Effects Of Population Density On Lodging-resistance Charactistic Of Stalk And Root In Maize

The planting of high density had been one of the key measures for improving yield of maize, while the increasing of population density increased the risk of lodging. The average precipitation each year was654.3mm and centralized in July and August, which was the key stage during tasseling to filling stage. Under the effects of high temperature and rainy, lodging had become one of the most important reason of reducing yield of maize. In the past, there were some studies about lodging of maize, while the systematic study about the effects of population density on stalk and root was infrequent. In this study, the effects of different population density on the morphology, dry matter and physiological characteristics of stalk and root were studied, and the relationship between lodging percentage and all indexes was determined to reveal the mechanism of lodging of maize, and provide theoretical foundation for breeding and cultivate of lodging-resistance.In this paper, four different varieties were used as the test material and seven density treatment levels were applied, and the random block design was used. The morphology, dry matter and physiological characteristics of stalk and root were measured, and the relationship between lodging percentage and all indexes was determined. In2012,11leading varieties of Jilin province were used. And the effects of Blavin typhoon on lodging and yield of maize were studied from the point of morphology and physiology.1、The results of stalk agronomic traits showed that:The ear height and ear height coefficient were increased with the increasing of density, and that of zhengdan958were not sensitive to the changes of density. Lodging percentage of xianyu335and xianyu420showed positive significantly correlation with ear height and ear height coefficient, while that of yifeng29and zhengdan958had not correlation significantly. The circumference of internode was decreased with the increasing of density, while the length of internode had not regular changes. Dry matter percentage and strength of stalk were increased first and then decreased with the increase of population density. The lodging percentage showed significantly correlated with the length, circumference, dry weight and strength of internode. Except plant height, other indexes of yifeng29and zhengdan958were higher than those of xianyu335and xianyu420. The stalk strength was positively correlated with K, Si and starch content, and was not positively correlated with Zn and soluble sugar content.2、The results of ligin and its key synthetase showed that:under different density, the content of ligin and cellulose, the activities of phenylalanine ammonia-lyase(PAL), tyrosine ammonia-lyase(TAL) and cinnamyl alcohol dehydrogenase(CAD) of yifent29were higher than those of xianyu420. The order of PAL and TAL activities was3th>4th>5th internode. The order of CAD activities in xianyu420was4th>3th>5th internode, while that of yifeng29was3th>4th>5th internode. The ligin content of xianyu420had a positive significantly correlation with CAD activity, while the ligin content of yifeng29had a positive significantly correlation with PAL and TAL activities. At tasseling and filling stage, the stalk strength of Yifeng29had a positive significantly correlation with ligin content, activity of PAL and TAL yet that of Xianyu420had only significant and positive correlation with TAL activity.3、The results of chemical components and mineral elements showed that:mineral elements including nitrogen(N),potassium(K),silicon(Si),calcium(Ca),magnesium(Mg) and zinc(Zn) were increased first and then decreased with the increase of population density. The peak occurred under the treatment of seven and eight thousand plants per hectare, which was different with variety and growth stage. The contents of N, K, Si, Ca, Mg and Zn of yifeng29were higher that those of xianyu420. The stalk strength was positively correlated with K, Si and starch content, and was not positively correlated with Zn and soluble sugar content.4、The results of root characterstics showed:The numbers of brace root and total root were increased first and then decreased with the increase of population density, which were the highest under the treatment of70,000/ha. The root dry weight of xianyu420was increase first then reduced,while those of yifeng29, xianyu335,xianyu420were decreased first. then increased, and then decreased, and the trough and peak occurred under the treatment of60,000/ha and70,000/ha. The activity of root was decreased under the treatment of80,000/ha, and the decreased degree reached the highest. At the tasseling stage of maize, SOD, POD and CAT activity of root had maximum value under the treatment of70,000/ha. At the filling stage, SOD and POD activities of Xianyu335presented the "M" shaped curve with the increase of density, while presented single-peak curve. The indicators of zhengdan958and xianyu335were higher than those of yifeng29and xianyu420. The malondialdehyde content is the opposite. The lodging percentage showed negative significantly correlation with the number of brace root and total root, dry matter percentage and root activity.5、Effects of the Blavin typhoon on lodging and yield of maize showed that:in the11test varieties, the ability of lodging-resistance, ear high coefficient, average diameter, dry weight of internode, soluble sugar content, ligin content, Si content and stalk strength were highest in liangyu99varieties. And the number of brace root, root dry weight and dry matter were all higher in liangyu99. The lodging-resistance of yihe32and yihe33were the poorest. Although liangyu99had strong ability of lodging-resistance, its yield was lower than zhengdan958and xianyu335. In2012, the yield of zhengdan958was decreased5.13percent compared to the average yield in2009-2011, which had strong yield stability.In summary, there were some effects of population density on the morphology, dry matter and physiological characteristics of stalk and root. In limited resources, too high or too low density was all bad to the growth of corn, which may product the density effect. Lodging of maize was the results of comprehensive effects including variety, cultivation technique, soil and climate. Thus, we have to consider all effects, and have rational close planting and fertilizer, and dress the trace elements to reduce the risk of lodging. There was not all positive correlation between the ability of lodging-resistance and yield. It was a challenge to breed the maize variety which had strong lodging-resistance and high yield, and play high-yield potential through the measure of cultivation technique. The study provided scientific foundation for lodging mechanism of maize.