The Photosynthetic Mechanism Of Intercropped Peanut Adaptation To Weak Light In Maize And Peanut Intercropping System

In the late stage of maize intercropping peanut, intercropping changed the field microclimate. Maize intercropping peanut improved the use efficiency of strong light by maize and that of weak light by peanut. It suggested that intercropping enhancing peanut using weak light ability was due to increase the ability of light trapping and transformation, but the mechanism of peanut adapt to weak light is not clear. So the study was conducted in 2014 year at Henan University of Science and Technology Farm. This test were divided into the sowing date and proportion two parts, respectively from duration and degree of shading two aspects to elucidate the photosynthetic adaptation mechanism of intercropping peanut. In this paper we study the characteristic of peanut function leaf absorption and use of weak light, and the change process of CO2 carboxylation ability, dry matter accumulation and distribution rules, clear the mechanism of intercropping peanut adapt to weak light, provide theoretical basis for the realization of the high production and efficiency. The results showed that:Maize intercropping peanut reduced the light intensity in the canopy of the peanut and the soil temperature. When shade time reached to 38d、23d、8d, compared with the single cropped peanut,the light intensity of IP-1、IP-2 and IP-3 decreased by 36.7%、27.1% and 1.6%, the light intensity of 2:2、 2:4 and 2:8 decreased by 38.1%,14.3% and 14.7%, the soil temperature respectively decreased by 1.9%-3.1%, It suggested that with the increasing of shade days and shade degree, the community microclimate of field was obviously influenced.Intercropping reduced the dry matter accumulation and leaf area index. Compared with the single cropped peanut, they were respectively increased by 2.4%-33% and 16%-49.3%, with the increasing of shading days and shading degree, the effect of dry matter accumulation of peanut was increased. The LER values of different intercropping systems were greater than 1, intercropping advantage reach to 610.1-2428.9 kg·hm-2, intercropping advantage mainly comes from corn.Compared with the single cropped peanut, intercropping significantly increased the relative content of peanut leaf chlorophyll, and the intercropping system increased by 16.5%-52.95%, the differences have reached the significant level. With the increasing of shading days and shading degree, chlorophyll content increased more. This is because the peanut adapt to weak light environment, the content of concentrate pigment protein was increased, so that the function leaves of peanut absorbed more light energy in low light conditions for photosynthesis.Intercropping clearly decreased the light compensation point, light saturation point, CO2 saturation point and compensation point. Intercropping significantly increased the apparent quantum efficiency of peanut leaves, and it increased by 7.1%-35.7%, along with the increasing of shading time, the apparent quantum efficiency of intercropping increased more. Intercropping reduced the carboxylation efficiency of peanut, they were decreased by 6.4%-46.7%, the differences have reached the significant level. The result shows that with the increasing of shading time and degree, intercropping improved the peanut using weak light ability but reduced the peanut using high CO2 ability.With the coexistence of time increasing, the fluorescence yield of K increased slowly, intercropping enhanced the peanut using weak light ability. Intercropping increased the relative variable fluorescence of peanut OJIP phase, and with the shading days and shading degree increased more. As the growth of time, intercropping increased the number of RC/CS, ABS/CS, and TR0/CS. Intercropping increased the maximum photochemical efficiency of peanut leaf, but reduced the thermal dissipation and the degree of close center. It suggested that in the late stage of maize intercropping peanut, intercropping enhancing peanut using weak light ability was due to increase the ability of light trapping and transformation.