Abstract
Plant hormones influence various physiological processes during the growth and development of plants, but their critical roles in influencing yield and antioxidant activities in dry-seeded rice (DSR) have not been adequately explored. This study aims to analyze the performance and antioxidant activity of contrasting genotypes of DSR in response to soil moisture regimes and foliar-applied hormones. The study comprised sixteen treatments that were evaluated under field conditions as per split-plot design in three replications. Treatments comprised combinations of two soil moisture tension regimes (10 kPa and 20 kPa) and two genotypes (PR-111, non-stay-green type and PR-123, stay-green type) applied to the main plots and foliar application of three hormones (gibberellic acid (GA3) 40 mg kg−1, abscisic acid (ABA) 20 mg kg−1, and cytokinin (CK) 40 mg kg−1)) and a control (unsprayed) to subplots. The non-stay-green genotype (PR-111) resulted in 34.6% more grain yield (6.48 t ha−1) than the stay-green genotype (PR-123) at the lower soil moisture tension regime (SMTR) (10 kPa) due to the increased number of filled grains per panicle and improvement in harvest index (HI). At the higher SMTR (20 kPa), the stay-green genotype (PR-123) produced 26.4% more grain yield (5.21 t ha−1) than non-stay green genotype (4.12 t ha−1) and showed enhanced superoxide dismutase (SOD) and peroxide dismutase (POD) activity that may have contributed in maintaining sink size through improved chlorophyll content. Grain yield (6.35 t ha−1) with foliar-applied GA3 (40 mg kg−1) at SMTR of 10 kPa was higher by 12.2% and 24.0% than with foliar-applied ABA (20 mg kg−1) and unsprayed treatments, respectively. Irrigation application at SMTR of 20 kPa and foliar application of ABA gave 24.1% higher grain yield (5.15 t ha−1) than the unsprayed treatment, but it was similar to foliar-applied GA3 and CK. This study implied that the stay-green genotype (PR-123) was more suitable under moisture stress conditions (20 kPa) in DSR, as it maintained sink size even under moisture stress conditions by improving dry matter translocation and enhancing SOD and POD activity. The study suggests the need to find out the endogenous level of these plant hormones in rice genotypes under a range of water regimes to develop high yielding and water use efficient genotypes of DSR.
Highlights
Rice (Oryza sativa L.) is the staple diet of more than 90% population of South Asia and an essential food for a majority of the world’s population [1,2]
The plant height of PR-111 with a foliar application of abscisic acid (ABA) and PR-123 with CK was significantly higher than that attained with control
Plant height with foliar-applied GA3 increased by 11% and 15% for PR-111 and PR-123, respectively, whereas it increased by 5% in PR-111 with foliar-applied ABA and 5% in PR-123 with foliar-applied CK, as compared to the water spray treatment
Summary
Rice (Oryza sativa L.) is the staple diet of more than 90% population of South Asia and an essential food for a majority of the world’s population [1,2]. In South Asia, transplanting seedlings into puddled soil is the most common method of rice cultivation. This practice of crop planting is highly water, energy, and labor-intensive. High water requirements of puddled transplanted rice (PTR) have resulted in groundwater depletion to alarming levels due to its over-exploitation [4]. Cultivation of PTR has lowered the water table and has increased the economic and energy resource costs required to extract water from deeper aquifer layers [5]. There is increasing concern that regional food security may be jeopardized in the near future due to the unsustainable water resources, energy, and labor requirements of PTR. There is urgent need to devise alternative methods of rice cultivation with reduced dependence upon such intensive resource requirements
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