| This experiment uses BAU-I infrared radiation thermometer to detect the temperatures of canopies of 12 different varieties of peanuts which have different genotypes within two consecutive years, with Using Luhuall, the national demonstrated and popularized variety in the local place, performing as a reference, to sort out typical cold-type peanuts and warm-type peanuts. We also measure part of the physiological characters for photosynthesis from functional leaves and physiological characters related to yielding, proved the method to sort out high yielding varieties using temperatures of canopy and characters of agricultural characters, and discussed the feasibility of nurturing peanuts at low temperatures. The results indicated as follows:(1) In a small range of identical atmosphere, soil and nurturing, the canopy temperatures of different varieties of peanuts varied in obvious two levels from fruiting period to filling-legume period, indicating that peanuts can be classified as cold-types and warm-types. Using Luhuall as a reference, the results showed that the canopy temperatures of Yuhua9331,Yuhua153 and Yuhua9327 were mostly below the standard level of 0.0℃, i.e. the canopy temperatures remained relatively low, making them cold-type peanuts. On the contrary, the temperatures of Puhua9506,Kainong41 and Wuming2 were all above the standard level, making them warm-types.(2) The distinguished discrepancy existed among different temperature-type peanuts in suface temperatures and transpiration rates. The soil surface temperatures of cold-types Yuhua9331,Yuhua 153 and Yuhua 9327 were apparently lower than those of warm-types Puhua9506,Kainong41 and Wuming2. The gap reached-1.7℃and-2.6℃respectively at fruiting period and filling-legume period. In addition, employing the method of Kruskal-Wallis Test to compare the transpiration rates, the results indicated that there were apparent distinctions between the two types in transpiration rates:all warm-types had higher transpiration rates. These proved that the heating effect of the second heat source on canopy was weaker in cold-types, and that stronger transpiration rates in cold-types could also take away more heat from the surface, in favor to temperature reduction. The synergy led to low canopy temperatures in cold-types.(3) Comparing with warm-types, the canopy temperatures and soil surface temperatures of cold-types were relatively lower. The maximum difference of canopy temperature occurred at 15:00, while that of soil surface temperature occurred at 14:00, thus making it more reasonable to measure those temperatures at 14:00-15:00, With the progress in growing season, the gap became maximum when filling-legume period.(4) There were distinct differences between those two types of peanuts in physiological properties of photosynthesis. The aging rate of functional leaves from cold-types(Yuhua153, Yuhua 9331 and Yuhua 9327) were slower than that of warm-types (Puhua9506, Kainong41 and Wuming2), with larger chlorophyll content when legumes completely filled, slower aging rate of leaves and longer period of staying green. Furthermore, the NPR (net photosynthesis rate) and the dry matter accumulation of cold-types had been always been higher than those of warm-types, indicating that warm-type peanuts have stronger photosynthetic capacity, thus producing and accumulating more photosynthetic product.(5) The chlorophyll fluorescence parameters among peanuts of various genotypes differ greatly. By surveying on cold-type and warm-type peanuts on six chlorophyll fluorescence parameters, we got the results showing that the cold-types Yuhua153, Yuhua 9331 and Yuhua 9327 had lower values of minimal fluorescence F0 and non-photochemical quenching coefficient qN, higher values of maximum fluorescence Fm, maximum photochemical efficiency Fv/Fm of PSII and total photochemical quantum yield of PSII Yield. The results indicated that more energy absorbed by leaf pigments of cold-types flowed to photochemical parts while less was emitted in the form of heat or fluorescence, which meant they could transform luminous energy to chemical energy more effectively and thus accumulated more energy for photosynthetic carbon assimilation in the dark reaction than warm-types. These characters could ensure more absorbed luminous energy to be used for photosynthesis.(6) The agricultural characters were related to the economic yield. Through correlation analysis, the various kinds of economic yield could be ranged as the weight per 100 pods, weight per 100 kernels, the number of pods per plant, the ratio of full pods, the number of branches, the height of the caulis, the length of lateral branches as the correlation went down. A further principle component analysis of the two revealed that the weight per 100 pods, weight per 100 kernels, the number of pods per plant affected the yield most greatly, whose load values on the first principle component were respectively 0.959,0.887 and 0.820.(7) The economic yield and canopy temperatures were closely related with the main agricultural characters (the weight per 100 pods, weight per 100 kernels and the number of pods per plant). This research showed that:Because of the low canopy temperature and superior characters, the economic yield of the cold-type peanut Yuhual53 was on top. On the contrary, the economic yield of the warm-type peanut Kainong41 was the lowest for the highest canopy temperature and low score for agricultural characters. Yuhua9331 and Yuhua9327 are both cold-type peanut, because of Yuhua9331 has the higher score for agricultural characters, the economic yield of Yuhua9331 is higher than Yuhua9327. Only varieties with low canopy temperatures and main dominant agricultural characters, could their economic yield be high, while merely the canopy temperature could not determine the economic yield. Through stepwise multiple regression analysis, the conclusion could be drew that canopy temperatures and agricultural characters should both be considered when sorting varieties with high yield.
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