Accumutation of Carbon and Nitrogen Compounds in Sweet Potato Plants Grown under Deficiency of N, P, or K Nutrients

概要

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Sweet potato(Ipomoea batatas L.var.Beniazuma)plants were grown in the field of Hokkaido University where the following treatments : (1)application of nitrogen, phosphorus, and potassium(C plot), (2)absence of nitrogen application(-N plot), (3)absence of phosphorus application(-P plot), and (4)absence of potassium application(-K plot)have been maintained for 76y. Results obtained were as follows. 1)Under nitrogen deficiency, total dry weight and tuberous root dry weight decreased. Harvest index for dry weight in the -N plot was highest, while the harvest index for nitrogen was the lowest among the treatments, suggesting that high nitrogen use efficiency was achieved in the -N plot. 2)Under phosphorus deficiency, total dry weight was the same as that in the C plot, while tuberous root dry weight was strictly restricted, suggesting that the construction of proteins of cellulose in leaves was stimulated, and the construction of atarch in tuberous roots was restricted in the -P plot. 3)Under potassium deficiency, since nitrogen absorption was not restricted compared with the control, and phosphorus absorption was restricted, the nutritional status of the plants showed a nitrogen excess, suggesting that nitrogen excess and disorder of phloem transport adversely affected the sweet potato growth.