1Agricultural Research and Extension Programmes, Langston University, P.O. Box 1730, Langston OK 73050, USA. E-mail: mmallik@luresext.edu.
2USDA-ARS-GRL, Langston University, P.O. Box 1730, Langston OK 73050, USA. E-mail: rdwms@luresext.edu.
*Corresponding author.
Growth promotion of plants by other plants and microorganisms, as well as that 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 the 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, stimulates the growth and yield of several crops. Chromosaponin I, isolated from etiolated pea seedlings, stimulates the growth of lettuce by 190%. Petunioside M stimulates the growth of cucumber and suppresses the 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 enhances the growth of Bradyrhizobium japonicum in broth culture.
Seed inoculation with selected strains of Pseudomonas capacia and P. putida enhances the growth and yield of wheat under field conditions. Inoculation of soybean seeds with a strain of Bacillus cereus enhances the growth and nodulation of soybean by indigenous nodulating bacterium. Several soil microbes, with appropriate precursors, produce plant growth regulators that enhance the plant growth. Tomatoes grown in soil amended with L-ethionine at the appropriate concentration produce more and larger fruits than the untreated soil. 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 the yield of agricultural products, while promoting sustainable agriculture.
Allantoin, auxins, cytokinins, ethylene, gibberellins, nitrogen fixation, petunioside, plant-microbe interaction, rhizosphere microorganisms, saponin, strygolactones
