不同光强处理对长茎葡萄蕨藻叶绿素荧光特性的影响

Effects of light intensity on chlorophyll fluorescence characteristics of Caulerpa lentillifera

通过调制叶绿素荧光仪(MINI-PAM),对长茎葡萄蕨藻(Caulerpa lentillifera)在10μmol/(m^2·s)、120μmol/(m^2·s)、360μmol/(m^2·s)光强下的叶绿素荧光特性进行了研究。结果表明:随着光照强度从10μmol/(m^2·s)上升到360μmol/(m^2·s),长茎葡萄蕨藻最大光量子产量(F_v/F_m)、实际光量子产量、相对电子传递速率(rETR)、快速光曲线初始斜率均呈下降趋势;用120μmol/(m^2·s)和360μmol/(m^2·s)光强处理的样品光化学猝灭(qP)较高,而非光化学猝灭(NPQ)较低;不同光强处理4 h和8 h时,与10μmol/(m^2·s)处理组相比,120μmol/(m^2·s)处理组最大相对电子传递速率(rETR_(max))、半饱和光强(I_k)均显著上升,360μmol/(m^2·s)处理组I_k显著上升,rETR_(max)明显降低;在360μmol/(m^2·s)光强下处理12 h与处理8 h相比,样品rETR_(max)、I_k均显著降低。上述结果说明长茎葡萄蕨藻偏向适应10μmol/(m^2·s)的低光条件,在120μmol/(m^2·s)和360μmol/(m^2·s)的高光条件下能通过不同的方式提高对光强的耐受能力,但是在360μmol/(m^2·s)光强下处理12 h会引起光氧化对光合结构造成破坏。

Chlorophyll fluorescence technique can provide an accurate, quick, and non-destructive assessment of the efficiency of photochemical conversion. One of the most commonly used fluorescence parameters is the maximal quantum yield of photosystem II （PSII） （Fv/Fm）, which has been shown to be a sensitive indicator of photoinhibition. Moreover, other fluorescence parameters, such as the effective quantum yield of PSII （yield）, the relative electron transport rate （rETR）, photochemical quenching （qP）, non-photochemical quenching （NPQ）, the initial slope of rapid light curve （a）, the maximum relative electron transport rate （rETRmax）, and the minimum saturating irradiance （Ik）, are also important in investigating photosynthesis. As such, chlorophyll fluorescence has become an increasingly powerful tool and widely used technique to study photosynthesis in marine algae. Caul- erpa lentillifera is a tropical macroalga that grows mainly in Okinawa, Malaysia, the Philippines, Vietnam, and other places. C. lentillifera is a potential healthy food with high nutritional value that contains a variety of essen- tial amino acids, vitamins, mineral elements, and unsaturated fatty acids. In addition, C. lentillifera also contains caulerpenynes, polysaccharides, and other physiologically active substances. It has beneficial effects for type II diabetes and cancer. C. lentillifera belongs to the marine benthic green algae, which are very sensitive to high light intensity. Light intensity reportedly has a significant effect on the growth of C. lentillifera, but the effect of dif- ferent light intensities on the photosynthesis process of C. lentillifera is still unknown. Therefore, there is a need to better understand the photosynthetic characteristics of C. lentillifera by investigating the effects thereon of differ- ent light intensities. In this study, the chlorophyll fluorescence characteristics of C. lentillifera were investigated with M1NI-PAM chlorophyll fluorometer under the light intensities of 10 μmol/（m2 s）, 120 μmol/（m2s）, and 360 μmol/（m2 s）. From 10 μmol/（m2 s） to 360 μmol/（m2 s）, the maximal quantum yield of PSI1, the effective quantum yield of PSII, the relative electron transport rate, and the initial slope of rapid light curve of C. lentillifera all decreased with increasing light intensities. The samples treated with light intensities of 120 μmol/（m2s） and 360 μmol/（m2s） had higher photochemical quenching and lower non-photochemical quenching than those treated with 10 μmol/（m2s）. The minimum saturating irradiance increased dramatically and the maximum relative elec- tron transport rate decreased sharply in C. lentillifera under 360 μmol/（m2s）, but both were significantly higher under the light intensity of 120 μmol/（m2s） than that in samples exposed to the light intensity of 10 μmol/（m2.s） for 4 h and 8 h. The minimum saturating irradiance and the maximum relative electron transport rate was substan- tially lower in C. lentillifera exposed to the light intensity of 360 μmol/（m2s） from 8 h to 12 h. These results sug- gest that C. lentillifera is a kind of seaweed adapted to a low light intensity of 10 μmol/（mZ.s）, and that it could improve light tolerance in different ways under high light intensities of 120 μmol/（m2s） and 360 μmol/（m2s）, but light intensity of 360 μmol/（m2s） for up to 12 h could cause photo-oxidation and damage its photosynthetic structure.