Physiological and Biochemical Perspective on Silicon Induced Salt Stress Tolerance in Proso Millet

Purpose

The challenges encountered in global food production are attributed to climate change, weather unpredictability and abiotic factors. These condition in plants result in detrimental effects on cellular structures, organelles and physiological activities. Grasses are renowned for their capacity to accumulate silicon (Si) and serve as a valuable model for investigating the physiological impacts of Si on plants. In this study, we aim to analyse the impact of salt stress and Si on morphology, photosynthetic pigments, phenolic, flavonoid compounds, anthocyanins and enzymes like PAL, TAL and PPO.

Methods

To find the role of Si in salt stress mitigation, we performed various morphological, physiological and biochemical studies.

Results

Salt stress inhibited plant growth, pigment production, and chlorophyll stability in a dose-dependent manner. The results of this investigation demonstrated that the application of 2 mM and 4 mM Si alone in proso millet led to a considerable elevation of 3.62% and 12% in chlorophyll a, and 5.58% and 21.3% in chlorophyll b. PAL, TAL, and PPO activity increased significantly in response to both NaCl treatments, by 12.16%, 28.65, and 13.92% at 150 mM NaCl and 62.84%, 63.43%, and 14.3% at 200 mM NaCl, respectively, compared to the control. When administered alone, Si significantly increased PAL, TAL, and PPO activity, with increases of 113.9% and 62.14%, 27.22% and 7.13%, and 12.14% and 14.28% at 2 mM and 4 mM, respectively, compared to the control. The combination of salt and Si further boosted the activity of these enzymes. Plants treated with Si alone or with NaCl showed an increase in TPC and TFC content, with the highest rise of 14.2% and 17.46% respectively at 150 mM NaCl + 2 mM Si.

Conclusion

This study found that Si improves the effectiveness of photosynthetic pigments, relative water content, and chlorophyll stability in proso millet under salt stress. Salt and Si treatments enhanced the activity of PAL, TAL, and PPO. These phenylpropanoid biosynthetic enzymes help to tolerate NaCl stress by generating phenolic compounds that scavenge reactive oxygen species to prevent oxidative damage. Thus, this study implies that low Si levels could be beneficial for sustainable agriculture techniques.