The Effect Of Bidirectional Chemical Control On Growth And Development Of High Yield Summer Maize (Zea Mays L.)

The construction of high-yield population is one of the important parts in research for high-yield maize.At the present,one of the major approaches to increase maize yield in China is to increase the planting density.With the increasing of plant density however,the risk of maize lodging increases which seriously restricts the stability of maize yield.The traditional chemical control aimed for lodging resistance also inhibited on the era development and grain yield to some extent.Therefore,exploring new chemical control methods with high and stable yield has become a key issue for the high-yield summer maize chemical control technique,while improving the lodging resistance capacity.In this paper,two major hybrid varieties of maize were used as materials to study the effect of bidirectional chemical control of “inhibition-promotion” on the growth and development of high-yielding summer maize in order to seeking for new approaches for chemical control methods in maize production.The results showed that:1.Bidirectional chemical control had certain influence on the morphological characteristics of summer maize plants,which decreased plant height,ear height,ear position coefficient and height of gravity at each density significantly,thus reduced lodging rate of summer maize plants,especially stem bending and root lodging under high population conditions.Bidirectional chemical control had a significant impact on root development of summer maize plants,which effectively promoted roots development of summer maize with increased root width,root numbers,especially the root numbers arised from the base 1 to 3 stem nods.Bidirectional chemical control significantly increased the root bleeding of the summer maize plants during the V12 and silking stages,which enhanced the root activity.Bidirectional chemical control had obvious regulation effects on the growth of internods of maize plants.It inhibited the elongation of the internodes in the early stage and promoted the elongation of the middle and upper internodes in the late stage.While significantly shortening the total length of the internodes below the ear position,the total internodes length above the ear position was significantly increased,which was beneficial to improving the resistance to lodging and the photosynthesis of the middle and upper leaves.2.Bidirectional chemical control significantly increased leaf area index(LAI)of summer maize population and effectively improved the late leaf area senescence caused by high plant density conditions,which could provide more powerful guarantee for photosynthesis of summer maize plants.The chlorophyll content of the ear-position leaf was increased in each measured developing period which slowed the senescence of the ear-position leaf.3.Bidirectional chemical control had a great influence on the accumulation of dry matter before silking,but the effect gradually disappeared after silking,which indicated that bidirectional chemical control had certain degree of compensation for the dry matter accumulation after silking and such compensation effect was obvious under high plant density conditions.Bidirectional chemical control increased the proportion of assimilation products partitioned in the leaves and stems,and reduced the proportion of partitioning in the grains at the same time.Although the bidirectional chemical control increased the fertilization rate and seed-setting rate of flore,and reduced the kernel abortion rate,the total number of inflorates,number of fertilized inflorates and the effective grain numbers were significantly reduced.The tgreater the plant density,the more obvious the effect was.4.Bidirectional chemical control and high plant density reduced the dry matter accumulation during grain filling period,but the reduction effect was not significant.In addition,bidirectional chemical control increased the calculated-maximum potential of grain weight for the two varieties significantly.Bidirectional chemical control significantly increased the content of nitrogen and potassium in the summer maize plant after 45 days of silking,but had little effect on the content of phosphorus.5.Under the bidirectional control treatment the summer maize population did not show an increased grain yield in the normal year.The grain yield significant increased in the year when windstorms occurred and caused lodging by windy weather.