Effect Of Drought Stress On Seeds Germination And Plants Physiological Characteristics Of Three Thyme Varieties

This study with Thymus victorious,Thymus vulgaris and Thymus pulegioides as the experimental materials,by using PEG-6000 to simulate drought stress conditions,to explore the thyme of seed desiccation tolerance ability.Study of thyme different organizational physiological response to drought stress throught the drought water control in weighing methed.The results of the study for thyme seed propagation,cultivation management and drought resistance mechanism of thyme,in order to provide certain theoretical basis.The results of the study are as follows:1.Choose concentration of 0,5%,10%,20%and 30%PEG-6000 to simulate drought stress conditions,to determine of thyme under drought stress seed germination rate,germination potential and seedling root,shoot length and leaf area.The results showed that under the 5%PEG-6000 drought stress treatment,thyme varieties seeds germination rate and germination potential were not significant.Low concentration(10%)of PEG could promote the seeds germination and growth,leaf area and shoot length of thyme seedling were significantly inhibited.The seeds germination indexes,shoot length and leaf area were inhibited with the increase of drought stress(>10%),and the greater the intensity of drought stress was,the more distinctly index changed.From three thyme to present a different response mechanisms of drought stress,will be reach in seed germination stage of thyme:the drought resistance size from high to low for Thymus victorious>Thymus vulgaris>Thymus pulegioides.2.Use the drought water control in weighing methed,set up four stress gradient,the soil moisture was 75%-85%for the normal level,60%-65%for mild drought,40%-45%for moderate drought,25%-35%for severe drought,to determine thyme photosynthetic pigment,soluble protein and free proline,SOD,POD and MDA.(1)Along with the drought stress level continued,Thymus victorious of carotenoid increased before they are reduced,total chlorophyll content decreased.Two kinds of photosynthetic pigment content of Thymus vulgaris and Thymus pulegioides were to raise first and then declined,and reached the maximum when the moderate drought.(2)Soluble protein content in leaf and root of Thymus vulgaris and Thymus pulegioidesin general have been dropped after rising trend since the stress level and the extension of time.Thymus victorious leaf soluble protein content increased,and roots in a trend of first fall later.(3)Three kinds of thyme leaves proline content are significantly higher than the roots since the drought stress level and stress time.Thymus victorious proline content of leaves and roots to rise after the fall;Thymus vulgaris leaves when stress 14 d lowered after the first,when stress 7 d and 21 d after the first drop,proline content in roots were very low,and a trend of "N";Thymus pulegioides leaves proline content lowered after the first,and have no obvious regularity in root.(4)With the increase of stress level,SOD and POD two protection enzymes of Thymus victorious leaves and roots were increased before;POD content of Thymus vulgaris leaves and roots reduced first increases,while SOD content were at the beginning of the stress droped,when stress later showed varying degrees of increase;POD and SOD content in leaf and root of Thymus pulegioides stress prolonged largely showed a downward trend after rise first,under the level of stress on the processing of two kinds of protective enzyme showed the opposite trend.(5)Malondialdehyde content in leaves and roots of Thymus victorious increased with the increase of drought degree generally after the first drop up trend,when stress 21 d were rising in leaves;MDA content in leaves and roots of Thymus vulgaris and Thymus pulegioides stress prolonged declined before they rised,each processing period no obvious regularity,the increase of content to some extent in the late stress.MDA content in leaves were higher than in the roots in three kinds of thyme.3.The use of membership function for drought resistance comprehensive analysis:the drought resistance size from strong to weak for Thymus victorious>Thymus pulegioides>Thymus vulgaris.