低温胁迫下不同乌菜光合及荧光特性的变化及耐寒性评价

为寻求有效的方法来鉴定乌菜的耐寒性,本研究以6个乌菜材料为研究对象。对6个材料分别进行梯度降温(昼/夜)处理:18℃/12℃、12℃/6℃、6℃/0℃,每个阶段温度处理3 d,共9 d;之后测定6份材料经梯度降温胁迫后的光合和荧光特性,以及几种生理生化指标变化和相关性,同时用隶属函数法对供试材料的耐寒性进行综合评价。结果表明,随着低温胁迫时间的延长,在快速叶绿素荧光动力学特性方面,大部分时间点‘12-7-10’的荧光信号最强,‘W16-9’最小,表明‘12-7-10’光系统Ⅱ(PSⅡ)反应中心捕获的能量很大一部分以荧光的形式耗散;‘12-7-10’在低温胁迫下受体侧性能较低,和‘W16-9’正好相反,说明‘W16-9’的电子传递效率较高;6个乌菜材料中,‘12-7-10’的性能指数、推动力和PSⅡ最大光化学效率也小于其它5种乌菜。在光合性能方面,随着梯度低温的变化,6种乌菜的净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)都有不同程度的下降,细胞间隙CO2浓度(Ci)则上升,说明Pn的下降是由非气孔因素导致的;‘SW-5’和‘W16-9’在低温处理前后其光合速率都较强,Tr和水分利用效率(WUE)也较大,说明‘SW-5’和‘W16-9’在低温环境下,具有较好的应对能力。结合其他耐寒性生理生化指标,采用隶属函数法综合评价乌菜材料的耐寒性:‘SW-5’的耐寒性最强,‘W16-9’、‘W5-7’、‘J-5-8’和‘S-15-6’次之,‘12-7-10’最弱。本研究为选育耐寒乌菜材料提供理论依据。

Changes of Photosynthetic Fluorescence and Evaluation of Cold Tolerance in Wucai(Brassica campestris L.) under Low Temperature Stress

In order to find an effective method to identify the cold resistance of Wucai,six Wucai materials were used as the research object.The materials were subjected to gradient cold(day/night)treatment:18℃/12℃,12℃/6℃,6℃/0℃.The temperature of each stage was processed for 3 d,a total of 9 d.The photosynthetic and fluorescence characteristics of six materials under gradient cold stress,as well as the changes and correlations of several physiological and biochemical indexes were measured.And cold tolerance of Wucai materials were comprehensively evaluated by using subordinate function based on cold resistant coefficient of these indexes.The results showed that with increasing time of low temperature,about the chlorophyll fluorescence characteristics,the fluorescence signal of’12-7-10’was the strongest at most time points,the’W16-9’was the smallest.It indicated that the’12-7-10’light systemⅡ(PSⅡ)reaction center captured a large part of energy dissipation in the form of fluorescence.’12-7-10’has lower receptor side performance under low temperature stress,and’W16-9’was just the opposite.The results indicated that the electron transfer efficiency of’W16-9’was higher.Among the six Wucai materials,the performance index,driving force and PSII maximum photochemical efficiency of’12-7-10’were smaller than the other five Wucai materials.In terms of photosynthetic performance,the net photosynthetic rate(Pn),stomata conductance(Gs)and transpiration rate(Tr)all decreased evidently,but the intercellular CO2 concentration(Ci)increased significantly under the low temperature stress.It is suggested that non-stomatal limitation became the main cause of the reduction of Pnin Wucai.’SW-5’and’W16-9’have strong photosynthetic rate before and after low temperature treatment.And Trand water use efficiency(WUE)were also large,indicating that’SW-5’and’W16-9’have strong cope force under low temperature conditions.Combined with several cold-tolerant physiological and biochemical indexes,the cold-tolerant of Wucai materials were comprehensively evaluated by subordinate function method:’SW-5’was the highest,followed by’W16-9’,’W5-7’,’J-5-8’,’S-15-6’,and’12-7-10’.This study may provide a theoretical basis for breeding materials under cold tolerance.