Research Regarding the Mechanism of Water Retention and Resistance to Drought of Sempervivum Cultivars

摘要

In the first part of this paper one mentions the landscape value of the Sempervirum plants. The research part has proposed to establish the behaviour of the Sempervirum tectorum and S. montanum rosettes tested in water and heat stress conditions, as well as in strong heatstroke conditions. The effects of these climatic factors, with values high over the maximum ones accepted, were appreciated according the quantity of water lost during the 12 days while the experiment was carried out. The results are expressed numerically in tables, through graphic curves and photo- images. One ascertained that, in the first day of the experiment, both normal developed rosettes and the young ones lost the highest part of the water quantity, equivalent to 19%-20% of their initial weight. In the next few days (2-3 days) the water losses are lower, 5%-16%, and decrease more, 1%-2%, starting the forth -fifth day.One also established that the water losses have not affected the entire rosette, but only the external leafs, which dry out, from outside to inside, towards the interior. The phenomenon stops when the rosette leafs are tight in the central rosette protecting each other, through coating.