Effect of Light Intensity and Sucrose on the Production of Gemma Cups and Gemmae in Marchantia nepalensis

Abstract

Low light intensity (5-10 foot-candles) inhibits the production of gemma cups in Marchantia nepalensis. Under 200 foot-candles gemma cups and gemmae are formed; their production is increased by a higher light in- tensity (600 foot-candles). Sucrose in the medium brings about in situ germina- tion of gemmae, and this effect is enhanced by increased light intensity. The production of gemma cups in Marchantia is influenced by several factors. Voth and Hamner (1940) reported that in M. polymorpha more gemma cups are produced under a short photoperiod of about eight hours than under a long photo- period of 17-18 hours. Voth (1941) found that under a long photoperiod of 18 hours the production of gemma cups is favored largely by a high nitrate level and a very low phosphate supply. He also observed that the number of gemma cups on the female plants was considerably less than on the male plants (1:6.6), and considered that this offers possibilities in identification of the sex of vegetative plants of this species. Subsequently, Voth (1943) reported that relatively high osmotic concen- tration of the nutrient solution results in the formation of a greater number of these reproductive bodies. Scott (1963) observed that in M. berteroana 150C favored pro- duction of more gemma cups than 5oC or 100C. He also reported that high humidity suppresses gemma cup production. Kaul et al. (1962), however, noticed that in M. nepalensis there were markedly fewer gemma cups and gemmae on solid cultures than in the corresponding liquid cultures. We have studied the effect of light intensity and sucrose concentration on the production of gemma cups and gemmae under a fixed photoperiod. MATERIALS AND METHODS Plants of Marchantia nepalensis L. & L. f., bearing gemma cups, were collected from Mussoorie in September, 1968. The gemmae were sterilized with 0.2% HgCl2, washed repeatedly with sterile water, and planted on semisolid medium (with 0.8% agar) containing Knop's mineral salts, Nitsch's trace element solution (1 ppm), ferric citrate (10 ppm), and sucrose (0%, 2% and 4%). The pH of the medium was adjusted to 5.8 before autoclaving. Thalli produced by a single gemma were multiplied and young, 5-6-mm-long thalli, of approximately the same age, were used as explants in the experiments. All the cultures were axenic. They were maintained under 25 ? 2?C and 55-60% relative humidity. The number of cultures per treatment was 12, and the experiments were repeated once. Observations were recorded 8 weeks after the start of experiments. Light was provided from a mixed source 1 We thank Professor B. M. Johri for facilities and Dr. M. Lal for going through the manuscript. The financial help of the U.G.C. to one of us (S.S.) is also gratefully acknowledged.