Regulation Mechanism of Planting Density and Spraying Ethephon on Lignin Metabolism and Lodging Resistance of Summer Maize

The purpose of this study was to investigate the regulation mechanism of planting density and spraying ethephon on lignin metabolism and lodging resistance characteristics and to explore the mechanism of planting density and ethephon application on lodging resistance characteristics of summer maize.

In this study, the summer maize hybrid, Xundan20, was grown by spraying water or ethephon at the seven-expanded-leaf stage under three different plant densities (60 000 plants/hm², low density, L; 75 000 plants/hm², medium density, M; 90 000 plants/hm², high density, H) in order to explore the effects of density and ethephon on plant morphology, the third internode microstructure, lignin metabolism and yield, etc.

Compared with LCK at milking stage, the internode length of the third stem under HCK increased by 19.75%. The stem diameter, stalk rind penetration strength, small vascular bundle number, small vascular bundle area and cortex thickness under HCK were 8.00%, 43.46%, 20.41%, 26.92% and 22.05% lower than those under LCK, respectively. The lignin accumulation and enzyme activity of PAL, 4-CL, CAD and POD under HCK were 24.04%, 33.81%、10.92%, 49.06% and 20.78% lower than those under LCK, respectively. Compared with HCK at milking stage, the internode length of the third stem under HE decreased by 34.84%. The stem diameter, stalk rind penetration strength, small vascular bundle number, small vascular bundle area and cortex thickness of HE were 14.22%, 66.10%, 22.71%, 22.11% and 35.96% higher than those under HCK, respectively. The lignin accumulation and enzyme activity of PAL, 4-CL, CAD and POD of HE were 28.28%, 30.74%, 13.01%, 59.26% and 16.99% higher than those under HCK, respectively.

Lodging resistance of summer maize decreased with the increasing of planting density. After the application of ethephon, the stem strength and lignin metabolism of summer maize were enhanced, the lodging resistance was enhanced, and finally maize yield was increased. The effect of spraying ethephon on the lignin metabolism and lodging resistance of XD 20 was the most significant when the planting density was 90 000 plants/hm², and yield was the highest.