Yield reduction in sweetpotato with changes in peroxidase and growth hormones induced by shoot removal
1995
Nguyen Ba Lieu
Of the three varieties, [VSP-2, UPL-SP1, and Miracle] VSP-2 had a bushy growth habit. It produced more branches with fewer and smaller leaves so the total shoots and roots harvested were lesser and the number of the smaller roots was greater. Topping decreased root yield by 17 and 32 percent when done three (once every four weeks) and five times (once every two weeks) within 105 days, respectively starting at 32 DAP. Unlike untopped plants which showed no increase in dry weight of vines and roots after 75 DAP, topped ones continued to increase in these parameters indicating that topping delayed maturity. The reduction in root yield could be ascribed to the decline in LAI as roots are being formed and to the formation of more branches which in turn increased ABA content in the roots. ABA inhibited root growth and import assimilate into the roots, thus contributing to the decrease root yield with low starch content. Topping also decreased IAA content but not cytokinin level in root tissues. On the other hand, topping increased peroxidase activity which in turn inhibited root growth. Non-significant correlations among IAA, cytokinin, and peroxidase at all stages suggest that changes in activity of these substances were independent from each other. Root weight contributed more to yield than the number of roots. The greater the frequency of shoot removal, the lesser the number of extra-large, large, medium roots and the more proportion of small and rejected roots obtained
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