Comparative study on the influence of silicon and selenium to mitigate arsenic induced stress by modulating TCA cycle, GABA and polyamine synthesis in rice seedlings

Abstract

Arsenic contamination of groundwater is a major concern for its use as drinking water and crop irrigation in many regions of the world. Arsenic is absorbed by rice plants from arsenic contaminated water during irrigation, hampers growth and agricultural productivity. The aim of the study was to mitigate the activity of TCA cycle, synthesis of γ-aminobutyric acid (GABA) and polyamines (PAs) in rice (Oryza sativa L. cv. MTU-1010) seedlings under arsenate (As-V) stress [25 µM, 50 µM and 75 µM] by silicon (Si) [2 mM] and selenium (Se) [5 µM] amendments, and to investigate which chemical was more potential to combat this threat. As(V) application decreased the activities of tested respiratory enzymes while the levels of organic acids (OAs) were increased in the test seedlings. Co-application of Si and As(V) increased the activities of respiratory enzymes, consequently further increased accumulation of OAs that were more than Se with As(V) application in the test seedlings. GABA accumulation along with the activities of its regulatory enzymes were enhanced under As(V) stress. During joint application of Si and As(V) and Se and As(V) said parameters were decreased showing defensive role of these chemicals to resist As(V) toxicity in rice but amendment of Si was more potential than Se amendment resulted reduction of stress induced damage in the test seedlings. PAs trigger tolerance mechanism against stress in plants. PAs viz., Putrescine, spermidine and spermine were synthesized more during Si and Se amendments in As(V) contaminated rice seedlings to combat the effect of stress. Si amendment substantially modulated the toxic effects caused by As(V) over Se amendment in As(V) challenged test seedlings. Thus in future application Si enriched fertilizer will be beneficial than application of Se enriched fertilizer to grow rice plants with normal vigor in arsenic contaminated soil.