| Seed vigor is the total sum of those properties of the seed which determine the potential level of activity and performance of the seed or seed lot during germination and seedling emergence. It reflects the potential activities of germination, seedling emergence, plant growth and production. That means seeds with high vigor level germinate rapidly and orderly, develope into strong seedlings that can resist environment stress, result in healthy plant growth and stable and high production. However, the seed vigor of Andrographis paniculata decline because of germ-plasm degeneration and other reasons, lead to variation of seed quality. This dissertation focuses on the following issues:establish the seed testing rules and seed quality grade standard for A. paniculata which mean testing method and quality evaluation. One qualified seed lot with high seed purity level was selected for pretreatment using atmospheric pressure dielectric barrier discharge air plasma with different dose. Seed invigoration effects and an optimal plasma treating dose which can increase seed vigor of A. paniculata, then accelerate the germination and seedling emergence, promote plant growth, finally increase yield, were investigated. Methods and results were as following:1. Establishment of seed testing rules for A. paniculata:Based on the Rules for agricultural seed testing and its implementation guide, testing rules of seed trueness, purity analysis, weight determination, moisture content determination, viability test by TTC method, and germination test were established. Weight of sampling seed lot, seed testing sample, and seed sample for purity analysis were prescribed as less than50kg, more than50g, and no less than5.0g, respectively;100seeds method was proposed for seed weight determination; high-temperature (130℃) baking method for moisture content determination. Germination test procedure was established as: seeds soaked in water at R.T. for18-20h, then cultured at27.5℃by TP method (top of paper) under light; germinated seed should be counted on the2nd and7th day after sowing for the first and last time, respectively.2. Establishment of seed quality grade standard for A. paniculata:Seed lots from main producing area in China were tested according to the testing rules for A. paniculata and based on the guideline of Rules for agricultural seed testing and its implementation guide. Data of germination percentage, moisture content,1000seeds weight, and seed purity were classified into3grades by K-means cluster analysis. Then, the seed quality grading standard was preliminarily established by cluster center in combination with actual institution, agricultural production needs and maneuverability. The germination percentage, moisture content,1000seeds weight, and seed purity of1st grade high quality seed were prescribed as no less than85%, no more than14.0%, no less than1.2g, and no less than85%, respectively; and2nd grade seeds prescribed as65.0-85.0%, no more than14.0%,1.1-1.2g, and80.0-85.0%, respectively; otherwise, the seed lot would be disqualified.Different grade seeds lots were used to conduct seedling emergence test, results showed that seedling emergence percentage of unqualified seeds (3rd grade) was poor, and had no cultivated value. In good agricultural practice, the1st grade seed lot is suggested to be chosen for cultivation.3. Effects of air plasma on germination, penetrability, ultra-microscopy surface characteristic of A. paniculata seeds:Germination test showed that germination percentage of seeds pretreated by air plasma excitated in5950V for60s showed no significant difference compared with the Ctrl (untreated). However, the primary root length of the treated seeds was significantly shorter than that of the Ctrl, resulted in lower germination vigor index. That means long time air plasma treatment can lead to germination suppression. The seed coat re-deposition effect of plasma observed by SEM was presumed to be the reason of suppression. Germination of the other treated seeds by lower voltage or shorter time had no significant change.The plasma exposure time in follow-up investigation was decreased as3400V.4250V.5100V,5950V treated for10s (group1-group4), and3400V,4250V,5100V,5950V for20s (group5-group8).Results showed that the germination energy of group1,2,3,4,5,6and8were higher than Ctrl; and the germination vigor index of group2,5,8were both significantly higher than Ctrl. It indicates that lower air plasma treatment could promote the germination.Electric conductivity (EC) determination of soaked seeds leakage showed that air plasma could change the permeability of A. paniculata seeds. The EC of seeds treated by5950V for10s was significant higher than that of Ctrl, which was explained as the etching effect of air plasma produced tiny holes on the seed coat observable by SEM, resulted in imbibition and germination acceleration. On the other side, EC of seeds treated by3400V for20s was significant lower than ctrl; and the presumable reason was predominant re-position effect by air plasma.4. Effects of air plasma seed pretreatment on emergence, growth, and protein accumulation, antioxidant enzyme activities, antioxidant isoenzyme expression of A. paniculata seedling:Results showed that seedling emergences were changed after air plasma seed pretreatment, effects varied in different dose. Seeds pretreated by air plasma excitated in5950V for10s achieved emergence acceleration, resulted in more amounts of strong seedlings. Seeds pretreated by5100V for20s had the similar effect, but had no significance compared with Ctrl. On the other side, pretreatment by5100V for10s and3400for20s presented inhibition effects.There were follow-up effects on seedling height and leaf area after A. paniculata seeds pretreated by air plasma. The seedling heights were significantly increased after air plasma pretreating excitated by5950V for10s and3400V for20s, but decreased by3400V for10s and4250V for20s. Leaf areas of seedlings pretreated by5950V for20s were significantly increased, but no significant change was shown in dry weight of the seedlings. Leaf areas of seedlings pretreated by3400V for10s,4250V for10s, and4250V for20s were significantly decreased. There were also rise trend of the seedling height and leaf area when the voltage rising with10s of treating time; on the other hand, falling trend of seedling dry weight presented when voltage rising by20s of treating time. In summary, the seedling growth promotion effects of air plasma seed pretreatment by5100V for10s,5950V for10s, and3400V for20s were shown beneficial for growth of the herb.After extraction of protein from50day seedlings, activities of SOD, POD, CAT, and content of MDA and protein were determined. Results showed that activities of antioxidant enzymes and cellular lipid peroxidation degree were change variously; protein accumulation was promoted by air plasma seed pretreatment. After seed pretreatment with5950V for10s, the CAT activity was increased and MDA content decreased, which meant alleviation of lipid peroxidation and enhancement of environment stress-resistant ability of the seedlings.SDS-PAGE analysis of seedlings'protein appeared no significant change in protein expression. However, native-PAGE analyses showed that isoenzymes expression of CAT, SOD, POD, and APX were changed variously after plasma seed pretreatment. There was an additional clear band of CAT-1after air plasma pretreatment by5950V for10s and3400V for20s, compared with ctrl. There was one more band of SOD-2after air plasma pretreatment by3400V,4250V,5100V for10s and20s. However, there was one narrow band less of POD-4or POD-1after pretreatment by5950V for10s and20s, respectively. Expression of APX isoenzymes were all changed after different dose treatment.Summarily, atmospheric pressure air plasma seed pretreatment have follow-up effects on seedling vigor. After seed pretreatment by5950V for10s, there were more rapid seedling emergence and strong seedlings, more accumulation of protein in seedlings, acceleration of seedling growth, promotion of CAT activity and its expression, less lipid peroxidation degree of seedling cells. Therefore, this air plasma dose is promising. As for dose of3400V for20s, the effects of increasing of seedling height, fresh weight and protein of seedling, and CAT expression were observed; however, the seedling emergence was retarded, and less strong seedlings were obtained, which means not an ideal dose.5. Effects of air plasma seed pretreatment on plant growth and yield of A. paniculata:Cultivation test was repeated. After planted for40d in1st cultivation test, plant growth were measured, but there were no significant difference between treated groups and ctrl group. However, after planted for30d in2nd cultivation test, data of seedling height, node number, and leaf number of treated groups were all smaller than ctrl. But, the3rd leaf areas of group3,4, and5(the treating dose were5100V for10s,5950V for10s, and3400V for20s) were larger than ctrl. Different results of these two cultivation tests were presumed to be the influence of the different development stage.As for the yield, there were increasing trend of fresh weight, dry weight, and ratio of dry weight with fresh weight, along with the increasing treating voltage when treating time was10s; especially, the data of group4(treated by5950V for10s) were significantly higher than ctrl.All in all, after air plasma seed pretreatment, germination and seedling emergence may be enhanced by effect of seed coat etching follow-up penetrability increase. The active species, charge particles in air plasma should play a key role in seed vigor change, lead to variation of seedling and plant growth. However, more direct evidence is required to explain the mechanism. In this study, A. paniculata seed treated by air plasma excitated at5950V for10s actually gained seed invigoration.
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