Abstract
Drought is a critical environmental constraint limiting plant growth and productivity. Chitosan has been utilized as a potential biostimulant and proven to be effective against drought stress in many plant species. The objective of this study was to determine the effects of pretreatment with different molecular weight (MW) chitosans on some physiological characteristics of rice seedlings under drought stress. Rice seedlings were treated with low (50-190 kDa), medium (190-310 kDa) and high (310-375 kDa) MW chitosans by seed priming and foliar spray. The seedlings were subjected to drought by withholding water for four days. The relative water content (RWC) was reduced from 93% in the control plants to 74% in the droughted plants. The results revealed that treating with chitosan, especially with low MW chitosan, promoted root growth under drought stress. All chitosan treatments led to higher relative water content and photosynthetic pigment under drought condition. Pretreatment with chitosan also induced sugar accumulation, and treating with low MW chitosan significantly increased starch accumulation under drought stress. In addition, chitosan treatments alleviated the effects caused by drought stress as represented by the decreases in electrolyte leakage, malondialdehyde (MDA) as well as hydrogen peroxide (H2O2), corresponding with the increases in activities of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (GPX) activity.
Highlights
The ongoing increase of the severity and frequency of drought in a warming climate negatively affects agricultural production and threaten food security worldwide
Chitosan pretreatment enhanced rice seedling growth under drought stress Drought stress resulted in the overall reduction of shoot and root growths of rice seedling as indicated by the decreases in shoot length, root length, shoot and root fresh weights as well as shoot and root dry weights (Figure 1A-F)
Effects of chitosan on some physiological characteristics of rice plant under drought stress The relative water content of leaf was significantly reduced when the plant was subjected to drought stress
Summary
The ongoing increase of the severity and frequency of drought in a warming climate negatively affects agricultural production and threaten food security worldwide. Thailand is one of the world’s largest producer and exporter of rice, but current rice production is still limited by rainfall variability and drought due to the most of farmers’ popular and famous rice varieties are susceptible to drought stress. Among these varieties, ‘Khao Dawk Mali 105’ (‘KDML105’) is famous in either the country or worldwide. Demand for this variety is increasing in both domestic and international markets; the cultivation is limited by infertile and drought soil (Yoshihashi et al, 2004).
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