Zs. P. Komáromy szerk.: Studia Botanica Hungarica 16. 1982 (Budapest, 1982)

Rajczy, Miklós: About the length of active life of some xerophytic cryptogams in the dry season

STUDIA BOTANICA HUNGARICA (Antea: Fragmenta Botanica) XVI. 1982 P6772 About the length of active life of some xerophytic cryptogams in the dry season By M. RAJCZY (Received November 30, 1981) Abstract: A whole night-long experiment was carried out with the aim of clearing up whether xerophytic mosses and lichens were able to live active life daily or only after rainfalls in the dry season. The dynamism of water content of the plants was studied in the field with the aid of gravimetric determinations. In this case a 6-7 hours' long (within it about 2 hours' photosynthetic) active life was proved in a Hungarian sandy steppe. A great number of authors have dealt with the water relations of mosses and lichens. It turned out already in the earliest experiments that these plants are able to take up water from the atmosphere, too (MÜLLER 1909, MÄGDEFRAU 1931 and others). The water uptaking capacity proved to be independent from the xerophytic character of the examined bryophytes in some experiments (PATTERSON 1943). Anyhow, PATTERSON did not examine the dynamism of this uptake. Indeed, xerophytic mosses take up water from the atmosphere 2-3 times quicker (MÄGDEFRAU 1931). Seasonal changes have a great effect, too. Plants collected in winter take up more atmospheric water and their resistence to desiccation is far greater (HOSOKAWA & KUBOTA 1957, VERSEGHY 1971). The importance of air humidity as water supply proved to be little in mesophytic bryophytes. According to KLEEPER (1963) Dicranum scoparium gametophytes depend only on rainwater. The leaves of Atrichum undulatum and Polytrichum commune remain crisped in the atmosphere saturated with water as to ANDERSON & BOURDEAU (1955). Another paper is inconsistent with these results. In the experiments of RAJCZY (1978) Atrichum undulatum under cave condition could live more than two years at 95-100% relative humidity (no leaves were crisped during this long period). The aim of my investigation was how long the active period in the life of real xerophytic mosses and lichens was. If they depend primarily on rain as water supply they will be active only on rainy days (KLEEPER 1963) i.e. 5-6 days monthly in the investigated territory in summer (Fig. 1). If they depend either on air humidity or on rainwater, they will be active every day at night and in the morning utilizing the high moisture content of the air and the dew.