Abstract
The objective of this study was to evaluate the allelopathic responses of rice seedlings under submergence stress at different temperatures (10, 25, 32, and 37 °C). The results showed that a wide range of allelopathic responses of rice seedlings depended on varieties and stress conditions, with temperature was being a key factor. It showed that the extracts of rice seedlings induced significant suppression on lettuce and radish seedling germination, but had negligible allelopathic effects on growth of barnyardgrass, whilst the emergence and growth of natural weeds was stimulated. In contrast, the root exudates of Koshihikari rice seedlings (K32) at 32 °C reduced the number of total weeds by ≈60.0% and the total dry weight of weeds by 93.0%; i.e., to a greater extent than other root exudates. Among the 13 identified phenolic acids, p-hydroxybenzoic, vanillic, syringic, sinapic and benzoic acids—at concentrations of 0.360, 0.045, 3.052, 1.309 and 5.543 μg/mL might be involved in allelopathic responses of K32, inhibiting the growth of barnyardgrass and natural weeds. Findings of the present study may provide useful information on allelopathic responses of rice under environmental stresses and thus further understand of the competitive relationships between rice and weeds under natural conditions.
Highlights
Allelopathy is defined as chemical interaction(s) between plants that interfere with plant growth, mediated by the release of plant-produced bioactive secondary metabolites, referred to allelochemicals [1]
The results of this study provide useful information for better understanding the allelopathic responses of rice seedlings under multiple stresses, expected to occur concurrently in a changing climate
The percentage of germination rate was significantly inhibited by all the samples, which ranged from 7.1% to 28.6%
Summary
Allelopathy is defined as chemical interaction(s) between plants that interfere with plant growth, mediated by the release of plant-produced bioactive secondary metabolites, referred to allelochemicals [1]. Numerous allelochemicals derived from plants have been described to stimulate and/or inhibit other species’ germination and growth. Intense scientific efforts have focused in the past on describing the mechanisms used by plants to self-regulate their own and other species’ densities and distribution or those found at the basis of biological invasions via allelopathic interactions [4,5]. Allelopathic crop varieties can release their own “phytotoxins” as allelochemicals to reduce the growth of weeds, permitting ecological weed management in cropping systems [6,7].
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