Role of putrescine in Lemna plants under potassium deficiency

Putrescine (1,4-diaminobutane) accumulation in potassium (K)-deficient plants was considered to be one of the factors causing K deficiency symptoms in plants. However, experiments using aseptic cultures of Lemna paucicostata 6746 and Lemna gibba G3 (duckweeds) led to opposite results; the growth of the plants under K deficiency recovered to some extent when putrescine was administered, although the content of putrescine in these plants was considerably higher than that in the plants which did not receive putrescine. Thus it is inferred that putrescine does not cause K deficiency symptoms but that it plays a role in the replacement of K as an organic cation in K-deficient plants. Experiments using putrescine biosynthesis inhibitors also in part supported this hypothesis.