Stimulatory and Inhibitory Role of Allelopathic Chlorogenic Acid in Seed Germination and Seedling Growth of Tall Fescue Grass (Festuca arundinaceae Schreb.) via pH Reprogramming

Exploring the effects of chlorogenic acid (CA) can allow its use in the sustainable management of natural fiber-producing grass species. Herein, the pH-dependent effect of CA on germination and the physiological response in tall fescue (Festuca arundinacea) seeds in comparison to gibberellic acid (GA₃) and fluridon (FD) was investigated. All CA treatments conferred significant reduction in germination index (GI), seed vigour, fresh seedling weight, coleoptile length, primary root length and root hairs compared to the control nutrient solution at pH 4. Above 2.82 mM CA, higher expression of total soluble protein, catalase and superoxide dismutase activities, lipid peroxidation, electrolyte leakage levels, and an induced prominent 28.4 KDa peptide were observed. CA (8.46 mM) significantly inhibited seed germination (50%, F = 4.56, P = 0.031, P < 0.05) at pH 4, and by contrast, conferred a strong stimulating effect at pH 6.8. The impact of pH on CA activity was significantly correlated to GI and percentage inhibitory and stimulatory effects (r = 0.96, p = 0.001). It is demonstrated that buffered CA differentially modified the expression of antioxidant enzymes activities and seed physiology thereby inhibiting seed germination at pH 4 compared to the herbicide FD (or the growth hormone) GA₃.