Comparison Of Photosynthetic Physiology For Two Varieties Of Xinjiang Early Fruit Walnut Under Typical Weather Conditions

Walnut (Juglans regia L.) has a high food and economic value.J. regia ’Xinwen185’ and J. regia’Xinxin2’, which are interactive cross-pollination, are the main early fruit cultivars in Xinjiang. Since thestudy deficiency of photosynthetic physiological characteristics differences of these two early fruit walnutsunder different weather conditions for a long time, which leads to a lack of in-depth understanding of itsphotosynthetic capacity. Through the studies of the light response curve, diurnal variation of fluorescenceparameters, diurnal variation of photosynthetic parameters under different weather conditions and theenvironmental factors influences on net photosynthetic rate, etc., aiming at having a more knowledge andunderstanding of photosynthetic physiology ecological characteristics differences of two Xinjiang earlyfruit walnuts, and in order to provide further guidance for its physiological and metabolic studies, scientificbreeding and cultivation of rational management. The main conclusions are as follows:Modified model of rectangular hyperbola was the most optimized model for the research ofphotosynthetic light response curve of two Xinjiang early fruit walnuts. The light compensation points(LCP) of two cultivars respectively were19.43μmolm-2s-1and22.21μmolm-2s-1. The light saturation points(LSP) respectively were1294.96μmolm-2s-1and1265.84μmolm-2s-1. The maximum net photosyntheticrate (Pn) respectively were22.94μmolm-2s-1and22.19μmolm-2s-1.The Fv/Fm diurnal mean values of two varieties of Xinjiang early fruit walnut were both at a lowlevel. But compared to J. regia ’Xinxin2’, the diurnal variation of Fv/Fm of J. regia ’Xinwen185’ could bemaintained over the a high level for the most of a day.The diurnal variations of Pn of different parts of two Xinjiang early fruit walnuts were a two-peakpattern curve in sunny day, and showed a ’midday depression of photosynthesis’ phenomenon, whichcaused by stomatal factor and also non-stomatal factor. While the diurnal variations of Pn of different partsof two Xinjiang early fruit walnuts were a single-peak pattern curve in overcast day, and there was no’midday depression of photosynthesis’ phenomenon. The diurnal mean values of Pn of different parts oftwo Xinjiang early fruit walnuts were both top＞external＞bottom＞internal in sunny day. While inovercast day, it of J. regia ’Xinwen185’ was external＞top＞internal＞bottom, and it of J. regia ’Xinxin2’was top＞external＞internal＞bottom.The air temperature (Ta) was the primary environmental factor to influence Pn of different parts oftwo Xinjiang early fruit walnuts; while it was the photosynthetic photon flux density (PPFD) in overcastday.The diurnal mean values of water use efficiency (WUE) of different parts of two Xinjiang early fruitwalnuts were both top＞external＞bottom＞internal in sunny day. While in overcast day, it of J. regia’Xinwen185’ was external＞top＞internal＞bottom, and it of J. regia ’Xinxin2’ was top＞external＞internal＞bottom.