| Undaria pinnatifida, with its important ecological and economic value, has become important research and culture materials. Both temperature and light intensity are important environmental factors restrained the growth and production of U. pinnatifida in wild and cultured. In this research young sporophyte was taken as the material. A single-factorial experiment was designed to study the effects of temperature (14℃,20℃,24℃ and 28℃) and light intensity (90μmolm-2s-1,180μmolm-2s-1 and 270μmolm-2s-1) on the chlorophyll fluorescence parameters and antioxidant system of U. pinnatifida. The main results were as follows:1. Different temperature influences on the chlorophyll fluorescence parameters of U. pinnatifida young sporophyteWith the decreasing temperature, F0 of U. pinnatifida young sporophyte rised at the first then decreased, the highest F0 was in 24℃. and there was a significant difference in the cycle. Fv/Fm maintenance between 0.65-0.7 in temperature of 14℃,20℃,24℃, it gradually declined in 28℃ treatment and significantly reduced after 24h; Fv/F0 and Fv/Fm change trend were consistent. NPQ to responding to the different temperature treatment in light period (before 12h,24h,48h)rised and dark period (12 h and 36 h,60 h) decreased significantly with temperature rise; Algal death after 28℃ treatment for 72h. Qp trends and Φ PSⅡ consistent, with the increase of processing temperature gradually reduced, significant difference after 24h. After 28℃processing the original reaction significantly reduced, may be the PS Ⅱ reaction center was destroyed by high temperature, photosynthesis decreased, dark cycle cannot recover, the algae death after 72 h. According to U. pinnatifida young sporophyte fluorescence parameters change, it can be summarized below, as the experimental treatment temperature 14℃ to 28℃ increased by process, when less than 24 ℃ algae body gradually adapt to the environment, the original reaction was not significant, fluorescent dissipation decreased, the fluorescence quenching in photoperiod rise and fall in the dark cycle.2. Different temperature influences on oxidation system of U. pinnatifida young sporophyteTemperature tolerance of U. pinnatifida under different treatments was limited, the algae response to high temperature may produce some toxic reactive oxygen species on algae, enabling a series of physiological and biochemical reaction, the antioxidant system played an important role in U. pinnatifida young sporophyte resistance to high temperature. Reactive oxygen species:O2- activity increased in the first 24h and after 72h according to temperature increment, when the temperature was 28℃ ROS activity was inhibited; H2O2 activated were relatively low in 24℃ and 28℃; The MDA content was corresponding to active oxygen content changes. Antioxidant enzymes SOD activity tendency and the temperature was significantly positively related; CAT and POD activity was significantly rise in 24℃.Antioxidants AsA and GSH significantly increased along with the rise of temperature before 48h, the peak appeared in 9h. AsA content and total antioxidant power change trend was same.In general, the high temperature environment will make U. pinnatifida young sporophyte photosynthesis decrease, which affect the growth of adult survival state, and further limits the over all U. pinnatifida group distribution in nature. In the process of algae body resistance to high temperature stress, antioxidant enzymes and antioxidants of U. pinnatifida young sporophyte resistant to high temperature environment has played an important role in different periods.3. Different light effects on chlorophyll fluorescence parameters of U. pinnatifida young sporophyteDifferent light intensities on the chlorophyll fluorescence parameters of U. pinnatifida young sporophyte, the light intensity was stronger, Fv/Fm was lower; When light intensity was 180μmolm-2s-1 、270μmolm-2s-1. Fv/Fm had a significant reduction in light cycle and rise in dark periodunder the same illumination, which was reversible. NPQ there was no significant difference belong light intensities:Under the same light intensity, NPQ change rule was photoperiod (0-12.24-36.48-60 h) rose, dark cycle (12 to 24 h.36-48h,60-72h) declined. Fluorescence quenching coefficient of Qp was similar to the changing rule of the ΦPS II. there were no significant differences between other light intensity, except the light 270μmolm-2S-1 slightly higher than the control group. Fv/Fo represented the potential activity of PS II. U. pinnatifida young sporophyte received the more light, Fv/F0 value was lower, the light intensity 270 umolm-2s-1 treatment group were decreased significantly, and the relative energy intake of algae in dark period is relatively small, alleviate the inhibitory effects of the potential activity of PS Ⅱ.Light intensity is too high may cause algae body "dynamic light inhibition", this experiment under the strong light U. pinnatifida young sporophyte photosynthesis rate decreased, but by raising the light cycle heat dissipation can effectively avoid the PSⅡ suffered irreversible damage, algal photosynthetic rate can recover again, even more than the original level in dark.4. Different light effects on antioxidant system of U. pinnatifida young sporophyteU. pinnatifida reactive oxygen species in specular environment H2O2 content in the 180μmolm-2s-1 270μmolm-2s-1 treatments group were higher than control group, significantly different; Under the condition of the specular highlights, H2O2 content in photoperiod was higher, dark cycle was lower. O2 -has little difference between treatments group and control group. MDA content change trend of high light treatment group than the control group in the first 24h, then decreased, and the cycle of light and dark cycles in the process of the experiment were lower after rising first cyclical changes. SOD activity was content of O2- change. POD activity in the whole experimental period were lower and maintain a relatively stable, when light intensity is 270μmolm-2s-1 to deal with the marked increase in the activity. CAT activity decreases with light intensity increase. Light intensity enhanced antioxidant AsA content rise difference was not significant; GSH content rose according to the light intensity increase and has a significant part in light period, during light and dark cycles GSH content were first raise then lower in the same light intensity ofthe first day. T-AOC. with light intensity enhancement in 24 to 30h significant difference in light period (0-9h.24-30h) (P< 0.05). decline with light intensity increase in the dark cycle (12-15h,48h). Despite the strong light can also produce high temperature, this study found that high lights the algae body under the action produced more H2O2, clearing agent was the main antioxidant enzymes and antioxidants (GSH POD). In addition, it also showed obvious circadian rhythms from light to darkness, algae under the condition of the high light cycle may suffer from a certain amount of stress, but in the dark cycle it could recovered. |
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