The Role of the Flag Leaf in Rice for Mitigating Sodicity-Induced Abiotic Stress
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Authors
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Manikandan Ayiramkan
Department of Soil Science and Agricultural Chemistry, Anbil Dharmalingam Agricultural College and Research Institute, Tamil Nadu Agricultural University, Tiruchirappalli, Tamil Nadu 620027, India
https://orcid.org/0009-0004-9596-1038
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T.Sherene Jenita Rajammal
Department of Soil Science and Agricultural Chemistry, Anbil Dharmalingam Agricultural College and Research Institute, Tamil Nadu Agricultural University, Tiruchirappalli, Tamil Nadu 620027, India
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Baskar Murugaiyan
Department of Soil Science and Agricultural Chemistry, Anbil Dharmalingam Agricultural College and Research Institute, Tamil Nadu Agricultural University, Tiruchirappalli, Tamil Nadu 620027, India
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Parthasarathi Rengasamy
Department of Soil Science and Agricultural Chemistry, Anbil Dharmalingam Agricultural College and Research Institute, Tamil Nadu Agricultural University, Tiruchirappalli, Tamil Nadu 620027, India
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Senthil Kuppusamy
Department of Soil Science and Agricultural Chemistry, Anbil Dharmalingam Agricultural College and Research Institute, Tamil Nadu Agricultural University, Tiruchirappalli, Tamil Nadu 620027, India
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S. Anandha krishnaveni
Department of Agronomy, Anbil Dharmalingam Agricultural College and Research Institute, Tamil Nadu Agricultural University, Tiruchirappalli, Tamil Nadu 620027, India
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Kanagavalli Arumugam
Department of Soil Science and Agricultural Chemistry, Anbil Dharmalingam Agricultural College and Research Institute, Tamil Nadu Agricultural University, Tiruchirappalli, Tamil Nadu 620027, India
Keywords:
Abiotic Stress, Antioxidant Defense, Flag Leaf, Ion Homeostasis, Reproductive Stage, Soil SodicityAbstract
Soil sodicity, defined by an exchangeable sodium percentage (ESP) > 15% and pH levels between 8.5 and 10.7, represents a critical bottleneck for rice (Oryza sativa L.) productivity globally, particularly in the Indo-Gangetic and Cauvery delta regions. Among plant organs, the flag leaf occupies a position of supreme physiological importance during the reproductive stage, acting as the primary source for the developing panicle sink and contributing 45% to 50% of the total photo assimilates required for grain filling. This review provides a comprehensive evaluation of the flag leaf's role in mitigating the "triple stress" of sodicity: osmotic stress, ionic (Na⁺) toxicity, and high pH-induced nutrient deficiencies. Tolerant genotypes like CSR36 and TRY 3 exhibit superior resilience through specialized sodium exclusion mechanisms, primarily mediated by High-affinity Potassium Transporters (OsHKT1;4 and OsHKT1;5), which protect the flag leaf blade from toxic sodium accumulation. Furthermore, the flag leaf serves as a biochemical fortress, upregulating enzymatic antioxidants such as Superoxide Dismutase (SOD), Catalase (CAT), and Peroxidase (POX) to neutralize reactive oxygen species. The evaluation of the "stay-green" trait and its correlation with sustained photosynthetic rates and spikelet fertility under alkaline conditions. The review highlights the importance of Na⁺/K⁺ homeostasis and micronutrient management specifically Zinc (Zn) and Iron (Fe) in maintaining flag leaf health, offering a framework for future breeding strategies and marker-assisted selection to enhance reproductive stage sodicity tolerance.
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