Physiological Foundation Of Root Interaction On Yield Of Corn

Roots of different species can interact by many mechanisms. Root can also have the ability to discriminate each other. The growth rate will descend when root contact even they come from plants of same species. There is a drastic root interference in field crops as a result of big plant density, yet the interactions of root from same variety is less studied. In order to explore the physiology mechanism of root interaction of same variety, we study the dynamics of biomass accumulation, root physiology activity and photosynthetic function of leaf. The effect of root interaction to the yield was evaluated. The main results as follows:1 The root distribution and competition ability difference of the two hybridsThere is a difference of root distribution and competition ability between the two hybrids when nitrogen was applied or not. In the treatments of nitrogen application, the two hybrids had a distinct biomass accumulation, but a similar Root/shoot ratio. The hybrid Denghai 3719 had a more distribution of shallow root that exhibited superiority in competition with Jinhai 5, plant under competition increased the nitrogen accumulation by 6% as well as biomass accumulation by 8% than treatment with same plants. Under the deficiency of nitrogen, Denghai 3719 took an increase of 4% in Root/shoot ratio compared to the one with nitrogen application, while Jinhai 5 showed a 21% increase in Root/shoot ratio. As a result of smaller Root/shoot ratio, less shallow root proportion and lower root vigor, the nitrogen and biomass accumulation of Denghai3719 decreased in mixture condition. This result indicated that the high-yielding hybrid Denghai 3719 had a disadvantageous adaptability to the nitrogen deficient environment, but it was more adapted to rich soil.2 The effects of root interaction on biomass and nitrogen accumulationThe effects of root interaction on aboveground biomass and nitrogen accumulation are different according to nitrogen application. In the nitrogen application treatments, the biomass accumulation rate had a fast descend in treatments with root interaction at the lagphase of grain filling, as a result a lower yield both in biomass and grain. Denghai 3719 had drop of 8.9% in biomass and 5.8% in grain yield, while Jinhai 5 is 6.6% and 6.3%, respectively. In the treatments with no nitrogen application, Root interactions make no difference on yield of biomass and grain.The effects of root interaction on nitrogen accumulation were similar to that of biomass. When nitrogen was applied, the treatments of root interaction had a distinct descend in accumulation of biomass and grain. While Denghai 3719 had a drop of 7%, Jinhai 5 was 5.8%. In treatments with no nitrogen application, there was no distinct difference in nitrogen accumulation between treatments with root interaction or not.3 The physiology response of plant to root interaction in nitrogen applicationThere is a unanimous response to root interaction in the two hybrids. Compared to compare, root interaction made no difference in leaf area in the two hybrids, but a lower content of chlorophyll carotenoid in ear leaves at lagphase of grain filling. The Net Photosynthetic rate and Stomatal Conductance were smaller in treatments with root interaction, while Intercellular CO2 Concentration was much higher. The activity of phosphoenolpyruvate carboxylase rubulose-1, 5-bisphosphate carboxylase that coherent to leaf function and the soluble protein content were lower in treatments with root interaction.The effects of root interaction on root biomass and R/S ratio and root vigor demonstrated difference at prophase of grain filling. Treatments with root interaction were lower in root biomass, R/S ratio and root vigor.4 The physiological effect of nitrogen deficiency on plantIn the treatments of nitrogen was not applied, the effect of root interaction on leaf and root was not significant, the parameters that represent the physiology effect of leaf and root were similar, the differences of root biomass and R/S ratio could be neglect. Compared to treatments with nitrogen application, the treatments without nitrogen application had a shrink of biomass active accumulation period, the content of chlorophyll and carotenoid in ear leaves were lower, the parameters of leaf photosynthesis were smaller especially at lagphase of grain filling, at same time, the activity of phosphoenolpyruvate carboxylase rubulose-1, 5-bisphosphate carboxylase were lower. With regard to root, the treatment without nitrogen application had bigger root biomass when pollinated, however, with time went on it had a straight decline. The root vigor in treatment of nitrogen application was significant lower than treatments with nitrogen application, especially at lagphase of grain filling.5 The effect of root interaction on yield with plant distance decreaseNo matter nitrogen was applied or not, the plant in close-sharing treatment had a lower carbohydrate accumulation in stalk, leaves, bracteal leaves, spike stalk and grain, and with time went on, less biomass were accumulated. When harvest, the biomass accumulation in close-sharing treatment was 11.9% lower than that of owner, and was 7.5% lower than sharing treatment. While the grain yield was 6.5% and 6.3% lower. When nitrogen was not applied, there was a lower accumulation in biomass by 11.8% and 9.5% compared to owner and sharing treatment respectively, While the drop in grain yield was 6.1% and 6.3%.The nitrogen accumulation in close-sharing treatment was lower than owner and sharing treatment. When nitrogen was applied, the nitrogen accumulation in close-sharing treatment was 16.1% lower than in owner and was 12.7% lower than sharing treatment. When nitrogen was not applied, the drop was 20.8% and 21.9% respectively. Compared to owner and sharing treatment, the Transportation efficiency, Contribution rate and N harvest index were much higher in close-sharing treatment.6 The effect of root interaction on root physiology and nitrogen absorption with plant distance decreaseCompared to owner and sharing treatments, the root biomass in close-sharing treatment was lower in each root layer. However, the shrink of biomass in 0-20cm layer was more than that of deep root layer. With regard to root vigor, plants in close-sharing treatment demonstrated lower vigor in each root layer than in owner and sharing treatment.Nitrogen absorbed after pollination took up about 60% of the whole absorption in plant. Nitrogen content in stalk was lower in harvest than flowering, and nitrogen translocation was more than 20%. Compared to owner and sharing treatment, the translocation rate was bigger in close-sharing treatment. When nitrogen was applied, nitrogen accumulation in root of owner and sharing increased when harvest than flowering, while plants in close-sharing treatment had a decrease. When nitrogen was not applied, all the treatments decreased in nitrogen accumulation in root. However plants in close-sharing treatment had a bigger translocation rate.