ALLELOPATHIC GROWTH STIMULATION OF PLANTS AND MICROORGANISMS.

Authors: MALIK, M.A.B. - LANGSTON UNIVERSITY; Williams, Robert

Submitted to: Allelopathy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2005
Publication Date: 10/21/2005
Citation: Malik, M., Williams, R.D. 2005. Allelopathic growth stimulation of plants and microorganisms. Allelopathy Journal 16(2):175-198.

Interpretive Summary: Allelopathy is defined in the dictionary as "the repression or destruction of plants from the effect of certain toxic chemical substances produced and released by other, or near by, plants." This aspect of allelopathy is the one generally referred to in the scientific literature. However, allelopathy can involve a stimulatory effect, and its broader definition includes both stimulatory, as well as inhibitory, plant responses. The stimulation of plants and microorganisms is often ignored in the literature. Here we review the literature and provide examples of how these allelochemicals stimulate plant and microbial growth, influence legume nodulation and nitrogen fixation, and impart resistance to plant diseases. These examples indicate that the allelochemicals from plants and microorganisms have potential to enhance yield of agricultural products, while promoting sustainable agriculture.

Technical Abstract: Growth promotion of plants by other plants and microorganisms, as well as of microorganisms by plants and other microorganisms, is discussed. Agrostemma githago in mixed culture with wheat, enhances growth and yield of wheat. Allantoin, a purine derivative and the principal component of agrostemin released from A. githago, is the growth factor. Soil amended with shoots of Solanum nigrum enhances soybean growth and nodulation. Growth and yield of several legumes are enhanced by mixed culture with Heliotropium peruvianum. Triacontanol isolated from alfalfa, and brassinolide from rape and alder pollen, stimulate growth and yield of several crops. Chromosaponin I, isolated from etiolated pea seedlings, stimulates growth of lettuce by 190%. Petunioside M stimulates growth of cucumber and suppresses cucumber mosaic virus. Strigolactones, isolated from host or non-host plants, promote seed germination of angiospermous parasites. Unidentified allelochemicals from Chenopodium album and Setaria viridis enhance growth of Bradyrhizobium japonicum in broth culture. Seed inoculation with selected strains of Pseudomonas capacia and P. putida enhances growth and yield of wheat under field conditions. Inoculation of soybean seeds with a strain of Bacillus cereus enhances growth and nodulation of soybean by indigenous nodulating bacterium. Several soil microbes, with appropriate precursors, produce plant growth regulators that enhance plant growth. Pearl millet inoculated with Azospirillum brasilense and grown in solution culture amended with tryptophan produces more lateral roots with greater root hair density than the control. Microbial metabolites enhance the growth of several Rhizobiuim species and promote reproduction in certain fungi. These examples indicate that the allelochemicals from plants and microorganisms have potential to enhance yield of agricultural products, while promoting sustainable agriculture.