Morphological, ecological and cytological studies on cultivated and wild butterburs, Petasites japonicus MAXIM. II

Abstract

Butterbur is a dioecious perennial vegetable. In this paper are presented the results of observations on the sex expression and secondary sex characters of the cultivated and wild butterburs collected from various localities of Japan. 1. In female plants, a head is composed of 20_??_100 female florets and several sterile ones. The sterile florets are found in the center of a head, and have a pistil and shriveled anthers, but never produce pollen nor seeds. The female florets are fertile and produce seeds. (Figs. 4, 5, 6 and 8) In male plants, a head is composed of fewer number (15_??_55) of morphologically hermaphroditic florets. The floret has a pistil and anthers which produce viable pollen, but never set seed even when artificially pollinated; so it is functionally a male floret. (Figs. 1, 2, 3 and 7) Monoecious plants which have female and male florets in the same head were scarecely found; only one plant was found among wild butterburs observed. 2. Sex ratio was approximately 1:1 in wild butterburs, and also in the seedlings of wild butter-burs (Table 2). In the cultivated varieties, how-ever, female plants were predominating in number; no male plants were found in the fields of “Aichi-wasebuki” in various localities, and 70_??_100 percent of the plants were female in the fields of “Mizubu-ki” and cultivated strains of “Akitabuki” (Table 3). 3. It was found that there were no differences in time of sprouting, time of flowering (Fig. 11), growth habit, size of leaves, etc. between female and male plants. 4. The sex of butterburs is a stable character and is not affected by age of stock, nutritional conditions and other factors. 5. The reason why female plants were predominating in the cultivated varieties was discuss-ed. It is assumed that more female plants have been introduced accidentally to cultivation, but this problem will be discussed further in the succeed-ing papers.