Biochemical and Molecular Effects Induced by Triacontanol in Acquired Tolerance of Rice to Drought Stress

To assess the effect of triacontanol (TRIA) on rice plants grown under normal or drought conditions, rice seeds were presoaked in TRIA (35 ppm) for two hours. After 20 days of sowing, rice seedlings developed from TRIA-treated or untreated seeds were subjected to drought stress. After 10 days of plant exposure to drought stress, data of major growth attributes and the content of photosynthetic pigments were recorded. Moreover, the effect of drought stress on stomatal conductance and the photochemical efficiency of PSII (Fv/Fm) were followed. The data obtained indicated that the species of rice (Oryza sativa L.) cultivar Giza 177 under investigation was sensitive to drought stress where there were significant decreases in the fresh and dry weights of shoots and roots and in stomatal conductance, as well as in the content of chlorophyll a, chlorophyll b, and carotenoids. Seed priming with TRIA enhanced both growth and acquired plant tolerance to drought stress. Thus, TRIA via the enhancement of stomatal conductance through the regulation of stomatal closure, the rate of water loss, ABA metabolism, the accumulation of osmolytes, and the regulation of aquaporins genes improved the water status of plants grown under water scarcity. Moreover, TRIA via increasing the content of free amino acids and sugars under drought stress may increase the chance of plant tissues to retain more water under scarcity conditions.

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Arabidopsis MADS-box factor AGL16 negatively regulates drought resistance via stomatal density and stomatal movement

Journal of Experimental Botany ◽

10.1093/jxb/eraa303 ◽

2020 ◽

Vol 71 (19) ◽

pp. 6092-6106 ◽

Cited By ~ 3

Author(s):

Ping-Xia Zhao ◽

Zi-Qing Miao ◽

Jing Zhang ◽

Si-Yan Chen ◽

Qian-Qian Liu ◽

...

Keyword(s):

Drought Stress ◽

Drought Resistance ◽

Molecular Mechanisms ◽

Stomatal Density ◽

Stomatal Closure ◽

Negative Regulator ◽

Stomatal Development ◽

Mads Box ◽

Mobility Shift ◽

Aba Metabolism

Abstract Drought is one of the most important environmental factors limiting plant growth and productivity. The molecular mechanisms underlying plant drought resistance are complex and not yet fully understood. Here, we show that the Arabidopsis MADS-box transcription factor AGL16 acts as a negative regulator in drought resistance by regulating stomatal density and movement. Loss-of-AGL16 mutants were more resistant to drought stress and had higher relative water content, which was attributed to lower leaf stomatal density and more sensitive stomatal closure due to higher leaf ABA levels compared with the wild type. AGL16-overexpressing lines displayed the opposite phenotypes. AGL16 is preferentially expressed in guard cells and down-regulated in response to drought stress. The expression of CYP707A3 and AAO3 in ABA metabolism and SDD1 in stomatal development was altered in agl16 and overexpression lines, making them potential targets of AGL16. Using chromatin immunoprecipitation, transient transactivation, yeast one-hybrid, and electrophoretic mobility shift assays, we demonstrated that AGL16 was able to bind the CArG motifs in the promoters of the CYP707A3, AAO3, and SDD1 and regulate their transcription, leading to altered leaf stomatal density and ABA levels. Taking our findings together, AGL16 acts as a negative regulator of drought resistance by modulating leaf stomatal density and ABA accumulation.

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miR2105 regulates ABA biosynthesis via OsbZIP86-OsNCED3 module to contribute to drought tolerance in rice

10.1101/2021.09.21.461241 ◽

2021 ◽

Author(s):

Weiwei Gao ◽

Mingkang Li ◽

Songguang Yang ◽

Chunzhi Gao ◽

Yan Su ◽

...

Keyword(s):

Drought Stress ◽

Drought Tolerance ◽

Transgenic Rice ◽

Crucial Role ◽

Agronomic Traits ◽

Stomatal Closure ◽

Plant Tolerance ◽

Rice Plants ◽

Transgenic Rice Plants ◽

Aba Biosynthesis

AbstractInduced abscisic acid (ABA) biosynthesis plays an important role in plant tolerance to abiotic stresses, including drought, cold and salinity. However, regulation pathway of the ABA biosynthesis in response to stresses is unclear. Here, we identified a rice miRNA, osa-miR2105 (miR2105), which plays a crucial role in ABA biosynthesis under drought stress. Analysis of expression, transgenic rice and cleavage site showed that OsbZIP86 is a target gene of miR2105. Subcellular localization and luciferase activity assays showed that OsbZIP86 is a nuclear transcription factor. In vivo and in vitro analyses showed that OsbZIP86 directly binds to the promoter of OsNCED3, and interacts with OsSAPK10, resulting in enhanced-expression of OsNCED3. Transgenic rice plants with knock-down of miR2105 or overexpression of OsbZIP86 showed higher ABA content, more tolerance to drought, a lower rate of water loss, more stomatal closure than wild type rice ZH11 under drought stress. These rice plants showed no penalty with respect to agronomic traits under normal conditions. By contrast, transgenic rice plants with miR2105 overexpression, OsbZIP86 downregulation, or OsbZIP86 knockout displayed less tolerance to drought stress and other phenotypes. Collectively, our results show that a regulatory network of ‘miR2105-OsSAPK10/OsbZIP86-OsNCED3’ control ABA biosynthesis in response to drought stress.One-sentence summary‘miR2105-OsbZIP86-OsNCED3’ module plays crucial role in mediating ABA biosynthesis to contribute to drought tolerance with no penalty with respect to agronomic traits under normal conditions.

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Germination and seedling characteristics of drought-stressed corn seed as influenced by seed priming with potassium nano-chelate and sulfate fertilizers

Acta agriculturae Slovenica ◽

10.14720/aas.2016.107.1.12 ◽

2016 ◽

Vol 107 (1) ◽

pp. 113 ◽

Cited By ~ 1

Author(s):

Maryam ZAHEDIFAR ◽

Sadegh ZOHRABI

Keyword(s):

Drought Stress ◽

Seed Priming ◽

Dry Mass ◽

Plant Tolerance ◽

Corn Seed ◽

Seedling Traits ◽

Corn Seedling ◽

Seminal Roots ◽

Mean Germination Time ◽

Seedling Characteristics

Effect of seed-priming with potassium (K) sources (K-nano-chelate, KNC, and sulfate (0, 2 and 4 %)) under drought stress (DS) conditions (0, -0.3, -0.6, -0.9, -1.2 and -1.5 MPa water potential) on the corn seedling traits was studied. Drought stress decreased the germination indices and seedling vigor. The highest germination, seminal root fresh and dry mass (RFM and RDM) was obtained in KNC primed seeds at -0.3 MPa DS. Mean germination time increased under DS conditions mainly in non-primed seeds. Increasing DS to -1.2 MPa led to decrease in RFM and RDM. Influence of DS on the fresh mass of shoots was more severe than on seminal roots. The highest shoots and seminal roots length was observed in 4 % KNC without any DS. Proper priming can be suggested to increase the plant tolerance under DS.

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Effect of Water Stress on Stomatal Conductance and Leaf Water Relations of Leaves Along Current-Year Branches of Peach

Functional Plant Biology ◽

10.1071/pp9890549 ◽

1989 ◽

Vol 16 (6) ◽

pp. 549 ◽

Cited By ~ 4

Author(s):

SL Steinberg ◽

MJ Mcfarland ◽

JC Miller

Keyword(s):

Water Stress ◽

Stomatal Conductance ◽

Water Potential ◽

Water Status ◽

Stomatal Closure ◽

Water Flux ◽

Leaf Water ◽

Leaf Water Status ◽

Mature Leaves ◽

Water Potentials

A gradation, that reflects the maturity of the leaves, exists in the leaf water, osmotic and turgor potential and stomatal conductance of leaves along current and 1-year-old branches of peach. Predawn leaf water potentials of immature folded leaves were approximately 0.24 MPa lower than mature leaves under both well-watered and dry conditions. During the daytime the leaf water potential of immature leaves reflected the water potential produced by water flux for transpiration. In well- watered trees, mature and immature unfolded leaves had a solute potential at least 0.5 MPa lower than immature folded leaves, resulting in a turgor potential that was approximately 0.8 MPa higher. The turgor requirement for growth appeared to be much less than that maintained in mature leaves. As water stress developed and leaf water potentials decreased, the osmotic potential of immature folded leaves declined to the level found in mature leaves, thus maintaining turgor. In contrast, mature leaves showed little evidence of turgor maintenance. Stomatal conductance was lower in immature leaves than in fully mature leaves. With the onset of water stress, conductance of mature leaves declined to a level near that of immature leaves. Loss of turgor in mature leaves may be a major factor in early stomatal closure. It was concluded that osmotic adjustment played a role in maintenance of a leaf water status favorable for some growth in water-stressed immature peach leaves.

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278 Gas Exchange and Water Relations of Diverse Tall Fescue Cultivars in Response to Drought Stress

HortScience ◽

10.21273/hortsci.34.3.490c ◽

1999 ◽

Vol 34 (3) ◽

pp. 490C-490

Author(s):

Bingru Huang ◽

Hongwen Gao

Keyword(s):

Drought Stress ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Tall Fescue ◽

Festuca Arundinacea ◽

Stomatal Closure ◽

Photochemical Efficiency ◽

Physiological Factors ◽

Relative Water

To investigate shoot physiological responses to drought stress of six tall fescue (Festuca arundinacea) cultivars representing several generations of turfgrass improvement, forage-type `Kentucky-31', turf-type `Phoenix', `Phoenix', and `Houndog V', and dwarf-type `Rebel Jr` and `Bonsai' were grown in well-watered or drying soil for 35 days in a greenhouse. Net photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (Tr), relative water content (RWC), and photochemical efficiency (Fv/Fm) declined during drought progression in all cultivars, but the time and the severity of reductions varied with cultivars and physiological factors. Pn, RWC, gs, and Tr decreased significantly for `Rebel Jr', `Bonsai', and `Phoenix' when soil water content declined to 20% after 9 days of treatment (DOT) and for `Falcon II', `Houndog V', and `Kentucky-31' when soil water content dropped to 10% at 15 DOT. A significant decrease in Fv/Fm was not observed in drought-stressed plants until 21 DOT for `Rebel Jr', `Bonsai', and `Phoenix' and 28 DOT for `Houndog V', `Kentucky-31', and `Falcon II'. The decline in Pn was due mostly to internal water deficit and stomatal closure under short-term or mild drought-stress conditions. After a prolonged period of drought (35 DOT), higher Pn in `Falcon II', `Houndog V', and `Kentucky-31' could be attributed to their higher Fv/Fm.

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Drought and cold stress responses in orostachys spinosa L.

Mongolian Journal of Agricultural Sciences ◽

10.5564/mjas.v22i03.954 ◽

2018 ◽

Vol 22 (03) ◽

pp. 77-81

Author(s):

Otgonsuvd B ◽

Ouyngerel Sh ◽

Altanzaya T

Keyword(s):

Electron Transfer ◽

Drought Stress ◽

Stress Responses ◽

Photochemical Efficiency ◽

Normal Growth ◽

Growth Conditions ◽

Photochemical Efficiency Of Psii ◽

Succulent Plant ◽

Drought Conditions ◽

Long Time

Orostachys spinosa L. is a succulent plant native to predominantly East Asia. The objective of this study was to identify physiological and morphological responses of O. spinosa L. species to cold, drought stress in laboratory conditions. Exposure of plants to a drought stress for 28 days slightly decreased the photochemical efficiency of PSII and the Fv/Fm values were 10-15% lower (0.75±0.01) compared with the control plants (0.85±0.01). For cold treatments, plants were exposed to 4°C for 60 days and for recovery transferred to normal growth conditions for 14 days. Fv/Fm photochemical efficiency of PSII can be used to monitor PSII photoinhibition. This parameter describes the efficiency of the electron transfer within PSII.The results of this study demonstrated that O. spinosa L. plants were better adapted to cold and drought conditions as they showed less visible symptoms and highest Fv/Fm levels at the long time chilling and drought stress.

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Leaf morphology, photochemistry and water status changes in resprouting Quercus ilex during drought

Functional Plant Biology ◽

10.1071/fp04137 ◽

2005 ◽

Vol 32 (2) ◽

pp. 117 ◽

Cited By ~ 41

Author(s):

Karen Peña-Rojas ◽

Xavier Aranda ◽

Richard Joffre ◽

Isabel Fleck

Keyword(s):

Drought Stress ◽

Quercus Ilex ◽

Structural Characteristics ◽

Water Status ◽

Stomatal Closure ◽

Severe Drought ◽

Clear Cut ◽

Leaf Mass Area ◽

Relative Water ◽

Moderate Drought

Functional and morphological (structural) characteristics of Quercus ilex L. leaves under drought stress were studied in the forest and in a nursery. We compared undisturbed individuals (controls) with resprouts emerging after clear-cut or excision. When soil water availability was high, gas-exchange was similar in resprouts and controls, despite higher midday leaf water potential, midday leaf hydration and relative water content (RWC). In moderate drought, stomatal closure was found to limit photosynthesis in controls, and in severe drought non-stomatal limitations of photosynthesis were also greater than in resprouts. Leaf structure and chemical composition changed under drought stress. Leaves tended to be smaller in controls with increasing drought, and resprouts had larger leaves and lower leaf mass area (LMA). The relationship between nitrogen (N) content and LMA implied lower N investment in photosynthetic components in controls, which could be responsible for their increased non-stomatal limitation of photosynthesis. Changes were more apparent in leaf density (D) and thickness (T), components of LMA. Decreases in D were related to reductions in cell wall components: hemicellulose, cellulose and lignin. In resprouts, reduced D and leaf T accounted for the higher mesophyll conductance (gmes) to CO2 measured.

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Effects of hydrogen peroxide application on agronomic traits of rice (Oryza sativa L.) under drought stress

Plant Soil and Environment ◽

10.17221/628/2020-pse ◽

2021 ◽

Vol 67 (No. 4) ◽

pp. 221-229

Author(s):

Weeraphorn Jira-anunkul ◽

Wattana Pattanagul

Keyword(s):

Hydrogen Peroxide ◽

Oryza Sativa ◽

Drought Stress ◽

Yield Loss ◽

Agronomic Traits ◽

Foliar Application ◽

Oryza Sativa L ◽

Seed Priming ◽

Grain Weight ◽

Signal Molecule

Drought stress is a major environmental factor limiting crop growth and productivity. Hydrogen peroxide (H2O2) plays an essential role during stress response by acting as a signal molecule that activates multiple stress tolerance mechanisms. In this study, the effects of H2O2 on agronomic traits were studied in rice (Oryza sativa L.) cv. Khao Dawk Mali 105 (KDML 105) was subjected to drought stress. H2O2 was applied by either seed priming or foliar application method with a concentration of 1, 5, and 15 mmol/L. The results showed that both seed priming and foliar application with H2O2 improved some yield components. The tiller numbers, number of panicles, number of filled grains, filled grain weight, and harvest index were improved approximately 1.13, 1.04, 1.23, 1.21, and 1.1 times compared to the untreated plants. Foliar application, however, helps the plant by reducing yield loss as indicated by a 0.5-time reduction in the number of unfilled grain and lower unfilled grain weight. It was suggested that 5 mmol/L H2O2 was the most effective concentration to alleviate the effect of drought stress during the reproductive stage in rice.

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Activation of the ABA Signal Pathway Mediated by GABA Improves the Drought Resistance of Apple Seedlings

International Journal of Molecular Sciences ◽

10.3390/ijms222312676 ◽

2021 ◽

Vol 22 (23) ◽

pp. 12676

Author(s):

Chenlu Liu ◽

Hongtao Wang ◽

Xiuzhi Zhang ◽

Fengwang Ma ◽

Tianli Guo ◽

...

Keyword(s):

Drought Stress ◽

Stomatal Conductance ◽

Stomatal Closure ◽

Carbon Dioxide Concentration ◽

Closure Rate ◽

Relative Water ◽

Leaf Tissues ◽

Mda Content ◽

Relative Electrical Conductivity ◽

Exogenous Treatment

Drought seriously affects the yield and quality of apples. γ-aminobutyric acid (GABA) plays an important role in the responses of plants to various stresses. However, the role and possible mechanism of GABA in the drought response of apple seedlings remain unknown. To explore the effect of GABA on apple seedlings under drought stress, seedlings of Malus hupehensis were treated with seven concentrations of GABA, and the response of seedlings under 15-day drought stress was observed. The results showed that 0.5 mM GABA was the most effective at relieving drought stress. Treatment with GABA reduced the relative electrical conductivity and MDA content of leaves induced by drought stress and significantly increased the relative water content of leaves. Exogenous GABA significantly decreased the stomatal conductance and intercellular carbon dioxide concentration and transpiration rate, and it significantly increased the photosynthetic rate under drought. GABA also reduced the accumulation of superoxide anions and hydrogen peroxide in leaf tissues under drought and increased the activities of POD, SOD, and CAT and the content of GABA. Exogenous treatment with GABA acted through the accumulation of abscisic acid (ABA) in the leaves to significantly decrease stomatal conductance and increase the stomatal closure rate, and the levels of expression of ABA-related genes PYL4, ABI1, ABI2, HAB1, ABF3, and OST1 changed in response to drought. Taken together, exogenous GABA can enhance the drought tolerance of apple seedlings.

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Physiological Responses of Diverse Tall Fescue Cultivars to Drought Stress

HortScience ◽

10.21273/hortsci.34.5.897 ◽

1999 ◽

Vol 34 (5) ◽

pp. 897-901 ◽

Cited By ~ 40

Author(s):

Bingru Huang ◽

Hongwen Gao

Keyword(s):

Drought Stress ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Drought Resistance ◽

Tall Fescue ◽

Physiological Responses ◽

Stomatal Closure ◽

Photochemical Efficiency ◽

Limiting Factors

Drought is among the most limiting factors for turfgrass growth. Understanding genetic variations and physiological mechanisms in turfgrass drought resistance would facilitate breeding and management programs to improve drought resistance. The experiment was designed to investigate shoot physiological responses of six tall fescue (Festuca arundinacea Schreb.) cultivars representing several generations of turfgrass improvement to drought stress. Grasses were grown in well-watered or drying (nonirrigated) soil for 35 days in the greenhouse. Net photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (Tr), relative water content (RWC), and photochemical efficiency (Fv/Fm) declined during drought progression in all cultivars, but the time and the severity of reductions varied with cultivar and physiological factors. The values of Pn, RWC, gs, and Tr decreased significantly for `Rebel Jr', `Bonsai', and `Phoenix' when soil water content declined to 20% after 9 days of treatment (DOT) and for `Houndog V', `Kentucky-31', and `Falcon II' when soil water content dropped to 10% at 15 DOT. A significant decrease in Fv/Fm was not observed in drought-stressed plants until 21 DOT for `Rebel Jr', `Bonsai', and `Phoenix' and 28 DOT for `Houndog V', `Kentucky-31', and `Falcon II'. The decline in Pn resulted mainly from internal water deficit and stomatal closure under mild drought-stress conditions. After a prolonged period of drought stress (35 DOT), `Falcon II', `Houndog V', and `Kentucky-31' maintained higher Pn than did `Rebel Jr', `Bonsai', and `Phoenix', which could be attributed to their higher Fv/Fm. This study demonstrated variation in drought resistance among tall fescue cultivars, which was related to their differential responses in photosynthetic capacity and water relations.

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