Effect of Drought Stress on Chlorophyll Fluorescence Parameters, Phytochemical Contents, and Antioxidant Activities in Lettuce Seedlings

This study monitored changes in chlorophyll fluorescence (CF), growth parameters, soil moisture content, phytochemical content (proline, ascorbic acid, chlorophyll, total phenol (TPC), and flavonoid (TFC)), antioxidant activities 12-day-old lettuce (Lactuca sativa L.) seedlings grown under drought stress (no irrigation) control (well irrigated) treatments controlled conditions for eight days. Measurements occurred at two-day intervals. Among ten CF parameters studied, effective quantum yield of photochemical energy conversion PSII (Y(PSII)), coefficient quenching (qP), variable based on the lake model (qL) significantly decreased drought-stressed from day 6 treatment compared to control. In contrast, maximum (Fv/Fm), ratio (Rfd), non-regulated dissipation (Y(NO)) were affected only end. All Proline started increasing 4 showed ~660-fold elevation 8 Chlorophyll, TPC, TFC, seedlings. Results major all prolonged stress. These findings clarify effects during progressive exposure will be useful seedling industry.