Effects of a chemical plant growth regulator and planting density on the leaf senescence and yield of spring maize in northeast china

Abstract

The study aims to analyze the effects of chemical applications on the leaf senescence and yield of maize under different planting densities in Northeast China. Dongnong 253 (hybrid maize), was planted at four densities, i.e. 50,000, 60,000, 70,000, and 80,000 plants ha-1. The leaves were sprayed with the plant growth regulator ‘Yuhuangjin’ (the main components of which include aminoacyl esters and ethephon) during the jointing stage. The results showed that the highest maize yield, i.e. 13290.95 kg ha-1, was obtained when the plants were treated with ‘Yuhuangjin’ and 70,000 plants ha-1 . As the planting density increased in the water treatment, the height gradually increased, the dry weight of individuals decreased, and the barren stem proportion and lodging risk increased. In contrast, ‘Yuhuangjin’ reduced plant height, increased the dry weight of individual plants, and reduced both the barren stem proportion and the lodging risk. As planting density increased, the degree of reduction in leaf SPAD increased and the degree of leaf senescence increased in water. However, ‘Yuhuangjin’ increased leaf greenness and delayed senescence. During leaf senescence process, the activities of antioxidant enzymes (SOD, POD, CAT) decreased, the MDA content increased, and the soluble protein content decreased in the water treatment in response to increasing density. Compared to the water, ‘Yuhuangjin’ increased the activities of SOD, POD and CAT as well as the soluble protein content but reduced the MDA content. Under high planting densities, ‘Yuhuangjin’ have important values with respect to increasing maize yields and delaying leaf senescence during the late growth stage. This research provides a theoretical and experimental basis for maize production in Northeast China.