紫茎泽兰茎和叶片色素及叶绿素荧光相关参数对不同温度处理的响应差异

Differences in pigments and chlorophyll fluorescence parameters between stems and leaves of Eupatorium adenophorum under different temperature treatments

通过人工模拟低温(12℃)、常温(25℃)、高温(35℃)生境,对紫茎泽兰茎和叶片色素(叶绿素a,b,类胡萝卜素,花青素)含量和组成、叶绿素荧光参数包括最大荧光效率Fv/Fm、光系统II效率ФpsⅡ、光化学淬灭系数qP、非光化学淬灭系数NPQ、热耗散速率HDR进行了动态测定。结果表明:在低温和高温胁迫处理过程中,茎和叶片的色素含量和组成随时间变化趋势基本一致,但茎的变化幅度明显低于叶片。与此类似,茎和叶片叶绿素荧光参数在不同温度处理过程中的变化趋势一致,但是茎各指标的变化幅度普遍小于相应叶片的变化幅度:低温下,茎的ФpsⅡ和ETR较对照最大降低44%,而叶片降低超过60%;高温下,茎的ФpsⅡ和ETR较对照下降16%～57%;而叶片则下降50%～80%。其产生原因在于:在温度胁迫条件下,叶片获取光能用于光化学过程的份额(qP)大幅下降,用于热耗散的份额(NPQ)大幅上升,茎的情况相反,所获取光能用于光化学电子传递的份额较常温下更多、用于热耗散的减少,这使得茎的耗散速率(HDR)升高的幅度显著低于叶片的升高幅度(p<0.05)。综合3个温度的测定结果,茎的叶绿素含量相当于叶片的1/3～1/6,茎的叶绿素a/b较叶片低20%左右,但是光合电子传导速率ETR与叶片相当,这使得茎的光合色素利用效率ETR/Chl远高于叶片。叶片和茎叶绿素荧光参数在不同温度处理下变化趋势一致、但叶片的变化幅度远大于茎的这一响应差异,使得在适宜温度下紫茎泽兰叶片光合对整体光合贡献增大,而在温度胁迫条件下茎的光合贡献增大,这种策略使得这一植物在适宜生境下通过叶片光合、快速生长迅速占据生境,而在逆境条件下茎等非同化器官光合贡献增加,有利于其在逆境中的保存。

The contents and compositions of pigments and chlorophyll fluorescence parameters including maximum fluorescence efficiency（Fv/Fm）,the actual photo II chemical efficiency（ΦPS Ⅱ）,the photochemical quenching coefficient（qP）,the non-photochemical quenching coefficient（NPQ） and the heat dissipation rate（HDR） in stems and leaves of Eupatorium adenophorum under low-temperature（12℃）,normal temperature as control（25℃） and high-temperature（35℃） were determined and their changing tendency and magnitude were discussed in this paper.During the processes of low-and high-temperature treatments,the same tendency was observed in the changes of different pigment contents and their compositions in stems and in leaves,however,the magnitude of these changes in stems was obviously smaller than those in leaves.Likewise,the dynamic changes of chlorophyll fluorescence parameters in stems and leaves were in a similar tendency,while the magnitude of such changes in stems was generally smaller than that in leaves,e.g.at the low-temperature treatment,the ΦPS Ⅱ and ETR in stems were 44% lower than the control,while it dropped over 60% in leaves;At the high-temperature treatment,these two parameters in stems and leaves decreased 16%-57% and 50%-80%,respectively.Possible reason for these observations was the partitioning differences of the absorbed light between photosynthetic quenching（qP） and non-photosynthetic quenching（NPQ）.In the case of leaves,an increasing percentage of the absorbed light was used in heat dissipation via a sharp increase in NPQ and a decreasing percentage of such light were used in photochemical processes via a sharp decrease in qP,while in the case of stems,the proportion of light energy used in qP was slightly decreased（even increased） and a sharp decrease were found in NPQ under temperature stresses.This made a much smaller increase in HDR at stems comparing with leaves（p〈0.05）.Pooling all data for averaging analysis,chlorophyll in stems accounted 1/3-1/6 for that in leaves,the chlorophyll a/b was 20% lower than that in leaves.ETR of stems and leaves were similar,thus the utilization efficiency of photosynthetic pigments（ETR/Chl） in stems was much higher than that in leaves.The feature of chlorophyll fluorescence parameters of leaf and stem acclimatization to temperature stress,i.e.dynamics changes had the similar tendency,but magnitude for leaf was much larger than that of stem,made a larger photosynthetic contribution from leaves in suitable temperature,but an increased contribution from stems in temperature stressed habitats when leaf photosynthetic capacity were largely depressed.This photosynthetic strategy may favor the flourish of this species at suitable environment through large leaf photosynthetic improvement,while survive at stressed environments through the relative stable photosynthetic capacity of stems.