Physiological responses of 10 maize genotypes to controlled and field deficit irrigation from emergence to the male flowering phase

This study was conducted during the sowing seasons of winter–spring, 2024 - 25, with 10 regional maize genotypes from Celaya, Guanajuato, Mexico, with the aim of evaluating water absorption, chlorophyll content, the normalized vegetation index (NDVI) and gas exchange response to deficit irrigation at osmotic pressures of -0.9 MPa, -1.5 MPa, and -2 MPa via polyethylene glycol and under field conditions, from emergence to the male flowering phase (VT). Water uptake and germination percentage were measured under both controlled and field conditions. The final plant height, chlorophyll content, maximum photosynthetic activity (NDVI) and transpiration were evaluated at VT. The humidity conditions caused a significant reduction on seeds water absorption under both experimental conditions, starting at -1.5 MPa. Under field conditions, final plant height, chlorophyll and NDVI were also reduced, with greater effects at -1.5 MPa and -2 MPa in most varieties.Photosynthesis showed stress intensities among 20% and 50%, whereas transpiration was the most affected, exceeding a stress intensity of 70% for most varieties. This study revealed genetic variability in the evaluated germplasms, demonstrating that all the genotypes are susceptible to continuous stress of -2 MPa from emergence to VT phase. Only Criollo Celaya, Roque 2020, and Peña Colorada x TNM87-C genotypes were classified as tolerant.