Stomatal responses at different vegetative stages of selected maize varieties of Bangladesh under water deficit condition

Drought stress causes stomatal behavior change in most plants. Water deficit condition caused by drought is one of the most significant abiotic factors reducing plant growth, development, reproductive efficiency, and photosynthesis, resulting in yield loss. Maize (Zea mays L.) holds a superior position among all the cereals due to its versatile use in the food, feed, and alcohol industries. A common demonstrative feature of a complex network of signaling pathways led by predominantly abscisic acid under drought conditions is stomatal aperture reduction or stomatal closure, which allows the plant to reduce water loss through the stomatal pore and to sustain a long time on water deficit condition. This study analyses the stomatal density, stomatal closure percentages, and guard cell aperture reduction using a microscopy-based rapid & simple method to compare guard cell response & morphological variations of three hybrid maize varieties viz. BHM (BARI hybrid maize)-7, BHM-9, and BHM-13 developed by Bangladesh Agricultural Research Institute (BARI). A drought treatment was applied to all varieties at two different vegetative stages, vegetative stage 3 (V3) and V5, until they reach V4 and V6, respectively. After drought exposure at the V4 stage, the percentage of closed stomata of BHM-7, BHM-9, and BHM-13 was 21%, 23%, and 33%, respectively. The reduction in the guard cell aperture ratio of BHM-7, BHM-9, and BHM-13 was 14.83%, 10.92%, and 33.85%, respectively. At the V6 stage, for the second set of plants, the closed stomata of BHM-7, BHM-9, and BHM-13 were 18%, 21%, and 34%, respectively. The rate of reduction in guard cell aperture ratio of BHM-7, BHM-9, and BHM-13 was 5.52%, 2.48%, and 38.75%, respectively. Therefore, BHM-13 showed maximum drought adaptation capacity compared to BHM-7 and BHM-9 due to the highest percentage of closed stomata and the highest percentage of reduction in aperture ratio.