Dandelion Physiological Response Under Drought Stress And Plasma Membrane Aquaporin Gene Expression

Dandelion(Taraxacum mongolicum Hand.-Mazz.) is the asteraceae perennial herbaceous plants which has the very important nutritional value and medicinal value. In recent years, along with the people for the favour of potherb, especially like the dandelion with functions of diet of wild vegetables, has been widely to the attention of the medical and nutrition experts. In recent years as global warming, drought adversity problems become increasingly serious. Dought adversity to become a limit plant growth, reduce crop yield one of the major problems. This study with dandelion as the research object. With the soil relative water content of 50%,75%, as drought stress gradient, for 9 days drought stress, after 9 days to re-watering, and after 7 days re-watering to determine in cell, physiological characteristic and chemical reaction. The main results are as follows:(1) At the middle water stress, the root activity of dandelion as the extension of processing time. At the severe water stress, the root activity of dandelion with the extension of time first increases then decreases and in the severe stress peak at the sixth day. When higher than this level, root activity would reduce, root-shoot ratio would increase. Root activity back to normal after re-watering. The water stress would have a promoting effect on the root growth, the re-watering would make dandelion root get compensation effect.(2) Under drought stress, SOD, POD, CAT activity of dandelion presents first the change trend of lowered later, peak appered MS on ninth day, SS on stxth day. Return to normal levels after re-watering. This show active oxygen removal system is able to in a long time after being foced to maintain balance, the plant is not susceptible to peroxide damage.(3) With the drought stress and stress level increase, the dandelion proline, solube sugar and soluble protein in different increase. After re-watering recovery ability is different.(4) With the increase of drought stress time, dandelion continues to increase content of chlorophyll a and b of the ratio between chlorophyll a and b complex changes, too. At the ninth day in stress. MS, SS chlorophyll a and b content is higher than that of CK, visible increased leaf photosynthetic capacity, but the total chlorophyll content is lower than that of CK, likely total chlorophyll content has certain hysteresis. After re-watering chlorophyll a and total chlorophyll did not change, only the chlorophyll b a certain compensation effect.(5) The change trend of Fo is similar to chlorophyll a, speculated that this correlation that may be associated with adversity stress types and plant species. Under MS and SS stress Fm downward after rising first, explains dandelion PSII destroyed when stress time increasing. As stress time grew, SS Fv/Fo, Fv/Fm are shown first not declined significantly, then fell significantly, MS Fv/Fo showed no significant first down, again is reduced significantly and Fv/Fm is not obvious decline.Show that dandelion PSII affected when under moderate stress, increase the potential activity of PSII center damage over time.Under severe stress PSII potential active center began to damage during the sixth day, higher heat dissipation, photosynthetic mechanism is damaged, the dandelion leaves will be captured by the ability of light energy into chemical energy is waning.Each index rise after water, return to CK level.(6) Stability of the Pn of CK group, the group of SS and MS as stress prolonged decline in the trend. And the SS group decline more than MS group, after re-watering become rose situation. Visible with a certain compensation effect. Stomatal conductance presented irregular change, but when the Gs values are in a low, transpiration rate was also in a low, have certain complex relationship between visible.(7) Increases with stress concentration increases, the CCP and CSP, Amax decreases, and the Rp is reduced, the initial carboxylation efficiency is lower, visible under drought stress, the dandelion light and ability is abated, the rise of CCP is reflected the more severe drought stress, plants consume more of a problem, and leaf dry matter decrease with consistent performance. SS, MS maximum net photosynthetic rate after re-watering didn't rise, CCP and CSP also maintained at the same level, still exist after water stress hysteresis, restoring force is not high.