Seed priming could be promoted as a potential alternative in alleviating drought stress challenges in rice cultivation. The present study was conducted as an attempt to verify potential performance of seed priming in improving seedling growth and harvestable grain yield of rice under reproductive stage drought stress (RS). Seed treatments involved were non-primed seeds as control (T1), hydro-primed (T2) and osmo-primed at -1.0 mPa with polyethylene glycol (PEG6000) (T3). Reproductive stage drought stress (RS) was imposed at soil water potential lower than -60 kPa. The well-watered plants served as control of the experiment. In general, seedling growth of T3 was better than T2 and T1 for all growth parameters in both planting seasons. Yield components were significantly lower in RS as compared to well-watered treatment (WW). The agronomic performance of primed seeds in T2 and T3 were not significantly different with T1 under both RS and WW for both planting seasons. As a conclusion, seed priming treatments used in this study was ineffective in improving agronomic performance of rice under RS. Therefore, other alternatives such as development of drought tolerant rice should be highly emphasized in order to minimize the impact of drought on growth and yield of rice plant.
Seed priming may improve germination performance of rice under drought. The present study was conducted to investigate the dynamics of seed biochemical changes during priming and post-priming germination under drought and to correlate those biochemical properties with the germination performance of primed seeds. The priming treatments were non-priming as control, hydro-priming and osmo-priming at -0.3, -1.0 and -2.2 MPa. All seeds were germinated under different levels of drought stress: 0 MPa as control, -0.2, -0.4, -0.6 and -0.8 MPa. The germination performance of hydro- and osmo-primed seeds at -0.3 and -1.0 MPa under severe stress (-0.8 MPa) was better compared with control and osmo-primed seeds at -2.2 MPa. Hydro-priming and osmo-priming at -0.3 MPa significantly improved germination performance while germinated seeds of -1.0 MPa osmo-primed seeds recorded the highest root and total seedling length. Proline accumulation was significantly higher in seeds that were hydro-primed or osmo-primed at -0.3 or -1.0 MPa as compared with non-primed control seeds and seeds osmo-primed at -2.2 MPa. In addition, proline was significantly correlated with the starch and glucose content and α-amylase activity. Higher α-amylase activity would accelerate the process of starch hydrolysis into soluble sugar for embryo growth and development resulting in enhanced germination processes.
Seed priming may improve seed germination and early seedling growth of plants under water deficit condition. The present study was conducted to investigate the effects of seed priming on the germination and early seedling growth of chili under water deficit condition and to identify the optimum rate of seed priming for higher seed germination and early seedling growth. The water deficit stress level towards early seedling growth also been identified. The priming treatments involved were non-priming as control, and priming with gibberellic acid (GA3) at 5 mg/L, 10 mg/L and 15 mg/L. Seed germination experiment was conducted using wet-tissue method for seven days duration. Germination percentage, germination index and seedling vigour index were recorded in the seed germination experiment. The germinated seeds were then sown and grown under five different levels of water deficit treatment in accordance with the frequency of watering mainly watering 8 times (S1), 4 times (S2), 2 times (S3), once (S4), and not watered (S5), in a duration of 14 days. The early seedling growth performance was based on plant height, and root length. Seed germination and early seedling growth performance of 5 mg/L GA3 primed seeds was significantly better as compared to other seed priming treatments. In addition, the S1 and S2 could be regarded as non-stress condition, S3 and S4 as mild to moderate stress and S5 as severe stress since all seedlings were not survived under S5 condition. In general, S2 was found to be the optimum watering treatment as it recorded the highest plant height and root length of the seedlings.
Drought stress significantly reduces grain yield (GY) due to poor spikelet fertility and anthesis quality. Aim of this study was to understand the changes of flowering capacity, anthesis quality traits and seed set in the re-watered drought stressed modern high yielding drought susceptible rice cultivar, IR64 at heading (DSH) and booting (DSB) stages. The well-watered plants served as control of the experiment. Results obtained suggest that spikelet moisture content at above 80% was required to maintain optimum anthesis process in rice. Anthesis process in DSH plant was suspended when leaf relative water content (LRWC) dropped to below than 70%. Effects of drought stress on the spikelet moisture were irreversible as compared to the leaf rolling and LRWC. Hence, seed set was failed to occur at the upper rachis branches of the DSH plant. Anthesis process in the re-watered drought stress plants was resumed on the third day after re-watering with about 50% and 80% of anthers managed to dehisce in the DSH and DSB plants. Consequently, percentage of spikelet fertility and seed set in the DSH and DSB plants were increased towards the lower parts of the panicle. The GY, number of seeds, spikelet fertility, and harvest index however were significantly lower in the DSH plant (0.30 g, 13, 16.40% and 14.81) as compared to DSB plant (1.34 g, 57, 59.14% and 48.30), respectively. In addition, all interrelated traits involved in the flowering process of rice could be collectively termed as the anthesis quality traits due to their significant correlation with the grain yield and other yield components.
Drought is regarded as one of the limiting factors in rice production nationally and globally. The present study was conducted to study morpho-physiological and biochemical responses of rice genotypes to drought stress, to identify potential traits for use as a selection criterion in breeding drought-tolerant rice at seedling stage and finally to identify rice genotype resistant to drought stress for use as parents in future breeding. The experimental design used was a split-plot design with three replications, with drought stress as the main plot and rice genotypes as the sub-plot. The main plots consisted of control (normal irrigation) and drought stress. The sub-plots consisted of twelve rice genotypes namely Apami (V1), Boewani (V2), Basmati 370 (V3), Cica- 4 (V4), Dular (V5), Jarom mas (V6), Kalarata (V7), Biris (V8), Haiboq (V9), Moroberekan (V10), MR 297 (V11) and Aerob 1 (V12). Results showed that drought stress led to a decrease in plant height, leaves size, root length, total dry weight, and number of leaves but an increment in proline content. The genotype Apami and Kalarata were found to accumulate higher proline content indicating potential resistant ability towards drought stress. Dular and Aerob1, along with tolerant control genotype, Moroberekan, on the other hand, recorded a lower SES score. Leave size, root length, and plant height could also be used as a selection criterion in breeding drought-tolerant rice due to high values of broad-sense heritability and genetic advance by percentage of mean (GAM). Nevertheless, further study on the genetics and physiological basis of tolerant ability at reproductive growth stages are necessary in order to assess grain yield potential of the potentially tolerant genotype reported in this study.
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