香梨两种树形净光合速率特征及影响因素

Study on characteristics of net photosynthetic rate of two kinds of tree shape and Impact Factors in Korla fragrant pear

以自然开心形和疏散分层形香梨树为试材,应用美国Li-cor公司生产的Li-6400光合作用测定系统测定其光合参数,分析了香梨两种不同树形叶片的光合特性以及叶片叶绿素含量、比叶重(SLW)与净光合速率(Pn)的关系,同时研究了气孔导度(Gs)、胞间CO2浓度(Ci)、蒸腾速率(Tr)及其它因子对不同树形Pn的影响。结果表明:自然开心形和疏散分层形香梨树叶片Pn日变化呈不对称双峰曲线,14:00左右出现光午休现象,且整个生长期疏散分层形香梨树叶片Pn峰值大于自然开心形,6月份Pn最小,这与气孔的调节作用密切相关。疏散分层形Pn日变化在11:00和15:30出现高峰,自然开心形Pn日变化高峰出现在11:00和17:00;同一品种同一时期的自然开心形树和疏散分层形树的叶绿素含量与其Pn值呈正相关,R2分别为0.9438和0.8952;自然开心形的Pn与SLW的相关性高于疏散分层形;Gs、Tr、RH与Pn呈正相关,与Ci、Cs和Pn呈负相关,且疏散分层形香梨树叶片的Pn与Gs、Tr和Cs的相关性均达到了极显著水平,与Ci、Ta、PAR和Hs均达到了显著水平,而在自然开心形中Pn与光合参数相关性不明显,这说明疏散分层形香梨树对影响光合作用的外界因素和内部因素的变化反应比自然开心形敏感。

The objective of this study was to investigate the diurnal variation curves of the net photosynthetic rate （Pn） and relationship between diurnal changes of Pn and the impact factors in open center shape and delayed-open central leader system in Korla fragrant pear. Diurnal changes of Pn and effect of environmental factors （i, e. photosynthetic available radiation, temperature and relative humidity） and physiology factors （i, e. stomatal conductance, transpiration rate and intercellular CO2 concentration） on Pn in leaves of Korla fragrant pear were measured using LI-6400 portable photosynthesis system. The relationship between Pn and environmental factors were analyzed by regression analysis and correlative analysis. In order to investigate the effects of tree shape on net photosynthetic rate, we analyzed the relationship between chlorophyll content, specific leaf weight, other photosynthetic parameters and Pn between delayed-open central leader system and open center shape in this study. The results showed that the Pn under two different tree shapes indicated a bimodal curve of the asymmetry, and the midday depression of photosynthesis phenomenon appeared at 14：00. During the full fruit period, the delayed-open central leader system tree had obviously higher net photosynthetic rate than the open center shape tree in each stage. This phenomenon maight be double impacted by stomatal and non-stomatal factors. Diurnally, photosynthesisincreased gradually with increasing light intensity and then decreased at noon. The peak of delayed-open central leader system tree leaves occurred at 11：00 and 15：30. The peak of open center shape tree leaves occurred at 11：00 and 17：00. The seasonal variation on Pn indicated the Pn is least in June in two shapes of Korla fragrant pear. The Pn increased with leaf chlorophyll （chl） content and specific leaf weight （SLW） increasing. There are positive relations, the correlation index of leaf chlorophyll （chl） content and Pn were 0.9438 and 0.8952 in two shapes of Korla fragrant pear. The photosynthetic pigment index of different kinds of tree shapes also had great differences. There were significant correlations between Pn and SLW in delayed-open central leader system and open center shape, but the later is higher than the former. Stomatal conductance （Gs）, transpiration rate （Tr） and relative humidity （RH） increased in response to increasing Pn in all the treatments. Sample CO2 concentration （Cs） and intercellular CO2 concentration （Ci） decreased in response to decreasing Pn in all the treatments. Besides, the Cs, stomatal conductance （ Gs）, Tr, and Pn have reached highly significant at P ~〈 0. 01 in delayed-open central leader system. There were significant at P 〈~ 0.05 between Ci, air tempreture （ Ta ） , photosynthetically active radiation （PAR）, RH and Pn in delayed-open central leader system. However, the relativity of photosynthetic parameters and Pn were unconspicuous in the open center shape tree, The findings demonstrate that delayed- open central leader system tree had obviously higher sensitivity to the influence factors of net photosynthetic rate than the open center shape tree in this study.