| With the development of ecological agriculture and sustainable circular agriculture,greenhouse tomato in organic media culture develops rapidly. However, due to the requirementof habits of plant and reduction of production costs, the reuse of medium become commonly. Itis more and more extrude that diseases and pets get heavier, the yield and quality of fruitsdecreased, both physical and chemical character become declined, and so on, which becomes amain bottleneck that restricts the sustainable development of the greenhouse tomato in organicmedia culture. The self-allelopathy is one of the most important reasons of continuous croppingobstacle, commonly found in protected vegetable cultivation. Therefore, in protected tomatocultivation system, to explore the different cropping rotation organic ecotype soilless culturemedia of environmental effects, allelopathy and allelopathic decreases the technique has animportant theoretical and practical significance. In this paper, to study the biological charactersand physicochemical characters, verified autotoxicity on cultivation, analyzes influencingfactors of allelopathy, isolation and identification of allelochemicals in four cropping rotations(i.e. the normal cropping, alternate cropping, continuous cropping2years and continuouscropping for3years). Meanwhile, the roles of ascorbic acid in the alleviation mechanism ofautotoxicity in tomato were studied. The main results were as follows:1. In continuous cropping media, the activity of protease, phosphatase, urease, catalase,invertase and dehydrogenase decreased, and organic matter content, nitrogen, ammoniumnitrogen, available nitrogen, total phosphorus, available phosphorus, total potassium andavailable potassium decreased too, but media bulk density and pH increased. While in normalcropping media, the media bulk density and pH, the activity of enzymes, the content of organicmatter and major nutrient were affected slightly. The chemical properties closely related with thephysical properties in the organic media under the normal cropping, alternate cropping andcontinuous cropping, thus led to the change of micro-ecological environment, which resultedthat the growth of plant was lowest, the diseases and pets get heavier, the yield and quality offruits decreased. The result indicated that the enzyme activity correlated with the content oforganic matter and main nutrients in rhizosphere media of greenhouse tomato under differentcropping rotations. Enzyme activity, the content of organic matter and main nutrients might beimportant factors in the material cycle of media. Therefore, the enzyme activity can be used tocharacterize the status and changes of organic matter and nutrient to some extent, whichreflected the intensity and direction of various biological activities in media. After continuouscropping, the activity of enzyme, content of organic matter and major nutrients so decreased,that nutrient source provided to tomato was reduced. It goes against the growth of tomato plants.While in first-planting treatment, the activity of enzymes and main nutrients of media were affected slightly. The biological and physicochemical characters of replanting media and newmedia has little difference.2. When the tomato seed was treated with different rotation systems and differentconcentions of aqueous extracts, the seed germination rate, germination energy and germinationindex, seedling root and epicotyl length, dry weight and fresh weight were significantlydecreased compared to the control, and the inhibition was increased with the increase ofconcentration. The plant height, stem diameter, increase amplitude of leave length and widthdecreased significantly after treatment with extracts of continuous cropping media aqueous, theresults show that the continuous cropping media aqueous extracts inhibit leaf growth. When theplant was treated with different media aqueous extracts, chlorophyll content in leaves and rootactivity of tomato seedlings decreased rapidly, the activity of superoxide dismutase dropped atfirst and rose later, the ascorbate peroxidase activity increased at first and then decreased anddecreased lastly, but also the activities of superoxide dismutase and ascorbate peroxidase werehigher than other treatments. The results indicated that the aqueous extract of3medias couldinhibit seed germination and seedling growth in tomato, and the aqueous extracts of continuouscropping media was greatly inhibited than other media, and inhibition effect is concentrationdependent, increasing with the increase of concentration. When the concentration of aqueousinfusion0.05g/mL had the largest effect on the inhibition of seed germination and seedlinggrowth.3. Allelopathy of various components and contents of allelochemicals on tomato wasstudied by aqueous extracts and methanol soluble components of continuous cropping media.The results indicated that the more allelochemicals content and composition, the stronger theinhibition effects of seed germination and seedlings growth, vice versa.The differentconcentrations of aqueous extracts, methanol soluble fractions of aqueous extracts and sterilizedaqueous extracts all inhibit seed germination, and with the increasing of concentration, theinhibition effect increases gradually. Lower concentration of continuous cropping mediaaqueous extracts sterilization or not had little effect on the seed germination and seedling growthof tomato, while the seed germination and seedling growth were affected by highconcentration(0.05g/mL) of aqueous extracts sterilization or not, but no obvious differenceunder the same concentration. It seemed that micro-organisms play a role in the allelopathicsystem, in which allelochemicals were the main affecting factors, microorganisms weresubsidiary.4. The results of each fraction bioassay showed that allelopathy of50%aether+50%ethylacetate fraction were the strongest in there cropping rotations media, in which the seedgermination rate, germination energy and germination index, seedling root and epicotyl length,dry weight and fresh weight were significantly decreased compared to the control. Furthermore, many organic compounds found in the extracts from50%aether+50%ethyl acetate fraction byGC-MS analysis, and it shows that the numbers of allelochemicals were significantly differentcropping rotations(normal cropping, alternate cropping, continuous cropping) media, they were14、20and19separately.5. The seed germination rate, germination energy and germination index are increased,seedling root and epicotyl grew faster, the protective enzyme activity and antioxidants contentincreased, the content of abscisic acid decreased, and the contents of glutathione, ascorbic acid,auxin, gibberellin and zeatin were significantly increased under treated by ascorbic acid of0.25,0.5and1mmol/L and media aqueous extracts of0.05g/mL compared with those treated by wateror aqueous media extracts only. It was illustrated that there were certain alleviate effects ofexogenous ascorbic acid on autotoxicity caused by aqueous extracts of continuous croppingmedia, among the ascorbic acid concentrations used,1mmol/L was the optimum concentrations. |
PDF Full Text Request