| Heilongjiang province has the feature of fertile soil and high level of mechanization, but the maize planting density was lower, so there was a greater potential to be tapped on the planting density and yield. The present study was aimed to coordination the conflicts among the high density to increase yield, the lodging, the degradation of photosynthetic performance, leaf senescence, etc., to explore the feasibility of the collaboration between high density and c hemical regulation to increase the yield and the variation of each index. This study was conducted in three aspects of the photosynthetic performance, the degree of aging of functional leaves and the lodging properties of maize group. ‘Dongnong 253’ was used as material in this experiment and was planted under the densities of 50000 plants/ha, 60000 plants/ha, 70000 plants/ha and 80000 plants/ha, and sprayed with the chemical regulator of “Yuhuangjin”(DA-6 and Ethephon as the main material) at the jointing stage. The experiment is carried out from the aspects of photosynthetic characteristics of leaf senescence, lodging resistance, light etc, results show:(1) During leaf senescence, with the increase of planting density, the activity of antioxidase(SOD,POD,CAT) were declined,the content of MDA was decreased and the content of soluble sugar was increased under the treatment of water. Compared with water treatment Yuhuangjin increased the activity of antioxidant enzyme(SOD, POD, CAT) and the content of s oluble sugar and decreased the content of MDA.The result of the correlation analysis and path analysis on effect of the factors to leaf senescence showed that, under the treatment of water, MDA> Soluble protein >CAT>SOD>POD, under the treatment of ‘Yuhuangjin’, MDA>Soluble protein>SOD>POD>CAT. The results show that under the water treatment with the increase of planting density,the population LAI increased, SPAD,Pn,Fv/Fm,Y(Ⅱ),qP value reduced, and Y(NO), qN increased; under the treatment of Yuhuangjin, the LAI was reduced, SPAD was increased, net photosynthetic rate( Pn) was increased, chlorophyll fluorescence parameters of Fv/Fm, Y(Ⅱ) were increased q P, and Y(NO), qN was reduced.(2) With the increase of the planting density of maize, the plant height, ear height and internode length was increased, the tensile strength decreases gradually under the treatment with water. Yuhuangjin treatment could shorten the internode, lower the ear position, increase dry weight of internodes, enhance the lodging resistance of plants. Yuhuangjin could increase the diameter of internode, internode length, this facilitates the transportation of nutrients and moisture to the ground and the formation of production.(3) Under this experimental conditions, the yield increased firstly and then decreased with the increase of planting density, and it up to the highest yield of 13290.95kg/ha at the planting density of 70000/ha under the treatment with Yuhuangjin.Research shows: The collaboration of high density and chemical regulation to increase yield was feasible in Heilongjiang Province. With the increase of the density the plant height, internode length was increased, stem diameter was decreased, indicators that were closely related to lodging would appear corresponding change. The research showed there were mutual restraint and mutual compensation effects among factors associated with aging. Yuhuangjing could delay leaf senescence by regulating the relationship between the factors, the content and activity of various factors associated with leaf senescence. The density and chemical regulation agent could regulate maize photosynthetic characteristics, the effect of the increase in planting dens ity on maize yield could be achieved through a variety of ways. With the increase of planting density, the aging process of leaf function was accelerated, and the application of Yuhuangjing can delay leaf senescence. |
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