Abstract:

The chlorophyll fluorescence kinetics of marine red alga Grateloupia turuturu Yamada, green alga Ulva pertusa Kjellm and brown alga Laminaria japonica Aresch during natural sustained dehydration were monitored and investigated. The pulse amplified modulation (PAM) system was used to analyze the distinct fluorescence parameters during thallus dehydration. Results proved that the fluorescence kinetics of different seaweed all showed three patterns of transformation with sustained water loss. These were: 1) peak kinetic pattern (at the early stage of dehydration fluorescence enhanced and quenched subsequently, representing a normal physiological state). 2) plateau kinetic pattern (with sustained water loss fluorescence enhanced continuously but quenching became slower, finally reaching its maximum). 3) Platform kinetic pattern (fluorescence fell and the shape of kinetic curve was similar to plateau kinetic pattern). A critical water content (CWC) could be found and defined as the percentage of water content just prior to the fluorescence drop and to be a significant physiological index for evaluation of plant drought tolerance. Once thallus water content became lower than this value the normal peak pattern can not be recovered even through rehydration, indicating an irreversible damage to the thylakoid membrane. The CWC value corresponding to different marine species were varied and negatively correlated with their desiccation tolerance, for example. Laminaria japonica had the highest CWC value (around 90%) and the lowest dehydration tolerance of the three. In addition, a fluorescence “burst” was found only in red algae during rehydration. The different fluorescence parameters Fo , Fv and Fv/ Fm were measured and compared during water loss. Both Fo and Fv increased in the first stage of dehydration but Fv / Fm kept almost constant. So the immediate response of in vivo chlorophyll fluorescence to dehydration was an enhancement. Later with sustained dehydration Fo increased continuously while Fv decreased and tended to become smaller and smaller. The major changes in fluorescence (including fluorescence drop during dehydration and the burst during rehydration) were all attributed to the change in Fo instead of Fv . This significance of Fo indicates that it is necessary to do more research on Fo as well as on its relationship with the state of thylakoid membrane.

持续脱水下海藻叶绿素瞬变荧光模式的三阶段转换及临界水量的发现
武宝王干¹  陈贻竹² 臧汝波³  曾呈奎³

（1.  暨南大学生物工程系，广州%510632；2.  中国科学院华南植物研究所，广州%510650；
3.  中国科学院海洋研究所，青岛266071）

摘要：在自然干燥条件下,跟踪研究了海洋红藻带形蜈蚣藻(Grateloupia turuturu Yamada) ,绿藻石莼(Ulva pertusa Kjellm)和褐藻海带(Laminaria japonica Are sch)的叶绿素荧光动力学曲线的变化,并用脉冲调制荧光仪分析了藻体脱水过程中的各个荧光参数.结果表明,在持续脱水过程中,3类海藻的荧光动力学曲线都显示出3个阶段的变化,即: 1)在脱水开始时正常的峰形曲线; 2)荧光上升至最高时持平、形成了高原型曲线 ; 3)荧光跌落变成平台型曲线.发现荧光跌落前藻体的含水百分数是一个重要的生理指标 ,称为临界水量(CWC),一旦藻体失水至低于此临界水量时,即便复水也不能使原来的峰形曲线得以恢复,说明脱水可能引起了叶绿体类囊体膜的不可逆损伤.临界水量可以用来衡量不同海藻的耐旱力,其数值高低随不同海藻而不同,并与其耐旱力成负相关.如在上述3 大类海藻中,海带的 CWC 值最高(约90%),但其耐旱性最差.此外,在红藻(只有红藻) 经受干燥后作复水处理时,观察到有荧光急剧上升(爆发)的现象.对海膜脱水前后的几个荧光参数(F0、Fv、Fv/Fm)作了测定和比较,发现F0和 Fv在脱水的第一阶段都上升,而Fv/Fm值维持基本不变.因此可以得出结论,活体叶绿素荧光对干旱的最初响应是立即增强,当继续失水时,F0保持上升而 Fv却下降并越来越低,故此时总荧光的变化(包括荧光的跌落和爆发)主要是由F 0的变化所引起的,因而进一步研究F0与脱水时类囊体膜状态变化的关系具有重要意义.

关键词： 海藻；叶绿素荧光；脱水；复水；调制荧光系统

Key words: marine algae, chlorophyll fluorescence, dehydration, rehydration, pulse amplified modulation fluorescence system