低温胁迫对6种珍贵树种苗木光合荧光特性的影响

Influence of low temperature stress on the photosynthetic fluorescence characteristics of 6 kinds of precious hardwoods seedling in winter

以格木(Erythrophleum fordii)、降香黄檀(Dalbergia odorifera)、闽楠(Phoebe bournei)檀香(Santalum album)、铁刀木(Cassia siamea)和樟树(Cinnamomum camphora)6种珍贵树种苗木为研究对象,分析自然降温过程中苗木相对叶绿素含量、气体交换参数及叶绿素荧光参数等指标的变化,探讨低温胁迫对这6种苗木光合荧光特性的影响,并利用隶属函数法对6种珍贵树种耐寒能力进行了评价,以期了解这几种植物的抗寒能力差异及低温对其光合能力的影响,为扩大引种和栽培提供依据。结果表明,与对照相比,低温胁迫下6种珍贵树种苗木净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)均有不同程度的下降,其中,格木、降香黄檀、闽楠、檀香、铁刀木净光合效率的下降很大程度上来源于非气孔因素抑制,而樟树净光合速率下降可能来源于气孔限制因素。闽楠、檀香和樟树水分利用效率(WUE)呈上升趋势,而格木与降香黄檀WUE均有不同程度的降低,表明闽楠、檀香和樟树能较好地协调碳同化和水分耗散。低温胁迫下6种珍贵树种Fm均有所下降,表明低温可对珍贵树种苗木叶片PSII反应中心的电子传递潜力产生明显的抑制,致使珍贵树种PSII的光能转换效率降低。降香黄檀、闽楠、檀香、铁刀木和樟树经历2次低温胁迫后qP呈现出持续下降的趋势,表明珍贵树种PSII反应中心的开放程度降低。在2次低温胁迫间格木、降香黄檀、闽楠和铁刀木qN差异不显著(p>0.05),表明珍贵树种具有过剩光能耗散机制,保护光合机构免受破坏。相关性分析结果表明,Pn与Gs、Tr、Fv/Fm、qP、qN、ETR和Fm存在极显著相关关系(p<0.01),表明Gs、Tr、Fv/Fm、qP、qN、ETR和Fm均可作为衡量植物光合能力的参数。隶属函数法分析结果表明,6种珍贵树种抗寒能力依次为格木>樟树>闽楠=檀香=铁刀木>降香黄檀。总之,低温胁迫破坏了这6种苗木光合机构可能是导致植物光合能力降低的主要原因,且不同植物对低温胁迫的响应程度不同,这是扩大引种和栽培需要考虑的因素。

The gas exchange parameters, chlorophyll fluorescence parameters and the relative chlorophyll content of 6 kinds of precious hardwoods seedlings ofErythrophleum fordii,Dalbergia odorifera,Phoebe bournei, Santalum album,Cassia siamea, and Cinnamomum camphorawere were measured in winter using the LI-6400 portable photosynthesis system, and the obtained data were analyzed to explore the relationship between these parameters and cold resistance. The method of subordination function was used to evaluate cold resistance comprehensively. The net photosynthetic rate （Pn）, stomatal conductance （Gs） and transpiration rate （Tr） of the six tree species seedlings declined in the process of low temperature stress comparing with controls. The decline ofPnofD. odorifera,S. album andC. siamea mainly caused by non-stomatal limitation, while ofC. camphora caused by stomatal limitation. The water use efficiency （WUE） of P. bournei,E. fordii andC. siamea increased in low temperature stress, while WUE of E. fordii and D.odorifera decreased,this showed thatP. bournei,E. fordii andC. siamea have better ability in coordinating the relationship between carbon assimilation and water dissipation. The maximum fluorescence （Fm） and Maximum quantum efficiency of PSII photochemistry（Fm/Fv）of each species decreased to some extent under low temperature stress which indicated that low temperature produced significant inhibition on the electron transfer potential of PSII reaction centers and reduced photochemical efficiency of PSII of the six tree species seedlings. The qP of D. odorifera,P. bournei,S. albumandC. siamea showed a declining trend after 2 times low temperature stress which indicated that the degree of openness of PSII reaction centers of precious hardwood decreased. The qN ofE. fordii,D. odorifera,P. bournei andC. siamea showed no significant difference （p〉0.05） after 2 times low temperature stress which indicated that those species had excess energy dissipation mechanisms and protected the photosynthetic apparatus from damage. Correlation analysis showed that there were significantly positive correlations betweenPn andGs,Tr,Fv/Fm, qP, qN, ETR, Fm（p〈0.01）. Therefore, those parameters could be used as parameters to measure the photosynthetic capacity. The mean value of the subordinate function indicated that their ability of low temperature resistance from high to lowE. fordii,C. camphora〉P. bournei=S. album=C. siamea〉D. odorifera. In short, low temperature stress destroy the 6 kinds of seedling photosynthetic organization which may be the reason that induce plant photosynthetic capacity reduction, and the degree of response of different plants to chilling stress are different, which should be taken into account when consider to expand the introduction and cultivation of those trees.