Chromium Stress Induced Alterations in Leaf Physiology and Morphology in Mung Bean (Vigna radiata L.)

Chromium (Cr) stress is a common abiotic stress that affects a variety of physiological, growth, and metabolic characteristics in plants. The toxicity of chromium at values up to 100 µM was examined in two common Indian Vigna radiata L. landraces: Digaphandi and Berhampur. Roots accumulated more chromium than leaves in both landraces, with Berhampur local absorbing more chromium than Digaphandi. Higher sub-stomatal carbon dioxide concentration and vapor pressure deficit did not affect stomatal conductance or transpiration rate efficiency in Digaphandi local, but both parameters decreased in Berhampur local treated plants. Berhampur local leaves treated with 100 µM dichromate showed decreased guard cell aperture area due to higher levels of abscisic acid, jasmonic acid, and jasmonic acid conjugate content. A decrease in three phytohormone levels resulted in no detectable change in the stomatal guard cell aperture area in treated Digaphandi local leaves. Non-glandular trichome density and length decreased significantly and non-significantly in the leaves of Digaphandi and Berhampur local treated plants respectively. Black substances accumulated in the trichomes of dichromate-treated plants in both landraces, possibly due to chromium deposition. The findings indicated that both landraces evolved distinct morphological and physiological adaptation mechanisms to survive chromium toxicity, with Berhampur local likely more vulnerable to chromium toxicity than Digaphandi local at higher doses of chromium.