Effects Of Drought Stress On Seed Germination And Seedling Growth Of Schizonepeta Tenuifolia(Benth.)Briq.

Schizonepeta tenuifolia(Benth.)Briq.is one of the important Chinese traditional medicine,which is also commonly used in landscape.The adaptability of vanilla plants is strong,not only widely used in flower beds,convex glass,gardens in the garden configuration,but also can meet the requirements of people on sight,smell all the year round.While vanilla application of plant landscaping in Shanxi Province is still in its infancy.The seeds of Schizonepeta tenuifolia(Benth.)Briq.were used for study the seed germination characteristics at 3 different temperature(15?16??20?22??26?28?)and under 6 PEG-6000 drought stress(CK?5%?10%?15%?20%?30%).And we investigated the physiological and biochemical responses of Schizonepeta tenuifolia(Benth.)Briq.under four different soil drought stress.The test aimed at understanding and revealing the adaptability of seeds and seedlings,it will provides a reference basis for drought resistance evaluation and for the breeding of drought-tolerant plants.The results showed that:1.Seed germination:The interaction of temperature and PEG-6000 drought stress had a significant impact on the germination rate,germination index,germination potential,GDRI,radicle length,plumule length and leaf area.Evaluation the drought resistance by using the GDRI showed that:at 15?16?,the drought resistance was higher significantly than other two temperatures under 5%PEG-6000 treatment.It indicated that the low concentration PEG treatment can improve the Schizonepeta tenuifolia(Benth.)Briq.seed vigor remarkably to enhance the ability to resist the drought stress.2.Morphologic changes:Under the different drought stress,the height of Schizonepeta tenuifolia(Benth.)Briq.reach peak when stress 14 days.Under the normal,moderate and severe drought,the seedling root shoot ratio was maximum.With the extension of stress time,root shoot ratio was decreased significantly under different drought stress.It turned out that the drought stress inhibited the plant growth.The seedling leaves area under mild,moderate and severe drought stress was reached peak at 14 days.When stress 21 days were separately decreased 4.02%,10.37%,7.42%.When stress 0,14 and 21 days,leaf area reached peak under the mild drought stress.3.Physiological changes:The seedling leaf water content can be maintained at a higher level,which indicated there has less influence on leaf under drought stress.And the leaf has a better ability to adapt the stress.Under the normal,mild and severe drought treatments,the chlorophyll-a?chlorophyll-b and chlorophyll contents of Schizonepeta tenuifolia(Benth.)Briq.seedling were reached peak when stress 14 days.With the increase of drought stress,the chlorophyll-a contents of mild,moderate and severe treatments were respectively increased by 7.42%,16.44%,10.81%than the normal.The chlorophyll-b contents were respectively increased by 5.74%,2.09%,17.23%than the normal.The chlorophyll contents were separately increased by 7.06%,13.16%,12.06%than the normal.With the extension of stress time,the soluble protein content of the Schizonepeta tenuifolia(Benth.)Briq.seedling stem and root under various drought stress levels were increased firstly and then decreased.The soluble protein were reached peak when stress 7 days.The proline contents of leaf were decreased firstly and then increased with the extension of time,which has a significant difference(P<0.05).Under the different drought stress levels,the proline contents of stem were reached peak when stress 14 days,which were separately increased by The soluble sugar contents of leaf under the various stress levels were decreased firstly and then decreased with the extension of time.The proline contents of stem and root under mild,moderate and severe treatment were increased 0.49,1.31,1.49 times with the normal.Under the various drought stress,the soluble sugar contents of leaf were decreased firstly and then decreased with the extension of stress time,which has a significant difference.While,the soluble sugar contents of stem and root were increased.The SOD activity of different parts under the various stress levels were increased with the extension of time.When stress 7 and 14 days,the SOD activity of stem and root has a significant difference under the various drought stress(P<0.05).The POD activity of leaf under the mild,moderate and severe were has a significant difference with the normal(P<0.05).When stress 7,14 and 21 days,there has a significant difference under the various drought stress.Under the severe drought treatment,the POD activity of stem and root were reached peak when stress 14 days,which has a significant difference with other stress times.With the increasing of drought stress and the extension of stress time,the MDA contents of different parts were decreased firstly and then decreased.When stress 7 days,the MDA contents under the mild,moderate and severe drought treatments were has a significant difference with the normal(P<0.05).And the MDA contents of leaf were higher than the stem and root.