Effects of exogenous abscisic acid on root morphogenesis and induced allelopathy of rice at seedling stage
Exogenous addition of chemicals can improve the allelopathic potential of rice,which is a sustainable weeding model that can be developed and utilized.Allelopathic rice PI312777 and non-allelopathic rice Lemont were cultured in rice/barnyard grass cultures in root boxes.The effects of exogenous abscisic acid on allelopathic potential,root morphological traits(root length,root surface area,root volume,and root tip number),and root placement patterns of the two rice varieties were investigated.The phenolic acid and endogenous hormone contents in rice leaves were determined using HPLC.Correlation analysis was used to assess the existence of linear relationships.The results showed that the total allelopathy values of allelopathy and non-allelopathy on plant height of barnyard grass were significantly higher than those of genetic allelopathy after 3 μmol/L abscisic acid induction.The ratio of induced allelopathy of Lemont to total allelopathy value(23％-31％)was similar to that of PI312777(24％-35％).Following the induction treatment,the root placement patterns of the two rice varieties changed from avoidance to invasion modes and the total root length,total surface area,and total volume of the two rice varieties significantly increased.HPLC showed that the total content of eight phenolic acids in allelopathic rice PI312777 and non-allelopathic rice Lemont leaves significantly increased by 20.22％and 20.47％,respectively,following induction treatment.Correlation analysis showed that the total root length,total volume,and total content of eight phenolic acids in allelopathic rice PI32777 leaves were significantly positively correlated with the inhibition rate of barnyard grass,whereas the total root length,number of root tips,and total content of eight phenolic acids in non-allelopathic rice Lemont leaves were significantly positively correlated with the inhibition rate of barnyard grass.The results showed that exogenous abscisic acid induction promoted root morphogenesis in rice,which could release more phenolic acids,thereby resulting in the high inhibition of barnyard grass.More importantly,exogenous induction can induce the allelopathy of non-allelopathic rice to allelopathic rice.
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