不同生育期榆树净光合速率对生态因子和生理因子的响应

Effect of ecological factors and physiological factors on the net photosynthetic rate of Ulmus pumila at various growth stages

利用Li-6400便携式光合作用系统,观测了内蒙古浑善达克沙地榆树(Ulmus pumila)的净光合速率(Pn)、上表皮气孔导度(Gs-u)、下表皮气孔导度(Gs-l)等生理因子及大气温度(Ta)、光合有效辐射(PAR)、大气二氧化碳浓度(Ca)和空气相对湿度(RH)等生态因子,应用相关分析、通径分析、决策系数分析及灰色关联分析,系统的研究了榆树Pn在不同生育期的日变化特征及其与生态因子和生理因子间的关系,为深入揭示其生理特征及浑善达克沙地榆树规范化种植提供理论依据。研究表明:1榆树Pn日变化在各生育期均呈双峰型曲线,表现出不同程度的光合"午休"。2榆树Pn在各生育期大小顺序为8月>7月>9月,其值分别为8.18、7.92μmol CO2m-2s-1和6.52μmol CO2m-2s-1。37、8、9月份PAR、Gs-u与榆树Pn呈显著正相关,且PAR的直接作用和决策系数均最大,Gs-u的直接作用大于其他因子的间接作用,且决策系数仅次于PAR,其他因子在各生育期也表现出对榆树Pn不同程度的影响。4不同生育期榆树对各生态因子和生理因子的响应有所不同,7月份Ta为Pn主要限制变量,8月份RH为Pn主要限制变量,9月份各因子均起增进作用。5不同生育期榆树Pn的变化主要受PAR和Gs-u的影响,但不存在简单的线性相关关系,是所有因子综合影响的结果。

This study measured physiological factors of Ulmus pumila,namely the net photosynthetic rate（ Pn）,upper epidermis stomatal conductance（ Gs-u）,and lower epidermis stomatal conductance（ Gs-l）,in Otinday Sandland（42°23＇N,115°37＇E） of Inner Mongolia using Li-6400 portable photosynthesis system. Ecological factors,namely the atmospheric temperature（ Ta）,photosynthetically active radiation（PAR）,concentration of carbon dioxide in the atmosphere（Ca）,and relative humidity of the air（ RH） were also examined. Based on the measured data,the relationship between Pndiurnal variation in U. pumila at various growth periods and ecological factors and physiological factors was assessed using correlation analysis,path analysis,decision coefficient analysis,and grey correlation analysis. This knowledge is essential to reveal the physiological characteristics and formulate generalizations regarding the cultivation of U. pumila in Otinday Sandland. Regardless of growth period,Pnexhibited bimodal diurnal variation with varying degrees of photosynthesis＂midnaps. ＂Pnwas highest in August（8. 18 μmol CO2m- 2s- 1）,lowest in September（8. 18 μmol CO2m- 2s- 1versus 6.52 μmol CO2m- 2s- 1）,and intermediate in July（7. 92 μmol CO2m- 2s- 1）. In the three months from July to September,Pnwas found to have significant positive correlations with PAR,which had the greatest direct influence and thus the largest decision coefficient,and Gs-u,which had the greatest indirect influence but a smaller decision coefficient than PAR. The other factors exhibited varying degrees of influence on Pn. The relative influence of ecological factors and physiological factors on Pndepended on the growth period. Taand RH were the main controlling factors in July and August,respectively,and all factors had positive contributions. Although Pnwas mainly influenced by PAR and Gs-u,regardless of growth period,a simple linear functional correlation was not found owing to interactive effects.