Effect Of Plant Density On Photosynthetic Senescence Physiology And Yield Of Spring Corn

Corn is one of China's three major grain crops, and the most important food crops by owners.It occupied a very important position in national economy and people's living. Heilongjiang province is located in the northest of China's corn belt, and it is China's biggest place of maize production , but the yield level is low, research shows that rational close planting is one of the key technologies to increase of yield. With three different type of spring corn as research object, the experiment study the relationship between plant density and photosynthesis, senescence physiology and the spring corn yield provides theoretical basis of Heilongjiang province increase maize yield by reasonable density.The experiment was carried on the farm of Northeast Agricultural University in 2008, there are three high yielding varieties: XY 335 (compact), JND 302 (half of compact), JY4 (flat type). There are five densities as flow: 45 000 plants/hm2 (B1), 52 500 plants/hm2 (B2), 60 000 plants/hm2 (B3), 67 500 plants/hm2 (B4), 75 000 plants/hm2 (B5), and they are repeated three times. Random blocks design was used in the experiment. Three varieties spring corn's photosynthesis indexes, senescence physiology and yield were researched under the condition of different density, the results were showed that:The changes of the LAI about three varieties of spring corns are curved shape as growth process, and reach the peak at the silk. With the increasing of density, the functional leaf photosynthetic rate, chlorophyll content, Fv/Fm, Fv/Fo decreases and LAI, Fo increases in their growth period , but after silking stage LAI declines apparently with the increasing of density. Compact type can still maintain higher photosynthetic rate in high-density conditions.The later of growth stage of three varieties spring corn, content of soluble protein of function leaf is decrease, and MDA is increase. Activity of SOD reach the peak in silking stage, and gradually declined after peak, rebounded slightly in milking. POD activity of functional leaf shows rising trend after tasseling stage, and reach the peak in silking stage, the lowest point in dough stage.With the density increase, content of soluble protein declined, of MDA increased and activity of SOD,POD increased before the lower. Compact varieties' advantage of anti-aging in high density is the most obvious. Under duress, flat type variety show the worst ability of anti-aging and the half compact type is batter than that.With the density increase, the plant height, ear position, barren ear tips length of three varieties spring corn be on the rise, but stem thick, ear length, ear thick be on general declines. There was a positive correlation between density treatment and plant height, ear position, barren ear tips length .There was a negative correlation between density treatment and stem thick, ear length, ear thick, and negatively influence to ear length is greater than to ear thick .With the density increase, effective ear of unit area fall after raise, Kernel number per ear to decline, 100-grain weight changes for varieties. With the increase of plant density, yield is not unlimited increase. When plant density higher than suitable density, group yield began to decline. The most suitable plant density of spring corn of different type in Harbin area is that compact type is 75, 000 plant/hm2, half compact is 60 000~67 500 plant/hm2 , flat type is 45 000 plant/hm2.There was a positive correlation between the yield of compact type corn and LAI, Fo. At the same time, there was a negative correlation between the yield of compact type corn and Pn, Fv/Fm , Fv/Fo. The correlationship of photosynthesis characters with yield of half compact type and flat type was opposite with compact type, and the level of flat type was higher than half compact type.There was a positive correlation between the yield of compact type corn and MDA content. At the same time, there was a negative correlation between the yield of compact type corn and the contents of soluble protein, SOD activity, POD activity. The correlationship of senescence physiology with yield of half compact type and flat type was opposite with compact type, and the level of flat type was higher than half compact type.