西南喀斯特典型树种光合特性的季节变化及主要影响因子

摘要

A study w as conducted to investigate the seasonal dynam ics of photosynthesis and the underlying regulating factors for three typical species, i.e., Styrax benzoinoides Craib, Ligustrum lucidum, and Cinnamomum saxatile, in Southw estK arst,C hina.Photosynthesis w as m easured using LI-6400 portable pothosynthesis system .N etphotosynthetic rates (Pn) of Ligustrum lucidum and Cinnamomum saxatile w ere higher in A pril and July, w hile low er in January and October,whileaclearseasonalpatternofPnforStyrax benzoinoides Craibwasnotobserved.Allthethreespecieswere found to exhibitthe phenom enon of‘noon break’,buteach had differentcurves.D ifferentfactors affected the Pn ofthe three species in different season. T he photosynthetic active radiation (PAR) and transpiration rate (Tr) w ere the m ain factors in January and O ctober.T he factors regulating Pn for the three species varied in A pril,w ith the intercellular C O 2 concentration (Ci) and PAR being the m ain factors for Ligustrum lucidum, and PAR and Tr being the m ain factors for Cinnamomum saxatile.N etherlessthe effectsofallthe factoron Styrax benzoinoides Craib w asnotsignificant.In July the m ain factors w ere stom ata conductance (Gs) and Ci.PAR w as the m ain factor affecting Pn of the three species in different season.W econcludedthatLigustrum lucidum,andCinnamomum saxatilecouldbemoreadaptivetotheenvironmentsof Karst,whileStyraxbenzoinoidesCraibwaslessadaptivetotheenvironmentsofKarstintheSouthwestChina.%为了解喀斯特典型植物光合作用季节变化特征，应用LI-6400便携式光合作用测定系统，对滇南安息香（Styrax benzoinoides Craib）、女贞（Ligustrum lucidum）和岩樟（Cinnamomum saxatile）3种喀斯特典型植物在自然生境中的光合季节动态及主要影响因子进行研究。结果表明：女贞和岩樟的光合速率季节变化表现为4月、7月较高而1月、10月低，滇南安息香的光合速率季节变化则不明显；3种植物都出现了光合“午休”现象，但不同树种的变化曲线不同；不同季节影响3种植物的净光合速率（Pn）的因子不同：1月和10月，3种植物共同的主要影响因子为光强（PAR）和蒸腾速率（Tr），4月3种植物的主要影响因子各不相同，胞间CO2含量（Ci）和光强（PAR）是影响女贞的主要影响因子，光强（PAR）和蒸腾速率（Tr）是影响岩樟的主要影响因子，而各因子对滇南安息香的影响不显著。7月影响3种植物净光合速率的因子主要是气孔导度（Gs）和胞间CO2含量（Ci）。光强是不同季节影响3种植物净光合速率最为主要的因子。通过对3种植物光合作用季节变化特征分析，女贞和岩樟能较好的与西南喀斯特环境相适应，而滇南安息香对西南喀斯特环境适应性较差。