The Effect Of Hydrogels On The Physiology And Biochemistry Of Magnolia Officialis Rehd. Et Wils. Under Drought Stress

One-year-old Magnolia officinalis Rehd. et Wils. Seedlings,from germinating towhich there were approximately12months, were used investigate the effects ofdrought stress and three different hydrogels on the physiology and biochemistry ofMagnolia officinalis Rehd. et Wils. to provide a scientific basis for the cultivation andquality improvement of Magnolia officinalis. The results are as follows:1. The daily transpiration: the beginning of the drought stress, the dailytranspiration in group without hydrogel （record as group N） and group with hydrogelcontained potassium （record as group K） were significantly greater than the othergroups. In the middle and later periods of drought stress, groups with functionalhydrogel （record as group X） and hydrogel contained potassium were higher thanthose without hydrogel and with hydrogel contained sodium （record as group Na）.Looking from the overall trend the fluctuations of daily transpiration in groups N andNa was bigger than it in groups X and K which were relatively smooth.Above resultsshowed that hydrogel contained potassium and functional hydrogel can supply waterfor the plant suffering adversity and resist drought stress.2. Relatively high growth rate（RHGR）: From all the groups, the seedlings grewwell under no drought stress. What’s more, differences between groups Na and Kreached extreme significance levels（P<0.01）. The RHGR in group K were2.5and1.25times as those of groups N and Na,2.38and1.19times as those of group Xrespectively. Under drought stress, the RHGR in group K were2.8and2.0times asthose of groups Na and N, and2.6and1.86times as those of group X respectively. Inthe four drought stress groups, groups K and X grew well while groups N and Nawere not so good as groups K and X.3. Fluorescence parameters: Under drought stress, Fm、Y （Ⅱ） and qP in groupN and Na decreased as NPQ and qN increased, which showed that drought stressinhibited the dark reaction of photosynthesis.4. Four antioxidant enzymes: CAT、APX、POD、SODUnder drought stress and no drought stress, four antioxidase activities showed aconsistent trend, that was, the activities in four antioxidant enzymes were higher ingroups N and Na than groups K and X in which the activities were low. It wasconcluded that groups N and Na received more severe drought stress and the four enzymes had played an positive role in the drought stress response.5. Osmoregulation substances: Under drought stress, the content of soluble protein,soluble sugar and proline were on the rise, which was implied that drought stresspromoted the accumulation of osmotic regulation substances. Under drought stressand no drought stress,the contents of three components in groups N and Na werehigher than that in groups K and X. However, the content of soluble sugar in group Kwas higher than group N.6. MDA、O₂^-、H₂O₂and chlorophyll: Under drought stress, the content of MDA、O-2and H2O2were high in groups N and Na, while there were no obvious differencebetween groups K and X. The content of chlorophyll decreased under drought stressbut increased obviously in the groups added hydrogels. Under no drought stress, Thecontent of chlorophyll in group N had significant difference compared with groupNa、K and X （P<0.05）. The highest content of chlorophyll was in groups K. Hydrogelcontained potassium and functional hydrogel played an better role in droughtresistance, and the former was superior to the latter.7. Magnolol and honokiol: The contents of both magnolol and honokiol in thestem bark were higher under drought stress. There were a great rise in groups N and K.The content of honokiol in group K was1.92times as in group N. All the resultsshowed that drought stress was beneficial to the accumulation of secondarymetabolites to some extent and in a certain time, but the synthesis of honokiol neededmore moisture.Above all, hydrogel contained potassium and functional hydrogel had played anbetter role in drought stress. Groups K and X reached significant difference levelsrespectively with groups N and Na. To some extent, hydrogel contained potassiumand functional hydrogel can effectively alleviate the drought stress and maintainplants’normal physiological function in certain time.