| At present,chemical regulation to increase planting density and lodging resistance cultivation techniques has become an indispensable main technical measure in the current high yield of maize.However,the adverse effects and yield reduction effects of it on the development of maize female ears have also attracted attention and continuous improvement,but there is still no consensus.In order to further clarify the regulatory mechanism of chemical regulation to increase planting density and lodging resistance cultivation techniques on maize yield formation,this study used Xianyu 335 as the experimental material at four density levels(6.0×104 plants/hm2,D1,7.5 X 104 plants/hm2,D2,9.0 X 104.plants/hm2,D3,10.5 × 104 plants/hm2,D4),with spraying clean water as the control(CK).It is proposed to explore the regulation mechanism of control and promotion combination regulation(HK)on summer maize ear development,grain formation and grain filling from the perspectives of ear development,canopy structure,source sink characteristics after anthesis,material accumulation and distribution,in order to clarify the hormone regulation mechanism of maize high yield and lodging resistance,and explore an effective way to further tap the yield potential of summer maize.The main research findings are as follows:1.The control and promotion combination chemical control treatment can significantly reduce the occurrence of empty stem rate and field lodging rate,increase the effective panicle number and thousand grain weight per unit area,and significantly reduce the number of grains per panicle;In the case of lodging,the application of chemical control technology is manifested as increasing production;Under the condition of lodging limitation,no increase in production will occur.In this study,in 2021,the yield of HK treatment was lower than CK at all densities,with a decrease of 9.8%to 14.9%;In 2022,under D1 and D3 densities,HK decreased by 4.2%and 3.8%compared to CK,while D2 and D4 increased by 3.8%and 1.2%.2.The control and promotion combination chemical control treatment has a significant inhibitory effect on the development of female ears in maize.Before and after flowering,the female panicles significantly decreased,and the IAA,sucrose content,and SS activity in the female panicles significantly decreased.The total number of differentiated flowers,fertilized flowers,and fertilization rate of small flowers significantly decreased,while the content of ABA and GA3 significantly increased.Correlation analysis showed that panicle size,total floret number,fertilized floret number and floret setting rate were significantly positively correlated with spike grain number;the size of female spikes is significantly positively correlated with sucrose content;the IAA content in female spikes is significantly positively correlated with sucrose content,total number of small flowers,and number of fertilized flowers,while the GA3 content is significantly negatively correlated with sucrose content and spike development indicators.This indicates that an increase in endogenous IAA content in female panicles help to increase sucrose content,promote the growth of female panicles and silks,increasing the number of fertilized flowers and fertilization rate,while GA3 has the opposite effect.3.The control and promotion combination chemical control treatment has a significant inhibitory effect on the individual development of summer maize,with a decrease in photosynthetic potential and dry matter accumulation per plant during the silking stage,but an increase in the proportion of stem and sheath dry weight,which is beneficial for cultivating robust plants.Compared with CK,the activities of SOD and POD in panicle leaves increased by 50.4%,34.5%;MDA was decreased by 22.8%,sucrose content and sucrose synthase activity increased by 4.6%and 17.8%,and the contents of amino acid,glutamine synthetase and soluble protein increased by 23.1%,52.4%and 17.26%,respectively.The activity of starch synthase in grains increased by 16.9%on average,and the content of polyamines increased by 19.3%.ZR,IAA,GA3 and ABA increased by 16.7%,33.0%,17.9%and 26.4%,respectively.The activity of carbon and nitrogen metabolism was strong,and the stem and sheath dry matter transport and contribution rate to grains were high,and the contents of soluble sugar,starch and sucrose in grains increased by 8.4%,39.6%and 8.7%,respectively.4.Path analysis shows that among the three factors contributing to yield,the number of effective ears has the greatest impact on yield,followed by the kernel numbers,and the weight of 1000 kernels is the smallest.Correlation analysis showed that dry matter accumulation,stem-sheath and leaf dry matter accumulation at silking stage were significantly positively correlated with kernel numbers per ear and 1000-kernel weight.Therefore,based on the above analysis,it can be concluded that increasing the kernel numbers per ear is the key to increasing yield in the chemical regulation to increase planting density and lodging resistance cultivation techniques.However,the stem and spike extend together;on the basis of controlling stem lodging resistance,flowering promotion and regulation should be carried out after the floret differentiation stage(V12)to promote the distribution of assimilation products to female panicles,increase the number of fertilized flowers and fertilization rate;at the same time,it promotes plant self-regulation,increases the length and height of internodes on the ear,shapes an efficient canopy,and maintains high physiological activity after flowering,forming a high-yield summer maize population with strong source and strong sink,laying a material foundation for improving the number and weight of grains per ear. |
PDF Full Text Request