were intermediate for LAI of 2 to 4. The PF irrigated and non-irrigated treatments had greater WUE than the control irrigated and non-irrigated treatments for VPD ≤2 kPa and there were no treatment effects for VPD > 2 kPa in the LAI range of 4 to 6. The PF non-irrigated was equivalent to the control non-irrigated treatment at VPD of 1 to 3 kPa, but was significantly lower at VPD of 3 to 4 kPa. PF irrigated and non-irrigated treatments had the greatest carbon isotope discrimination (δ13C), the control non-irrigated treatment had the lowest δ13C, and the control-irrigated treatment was intermediate. Oxygen isotope enrichment (δ18O) was positively correlated with the mean growing season VPD and mean growing season evapotranspiration. δ13C was significantly and positively correlated with δ18O. Seasonal WUE was negatively correlated with δ13C and there was an interaction with LAI. The seasonal water use of apple is better evaluated with stable isotope discrimination integrating seasonal variation rather that the use of whole canopy gas exchange measurements that measure WUE for brief periods of time. δ13C was an accurate measurement of apple WUE and indicated that the PF irrigated treatment had the greatest δ13C and so the lowest WUE compared with the control non-irrigated treatment at LAI from 4 to 6. The reduced WUE of the PF irrigated treatment compared with the control non-irrigated treatment is likely due to increased gS from lower canopy temperature and increased canopy photosynthetically active radiation diffusion that drove increased A. δ18O was an indicator of seasonal water use over six growing seasons due to its high correlation with ETo. In 'Empire' apple, A can be increased with PF and irrigation treatments, but at the cost of decreased WUE. [ABSTRACT FROM AUTHOR]

The article presents a study on how leaves of early angiosperms can transport a water. Researchers at the University of Tasmania in Australia, and at the University of Tennessee, Knoxville, has revealed that leaves of early angiosperms appeared to contain less veins that those of angiosperms that evolved afterwards. They also showed that the vein density of the angiosperms is significant to the ability of the plant to photosynthesize.

The article discusses the ability of trees to photosynthesize at extremely low temperatures. The author explains this evidence was discovered after a survey produced by ecologists at the University of Pennsylvania. The article also contains detailed results for the surveys and what this could mean for photosynthesis.

The article announces the winners of the Institution of Engineering and Technology's Paper Awards, which include "Simulation of Potato Gas Exchange Using SPUDSIM," "Vision-based Trackway Analysis in Dairy Cow's Locomotion," and "Dielectric Study of Water Binding in Grain."