A comparative assessment of fluoride uptake and toxicity in four major crop seedlings: reduction of α-amylase activity and gibberellic acid

Abiotic stresses including fluoride (F − ) affect the quality and quantity of plant growth right from germination. The present study comparatively evaluates physiological and biochemical changes in four staple crops ( Oryza sativa , Triticum aestivum, Zea mays and Pennisetum glaucum ) against F − toxicity (50, 100, 150, 200 and 250 µg mL −1 ) during germination. Fluoride (µg g −1 ) accumulation in tissues of seedlings exhibited: O. sativa (8.9) > Z. mays (7.89) > P. glaucum (6.5) > T. aestivum (6.17) against 250 µg F − mL −1 , in 15d-old seedlings. T. aestivum was most sensitive among the studied crops, owing to its lowest LC 50 (132 µg mL −1 ), F − accumulation, correspondingly highest reduction in phytohormone (gibberellic acid, 32.6%), glycolytic enzyme (enolase, 46.38%), starch hydrolysis enzyme (α-amylase, 40%), total chlorophyll (7.81%) and fresh weight (20.83%) against 50 µg F − mL −1 . Contrarily, P. glaucum had the highest LC 50 (188 µg mL −1 ) and the highest K m value (167.2), exhibiting tolerance towards F − . Enhancement in the expression of oxidative stress markers and antioxidant enzyme activity were in the order: O. sativa > T. aestivum > Z. mays > P. glaucum . Further, F − stress also distorted the stomatal shape and reduced the number and diameter of metaxylem in all the F − -treated seedlings, against all F − concentrations.