The effect of shoot spacing on the growth and branch development of the moss Rhytidiadelphus triquetrus



The effects of a range of shoot spacings (5, 10, 20, 50 mm) on the growth and development of the moss Rhytidiadelphus triquetrus (Hedw.) Warnst. within artificial colonies were studied under conditions of intermittent moisture supply. Growth of the main axis was promoted by decreased spacings of the shoots, probably due to increased resistance to evaporation and prolongation of the period of metabolic activity. Etiolation of shoots occurred at close spacings but no self-thinning was observed. The growth of determinate lateral branches was also stimulated by decreasing shoot spacings but the closest plantings led to inhibited branch growth for shoots in the centres of the colonies. Marginal shoots generally showed less growth of the main axis and branches than central shoots except at the 5 mm spacing.

The numbers of offshoots of indeterminate growth produced at each shoot spacing were low and only a slight trend of increasing offshoot production with increasing spacing was observed over the range 5–20 mm.

Overall growth of shoots was optimal at or near to the closest spacing. Calculated productivity was, therefore, greatest for the densest colonies (1000 shoots dm a) indicating that the advantage of reduced water loss, conferred by dense packing of shoots, greatly outweighs the disadvantage of reduced irradiance.