几种酚酸类物质对山桃种子萌发后根系的化感效应

Allelopathy effect of some phenolic acids on roots of germinated Prunus davidiana(Carr.) Franch seeds

【目的】探讨常见酚酸类化感物质对桃的化感效应强度,为桃连作障碍研究提供理论依据。【方法】以山桃种子为受体材料,研究不同浓度梯度的几种常见酚酸类化感物质香草醛、苯甲酸、苯甲醛、对羟基苯甲酸、没食子酸、阿魏酸对山桃种子萌发后主根长度、侧根发生数量等的影响。计算不同浓度化感效应的敏感指数SI,并以其绝对值为抑制效应,经转换为概率值后估计回归方程,测算抑制效应为0.5时对应的所需浓度SI0.5,即为该种物质对山桃的化感效应强度。【结果】香草醛、苯甲酸、苯甲醛、对羟基苯甲酸、没食子酸、阿魏酸处理质量浓度分别达到10、10、0.1、10、10、0.1 mg·L-1时,即可对山桃种子萌发主根的长度产生明显的抑制效应(P<0.01),对照清水处理的种子主根上侧根数量平均超过20条,不同化感物质在不同浓度处理下,随着处理浓度的增大,侧根数量减少。香草醛、苯甲酸、对羟基苯甲酸、没食子酸、阿魏酸等物质对侧根数量的抑制效应较大,在低质量浓度1 mg·L-1时SI值就可以达到-0.2,而同样浓度下对应的主根SI值为-0.08^-0.15。主根长和侧根数量2种参试指标所得到的SI0.5浓度基本相同,说明2者均可作为酚酸类物质对山桃的化感效应强度评价指标。【结论】采用山桃种子萌发主根长度和侧根数量作为测评指标,经综合比较,参试的几种酚酸类化感物质的SI0.5(即化感作用强度)由小到大依次为阿魏酸、苯甲醛、苯甲酸、香草醛、没食子酸和对羟基苯甲酸。

[ Objective ]One of the important factors leading to the continuous cropping obstacle in fruit pro- duction is allelopathy, and the chemical substances which cause allelopathy are called allelochemieals. Allelochemicals from the roots of plants are released directly into the soil. They are also released from dis- sociated matters of leaching residues via microbial transformation from the above-ground and finally stay in the soil. They accumulate and maintain activity in root zone as a result of detention, transformation and migration, and create the problem of continuous cropping obstacle when they accumulate to certain con- centration. Phenols are important secondary metabolites produced in plants. In the plant ecosystem, the main phenolic acids are ferulic acid, cinnamic acid, hydroxy benzoic acid and so on. Root exudates and extracts from branches, leaves and roots of peach have obvious autotoxicity to the plant, which has been demonstrated by several reports. However, most of the reports studied mixed allelopathic effects of several allelochemicals. Allelopathy effect of a specific phenolic acid in peach has been rarely reported, except for benzoic acid. Phenols at high concentrations can inhibit the growth of plants, soil microorganisms and soil enzyme activities, while at low concentrations to some extent promote plant growth and improve soil enzyme activity. Some phenolic substances also stimulate the growth and reproduction of soil microbes, indicating that there is a threshold concentration for the effect of phenolic compounds on plant growth. Prunus davidiana （Carr.） Franch is the main peach rootstock in northwest of China. P. davidiana （Carr.） Franch seeds were used as the material to test allelopathy effect of several phenolic acids on seed germina- tion characteristics, in order to bring some understandings on continuous cropping obstacles in peach tree. [ Methods ] Allelochemicals tested included phenolic acids, alkaloids, glycosides, terpenes, etc. The main phenolic acid allelochemicals in stone fruits have been reported to include benzoic acid, benzaldehyde, p- hydroxybenzoic acid, gallic acid, and vanillin. P. davidiana seeds, which had been refrigerated for dor- mancy removal, were surface disinfected with 75% alcohol, and then immersed in distilled water for 12 h before they were taken out and placed in a Petri dish covered with a wet towel and placed in a 4 ~C refrig- erator for about 4 weeks. Then, after several different concentrations of vanillin, benzaldehyde, benzoic ac- id, p-hydroxybenzoic acid, gallic acid, ferulic acid were applied, the seeds were cultured for 14 days at 20 ~C and a light/dark cycle of 8/16 h in an artificial climate chamber. The taproot length and lateral root number were collected and the allelopathic effect at different concentrations used to calculate the sensitiv- ity index （SI）. The absolute value of the inhibition effect were converted into the value of probability for the regression equation, from which half inhibitory effect concentration （SI05） was estimated and served as the allelopathic effect strength of the tested substance. [ Results ] Vanillin, benzaldehyde, benzoic acid, p- hydroxybenzoic acid, gallic acid, and ferulic acid displayed a significant inhibitory effect （P〈0.01） on tap- root elongation at concentrations above 10, 10, 0.1, 10, 10 and 0.1 mg. L-~, respectively. The lateral root number was more than 20 in average. With the increase in concentration of different allelochemicals, later- al root number decreased. Vanillin, benzoic acid, p-hydroxybenzoic acid, gallic acid and ferulic acid at the low concentration of 1 mg. L-~ had a greater inhibitory effect on the number of lateral roots, with an SI value that could reach -0.2. At the same concentration of the corresponding allelochemicals, the SI value evaluated by taproot length was between -0.08 to -0.15. The SI0s values obtained from the effects on tap- root length and on lateral root number were similar. These two indexes can be used to evaluate the allelo- pathic effects on phenolic acids. With DPS software quantitative data bioassay module, the absolute value of the allelopathic effect index （SI） was transformed to Probit value and nonlinear parameter estimation was used to obtain regression equation. The slope of the regression curve was also correlated with allelo- pathic effects of different phenolic acids. When the number of lateral roots was used as parameter, the slope of the equation was consistent with the intensity of the sense effect calculated by SI05 method. How- ever, when the length of the main root was used as the parameter, the result was not consistent, which might be mainly caused by the difference in response of seed germination of peach to low concentrations of phenolic acids. [Conclusion] This study used P. davidiana taproot length and lateral root number as the evaluation indexes, through comprehensive comparison, SI05 （i.e. allelopathy strength） of phenolic ac- ids tested was in the order of ferulic acid〉 benzaldehyde〉 benzoic acid〉 vanillin〉gallic acid 〉 p-hydroxy- benzoic acid.