Influence Of Light Intensity On Photosynthetic Characteristics, Yield And Quality Of Peanut And Its Growth Model

The research was carried out at agronomy experimental station of Shandong agricultural university in 2007 and 2008. Shading experiments were designed according to low light intensity problem caused by intercropping system of peanut with maize or wheat et al. Fenghua1 and Fenghua2 were adopted in the experiment of four light intensity levels (CK in which the plants were grown under natural light, 27% shading, 43% shading and 77% shading), which carried out at three growth stage using black sunshade net. And the three stages were seedling phase, pod-setting phase and pod-maturing phase. The aim of this study was to investigate the effects of low light on the photosynthetic characteristics, luminous energy distribute of PSⅡ, RuBPCase activitiy, plant morphogenesis, dry matter production, pod yield and quality of peanut at different stages, defined the relationship between dry matter accumulation and PAR, relationship of efficiency for solar energy utilization and PAR, and then set up the dry matter production and yield formation model on the basis of the experimental data. The main results were as follows.1 Effect of light intensity on photosynthetic and fluorescence characteristics of peanut leavesShading treatment at seedling phase could increase content of chlorophyll(a+b) (Chl(a+b)), enhance the actual photochemical efficiency of PSⅡ(ФPSⅡ) and optimal photochemical efficiency of PSⅡin the dark(Fv/Fm) significantly along with the weakening of treatment light intensity. While could depress the ratio of chlorophyll a to chlorophyll b (Chla/b) and photosynthetic rate (Pn). When the treatment ended, Pn, stomatal conductance (Gs) decreased and intercellular CO2 concentration (Ci) increased with the weakening of treatment light intensity when measured under high light intensity (1200μmol·m-2·s-1). And Pn raised, Gs and Ci reduced when measured under low light intensity (276μmol·m-2·s-1). The ratio of Pn measured in low light to high light had significant positive-correlation with treatment light intensity. When the shading treatment ended and recovered to natural light, Pn,ФPSⅡand Fv/Fm were immediately decreased and then ascended gradually after 3-5 days. The recovery extent and shading degree were negative correlation. After recovery of 15 days, Pn,ФPSⅡand Fv/Fm of 27% shading treatment could recover to the CK level. Content of Chl(a+b), Pn andФPSⅡof Fenghua1 were higher than those of Fenghua2 at the same treatment. So the ability of using low light was improved and the ability of using high light was decreased. The shading treatment at pod-setting phase had similar rule. Pn of shading treatments at pod-maturing phase had similar variation law with seedling treatment when measured under treatment light intensity and low light intensity (276μmol·m-2·s-1), while had opposite law when measured under high light intensity (1200μmol·m-2·s-1). So shading treatment depressed the photosynthetic capacity of peanut leaves, improved the ability of using low light, and decreased the ability of using high light. Peanut has adaptability to weak light, and peanut under light shading treatment resume growing in a period when growth in natural light.2 Effect of light intensity on diurnal variation of photosynthesis and photosynthetic curve parameter of peanut leavesThe diurnal variation of net photosynthetic rate was a single peak curve. Shading treatment has no effect on the tendency of change, but depressed the peak of the curve and increased Pn in weak light in the afternoon. In seedling shading treatment, light compensation point and light saturation point of peanut which cultured under treatment light intensity conditions were lower than that cultured under natural light, while the apparent quantum yield were higher. The weaker the light intensity was, the larger amplitudes were. Compared with peanut cultured under nature light, light saturation point of peanut of 27% shading had not significant difference, while the light saturation point of peanut of 43% shading and 77% shading percentage fell by 14%, 29% respectively and were remarkable difference. The light compensation point of nature light, 27% shading, 43% shading and 77% shading were respectively 52.7, 45.9, 21.3, 9.6μmol·m-2·s-1, and the apparent quantum yield of the four treatment were respectively 0.0269, 0.0317, 0.0337, 0.0317μmol·mol-1. Shading treatment depressed the CO2 compensation point and CO2 saturation point, and the two indexes of 43% shading and 77% shading treatment had significant difference from the contrast. 3 Effect of light intensity on photosynthetic enzymatic and antioxidant enzyme activity of peanut leavesRuBPCase activity of peanut leaves which cultured under low light ware significantly depressed according to the weakening of treatment light intensity in seedling phase. RuBPCase activity of peanut cultured under 27% shading, 43% shading and 77% shading treatment condition were decreased by 21.7%, 45.9% and 81.9% respectively compared with those cultured under natural light. When the seedling shading treatment ended, all the peanut plant were made growth in natural light for one day in order to eliminate the influence of immediate light intensity effect. RuBPCase activity increased slightly but also significantly depressed according to the weakening of treatment light intensity. The later data showed the difference of RuBPCase activity potential, that is to say seedling shading treatment was likely to damage the function of RuBPCase. PEPCase activity had the similar variation law to RuBPCase activity, while had lower amplitudes. The result indicated that immediate light intensity and long time shading treatment can all influence RuBPCase and PEPCase activity.SOD, POD activity of peanut leaves cultured under low light were significantly increased according to the weakening of treatment light intensity at seedling phase, while CAT activity decreased significantly. After 15 days'growth under natural light when the treatment ended, SOD, POD, CAT activity all showed similar rules, while the disparity between the CK level minished. SOD activity depressed as the weakening of treatment light intensity in pod-setting phase and pod-maturing phase treatment, while POD and CAT activity increased. The SOD activity was significantly lower than CK level after 15 days'growth under natural light when the pod-setting shading treatment ended, while POD and CAT activity were higher than CK level but had not significantly difference.4 Effect of light intensity on vegetative growth of peanutShading treatment at seedling phase had the most influential effect on peanut plant characters; shading at pod-setting phase took the second place; while shading at pod-maturing phase had the least influence. Shading treatment at seedling phase promoted the elongation of main stem and lateral branch, but reduced the branch number of the plant. Shading at the three phase all have great influence on leaf area index; among them 43% shading and 77% shading at seedling phase decreased leaf area index mainly because depressed the growth rate; shading at pod-setting phase mainly reduced the growth rate of leaf area, and depressed the descending rate at anaphase of peanut growth; shading at pod-maturing phase mainly quickened the degressive velocity of leaf area. Plant biolobical yield all significantly reduced at the three phase shading treatment, among them shading treatment at pod-setting had the extremum decreasing amplitude, shading treatment at pod-maturing phase took the second place, while shading at seedling phase had the least influence.5 Effect of light intensity on pod yield and kernel quality of peanutYield reduction occurred under all treatments. There were little reduction under 27% and 43% shading at seedling phase, while the maximal yield reduction occurred under shading at pod-setting phase. Decrease of pods per plant and plumpness were main reason of reduction of yield. Shading at seedling phase had little influence on quality, while had great influence at the other two phases. The yield rate of export pod and kernel were all decreased. Decreasing ranges of oil content were 0.4～2.0, 0.6～3.2 and 1.6～6.0 percentage point at the three phases respectively, while protein and total soluble sugar content increased by a small margin. The oil content of typical samples was 0.7～2.6, 0.7～3.4 and 0.7～4.9 percentage point higher than random samples at the three phases respectively. There were significant correlation between nutrition content and plumpness. So it was very potential in improving the quality of peanut production by way of increasing plumpness with cultivation measures.6 Relationships between dry matter accumulation and PAR, and between efficiency for solar energy utilization and PAR were specifiedThe relationships between dry matter accumulation and PAR and the relationship between efficiency for solar energy utilization and PRA were studied systemically. And it showed dry matter accumulation rate and PAR followed the logarithm curve at seedling phase, exponential curve at pod-setting phase and S shape curve at pod-maturing phase. Relative rate of dry matter accumulation of the three phases were all followed exponential curve. And the two rates of dry matter accumulate in pod were all followed exponential curve at pod-setting phase and pod-maturing phase. That's to say there's significant correlation between dry matter accumulation and PAR, and it will be the basic to make dry matter accumulation model. Efficiency for solar energy utilization was calculated, and the results as followed: 5.19% in the whole growth period, 2.33% at seedling phase, 7.33% at pod-pin phase, 8.87% at pod-setting phase and 7.72% in pod-maturing phase. There were negative correlation between efficiency for solar energy utilization and PAR at seedling phase, and positive correlation at pod-setting phase and pod-maturing phase. There were positive correlation between efficiency for solar energy utilization and LAI. 7 Simulation model of peanut population dry mater accumulation and yield formation were set upPeanut population dry matter production model and yield formation model were founded by adopting two kinds of method based on the theories of peanut growth physiology. The first kind of model considered the physiological processes of leaf area dynamic, coronal luminous energy allocation, photosynthesis and so on based on the"material---energy transform--- energy balancing"theory and crop physiology fundamental principle. The test result of population dry matter production model is: R=0.9505, RMSE=16.76%; and test result of yield formation model is: R=0.9236, RMSE=17.58%. That's the first peanut model found by this way. In the second kinds, solar radiation and leaf area index had been taken into account in dry matter model Wi=a*Qi*(1-e-k*Li) as CERES used for reference. According as the growth center is different in every period, the entire phenology course is detached to two phases, seedling to Pod-setting and Pod-setting to Pod-maturing. The test result of population dry matter production model is: R=0.9967, RMSE=7.18%; and test result of yield formation model is: R=0.9758, RMSE=9.88%. As compared, the first kind of model was much more mechanism, and the CERES model was batter in simulating precision.