EXPERIMENTAL CONTROL OF FLOWERING IN LEMNA I. GENERAL METHODS. PHOTOPERIODISM IN L. PEPUSILLA 6746

Hillman , William S. (Yale U., New Haven, Conn.) Experimental control of flowering in Lemna. I. General methods. Photoperiodism in L. perpusilla 6746. Amer. Jour. Bot. 46(6): 466–473. Illus. 1959.—Lemna perpusilla strain 6746 flowers as a typical short-day plant when grown aseptically in Hutner's medium (containing ethylenediaminetetraacetic acid, EDTA]) at 26–28°C. A method is described for quantitatively assaying the degree of flowering in a culture. Maximal flowering takes place under photoperiods of 6–11 hr., and none under photoperiods exceeding 15 hr. The flower-promoting effects of long nights are inhibited by brief interruptions with red light, such interruptions being most effective in the middle of the dark period. A single long night will cause the subsequent production of flowering fronds, but vegetative growth in the culture is resumed after a time. Only frond primordia at a very early stage of development appear to be sensitive to induction. Quantitative flowering experiments lasting a week or less can easily be performed with this plant; it is ideally suited for studies of the effects of light, darkness, temperature, organic compounds and other factors under highly controlled conditions.