Metal uptake, oxidative metabolism, and mycorrhization in pigeonpea and pea under arsenic and cadmium stress

Presence of arsenic (As) and cadmium (Cd) at elevated levels in the soils is threatening agricultural productivity. Arbuscular mycorrhizae (AM) enhance plant resistance to metal(loid)s by sequestering them into roots, thus restricting their translocation into leaves. The present study evaluated differential responses of AM-colonized Cajanus cajan and Pisum sativum plants to As and Cd uptake and oxidative metabolism under As and Cd stress (0, 30, and 60 mg kg^–1). Arsenic uptake was significantly higher than Cd uptake, which caused greater growth inhibitions and induced oxidative stress. Pea was more sensitive, with higher toxicity symptoms in roots than leaves. Mycorrhizae were tolerant to metal toxicity and formed stronger association with the roots of pigeonpea than pea. However, mycorrhization arrested metal(loid) uptake, reduced oxidative stress, and strengthened antioxidant enzyme activities. Stronger antioxidant enzyme activity and mycorrhizal symbiosis in pigeonpea when compared with pea could explain the differences in their metal(loid) tolerance.