Effect Of Sowing Density On Physiological Mechanism Of Spring Maize And Chemical Regulation

The experiment was conducted at the Gongzhuling experimental station of Chinese Academy of Agricultural Sciences in 2014-2015. The different genotypes of maize Zhongdan909(ZD) and Jidan35(JD) were taken as material, and we set density and chemical regulation as treatment. The sowing density treatment was set to 4.5, 7.5 and 10.5×104 plants hm-2 three population densities, chemical regulation treatment was that, in 2014 T1 was for application of Paclobutrazol(PP333) 0.68×10-3mol/L at six leaf stage and 1.36×10-3mol/L at nine leaf stage, T2 was for application of Gibberellin(GA3) 0.68×10-3mol/L at six leaf stage and 1.36×10-3mol/L at nine leaf stage, and control(CK) spraying water of the same volume. In 2015, T1 was for application of Ethylene-Chlormequat-Potassium(ECK) 2ml/L at six leaf stage and Gibberellin-Kinetin(GB) 2ml/L at nine leaf stage, T2 was for application of ECK at six leaf stage and PASP-KT-NAA(PKN) 2ml/L at nine leaf stage, T3 was for application of PP333 1.36×10-3mol/L at six leaf stage and 2.72×10-3mol/L at nine leaf stage, T4 was for application of GA3 1.36×10-3mol/L at six leaf stage and 2.72×10-3mol/L at nine leaf stage, and CK spraying water of the same volume. In morphology, enzyme and hormone levels, we have studied the development of two cultivars in different population density plants female ear dynamic growth and development, carbon and nitrogen metabolism in leaves of key enzyme activity, grain filling process and dynamic changes of endogenous hormones and other indicators, to explore the mechanism of the effect of sowing density on physiological mechanism of spring maize; on this basis, we have studied the effect of different plant grothtw regulators on this mechanism. The results were as follows:1. With the increasing of planting density, maize ear long, grain weight and other yield components showed a decreasing trend, bald tip length was increased, and the density has little effect on the number of rows per ear, population yield was first increased and then decreased trend. GA3 and PP333 are not conducive to the formation of medium and high density population,and high concentration of GA3 and PP333 is not conducive to improve the yieldd. ECK+GB and ECK+PKN has a great influence on 1000-grain weight. ECK+GB treatment has little effect on yield, and ECK+PKN treament significantly increase the yield of medium density population, and has little influence on low density and hight density population. 2. Planting density significantly affected female ear growth. The higher the density of female ear growth speed is slow, the female ear differentiation process is delayed and silking period is delayed for 1-3 days. Before the maletetrad stage, density gradient has no effects on female ear length.After the maletetradstage, density significantly affect female ear length, as the density increase, female ear length shortening. The ear growth rate, ear length and grain filling rate were different in different plant growth regulators and their treatments. ECK+PKN and ECK+GB improves the ear elongation rate and increase the length of female ear, but have no significant effect on the female ear differentiation process. 3. With the increasing of sowing density, the leaf NR, GS and GPT activity decreased. GOT activity has little effect of density. The activity of NR decreased with the increase of leaf ages. GS activity showed a single peak curve, and the GS activity reach peak at 30 d after anthesis. GOT activity changes little in 10-50 d after anthesis. Chemical regulations of ECK+PKN and ECK+GB improve NR and GS activity of ear leaf in low and medium density population. ECK+GB and ECK+PKN enhanced the activity of key enzymes of nitrogen metabolism of leaf and ear of two cultivars of low and medium density groups, and promoted nitrogen uptake and assimilation. 4. With the increasing of plant density, key enzymes of carbon metabolism of SPS and SS activity of ear leaf decreased. ECK+GB and ECK+PKN improve the capacity of sucrose synthetic of ear leaf of two varieties of low and medium density population, especially to improve the ability of sucrose synthesis and sucrose transport of ear leaf in the later stage.They also increase sucrose cleaving enzyme activity, sucrose, improve the utilization ability of sucrose in grain during late grain filling period. 5. With the increasing of the density, maximum grain filling rate(Gmax), grain filling rate of maximum weight(Wmax) and reached maximum grain filling rate of time(Tmax) decreased, active grain filling period(P) and duration of linear stage reduced, and initial time of linear stage is not affected. Grain filling rate showed a single peak curve, and the time of reached Gmax is basically the same. ECK+GB and ECK+PKN improve Wmax and Gmax, PP333 and GA3 with high concentration decreased Wmax. Effect of chemical control treatment on the grain filling characteristics of different density groups during the grain filling period is different. ECK+GB and ECK+PKN greatly increase the Gmax on medium density population, and increased the grain size, increased the dehydration rate of 50 d to the mature stage, and promoted the grain maturity.They also improve the grain volume, accelerate the rate of dehydration in the late, promoting the grain maturity. 6. Increasing planting density changed the endogenous hormone levels in different developmental stages, and ECK+GB and ECK+PKN coordinate endogenous hormone balance.With the increasing of density, the content of GA3 reduced, and IAA, ZR, ABA increased. The ear length and IAA, ZR, ABA content are extremely significant negative correlation, and GA3 content was very significantly positive correlation. Chemical control treatment has different effect on endogenous hormone content in different periods. ECK+GB decreased the IAA content in the early stage of female ear growth, increased the content of late stage.It increased the content of ZR and GA3 in the late stage(57-63 d after emergence) of low and high density group, but ABA content increased mainly in 51-57 d after emergence. ECK+PKN treatment decreased the IAA, GA3 and ZR content in the early stage(39-51 d after emergence), and increased the content of GA3, IAA and ZR in the late stage(57-63 d after emergence), and the effect on the ABA content is different between cultivars and densities. 7. Different types of endogenous hormones regulate the different processes of grain development. With the increasing of grain weight, the contents of IAA, ZR and ABA decreased in 10-50 d after anthesis, but GA3 content and grain weight are positively correlated. The instantaneous filling rate and GA3 content are significantly positive correlation, but ZR and ABA were highly significant negative correlation with instantaneous filling rate. The effects of ECK+GB and ECK+PKN on endogenous hormones are different, but they all increase ABA content in the late filling stage.