| The allelopathy might be one of causing cotton's continuous cropping obstacle.the methods of bioassay and pot experiment were adopted to explore allelopathic effects of cotton aqueous extract and autotoxicity.Along with simulated the process of cotton's allelopathy. the cotton's phenolic acids was measured by chemical extraction and HPLC. We explored the allelopathic effect and mechanism of cotton. which provide academic evidences for diclosing continuous cropping obstacle and founding efficient rational cultivate system.1.cotton's aqueous extract could showed allelopathic effects on several plant acceptors. The growth index of plant acceptors was increased at lower concentrations aqueous extract,but decreased at higher concentrations.And the effect of aqueous extract of the stems and leaves more than that of root. Its aqueous extract could show allelopathic effects on Raphanus sativus,Brassica campestris,Lactuca indica L.,Brassica campestris L.,Echinochloa crusgalli L,Setaria viridis and Abutilon theophrasti Medic. and its inhibitory effect started to be strengthen gradually with increased of concentration. While the aqueous extract of the stems and leaves of cotton was 0.02g·ml-1, the root length,shoot length,the number of side root and dry weight were promoted;All acceptors were inhibited strongly at 0.1g·ml-1.2.Cotton had an autotoidity effect that hindered the growth of cotton's root,which mainly showed that root length,side root's number,dry weight,root activity and SOD activity were decreased.while POD and MDA content were increased so as to restrict root to absorb nutrition and water.and affected the normal growth of cotton.But cotton's seeds were merely affected besides high concentration. While the aqueous extract of the stems and leaves of cotton was 0.02g·ml-1, the root length,shoot length,the number of side root and dry weight were increased up to 10.3%,3.1%,22.9% and 2.4% above control , respectively.Above-mentioned index were lower than control 34.5%,39.2%,40.5% and 19.1% as much.Meanwhile the inhibition of activity and SOD of root were lower than control 38.2%,36.75%,but POD and MDA were increased up to 52.3% and 36.4% above control at 0.1g·ml-1.3.Cotton also represented difinite allelopathic Autotoxicity effects after stalks returned soil.especially at 10g/kg,the growth of cotton was accelerated,however,it was restrained obviously at 90g/kg.the result showed that the bourgeon time was delayed and fresh weight decreased, the root's activity begin to weaken,while MDA and ezyme activity were gradually enhanced,meanwile,Pn and gas exchange was also inhibited.4.The cotton's phenolic acids was measured by continuous collecting root's secretion and aqueous extract. Some phenolic acids of cotton were estimated through high-performance liquid chromatography methods.the result indicated that p-hydroxybenzoic and ferulicids was the most in root's secretion,while in aqueous extract, p-hydroxybenzoic acid and Gallic acid were often tested, includingly,the quantity of p-hydroxybenzoic acid was high. The quantity of phenolic acids of overground,underground section and root's secretion reached 42.388,32.166 and 26.211μmol/L respectively.5.The biological activity was analysised on the above four phenolic acids,the result showed the four phenolic acids affected the growth and physiological activities of cotton.There existed appeared allelopathy effect's distinction at different concentration.especially about inhibiting effect, FA>p-HA>VA at high concentration. |
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