Effect of nutrients and chemical supplements on the development of nodules in certain leguminous crops

Abstract

Experiments were performed to study the effects of nutrients and certain chemi-cals including hormones on the development of nodu-les in Phaseolus aureus Roxb plants. The results obtained in the experiments are abstracted as follows: The growth of Phaseolus aureus plants, production of nodules, dry weights of the plants and nodules are affected by environmental and other factors. Phaseolus aureus plants are inoculated with Rhizobia taken from culture medium cause increased number of nodules and dry weight of the plants. Dilute solution of nitrate nitrogen enhances growth of Phaseolus aureus plants and their nodules.Nitrate nitrogen is essential for initiation of nodules in Phaseolus aureus plants. However, increased concentration of nitrate nitrogen in the soil lead to effects resulting in lesser number of nodules. Water-stress and water-logging seriously affect the production of nodule and dry matter in Phaseolus aureus plants. Nitrogen free nutrient solution causes increased number of nodules in Phaseolus aureus plants while nitrogen containing solution causes enhanced dry weight of plants and their nodules. Root aeration induces production of greater number of nodules.Filter paper technique described in this thesis is an improved way of aerating roots for facilitating production of greater number of nodules in P.aureus plants. Phaseolus aureus plants to be more efficient in nodule production need early infection by Rhizobium. 2-10 day-old seedlings are found to be most efficient in this respect. Of the different forms of nitrogen supplied to Phaseolus aureus plants,viz. nitrate nitrogen,ammonium nitrogen and urea,only a very dilute concentration of nitrate nitrogen is suitable for triggering nodulation. The other two forms of nitrogen are not effective. The nodules produced in P. aureus plants grown in nitrogen free nutrient solution interestingly have nitrogen contents more that is to say they are able to fix more nitrogen. Growth of plants, production of nodules and fixation of nitrogen in the nodules of...