Corn (Zea mays L.) Physiology and Yield Affected by Plant Growth Regulators Under Drought Stress

It is important to find methods, which may improve corn physiology, including nitrogen (N) metabolism, and yield production under drought stress. The use of plant growth regulators (PGR) is among the methods, which has been found effective on the alleviation of drought stress on corn physiology and yield. However, in this research, some new PGR, which has been rarely investigated and may improve plant nitrogen (N) under drought stress including (A) control, (B) 6-benzyl adenine (10,000 mg/L), (C) proline (2.5 ml/L), (D) glutamine (1 ml/L), (E) B + C, (F) B + D, (G) B + C + D, and (H) superoxide dismutase (2.5 ml/L) were proposed and examined on corn (genotype Single Cross 640) physiology and yield components under field conditions. The experiment was a split plot on the basis of a completely randomized block design with three replicates, and in addition to PGR (subplots) the main plots (drought stress) based on 70 (D1), 90 (D2) and 110 mm (D3) of evaporation from an evaporating pan were examined. Different corn physiology- and yield-related components including relative water (RW) and proline contents (Pro), weight of 100 grains (100GW), number of grains per corn (NGC), biological yield (BY), corn fresh yield (CFY), and grain yield (GY) were determined. According to the results, corn physiology and yield components were significantly affected by drought stress as Pro increased and RW and yield-related components decreased. However, interestingly the use of PGR (treatment G) significantly improved corn physiology and yield components by increasing RW (to a maximum of 63.81%), CFY (from a minimum of 80,542 kg/ha at control to a maximum of 100,263 kg/ha), and BY (from a minimum of 49,842 kg/ha at control to a maximum of 62,277 kg/ha). Although the effect of PGR was not statistically significant on GY, treatment G resulted in a 2500-kg increase compared with control. The interaction of drought stress and PGR significantly affected different corn physiology- and yield-related components except NGC and BY. The most effective PGR treatment on the alleviation of drought stress on corn physiology and yield production was treatment G containing 6-benzyl adenine, proline, and glutamine. It is possible to improve corn physiology and yield production under drought stress using the PGR tested in this research.