Morpho-physiological and biochemical responses of maize (Zea mays L.) cultivars to drought stress at different growth stages

Background Drought is a major abiotic stress and a global threat to sustainable agriculture, severely constraining maize (Zea mays L.) productivity. It is estimated that drought stress can cause up to 15-20% grain yield losses in maize worldwide. Understanding the morpho-physiological and biochemical responses of different maize cultivars under drought conditions is essential for developing drought-tolerant varieties.Methods This study investigated the impact of drought stress on two maize cultivars, Haq Nawaz (drought-sensitive) and CIMMYT PAK (drought-tolerant), at three developmental stages: seedling, flowering, and grain filling. Morphological parameters (plant height, leaf length), physiological traits (chlorophyll a and b, proline, membrane stability index, soluble sugars), and biochemical components (nitrogen (N), phosphorus (P), and potassium (K)) were analyzed under well-watered and drought-stressed conditions using standard protocols.Results Drought stress significantly reduced plant height, leaf length, and chlorophyll content at all growth stages, with the greatest reduction observed during grain filling. Under drought, chlorophyll a and b were markedly affected, particularly in the sensitive cultivar. Proline, membrane stability index, soluble sugars, and potassium levels increased by 23.34%, 2.67%, 18.24%, and 5.72% in CIMMYT PAK, and by 24.09%, 9.05%, 22.97%, and 6.77% in Haq Nawaz, respectively. Conversely, nitrogen and phosphorus contents decreased by 5.88% and 6.19% in CIMMYT PAK, and by 6.29% and 19.34% in Haq Nawaz, respectively.Conclusions The results demonstrate that drought stress negatively affects maize growth and metabolism, with more pronounced impacts on the sensitive cultivar. The higher accumulation of osmolytes (proline and soluble sugars) and better maintenance of K+ content in CIMMYT PAK indicate its superior adaptive mechanisms to drought-induced oxidative stress. These findings highlight the importance of screening drought-responsive morpho-physiological and biochemical traits to identify tolerant genotypes. The insights gained could support breeding programs aimed at enhancing drought tolerance in maize grown under water-limited environments.