| The global warming has been changing the ecological environment that human beings survived on, which becomes the severest problem for the survival and social sustainable development of mankind and impact on protection and utilization of biodiversity. To explore the growth, photosynthetic characteristics, resistant physiological parameters, endogenous hormones and medicinal constituents in Epimedium acuminatum Franch and Epimedium wushanense Ying, a warming experiment was conducted under the increasing 2℃(+2℃) and 5℃(+5℃) conditions, respectively by open-top chamber (OTC). The research was made to understand the two specices responding to the increasing temperature.These can provide basis for the protection of Epimedium plants under the changing climate condition.1. Temperature increased obviously influenced the growth of the plants and floral trait. The height, the length of leaf, width of leaf and leaf area by increasing+2℃ were larger than the data under the contrast and increasing+5℃ in two Epimedium plants. The plant growth rate of E. wushanense was higher than E. acuminatum under wariming conditions. In floral trait, the E. acuminatum and E. wushanense showed differences after being treated differently. By increasing+2℃, the E. acuminatum had an increase in quantitative trait in floral trait (spur, sepals, etc.), and a decrease in quantitative trait by +5℃. However, the E. wushanense had an increase in quantitative trait in floral trait both increasing+2℃ and+5℃.2. The photosynthetic characteristic parameters of the two Epimedium plants showed an obvious difference under warming conditions.(1) The diurnal variation of photosynthesis in two Epimedium plants had obvious "midday depression" phenomenon. There was a significant positive correlation between net photosynthesis and PAR, Cond in two Epimedium plants. The net photosynthesis and leaf temperature showed a significant negative correlation in treatments of+2℃ and+5℃. The tolerance range of temperature in E. wushanense was significantly higher than E. acuminatum.(2) The rectangular hyperbola improved model is the best fitted model for photosynthetic-light response of two Epimedium plants. The fitted values showed a significant difference in control,+2℃ and+5℃ treatments in E. acuminatum, Pmax and LSP increase first and then decrease. Pmax values were 4.634±0.093μol·m-2·s-1, 5.019±0.028μmol·m-2·s-1 and 4.719±.0.0383μmol·m-2·s-1, respectively in three threatment. The LSP values were 446.234±10.048μmol·mol-1, 577.640±8.829μmol·mol-1 and 507.918±9.500μmol·mol-1, respectively. The LCP showed a trend of increase, with values being 5.201±10.048μmol·mol-1, 4.209±0.469μmol·mol-1 and 14.825±1.739μmol·mol-1, respectively. The fitted values of E. wushanense showed a significant difference with control,+2℃ and+5℃ treatments. The Pmax and LSP showed a trend of decrease, Pmax values were 6.575±0.219μmol·m-2·s-1,6.096±0.108μmol·m-2·s-1 and 4.353±0.062μmol·m-2·s-1, respectively; and LSP values were 733.856±18.483μmol·mol-1,588.985±9.297 μmol·mol-1 and 510.241±14.603μmol·mol-1, respectively. The LCP showed a trend of increase, with values being 5.443±0.776μmol·mol-1,5.360±0.408μmol·mol-1 and 8.667±0.617μmol·mol-1, respectively. In the control and temperature-increasing treatment of the light response curves changeed differently in two Epimedium plants, the parameters of E. wushanense were higher than those of E. acuminatum.(3) The improved exponential model is the best fitted model for photosynthetic-CO2 response of the two Epimedium plants. In this model, it indicated that Pmax and Csp showed an increase-decrease trend, with the control,+2℃ and + 5℃ treatments. Pmax values were 7.478±0.091μmol·m-2·s-1,8.776±0.313μmol·m-2·s-1 and 7.660±0.635μmol·m-2·s-1, respectively, Csp values werel266.673±7.610μmol·m-2·s-1, 1315.516±7.698μmol·m-2·s-1 and 1236.689±10.575μmol·m-2·s-1, respectively. Γ showed a trend of decrease-increase, with its values 68.247±8.129μmol·m-2·s-1,43.261±3.106 μmol·m-2·s-1 and 57.342±5.381μmol·m-2·s-1, respectively. Pmax showed a trend of decrease in E. wushanense with control,+2℃ and +5℃ treatments, with its values 21.802±0.699μmol·m-2·s-1,12.845±0.328μmol·m-2·s-1 and 13.713±0.576μmol·m-2·s-1, respectively, Csp and Γ showed a trend of increase. Csp values were 1552.754± 13.770 μmol·m-2·s-1,1728.862±8.058μmol·m-2·s-1 and 1809.212±14.035μmol·m-2·s-1, respectively. Γ values were 67.524±5.081μmol·m-2·s-1,81.639±3.855μmol·m-2·s-1 and 105.795±7.952μmol·m-2·s-1, respectively. The CO2 response curves between the two Epimedium plants changed differently in control and temperature-increasing treatment, which the parameters of E. wushanense were higher than those of E. acuminatum.(4) Chlorophyll fluorescence parameters analysis indicated that the chlorophyll fluorescence kinetic parameters (eg. Fv/Fm, ETR, etc.) of E. wushanense were increased obviously after temperature-increasing. It suggested that temperature-increasing maked the plant had a higher intrinsic light energy conversion efficiency, photosynthetic electron transport rate and electron transport activity, which contributed to potential improvement of photochemical efficiency. This demonstrated a higher adaptability of the plant to the environment and to temperature-increasing. There were similar with the height growth rate of E. wushanense.3. The two species Epimedium plants showed different resistance capacities under the condition of temperature-increasing, even the different organs of the plant showed different resistance capacities. Under the same condition, the content of MDA and H2O2 produced by E. wushanense was less than that produced by E. acuminatum. The H2O2 produced by the leaves of E. acuminatum was higher than that produced by other organs. Activity of antioxidant enzyme was also changed. The content of H2O2 produced by the root of E. wushanense was higher than that produced by other organs. Summary, the total antioxidant capacity of the leaves was higher than other organs in two Epimedium plants. The antioxidant capacity of E. wushanense was higher than that of E. acuminatum.4. The response to temperature of endogenous hormone in different organs of the two Epimedium plants was different when they were in different periods of growth. During the growth stage, abscisic acid (ABA) content of the root had an increased trend. The zeatin (ZR) from new and old stem content showed the trend of decreasing from flowering to fruit dropping period. With the temperature gradually increased, two Epimedium plants of gibberellin (GA3), auxin (IAA) and ZR showed+2℃> control>+5℃, which were similar with growth regularity of Epimedium plants in different temperature conditions. Overall, the content of endogenous hormones in E. wushanense was higher than E. acuminatum.The nutritional organs, the root and the stem, showed a same trend in terms of the specific value:(IAA+GA3+ZR)/ABA. The specific value of old and new from the root and the stem showed a trend of decrease to a certain degree with the advancement of the growing period in two Epimedium plants.5. There was a significant effect on medicinal components of two Epimedium plants under warming condition. The temperature-increasing by +5℃ to the E. acuminatum was good for the accumulation of icariin. However, the content of icariin of the leaves in E. wushanense dropped with temperature-increasing by+5℃. After temperature-increasing, the icariin of E. wushanense had dropped to a certain degree, the root, the stem and the leaf had the similar trend, Control>+2℃>+5℃. There was no obvious difference before and after temperature-increasing in flavonoid content of the root and the stem in E. wushanense, but the flavonoid content of the leaf with+5℃ treatment was greatly lower than that other treatments. The flavonoid content of the root in E. acuminatum was no obvious different, but the flavonoid content of the stem with +5℃ treatment was greatly lower than that other treatments, and the content with the leaf, after temperature increased by+2℃, was obviously higher than the Control.Correlation analysis showed that there was a significant negative correlation between the flavonoids content and temperature, the correlation coefficient was -0.998, which meaned the temperature increased, and the time flavonoids content decreased significantly. There was a significant positive correlation between the flavonoids content and inhibit free radical ability, the correlation coefficient was 1.000. |
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