Abstract
The effects of nitric oxide (NO) as 100 µM sodium nitroprusside (SNP, NO donor) on photosynthetic-nitrogen use efficiency (NUE), photosynthetic-sulfur use efficiency (SUE), photosynthesis, growth and agronomic traits of rice (Oryza sativa L.) cultivars, Taipie-309 (high photosynthetic-N and SUE) and Rasi (low photosynthetic-N and SUE) were investigated under high temperature stress (40 °C for 6 h). Plants exposed to high temperature stress caused significant reduction in photosynthetic activity, use efficiency of N and S, and increment in H2O2 and thiobarbituric acid reactive substance (TBARS) content. The drastic effects of high temperature stress were more pronounced in cultivar Rasi than Taipie-309. However, foliar spray of SNP decreased the high temperature induced H2O2 and TBARS content and increased accumulation of proline and activity of ascorbate–glutathione cycle that collectively improved tolerance to high temperature stress more effectively in Taipie-309. Exogenously applied SNP alleviated the high temperature induced decrease in photosynthesis through maintaining higher photosynthetic-NUE and photosynthetic-SUE, activity of ribulose 1,5 bisphosphate carboxylase/oxygenase (Rubisco), and synthesis of reduced glutathione (GSH). The use of 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxy-3-oxide (cPTIO, NO scavenger) substantiated the study that in the absence of NO oxidative stress increased, while NO increased photosynthetic-NUE and photosynthetic-SUE, net photosynthesis and plant dry mass. Taken together, the present investigation reveals that NO increased heat stress tolerance and minimized high temperature stress adversaries more effectively in cultivar Taipie-309 than Rasi by enhancing photosynthetic-NUE and SUE and strengthening the antioxidant defense system.
Highlights
Rice (Oryza sativa L.) is the staple food of an estimated 3.5 billion people worldwide and has the third-largest cereal production with 741.5 million tons recorded in 2014 [1].India ranks second worldwide in rice production, contributing about 20% of the world rice production [2,3]
The objectives of this study were (i) to determine the response of high and low nutrient-use efficient rice cultivars to high temperature stress, and (ii) to evaluate the effect of exogenous sodium nitroprusside (SNP) application on photosynthetic nitrogen and sulfur-use efficiency and to observe how this helped in mitigating high temperature stress induced negative effects on photosynthesis, growth, and agronomic traits of rice cultivars
Application of SNP significantly reversed high temperature stressinduced photosynthetic inhibition in rice cultivars which were related to changes in Rubisco activity, photosystem II (PSII) activity, and photosynthetic-nitrogen use efficiency (NUE) and sulfur use efficiency (SUE)
Summary
Rice (Oryza sativa L.) is the staple food of an estimated 3.5 billion people worldwide and has the third-largest cereal production with 741.5 million tons recorded in 2014 [1]. India ranks second worldwide in rice production, contributing about 20% of the world rice production [2,3]. According to Shahbandeh [4] there has been a slight increase in global rice consumption over the last several years. In the year (2008/2009) global consumption of rice was about 437.8 million metric tons, while in (2018/2019) it was about 490.27 million metric tons, and it is expected to further increase due to increase in population and urbanization. The increasing global average temperature has become a key concern for rice productivity worldwide. According to the fifth assessment report of (IPCC, 2018)
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