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

Results On the 19th and 20th of July the cloud was over but there was no rain. The relative humidity of the air varied between 80-90% in day-time. At the beginning of the experiment it was 91% at ground level (microclimatic data are given on Fig. 2 - the temperature of the soil at -1 cm was practically identical with that measured under the moss tuft every time). The leaves of the moss samples were crisped, the lichen thalli were dry to the touch. In the course of the time the plants took up water from the air fast (Fig. 3). Between 22.00 and 23.00 hours the moss leaves became squarrose and the lichen thalli became wet to the touch. At the same time the velocity of water uptake dropped quickly (Fig. 4). Between 1 and 3 o'clock a.m. the plants took up no water, moreover they lost weight. It was dawning from about 3.15 (D on Figs. 2-4) and the weight of the plants increased again. The lowest temperature and the highest air humidity (100%) were measured at sunrise (4.15S on Figs. 2-4). This was the time of the morning dew. After sunrise the plants were running become dry at an increasing speed (Fig. 4). From sunrise on samples F2, C2 and T2 were in sunlight, that is why their velocity of drying out was higher and it decreased earlier than that of those being in the shade (FI, Cl and Tl). The moisture content of the plants reached the critical level (see above) between 6 and 7 o'clock a.m. From that time on the moss leaves were crisped and the lichen thalli were dry to the touch again. Fig. 2. Microclimatological measurements: relative air humidity ( - . — ) at ground level; air temperature at ground level ( ); the temperature in the moss-tuft ( ).; the temperature under the moss-tuft ( ) (T - temperature; t - time; H - relative air humidity; D - beginning of dawning; S - sunrise)