Ascertain the Effect of PEG and Exogenous ABA on Rice Growth at Germination Stage and Their Contribution to Selecting Drought Tolerant Genotypes
ABSTRACT In this study, the effect of exogenous ABA on radicle and plumule growth at germination stage was investigated, compared with PEG osmotic stress culture condition and the consistency between genotypic variation in exogenous ABA and PEG sensitivity at germination stage and in water deficit treatment at reproductive stage in the field was evaluated. Fifteen rice ( Oryza sativa L.) cultivars with different drought resistant ability were studied, 7.8x10-6 mol L-1 ABA and 30% PEG1500 (-1.1 MPa) were used to culture the germinated seeds for 5 days and the length, fresh and dry weight of radicle and plumule were measured and compared with normal condition (distilled water). In the field water stress experiment, drip irrigation was served for all plots every other day and water was discontinued for 14 days when the flag leaf reached stage 0 for the main stems in the plot. In this study, both PEG and ABA applied could inhibit the growth of plumule and radicle and significant difference existed among genotypes in the reduction rate of plumule and radicle. While for most of the tested genotypes, the response to ABA was similar to PEG and water stress in the field as well, which indicated the genotypes variation and ranking for the treatment with ABA based on the reduction rate of radicle and plumule growth parameters and with PEG based on reduction rate of plumule growth were rather similar to the same genotypes in field water deficit experiment based on the yield reduction rate. So exogenous ABA at germination stage could be and even more effective compared with PEG to quantify the drought resistance among genotypes in rice.
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ABSTRACT: The role of plant hormone abscisic acid (ABA) in plants under drought stress (DS) is crucial in modulating physiological responses that eventually lead to adaptation to an unfavorable environment; however, the role of this hormone in modulation of glycinebetaine (GB) metabolism in maize particularly at the seedling stage is still poorly understood. Some hydroponic experiments were conducted to investigate the modulation role of ABA on plant growth, water relations and GB metabolism in the leaves of two maize cultivars, Zhengdan 958 (ZD958; drought tolerant), and Jundan 20 (JD20; drought sensitive), subjected to integrated root-zone drought stress (IR-DS) simulated by the addition of polyethylene glycol (PEG, 12% w/v, MW 6000). The IR-DS substantially resulted in increased betaine aldehyde dehydrogenase (BADH) activity and choline content which act as the key enzyme and initial substrate, respectively, in GB biosynthesis. Drought stress also induced accumulation of GB, whereas it caused reduction in leaf relative water content (RWC) and dry matter (DM) in both cultivars. The contents of ABA and GB increased in drought-stressed maize seedlings, but ABA accumulated prior to GB accumulation under the drought treatment. These responses were more predominant in ZD958 than those in JD20. Addition of exogenous ABA and fluridone (Flu) (ABA synthesis inhibitor) applied separately increased and decreased BADH activity, respectively. Abscisic acid application enhanced GB accumulation, leaf RWC and shoot DM production in both cultivars. However, of both maize cultivars, the drought sensitive maize cultivar (JD20) performed relatively better than the other maize cultivar ZD958 under both ABA and Flu application in view of all parameters appraised. It is, therefore, concluded that increase in both BADH activity and choline content possibly resulted in enhancement of GB accumulation under DS. The endogenous ABA was probably involved in the regulation of GB metabolism by regulating BADH activity, and resulting in modulation of water relations and plant growth under drought, especially in the drought sensitive maize cultivar JD20.International Journal of Molecular Sciences 01/2012; 13(3):3189-202. · 2.34 Impact Factor
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ABSTRACT: We studied the physiological responses to abscisic acid (ABA) when 2-year-old potted plants of kiwifruit (Actinidia deliciosa) were grown under moisture stress. Leaves treated with 60μM exogenous ABA through various means had less severe damage when water was limiting, and sprayed plants showed relatively greater drought resistance. This indicates that ABA improves tolerance in kiwifruit, reducing membrane permeability and enhancing the activities of antioxidant enzymes, e.g., peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR). Exposure to ABA led to higher levels of antioxidants, such as ABA and glutathione (GSH), while altering the amounts of endogenous hormones—ABA, indole-3-acetic acid (IAA), and Gibberellin (GA)—and organic oxalate, malate, and citrate in the leaves. Although daily applications of ABA were more effective than a single spray event, the effect of treatment, i.e., avoiding tissue damage and increasing plant resistance, was more apparent on Day 4 than on Day 6. No difference in response was apparent between control plants (regular irrigation) and those sprayed with ABA on Day 4 of the drought period. KeywordsAbscisic acid– Actinidia deliciosa –Drought–Physiological characteristicsPlant Growth Regulation 64(1):63-74. · 1.63 Impact Factor