Abstract
The benefits of silicon (Si) in improving crop fitness by biotic and abiotic stress resistance are widely reported. However, investigations about its protective mechanisms for plants facing multiple stresses are very limited. Two contrasting rice cultivars, KS- 282 (salt-tolerant) and IRRI-6 (salt-sensitive), were grown in a pot experiment to study the interrelation between Si supplementation (0 and 150 mg kg -1 ) and boron (B) toxicity (0 and 2.5 mg kg -1 ) under salinity stress with emphasis on growth response, mineral contents, physiology, and enzymatic antioxidant system response. The results revealed that adverse growth conditions, particularly the combined stress of salinity and B toxicity, severely affected the physiological attributes of rice. It reduced plant biomass by damaging the membrane, reducing special products analysis division values and photosynthetic efficiency, but Si application counteracted the adverse effects of stress by reducing the uptake of toxic ions such as sodium (Na + ) and B, lowering transpiration rate. Increased relative water contents and photosynthetic efficiency due to a higher Si and K + uptake ultimately led to better growth performance. Si significantly affected activities of enzymatic antioxidants in both genotypes, with increased ascorbate peroxidase, increased guaiacol peroxidase, and reduced catalase activity suggesting relieved stress by reduced oxidative damage. The response to stress and Si differed genotypically, with maximum damage to the salt-sensitive genotype (IRRI-6), particularly under the combined stress of salinity and B toxicity. In contrast, supplied Si improved the growth of the salt-tolerant genotype (KS-282) better than the IRRI-6 (salt-sensitive) genotype. These results support the protective role of Si in the regulation of salinity and/or B toxicity stress by improving growth, K + /Na + ratio, physiology, and antioxidant capacity, suggesting it as a potential candidate for crops grown under such deteriorated soil conditions.
Highlights
Salinization is widespread in irrigated agriculture as about 20% of the irrigated lands of the world are affected by salt, in countries of Asia and Africa, and with large proportions of the irrigated land affected in Argentina, Egypt, Iran, Pakistan, and the USA (Ghassemi et al, 1995)
The impact of salinity is most serious in countries where all or most of the agricultural production is based on irrigation, such as in Egypt and Pakistan, and where agriculture is a substantial part of the national economy (Rengasamy, 2001)
The results of the present study showed that salinity and/or B toxicity stress significantly hampered plant growth, when no Si was added to the growth medium
Summary
Salinization is widespread in irrigated agriculture as about 20% of the irrigated lands of the world are affected by salt, in countries of Asia and Africa, and with large proportions of the irrigated land affected in Argentina, Egypt, Iran, Pakistan, and the USA (Ghassemi et al, 1995). The demands on soil and water resources for food and fiber have been increasing tremendously in such countries including Pakistan due to a building population pressure. Most of the available good land is already under cultivation so it is very hard to increase the area under crop production. Increased salt and B tolerance of crops is required to enhance food production and sustain agriculture in Pakistan to feed the increasing population
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