Karwa Sourabh, Taunk Jyoti, Maurya Sadhana, Das Adhip, Krishna G K, Arya Sunder Singh, Kumar Awadhesh, Kumar Sudhir, Kumar Pramod, Chinnusamy Viswanathan, Pal Madan
Division of Plant Physiology, ICAR-Indian Agricultural Research Institute, New Delhi, India.
Department of Botany, Maharshi Dayanand University, Rohtak, Haryana, India.
Front Plant Sci. 2022 Dec 2;13:1027662. doi: 10.3389/fpls.2022.1027662. eCollection 2022.
Rice productivity is severely hampered by heat stress (HS) which induces oxidative stress in this crop. This oxidative stress can be alleviated using various exogenous chemicals, including spermidine (Spd). Therefore, the present study was carried out to characterize HS components and to elucidate the role of exogenous Spd application in rice at the flowering stage.
Two contrasting rice genotypes, i.e. Nagina22 (N22) and Pusa Basmati-1121 (PB-1121) were placed in temperature tunnels and exposed to HS (38-43°C) with and without Spd (1.5 mM) foliar application during the heading stage till the end of the anthesis stage.
Heat stress induced the production of HO and thiobarbituric acid reactive substances, which resulted in lower photosynthesis, spikelet sterility, and reduced grain yield. Interestingly, foliar application of Spd induced antioxidant enzyme activities and thus increased total antioxidant capacity resulting in higher photosynthesis, spikelet fertility, and improved grain yield under HS in both genotypes. Under HS with Spd, higher sugar content was recorded as compared to HS alone, which maintained the osmotic equilibrium in leaf and spikelets. Spd application initiated polyamine biosynthesis, which increased endogenous polyamine levels.
This study corroborates that the exogenous application of Spd is promising in induction of antioxidant defence and ameliorating HS tolerance in rice improved photosynthesis and transpiration. Thereby, the study proposes the potential application of Spd to reduce HS in rice under current global warming scenario.
热胁迫（HS）严重阻碍水稻生产力，热胁迫会在这种作物中引发氧化应激。可以使用包括亚精胺（Spd）在内的各种外源化学物质来缓解这种氧化应激。因此，本研究旨在表征热胁迫成分，并阐明在水稻开花期外源施用亚精胺的作用。
将两种对比鲜明的水稻基因型，即纳吉纳22（N22）和普萨巴斯马蒂 - 1121（PB - 1121）置于温度隧道中，在抽穗期直至开花期末，分别在有和没有叶面喷施Spd（1.5 mM）的情况下暴露于热胁迫（38 - 43°C）。
热胁迫诱导了羟基自由基（HO）和硫代巴比妥酸反应性物质的产生，导致光合作用降低、小穗不育和籽粒产量下降。有趣的是，叶面喷施Spd诱导了抗氧化酶活性，从而提高了总抗氧化能力，使得两种基因型在热胁迫下的光合作用、小穗育性提高，籽粒产量增加。在热胁迫下喷施Spd时，与单独热胁迫相比，糖分含量更高，这维持了叶片和小穗中的渗透平衡。施用Spd启动了多胺生物合成，增加了内源多胺水平。
本研究证实，外源施用Spd有望诱导抗氧化防御并改善水稻对热胁迫的耐受性，改善光合作用和蒸腾作用。因此，该研究提出了在当前全球变暖情况下，Spd在减轻水稻热胁迫方面的潜在应用。
