An experimental study of growth in relation to morphology and shoot water content in maritime Antarctic mosses
The dependence of shoot growth and growth form on water availability was studied experimentally in six species of maritime Antarctic moss. Under all conditions the largest growth increments were observed in the hydric species Brachythecium austro-salebrosum and Drepanocladus uncinatus. The xeric Andreaea depressinervis grew the least. Lateral shoot production varied within and between species. Over 50 % of the biomass produced in D. uncinatus was derived from lateral shoot production, whereas Polytrichum alpestre produced very few lateral shoots and A. depressinervis produced none. Leaf density and leaf size also varied with total water content.
In all species growth ceased at total water contents of 100% d. wt or less. However, the total water content at which maximum growth was observed differed between species. Racomitrium austro-georgicum (mesic/xeric) had the lowest optimum for growth at 370% of d. wt and D. uncinatus (hydric) exhibited maximum growth between 890 and 2300% d. wt. Optimum total water contents for growth were greater than those at full turgor and published optima for net assimilation.
Growth and total water content of these Antarctic mosses were similar to those reported for temperate species.