Effects Of NaCl Stress On The Growth And The Chlorophyll Fluorescence Characteristic Among Pepper Seeds And Seedlings

Eight capsicum cultivars are chose to be the materials,they are MeiJia、ZaoLa Wang、QiangFeng7301、BaoXi、QiuYan YiXianTia、FuChengQingJiaoFl and JiangHuan no.2.Our Experiment is designed to test the germination rate under NaCl stress.According to the germination potential, germination rate, germination index, vitality index and relative rate of salt injury,we will filter haloduric cultivar and weak salt resistance cultivar, We will explore the difference of resistance to salt in seedling stage by test physiological and biochemical indexes and chlorophyll fluorescence characteristic of the two kinds cultivars.The main research results are as follows:The degree of the NaCl stress influence on the eight cultivars was different, although the germination stage was all apparently affected by the NaCl stress.When the concentration of NaCl was 50 mmol·L-1,the germination rate was higher than the control,while the concentration of NaCl was 250 mmol·L-1,the phenomenon was in reverse.However the influence of NaCl stress on germination potential were even more apparent, when the concentration of NaCl was above 150mmol·L-1, it will postpone the germination of the seeds.According to the comprehensive analysis of the indexes,we found that QiangFeng7301 has the highest ability of NaCl tolerance, MeiJia,ZaoJiaoWang,BaoXi,YiXianTian,FuChengQingJiaoFl and JiangHuai no.2 come second, while QiuYan comes third.During the period of the pepper seedlings growth, low NaCl concentration has an effect on the part of the pepper varieties that promote the plant growth, while as the concentration increasing, the plant will show the symptoms of NaCl injury.Under the same concentration,different pepper varieties have different reflection, when with higher NaCl concentration, QiangFeng7301and MeiJia have lower relative NaCl injury rate, while QiuYan and FuChengQingJiaoFl have higher relative NaCl injury rate.Under the NaCl stress, the activity of the protective enzyme SOD,POD and CAT all have a upward tendency in the two varieties which show different tolerance to the NaCl. When the stress come to a certain degree,the activity of the protective enzyme decreased. When under higher NaCl concentration, the activity of the protective enzyme SOD,POD and CAT in the QiangFeng7301 which have a higher tolerance ability to NaCl still maintain a higher level. Content of osmotic adjustment substances like soluble protein, proline and soluble sugar etc increased first, and then decreased under the NaCl stress.With the extension of NaCl treatment, the chlorophyll content of the two varieties all show rising first and then decreasing:In terms of chlorophyll fluorescence, The value of the minimal fluorescence(Fo) and the non-photochemical quenching (NPQ) are all on the rise, while the value of maximal photochemistry efficiency of (Fv/Fm)、photosynthetic electron transport rate(ETR)、photochemical quenching coefficient(QR), actual photochemical efficiency Y(Ⅱ) show the opposite trend. As NaCL stress can lead to the decline of the photosynthesis and the destroy of the reaction center of PS Ⅱ, then lead to the decrease of the light energy assimilation rate, the rise consumption of the thermal radiation, as a result, the photosynthesis ability of the pepper seedlings show decrease.Salt tolerance in plants is not determined by the single factor, but a lot of osmotic regulation substances and lots of protective enzyme, which they act together,that lead to the different reflection to salt stress.