Growth Rate and Temperature Responses in Bryophytes: I. An Investigation of Brachythecium Rutabulum

(1) The growth of the perennial pleurocarpous moss Brach 'thecium rutabulum under controlled conditions of temperature, irradiance, moisture and inorganic nutrient supply was analysed. (2) Over a period of 30 days, the species maintained exponential growth and attained a relative growth rate of 0 071 day-'-a value exceeding the reported maxima for seedlings of ten vascular plant species. (3) In a temperature gradient, maxima in relative growth rate, shoot length and leaf area occurred at about 19 IC but at 5 ?C the reduction in relative growth rate was less than 40%. (4) The comparatively high relative growth rate of B. rutabulum is consistent with the large amplitude of seasonal change in biomass and rapid turnover of shoots observed under natural conditions. The capacity to grow at low temperature may be related to the tendency of the species to exploit the cool conditions of spring and autumn and may also explain the ability of the species to co-exist with productive vascular plants.