Abscisic Acid Solution Research Articles

Abscisic acid reduced methoxypyrazines concentration and its derived unpleasant odors in Cabernet Sauvignon grapes and wines.

The influences of abscisic acid (ABA) applications on precursors and gene expression in 3-alkyl-2-methoxypyrazines (MPs) biosynthetic pathway, MPs concentration and sensory evaluation of its derived peculiar odors in Cabernet Sauvignon grapes and wines were investigated. At the vineyard, ABA solution with 25, 100 and 400 mg L-1 (AT1, AT2 and AT3, respectively) and an aqueous solution (control) were sprayed three times from veraison to pre-harvest. Higher concentration ABA applications (AT2 and AT3) in grapes could significantly reduce MPs concentration and its derived peculiar odors in grapes and wines compared to a lower concentration ABA application (AT1) and control, with AT2 application having the strongest effect. The changes in MPs were mainly a result of the downregulated expression of VvOMTs genes at higher concentration ABA applications, independent of the levels of their potential precursors. The present study reveals that ABA application had the potential to decrease production of MPs in Cabernet Sauvignon grapes and wines, and this result provides reference values for the removal of unpleasant vegetable odors from Cabernet Sauvignon wines in production. © 2024 Society of Chemical Industry.

Individual and Interactive Ecophysiological Effect of Temperature, Watering Regime and Abscisic Acid on the Growth and Development of Tomato Seedlings

Climate change is a major concern to people all over the world. Most studies have considered singular or dual effects of climate change implications on plant growth and development; however, the combination of multiple factors has received little attention. We therefore studied the single and combined effects of two environmental stress factors (high temperature and water stresses) and abscisic acid on tomato seedlings (Solanum lycoperscum L.). Plants were grown in controlled environment growth chambers under two temperatures (22/18 °C or 28/24 °C; 16 h light/8 h dark), two watering regimes (well-watered or water-stressed), and two abscisic acid treatments (0 and 100 µL of 1mM abscisic acid solution, every other day). Plants were placed under experimental conditions for a total of 33 days, including a 13-day period of initial growth and hardening. Morphological, biochemical, and physiological parameters were measured to assess the growth and development of plants in response to the three factors. ANOVA and Scheffé’s multiple-comparison procedures were used to establish significant differences among treatments and among the three factors being manipulated. All three factors decreased plant height and growth rate. Dry mass accumulation was negatively affected by high temperatures. Transpiration, stomatal conductance, and gas exchange parameters were negatively affected by all three factors; additionally, net carbon dioxide assimilation was reduced by water stress and abscisic acid application. Non-photochemical quenching was decreased in plants grown under higher temperature and in abscisic acid-treated plants. Though it was not significant, abscisic acid appears to mitigate the negative effect of higher temperature and water stress on the nitrogen balance index and total chlorophyll content.

Abscisic Acid May Play a Critical Role in the Moderating Effect of Epichloë Endophyte on Achnatherum inebrians under Drought Stress.

Water scarcity is a major constraint that adversely affects plant development and growth. Abscisic acid (ABA) is a plant stress hormone that is rapidly synthesized and can induce stomatal closure to conserve water, thereby alleviating the drought stress of plants. The Epichloë endophyte enhances the drought tolerance of Achnatherum inebrians (drunken horse grass, DHG). To better understand how the Epichloë endophyte enhances drought tolerance, DHG plants without (EF) and with (EI), an Epichloë endophyte, were grown under 20% and 60% soil water conditions (SWC), and the leaves of the three treatments of EF and EI plants were sprayed with ABA solution (1 mg/L); fluridone (FLU), the ABA biosynthesis inhibitor solution (1 mg/L); and distilled water, respectively. Four-weeks later, the results indicated that the exogenous ABA application promoted plant growth, stomatal conductance, and photosynthetic rate, while the opposite effect occurred with plants sprayed with FLU. The differences between EI and EF plants in tiller number, height, chlorophyll content, stomata conductance, and photosynthetic rate were highest when sprayed with ABA. Thus, it is concluded that ABA might be involved in the moderating effect of Epichloë endophytes on DHG plants exposed to drought by maintaining growth and improving photosynthetic efficiency.

Aggregative movement of mesophyll chloroplasts occurs in a wide variety of C4 plant species

• Redistributions of chloroplasts in 36 C 4 monocots and eudicots were examined. • Mesophyll chloroplasts in 35 C 4 plants aggregated towards the bundle sheath. • This chloroplast movement would be a general physiological response in C 4 plants. • Mesophyll chloroplasts in monocots aggregated more strongly than in eudicots. • Degrees of movement in NADP-ME were lower than in PCK species. C 4 plants have two types of photosynthetic cells, mesophyll (M) and bundle sheath (BS) cells with different subcellular structures. In C 4 plants, maize and finger millet, the chloroplasts of M cells are normally distributed toward the periphery but redistribute toward the BS cell side in response to environmental stresses. This directional movement of M chloroplasts is called aggregative movement, of which physiological significance remains unknown. Furthermore, few C 4 plant species have been examined for aggregative movement, and it has not been established whether this is a common phenomenon in C 4 plants. Hence, this study aims to investigate whether the aggregative movement is widely observed and diverse in C 4 plants. Thirty-six monocotyledonous and dicotyledonous C 4 plant species (Poaceae, Amaranthaceae, Asteraceae, and Portulaceae) including all three C 4 subtypes were examined. Leaf segments were infiltrated with the abscisic acid solution and irradiated with blue light to induce aggregative movement of M chloroplasts. Aggregative movement of M chloroplasts was observed in 35 C 4 species across 11 evolutionary lineages. The degree of aggregative movement was significantly greater in monocots than that in eudicots; phospho enol pyruvate carboxykinase subtype C 4 plants showed significantly greater aggregative movement than NADP-ME type C 4 plants. The aggregative movements would be broadly shared stress responses in C 4 plants. The differences in the degree of aggregative movement could be related to morphological and physiological differences between monocots and eudicots, and among C 4 subtypes.

Comparative analysis of the germination of barley seeds subjected to drying, hydrogen peroxide, or oxidative air plasma treatments

AbstractAcceleration in germination time by 12–24 h for barley seeds treated with atmospheric air plasmas may have a significant economic impact on malting processes. In this study, the increase in germination rate and decrease in contamination level upon plasma treatment could not be directly correlated with any significant increase in the water uptake capacity, except for seeds exposed to mild drying treatment. A variety of germination essays have been carried out with seeds impregnated with an abscisic acid solution, a retarding factor of germination, treated with a peroxide solution, and/or subjected to the plasma and drying treatments. Results suggest that plasma and hydrogen peroxide treatments induce the formation of reactive oxygen and nitrogen species that affects the abscisic acid factor and accelerate the germination rate.

Acclimation to Ex Vitro Conditions in Ninebark

Acclimation is the final phase of micropropagation and often decisive for its economic output. The aim of the experiments was to evaluate the effect of abscisic acid (ABA) and supplementary light on acclimation and leaf anatomy of the in vitro-rooted plants of ninebark (Physocarpus opulifolius L.). The initial material came from 8–10-week-old in vitro cultures on ½MS supplemented with 1 mg·L−1 IBA. After potting, plantlets were sprayed with ABA solutions or distilled water and were grown either under natural daylight or under supplemental sodium light at 230 μmol·m−2·s−1 between 2 and 9 p.m. All measurements and anatomical observations were done after eight weeks in the greenhouse. Supplementary lighting significantly increased the percentage of acclimatized plants, plant height and the internode number. Plant growth was also positively affected by 1 mg·L−1 ABA. During acclimation, the photosynthesis rate increased while the transpiration and stomatal conductance dropped. The assimilation pigment contents increased under supplemental lighting while ABA had no detectable effect. However, relative to water controls, ABA increased photosynthesis, reduced transpiration, and stomatal conductance in plants growing under both light conditions. Leaves from the in vitro plants were about two times thinner than those from plants growing in soil, with only a single layer of the palisade parenchyma, hence with lower proportion in relation to the spongy parenchyma. Supplementary light during acclimation increased leaf thickness but only in the water control while it decreased it in the ABA-treated plants. ABA increased the mesophyll thickness but only in plants growing under natural light. In conclusion, supplementary light and treatment with ABA enhance acclimation of micropropagated ninebark plants.

Physiological changes during heartwood formation induced by plant growth regulators in Dalbergia odorifera (Leguminosae)

Abstract There is a need to better understand and promote formation of ‘Jiang Xiang’, the highly valuable heartwood of Dalbergia odorifera T. Chen. Plant growth regulators are the most widely used and generally most effective promoters of heartwood formation. However, to date no method has been proved effective for D. odorifera as little is known about biochemical and physiological change during heartwood development. Four potential heartwood induction substances viz. ethephon, methyl jasmonate, salicylic acid and abscisic acid solutions were injected into the trunk of D. odorifera to determine the effect on heartwood formation and related physiological responses. Non-structural carbohydrates, wood properties, essential oil and histochemical and structural observation were assessed in the post-treatment period. As also observed in the formation of natural heartwood, growth regulator-induced Jiang Xiang production was accompanied by sapwood dehydration, non-structural carbohydrates consumption and synthesis of heartwood specific substances. These substances were synthesized in the ray and axial parenchyma and than transported into the vessels through the pits. As the heartwood substances accumulated, basic density and essential oil content increased gradually, thereby Jiang Xiang was finally produced. In this process, physiological parameters of discoloured sapwood gradually evolved to resemble those of natural heartwood. Ethephon-induced Jiang Xiang was closest to natural heartwood and its density, essential oil content, composition and relative amounts met the standards for high-quality Jiang Xiang, while the other inducers had unsatisfactory induction effects. This study supports the hypothesis that ethephon could be applied to induce formation of Jiang Xiang in D. odorifera.

Close arrangement of CARK3 and PMEIL affects ABA‐mediated pollen sterility in Arabidopsis thaliana

Abscisic acid (ABA) signaling is a vital plant signaling pathway for plant responses to stress conditions. ABA treatment can alter global gene expression patterns and cause significant phenotypic changes. We investigated the responses to ABA treatment during flowering in Arabidopsis thaliana. Dipping the flowers of CARK3 T-DNA mutants in ABA solution, led to less reduction of pollen fertility than in the wild type plants (Col-0). We demonstrated that PMEIL, a gene located downstream of CARK3, directly affects pollen fertility. Due to the close arrangement of CARK3 and PMEIL, CARK3 expression represses transcription of PMEIL in an ABA-dependent manner through transcriptional interference. Our study uncovers a molecular mechanism underlying ABA-mediated pollen sterility and provides an example of how transcriptional interference caused by close arrangement of genes may mediate stress responses during plant reproduction.

Effects of exogenous melatonin and abscisic acid on osmotic adjustment substances of ‘Summer Black’ grape under drought stress

In this study, seedlings of grape ‘Summer Black’ were used as the experimental materials to investigate the effects of melatonin (MT) and abscisic acid (ABA) on osmotic adjustment substances under drought stress, by root irrigating 100μmol/L MT and spraying 50μmol/L ABA solutions before or during the drought treatment. The results showed that the content of malondialdehyde and relative conductivity were significantly lower in the MT group than that in the drought control group, and the contents of soluble protein and hydrogen peroxide were significantly higher in the ABA treatment than that in the drought control group. However, regardless of the application of ABA or MT, the relative water content in leaves did not change much. The results suggested that the concentration of exogenous substances and the sampling time were unsuitable to improve drought tolerant at 18d, which provided a theoretical basis for MT and ABA appliance in grape planting.

Formation of Erysiphe necator Chasmothecia in the Pacific Northwest United States.

In the Pacific Northwest, chasmothecia formation is not observed in vineyards until the beginning of véraison despite heavy infestations whereby 100% of leaf tissue is covered by Erysiphe necator. Mating type proximity and distribution were sampled from individual lesions (∼71 mm2) on leaf tissue in a stratified sampling from three canopy heights at three times during the 2013, 2014, and 2015 growing seasons. Both mating types were observed at every sampling point and within the same lesions at all sampling dates and canopy heights. Effect of temperature and day length were examined by inoculating seedlings with known mating type 1 and 2 isolates and placed in incubators at different temperatures (5, 10, 15, 20, 25, and 30°C) or different day length changes (long day to long day, long day to short day, short day to short day, and short day to long day). Chasmothecia were produced at all temperatures that E. necator was able to colonize tissue, and the greatest number of chasmothecia were produced at 15 and 20°C (P ≤ 0.02). Day length shifts from short day (8 h) to long day (16 h) resulted in a significant increase in chasmothecia production (P < 0.001). End of season plant stress observed in the Pacific Northwest, such as water stress or host senescence, was assessed under naturally infested field conditions by either girdling canes or applying 150 mg·liter-1 abscisic acid solution to vines, respectively, and quantifying chasmothecia production. No differences were observed in chasmothecia production in the plant stress assessment, likely due to the high vigor and ability for plants to overcome stress treatments.

Longevity of wild pansy flowers treated with growth regulators

The objective of this study was to evaluate the growth regulators action on the senescence of wild pansy flowers. In the first experiment, floral stems were treated with ethylene for 24 hours at concentrations of 0.1, 1.0, 10, 100 and 1000 μL L-1 and control without the hormone. In a second experiment, the flowers were immersed in solutions of abscisic acid (ABA) containing 5, 20, 50 and 100 μM for one minute and control with water. In a third experiment, 1-methylcyclopropene (1-MCP) was applied at concentrations of 0.5, 1.0 and 1.5 μL L-1 and control without the chemical. In a fourth experiment, 1-MCP and ethylene were applied, where 1-MCP was first applied followed by ethylene. After the treatments with 1-MCP and ethylene, the floral stems were removed from the hermetic chambers and kept in a vessel containing distilled water at 25 °C, 10 μmol m-2 s- 1 white fluorescent light and 50-70% relative humidity as for the ABA treatment. Flowers treated with ethylene did not present significant differences among the concentrations for visual senescence, showing evidence that this flower is not sensitive to ethylene. Treatment with 1000 μL L-1 of ethylene led to a slightly higher fresh weight loss than other treatments, which had a loss of about 33% at end of the experiment. For the ABA treatment, the flowers showed similar fresh weight loss among the different treatments; however, higher concentrations induced slight senescence of flowers. The use of 1-MCP increased the longevity of wild pansy flowers. These results show that 1-MCP is beneficial in maintaining the flower water status, even in the presence of exogenous ethylene, although ethylene may not be directly involved in the senescence of wild pansy flowers.

Differential Expression of Induced Resistance Genes by Abscisic Acid (ABA) Against Potato Early Blight Disease

Abscisic acid (ABA), a plant hormone involves in various plant physiological processes including, response to biotic and abiotic stress conditions. ABA was tested to study its ability to enhance disease resistance of two potato cultivars i.e., Nicola and Spunta, to the infection by the early blight fungus Alternaria solani (A. solani) under greenhouse conditions. Treatment with ABA solution (10 μM) reduced the early blight disease severity for both cultivars compared to the untreated infected plants. Differential display gene analysis for treated plants revealed three clear bands. These bands showed significant homology to well-known genes in the GenBank database and identified as superoxide dismutase (CuZnSOD), WRKY transcription factor (StWRKY) and Endoglucanase from potato genome. Real-Time PCR was used to detect the changes in gene expression of CuZnSOD and WRKY-type genes after infection with A. solani for both Nicola and Spunta potato cultivars and in different time intervals. The expression level of CuZnSOD and WRKY genes in potato leaves of both cultivars were increased for ABA treated and infected plants and for untreated/infected plants compared to the untreated/uninfected plants. Both genes were over expressed in infected plants treated with ABA than untreated ones and reached the maximum level of expression after two days of inoculation. The highest increase of both genes expression was observed in potato leaves of cv. Nicola compared to cv. Spunta.

Effects of Abscisic Acid on Capsanthin Levels in Pepper Fruit

Abscisic acid (ABA) is an important plant hormone that plays an important role in stress responses. Previous studies have suggested that ABA can also accelerate ripening in climacteric and nonclimacteric fruit. Capsanthin is a carotenoid that confers red coloration to mature pepper (Capsicum annuum) fruit. However, the effect of ABA on capsanthin accumulation in pepper fruit has not been thoroughly studied. Herein, we aimed to evaluate the effects of ABA treatment on capsanthin accumulation in pepper fruit and on the expression of key genes involved in the capsanthin biosynthetic pathway. For this purpose, we treated pepper fruit with ABA at green mature stage. Our results indicate that ABA treatment increased capsanthin content in pepper fruit, with the best result obtained with 150 mg·L−1 ABA solution. Application of exogenous ABA also increased the expression levels of the capsanthin synthesis genes phytoene synthase (Psy), lycopene β-cyclase (Lcyb), β-carotene hydroxylase (Crtz), and capsanthin/capsorubin synthase (Ccs), likely explaining the significant capsanthin content increase in pepper fruit.

ABA and GA3 increase carbon allocation in different organs of grapevine plants by inducing accumulation of non-structural carbohydrates in leaves, enhancement of phloem area and expression of sugar transporters.

Grape quality for winemaking depends on sugar accumulation and metabolism in berries. Abscisic acid (ABA) and gibberellins (GAs) have been reported to control sugar allocation in economically important crops, although the mechanisms involved are still unknown. The present study tested if ABA and gibberellin A3 (GA3) enhance carbon allocation in fruits of grapevines by modifying phloem loading, phloem area and expression of sugar transporters in leaves and berries. Pot-grown Vitis vinifera cv. Malbec plants were sprayed with ABA and GA3 solutions. The amount of soluble sugars in leaves and berries related to photosynthesis were examined at three points of berry growth: pre-veraison, full veraison and post-veraison. Starch levels and amylase activity in leaves, gene expression of sugar transporters in leaves and berries and phloem anatomy were examined at full veraison. Accumulation of glucose and fructose in berries was hastened in ABA-treated plants at the stage of full veraison, which was correlated with enhancement of Vitis vinifera HEXOSE TRANSPORTER 2 (VvHT2) and Vitis vinifera HEXOSE TRANSPORTER 6 (VvHT6) gene expression, increases of phloem area and sucrose content in leaves. On the other hand, GA3 increased the quantity of photoassimilates delivered to the stem thus increasing xylem growth. In conclusion, stimulation of sugar transport by ABA and GA3 to berries and stems, respectively, was due to build-up of non-structural carbohydrates in leaves, modifications in phloem tissue and modulation in gene expression of sugar transporters.

Involvement of abscisic acid in postharvest water-deficit stress associated with the accumulation of anthocyanins in strawberry fruit

Fruits are prone to suffer water-deficit stress and accelerated senescence after harvest. To understand the effect of postharvest water-deficit on the senescence progress of strawberry fruit, fruit peduncles were dipped into water or abscisic acid solution and stored at 20°C with 50% relative humidity in the dark. The results showed that detached fruit without water supply through the peduncles suffered serious water-deficit stress with great weight loss and low moisture content. However, fruit absorbing water through their peduncles successfully avoided the water-deficit stress with a slight change of weight loss and moisture content. Water-deficit significantly promoted anthocyanin levels with increased PAL, C4H and DFR activities. The expressions of transcriptional factors that regulate anthocyanin biosynthesis (FaMYB1, FabHLH3 and FaTTG1) were also up-regulated under water-deficit stress. Meanwhile, stress elevated the abscisic acid level as well as FaNCED1 and FaASR expression in strawberry fruit. Furthermore, exogenous ABA application exhibited the similar features with water-deficit stress. These results suggested that postharvest water-deficit would accelerate anthocyanin accumulation in strawberry fruit and that abscisic acid may play a role in the response to water-deficit stress.

Antitranspirational Efficacy and Longevity of Abscisic Acid and a Synthetic Abscisic Acid Analog in Pansies (Viola ×wittrockiana)

Physiological antitranspirants can reduce financial risks to growers by temporarily preventing drought stress, improving product quality, and extending the shelf life of ornamental bedding plants. Exogenous abscisic acid (ABA) is an effective antitranspirant that induces stomatal closure in a rate-dependent manner, reducing transpirational water loss in many species. However, it may also cause chlorosis, which reduces product quality. Synthetic ABA analogs have similar effects on stomatal conductance (gS) but are not known to induce chlorosis. We studied the effects of ABA and its analog 8′ acetylene ABA methyl-ester (PBI 429) on gS and net photosynthesis (Pn) in pansies (Viola ×wittrockiana), compared the efficacy and longevity of each compound, and quantified the resulting chlorosis. Plants were treated with spray solutions of ABA (0 to 2000 mg·L−1) and PBI 429 (0 to 200 mg·L−1) and irrigated daily. Gas exchange and leaf chlorophyll measurements were made twice weekly for 2 weeks. Additional measurements were taken once or twice weekly through 47 days. Abscisic acid reduced leaf chlorophyll content and Pn in a rate-dependent manner for 14 days after application but reduced gS for only 11 days, whereas PBI 429 reduced Pn and gS similarly for 7 days and did not reduce leaf chlorophyll content. Reductions in gS and Pn were greatest on the first day after treatment for both compounds. Our results demonstrate that ABA is more effective than PBI 429 at 100 and 200 mg·L−1, but also causes chlorosis, whereas PBI 429 is an effective antitranspirant without this phytotoxic effect.

Concentrated Exogenous Abscisic Acid Drenches Reduce Root Hydraulic Conductance and Cause Wilting in Tomato

Previous work has shown that exogenous abscisic acid (ABA) applications can reduce transpiration, delay wilting, and thereby extend the shelf life of unwatered plants. Paradoxically, we have seen that drenches with concentrated ABA solutions may actually induce wilting. These wilting symptoms occur despite the presence of ample water in the substrate, suggesting that ABA may interfere with the ability of roots to take up water. Our objective was to develop a better understanding of this wilting effect using tomato (Solanum lycopersicum) as a model. In the first study, ABA drenches (125–2000 mg·L−1) reduced transpiration and water use compared with the control plants, yet the relative water content (RWC) of the leaves of ABA-treated plants was lower than that of control plants at 24 h after the ABA drench. Control plants had a leaf RWC of 97%, whereas plants treated ABA had a RWC of 57% to 62%. ABA concentrations of 500 mg·L−1 or higher caused the plants to wilt within 24 h despite the presence of ample water in the substrate. Leaf ABA concentrations 24 h after the ABA application ranged from 2.6 (control) to 62.6 nmol·g−1 fresh weight (FW) in the 2000-mg·L−1 ABA treatment, indicating effective transport of ABA from the roots to the leaves. The reduced leaf RWC suggests that ABA drenches are limiting water transport through the roots to the leaves. The effects of ABA on the hydraulic conductance of the roots and stems of tomatoes were quantified to determine if ABA drenches limit water transport through the roots. The cumulative volume of water conducted by the root systems during a 4-day period ranged from 36.7 mL in the control treatments to 8.1 mL in roots systems drenched with 1000 mg·L−1 ABA, a reduction of 78%. When the conductance study was repeated using decapitated roots and excised stems, root water flux was again reduced by ABA, but water flux through internodal stem sections did not show an ABA effect. Results suggest that ABA-induced wilting is caused by a reduction in root conductance and we hypothesize that ABA affects aquaporins in the roots, limiting water uptake.

Determining the Effects of Abscisic Acid Drenches on Evapotranspiration and Leaf Gas Exchange of Tomato

It is common for plants in the retail market to receive inadequate water and lose aesthetic value within a short period of time. The plant hormone abscisic acid (ABA) is naturally produced in response to drought conditions and reduces transpiration (E) by closing the stomata. Thus, ABA may lengthen shelf life of retail plants by reducing water loss. Two studies were conducted to look at effects of ABA on plant water use and shelf life over a 13-day period and short-term effects of ABA on leaf physiology. The objective of the short-term study was to determine how quickly 100-mL drenches of 250 mg·L−1 ABA solution affect leaf gas exchange of tomatoes (Solanum lycopersicum ‘Supersweet 100’). ABA drenches reduced stomatal conductance (gS), E, and photosynthetic rate (Pn) within 60 min. After 2 h, E, gs, and Pn were reduced by 66%, 72%, and 55% respectively, compared with the control plants. In the13-day study, ABA was applied to tomatoes as a 100-mL drench at concentrations ranging from 0 to 1000 mg·L−1 and ABA effects on water use and time to wilting were quantified. Half of the plants were not watered after ABA application, whereas the other plants were watered as needed. In general, higher ABA concentrations resulted in less water use by both well-watered and unwatered plants. ABA delayed wilting of unwatered plants by 2 to 8 days (dependent on the dose) as compared with control plants. In well-watered plants, ABA reduced daily evapotranspiration (ET) for 5 days, after which there were no further ABA effects. Negative side effects of the ABA application were rate-dependent chlorosis of the lower leaves followed by leaf abscission. These studies demonstrate that ABA drenches rapidly close stomata, limit transpirational water loss, and can extend the shelf life of retail plants by up to 8 days, which exemplifies its potential as a commercially applied plant growth regulator.

Effects of abscisic acid on ethylene biosynthesis and perception in Hibiscus rosa-sinensis L. flower development.

The effect of the complex relationship between ethylene and abscisic acid (ABA) on flower development and senescence in Hibiscus rosa-sinensis L. was investigated. Ethylene biosynthetic (HrsACS and HrsACO) and receptor (HrsETR and HrsERS) genes were isolated and their expression evaluated in three different floral tissues (petals, style–stigma plus stamens, and ovaries) of detached buds and open flowers. This was achieved through treatment with 0.1 mM 1-aminocyclopropane-1-carboxylic acid (ACC) solution, 500 nl l−1 methylcyclopropene (1-MCP), and 0.1 mM ABA solution. Treatment with ACC and 1-MCP confirmed that flower senescence in hibiscus is ethylene dependent, and treatment with exogenous ABA suggested that ABA may play a role in this process. The 1-MCP impeded petal in-rolling and decreased ABA content in detached open flowers after 9 h. This was preceded by an earlier and sequential increase in ABA content in 1-MCP-treated petals and style–stigma plus stamens between 1 h and 6 h. ACC treatment markedly accelerated flower senescence and increased ethylene production after 6 h and 9 h, particularly in style–stigma plus stamens. Ethylene evolution was positively correlated in these floral tissues with the induction of the gene expression of ethylene biosynthetic and receptor genes. Finally, ABA negatively affected the ethylene biosynthetic pathway and tissue sensitivity in all flower tissues. Transcript abundance of HrsACS, HrsACO, HrsETR, and HrsERS was reduced by exogenous ABA treatment. This research underlines the regulatory effect of ABA on the ethylene biosynthetic and perception machinery at a physiological and molecular level when inhibitors or promoters of senescence are exogenously applied.

Abscisic acid treatment has inconsistent effects on the water relations and longevity of cut Acacia holosericea foliage

SummaryPost-harvest application of abscisic acid (ABA) can induce stomatal closure in the leaves of cut flower and foliage crops.This effect may be helpful in reducing water deficit stress. Acacia holosericea, a novel cut-foliage line with a short vase-life, was subjected to ABA treatments applied by dipping, pulsing, or in-vase solution, with a view to improving its water balance and extending its longevity. In the first of four experiments, cut single Acacia phyllodes (leaves) were dipped into 0.1, 1.0, or 10.0 mg l–1 ABA for 60 s. In the second experiment, phyllodes were pulsed with these same ABA concentrations for 24 h at 20° ± 2°C. In the third experiment, ABA, at the same concentrations, was supplied to phyllodes as a vase solution. In the fourth experiment, cut Acacia whole stems were either dipped in 0.1 mg l–1 ABA solution, pulsed in 0.1 or 1.0 mg l–1 ABA, or stood in 0.01 or 0.10 mg l–1 ABA as vase solutions. Certain ABA dipping and pulsing treatments extended the vase-life of cut phyllodes by up to approx. 1.8-fold and 1.5-fold, respectively. Moreover, the application of ABA as a pulse or vase solution could reduce the uptake of vase solution by cut phyllodes, suggesting the induction of stomatal closure. Lower concentration ABA dip (1.0 mg l–1) and pulse (0.1 mg l–1) treatments extended the longevity of phyllodes, but high ABA dip and pulse concentrations (10.0 mg l–1) were ineffective. ABA in the vase solution at 0.01 mg l–1 extended the vase-life of cut stems, but did not reduce the uptake of vase solution. Overall, despite some vase-life and water balance benefits, post-harvest ABA treatments were not of value for cut A. holosericea foliage stems because of their inconsistent effects.