Abstract

Drought is a critical factor affecting the growth of maize seedlings, particularly their ability to maintain photosynthetic efficiency and gas exchange capacity. This study aimed to evaluate the soil application of zinc in the form of zinc sulfate heptahydrate (ZnSO₄•7H₂O) and recycled gelatin from medicinal capsules (recycled gelatin: RGel) under varying soil pot water holding capacities (pot water holding capacity: pot WHC) using the Suwan 5720 hybrid maize variety. The results revealed at 14 days after planting indicated that quantum yield, electron transport rate, and chlorophyll a content showed no significant differences compared to the control group. However, under limited water conditions at 50% pot WHC, chlorophyll b and total chlorophyll contents decreased by 26% and 29%, respectively. Regarding gas exchange parameters, seedlings receiving 100% pot WHC exhibited a stomatal conductance of 0.084 mol/m2/s and a transpiration rate of 0.983 mol/m2/s, which were 36% and 26% higher than those at 50% pot WHC, respectively. In contrast, vapor pressure deficit showed no statistical difference among treatments. In conclusion, while certain components of the photosynthetic apparatus remained functional during the seedling stage, water deficit directly resulted in pigment degradation and stomatal closure. The soil application of ZnSO₄•7H₂O and RGel during the study period did not clearly demonstrate any alleviating effects on the impacts of drought stress.