Allelopathic Influence of Aquatic Weeds on Agro-Ecosystems: A Review

Abstract

Aquatic weeds are higher plants found in the aquatic ecosystem and in anaerobic rice fields, where they have no economic benefits. The continuance of aquatic weeds is more widespread than terrestrial weeds because in aquatic ecosystems there is very little fluctuation in the environmental conditions compared with terrestrial ecosystems. Scientists have been working to address the harmful allelopathic effects of aquatic weeds on the aquatic ecosystem, but limited information is available on the allelopathic influence of aquatic weeds on agro-ecosystems through the release of phytotoxic compounds. Phytotoxic chemicals released by different aquatic weeds into irrigation water and/or directly into rice ecosystems might have a significant inhibitory influence on germination, growth and yield field crops, soil properties and nutrients availability, population and community structure, and weed invasion. However, aquatic weeds might also be used as a potential organic alternative to chemical weed-control, due to the higher susceptibility of terrestrial weeds to the phototoxic chemicals released by aquatic weeds. Natural alternatives to chemical weed control are need of time and are crucial for a sustainable weed control. Chemical weed control is challenged, due to recent increases in herbicides resistance from weeds and to the harmful side-effects of herbicides on the environment. This review is focused on the influence of aquatic weeds on agro-ecosystems, with examples of common weeds in aquatic ecosystems and invasive aquatic weeds found in anaerobic rice.

Exploring the Herbicidal Potential of Achyranthes aspera Against Some Weeds

“…There are different chemical groups of allelochemicals, e.g., alkaloids, phenolics, saponins, oleonolic acid and dihydroxy ketones (Srivastav et al, 2011: Soltys et al, 2013. The allelopathic influence of various weed species has been explored against field crops and weeds (Abbas et al, 2017b). Inhibition of seed germination of other plants is one of the most common allelopathic strategies employed by A. aspera (Khan and Shaukat, 2006;Abbas et al, 2017b).…”

“…Ecological interference of weeds refer to a phenomenon by which weed plants release phytotoxic chemicals that inhibit germination and growth of surrounding crops or weed plants (Zimdahl, 2007). The literature has reported a significant inhibitory effect of various weed-released phytotoxins on germination and growth of other weed plants (Abbas et al, 2017b). For instance, Achyranthes aspera, Alternanthera philoxeroides, Datura metel and Rumex dentatus cause momentous reductions in germination and growth of invasive weed Parthenium hysterophorus (Safdar et al, 2016).…”

“…Maximum inhibition has been shown by the whole plant extract of A. aspera. Abbas et al (2017b) reviewed the herbicidal potential of different weed species, including Ageratum conyzoides, Alternanthera, Philoxeroides, Alternanthera sessilis, Echinochloa crus-galli and Echinochloa colona, against other weed species in cultivated land.…”

“…It can potentially grow on undisturbed waste land and major weed of cultivated crops including maize, sugarcane and wheat (Shah et al, 2006). Achyranthes aspera plants contain various phytotoxic compounds that potentially work as a herbicide to inhibit germination and growth of other weed species (Rameshwar and akito, 2007;Srivastav et al, 2011, Abbas et al, 2017b. Safdar et al (2016), explored the herbicidal potential of A. aspera as a natural herbicide against exotic invasive weed P. hysterophorus.…”

Investigating the use of aquatic weeds as biopesticides towards promoting sustainable agriculture

“…Although floating aquatic weeds are capable of sequestering and storing high concentrations of phosphorus (P) from the drainage water and sediment, they release this nutrient back into the ecosystem once they senesce and die [2,3]. Large populations of floating aquatic weeds can reduce light penetration to the deep layer of the waterbody, thus resulting in a reduced primary production [4]. Moreover, excessive presence of aquatic weeds in farm canals can block water outlets during irrigation, clog canals, and impede water flow, resulting in low oxygen and poor water quality [5].…”