The Effects of Long and Short Photoperiods on the Rate of Growth and Gemmae Cup Production in Marchantia polymorpha L.

Abstract

For many years botanists have been interested in determining what factors are responsible for gemmae cup production in Marchantia polymorpha L. Voth (1943) performed a series of greenhouse experiments using various concentrations of nutritive solutions. In these studies it was noted that the omission of K, Ca, NO3 and PO, ions resulted in some distortion in the gross appearance of Marchantia, and the absence of calcium resulted in the death of the growing tips. Previously Voth and Hamner (1940) had conducted extensive research into the nutritional requirements of Marchantia, and in this work gave consideration to the photoperiod requirements for both total growth and gemmae cup production. It was reported that irrespective of the range of nutrient supply, plants on long photoperiods were larger and had greater dry weight, but produced fewer gemmae cups than plants grown on a shorter photoperiod. Benson-Evans (1961) has more recently published the results of additional studies concerning photoperiod and reproduction in the Bryophyta. In these studies it was shown that growth in Marchantia responded to increased light intensities, but the day-length influences the number of gametophores that were produced. The primary objective of this research was to compare and measure the rate of growth and the rate of gemmae cup production in a long photoperiod (16 hours) and short photoperiod (eight hours). This study duplicates one aspect of the experiments conducted by Voth and Hamner, that of measuring the total growth and the total numbers of gemmae cups produced. Its main purpose, however, was to determine the age and size of the thallus at the time the first gemmae cups were produced and to record the numbers produced in the ensuing weeks, while recording the increase in the size of the thallus. It was noted in earlier pilot studies that there is considerable variation in the numbers of gemmae cups produced on sections of thallus