The Effect of Paclobutrazol on some morphologic and physiologic characteristics of forage corn under drought tension

The present research was carried out as factorial experiment based on randomized complete blocks design with three replications on forage corn hybrid ZP600 in Mashhad in 2017. The experimental factors included Paclobutrazol with concentrations zero, 10, 20 and 30 milligram per liter and drought tension levels including irrigation after 50 millimeters (without tension), 70 millimeters (mild tension), 100 millimeters (moderate tension) and 150 millimeters (severe tension) evaporation from evaporation pan class A. Foliar application of Paclobutrazol was applied in two steps (at 6-8 leaf stage and was repeated 2 weeks later). The results showed that plant height, leaf number, leaf area index, leaf dry weight and fresh forage yield decreased by drought tension and proline content of leaf and insoluble fiber in neutral detergent increased significantly, but protein percentage and protein yield did not change significantly. Application of Paclobutrazol in medium and severe tension increased plant height, leaf area index, leaf dry weight and fresh forage yield, and decreased proline and insoluble fiber content in neutral detergent. Paclobutrazol also increased protein yield under tension and non –tension conditions. The highest fresh forage yield (103 tons per hectare) was obtained in 20 milligram per liter Paclobutrazole treatment under severe tension conditions and the lowest fresh forage yield (72 tons per hectare) in non-application of Paclobutrazol in severe tension. Application of Paclobutrazol at a concentration of 20 milligram per liter in moderate and severe tension could reduce the effect of drought tension by 24 and 43 percent, respectively.