Evaluation Of Rice Allelopathic Potential By Morphological And Physiological Indicators Of Rice Seedlings As Well As Phenolic Acid Content And Inhibition Rate

In this paper,the allelopathic potential of 132 rice cultivars were screened in laboratory bioassay used their hydroponic solutions,and allelopathic rice PI312777(PI)and Taichung Native 1(TN),and non-allelopathic rice Lemont(LE)were used as contrast cultivars.The morphological and physiological indexes of rice seedlings,and the total phenolic content of culture solutions were determined.Ten strong allelopathic cultivars from above experimental results were further evaluated by the rice/barnyard grass circle method in soil.And the physiological and biochemical indicators,the contents of total phenolic and eight phenolic allelochemicals were determined,as well as the inhibitory rates of their solutions.The main results are as follows:(1)The screening results showed that 25 of 132 cultivars were classified as the same group of the PI and TN,based on the inhibition rate on lettuce root length;9 cultivars were classified as the same group of the PI and TN,based on multi-cluster analysis results of the morphological and physiological indicators of rice seedlings;and 11 cultivars were classified as the same group of the PI and TN,based on the total phenolic contents.By synthesized above results,there are 6cultivars,which are 187,197,213,287,326 and 371,that can be classified into TN and PI.(2)The 6 allelopathic cultivars and one non-allelopathic cultivar(203)obtained above,together with 4 allelopathic rice cultivars(169,170,208,297)which obtained in our previously study,further evaluated by the rice/barnyard grass circle method in soil.The results showed that the inhibition rate of these allelopathic rice cultivars on the plant height and plant fresh weight of barnyard grass was significantly higher than that of LE and 203.The PAL,SOD,CAT and POD activities of rice leaves with allelopathic potential were higher than that of LE and 203.In LE and 203,the MDA content was higher.The phenolic acid content in the allelopathic rice leaves was significantly higher than that in LE and203.There was a significant positive correlation between the inhibition rate of rice plant height and the phenolic acid content of rice leaves.The phenolic acid content of rice leaves was significantly positively correlated with the inhibition rate of leaves extracts on lettuce root length.(3)HPLC results showed that the total amount of eight phenolic allelochemicals in leaves of allelopathic rice cultivars(59 – 68 μg/g leave)was higher than that of LE(47.67 μg/g leave)and 203(50.61μg/g leave),and the content of benzoic acid derivatives in rice leaves was higher than that of cinnamic acid derivatives,Phenolic acids may play a role in the rice allelopathic in a combined manner,with the benzoic acid type contributing more to allelopathic effects.In summary,this study obtained 6 rice cultivars with allelopathic potential.Enzyme activity of PAL and protective enzymes of rice leaves were positively correlated with rice allelopathic effects,and inhibition rate of rice on plant height of barnyard grass were positively correlated phenolic acid content in rice leaves.Salicylic acid and cinnamic acid may play a greater role in rice allelopathy.