Research Progress on the use of Plant Allelopathy in Agriculture and the Physiological and Ecological Mechanisms of Allelopathy

Abstract

Allelopathy is a common biological phenomenon by which one organism produces biochemicals that influence the growth, survival, development, and reproduction of other organisms. These biochemicals are known as allelochemicals and have beneficial or detrimental effects on target organisms. Plant allelopathy is one of the modes of interaction between receptor and donor plants and may exert either positive effects (e.g., for agricultural management, such as weed control, crop protection, or crop re-establishment) or negative effects (e.g., autotoxicity, soil sickness, or biological invasion). To ensure sustainable agricultural development, it is important to exploit cultivation systems that take advantage of the stimulatory/inhibitory influence of allelopathic plants to regulate plant growth and development and to avoid allelopathic autotoxicity. Allelochemicals can potentially be used as growth regulators, herbicides, insecticides, and antimicrobial crop protection products. Here, we reviewed the plant allelopathy management practices applied in agriculture and the underlying allelopathic mechanisms described in the literature. The major points addressed are as follows: (1) Description of management practices related to allelopathy and allelochemicals in agriculture. (2) Discussion of the progress regarding the mode of action of allelochemicals and the physiological mechanisms of allelopathy, consisting of the influence on cell micro- and ultra-structure, cell division and elongation, membrane permeability, oxidative and antioxidant systems, growth regulation systems, respiration, enzyme synthesis and metabolism, photosynthesis, mineral ion uptake, protein and nucleic acid synthesis. (3) Evaluation of the effect of ecological mechanisms exerted by allelopathy on microorganisms and the ecological environment. (4) Discussion of existing problems and proposal for future research directions in this field to provide a useful reference for future studies on plant allelopathy.

Keywords: agricultural sustainable development; agriculture practice; allelochemical; allelopathy; ecological mechanism; microorganism; physiological mechanism.

FIGURE 1

Structures of some of the allelochemicals produced by plants.

FIGURE 2

Field trial on rye mulch preceding a tomato crop in a biological farm (Schulz et al., 2013). Left, test plot with rye mulch left on the soil surface, showing the good weed suppression ability. Right, control plot without rye mulch, split into two treatments: left side, untreated sub-plot in which tomato plants are almost completely overgrown by weeds; right side, sub-plot with mechanical control by cultivation, in which tomato plants grow as well as those in the test plot.

FIGURE 3

A schematic diagram showing the various roles of microbes in modulating the interaction of allelopathic donor-receiver species (Barazani and Friedman, 1999; Bais et al., 2006; Mishra et al., 2013). Red arrows with double lines indicate the phenomenon of allelopathy, and blue arrows with single lines indicate the involvement of various microbial processes in reducing/enhancing allelopathic inhibition by soil microorganisms. This figure explains that beneficial rhizobacteria can minimize the phytotoxicity of the allelopathic donor toward the allelopathic receiver by using various rhizospheric processes such as rhizosphere colonization, biofilm formation, and degradation/transformation of toxic allelochemicals or modulation of the defense mechanism in receiver species by inducing the expression of stress responsive genes or the activity of antioxidant enzymes. Furthermore, microbes also can play an important role in the activation of allelochemicals, e.g., through the release of non-toxic glycosides followed by microbial degradation to release the active allelochemical.

FIGURE 4

Induction of allelochemical production by the plant itself and environmental factors (Part of this figure was modified from Albuquerque; Albuquerque et al., 2010). The plant factors include species, variety, growth stage, tissue type, etc. Environmental factors include abiotic factors (irradiation, temperature, nutrient limitation, moisture, pH) and biotic factors (plant competition, diseases, insects, animal attack and receptor feedback regulation).