吉林不同生境防风夏季光合特性

采用LCpro+全自动便携式光合仪同时测定了长春、长岭和白城3个生境防风的光合作用及环境因子,研究不同生境防风净光合速率、蒸腾速率及水分利用效率等日变化特征及其与生态因子之间关系,并采用通径分析法分析各环境因子对防风净光合速率的直接和间接影响,探讨防风的光合生理规律,为进一步研究防风的光合生理提供依据。结果表明,各环境因子之间存在相互作用,在影响防风光合作用的环境因子中,光合有效辐射(PAR)是驱动因子,它的变化驱动了大气温度(Ta)、叶片温度(Tl)变化,Ta升高引起空气密度的变化是午间相对湿度(RH)和大气浓度CO2(Ca)降低的一个重要原因。环境因子中对Pn直接作用由大到小长春为TlTaPARCaRH,长岭为PARTlRHCaTa,白城为TaTlRHPARCa。长春、长岭PAR与Pn相关系数最大,而白城地区Ca与Pn相关系数最大,说明防风叶片对不同环境因子的反应有所不同。8月份3个地区防风净光合速率日变化均呈双峰型曲线,具有明显的光合"午休"现象。长春、长岭地区防风光合"午休"现象主要由气孔因素引起,白城地区防风光合"午休"现象主要由非气孔因素引起的。3个生境防风的Pn与Gs之间均呈显著的正相关关系,白城的Gs比长春、长岭地区的低44%左右,这是防风为适应高温干旱的环境而形成的生理反应。不同生境土壤含水量间差异显著,白城地区土壤水分含量很低,只有20.35%,仅是长春土壤含水量的56.50%,而空气温度较高,强辐射使气孔叶片蒸腾失水加剧,导致叶片含水量也很低,仅仅为56.60%,高温干旱使防风叶温升高,防风磷酸化、电子传递、酶活性等受到抑制,导致光合速率降低。因此,白城地区长期高温胁迫是限制防风Pn的主要原因。

Photosynthetic characteristics of Saposhnikovia divaricata in different habitats in summer

Photosynthesis of Saposhnikovia divaricata (Turcz.) Schischk. and environmental factors were measured by using LCPro+ portable photosynthesis system in Changchun, Changling and Baicheng, the diurnal changes in net photosynthetic rate (P_n), transpiration rate (E) and water use efficiency (WUE) of S. divaricata and their relationships with environmental factors were studied, and direct and indirect effects of environmental factors on net photosynthetic rate were calculated through the path analysis in different habitats in order to discuss photosynthetic physiology rule of S. divaricata . This knowledge could provide basis for further study the photosynthetic physiology of S. divaricata . The results showed that there were significant interactions among environmental factors, variation of photosynthetically active radiation (PAR) triggered the fluctuations of air temperature (T_a) and leaf temperature (T_L), and T_a was closely related to the air density, which had significant impacts on the air CO₂ concentration (C_a) and relative humidity (RH), the reduce of air density affected by increase of T_a was the one of important causes, which decreased the RH and C_a at noon. Environmental factors driven intrinsically by PAR superposed an integrative effect on P_n. And the responses of the species to the environmental factors were different in different habitats, and the direct effects of environmental factors in three different habitats were of the order: T_l >T_a > PAR >C_a >RH in Changchun, PAR >T_l >RH >C_a >T_a in Changling and T_a >T_l >RH > PAR >C_a in Baicheng. The correlation coefficients between PAR and P_n were the biggest in Changchun and Changling, but C_a and P_n was the biggest in Baicheng. The diurnal changes in P_n of the species in different habitats were similar and could be expressed as two-hump curves, reflecting a significant middy depression at noon. The decrease in P_n during midday was mainly resulted from stomatal limitation in Changchun and Changling, but non-stomatal limitation occurred in Baicheng. There were significant positive correlations between P_n and G_s in three ecological regions, G_s in Baicheng was about 44% lower than in Changchun and Changling, this was a physiological reaction in order to response to high temperature and drought in Baicheng. The soil water content differed significantly in different habitats, it was only 20.35% in Baicheng, and that was 56.50% of that in Changchun, but air temperature in Baicheng was high, leaf water content was only 56.60%, which resulted from leaf strong transpiration and water loss affected by intense radiation. So the net photosynthetic rate decreased because of that the phosphorylation, electron transfer and enzyme activities of S. divaricata were restrained by high leaf temperature. So heat-stress was one of critical factors constraining P_n in Baicheng.