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Mungbean residue effects on the growth parameters of a succeeding mungbean crop

University of British Columbia

Investigations of mungbean (vigna radiata (L.)Wilczek) residues, which have been found to have adverse effects and cause substantial yield reduction on subsequent mungbean crops grown in rapid rotation, were undertaken to determine the source of phytotoxin and study its effects on growth parameters. There was no effect on plants grown in pots of steam-sterilized soil that had received leachates from actively growing mungbean plants in sand culture, or in pots that had received leachates of roots and leaves decomposing in sand. Effects from residues of previous mungbean crops were demonstrated when succeeding mungbean crops were grown such that their roots were in direct physical contact with the residue. Plants grown in soil in which root-leaf residue mix had been incubated for one week prior to seeding were about 50% of control in total dry weight at any sampling date. Total dry weight was further reduced to about 40% when incubation time was increased to three weeks. Separate experiments with root and leaf residues showed that leaf residues were about 12.3% more toxic than root residues on a proportionate residue weight basis. The combination of leaf and root residues did not show additive effects. Incorporation of the residues into the soil prevented normal seedling development. Plants growing from residue-treated soil had more assimilates allocated to the leaves during the vegetative stage compared to those from residue-free soil. During this stage net assimilation rate, relative growth rate, relative leaf area growth rate, and leaf area ratio became considerably greater than for controls. Although, relative leaf area growth rate was increased, which may have been due to more assimilates being allocated to the leaves, the greater magnitude of the increase in relative growth rate over that of the relative leaf area growth rate may account for the increase in the value of net assimilation rate. This would be possible if there was a reduction in respiratory losses, caused by the release of a respiratory inhibitor from the residues.

Text

2010-03-24

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http://hdl.handle.net/2429/22459

Plant Science

University of British Columbia

Graduate