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 LC₅₀ (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 LC₅₀ (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. [ABSTRACT FROM AUTHOR]