Growth and Physiological Responses of Maize to Water Stress.

Maize (Zea mays L.) is one of the most important crops grown for food, biofuel, feed, and fodder all over the world. Maize is more susceptible to water stress during early reproductive stages of development, which usually occur during a period of high air temperature and high risk of dry spells in Northern Wyoming. An experiment was conducted at the University of Wyoming Research and Extension Center, Powell, WY during the 2014 growing season. The objective of the study was to determine the effect of drought on growth and some physiological traits of maize. The hybrid ‘P8107HR’ was planted under four levels of water stress (T1:100ETc, T2:80ETc, T3:60ETc, and T4: no water from V9 to R3 growth stage) managed with an on-surface drip irrigation system. An infrared gas analyser (LI-6400XT; LI-COR Inc., Lincoln, NE, USA) was used to obtain photosynthesis (A), stomatal conductance (g_s), transpiration (E), and intrinsic water use efficiency (iWUE) from August 10 to August 28, when maize was at its maximum water requirements (V14 – R2). Above ground biomass, canopy height, leaf area index (LAI), specific leaf area (SLA), and water use efficiency (WUE) were determined at harvest. Total dry matter yield was greatly affected by water stress, resulting in 50% yield reduction compared to control (7961 vs. 15981 kg ha^-1). Canopy height and LAI decreased and SLA increased with water deficit. Our results showed that water-stressed maize during a period of high water requirements affected its ability to perform gas exchange (A, g_s, and E); the rates of A, g_s, and E were reduced, ultimately affecting aboveground biomass yield and WUE. Although not significant, differences on iWUE were observed.