Radim Adolt – Diploma thesis – 2001 – Mendel University of Agriculture and Forestry Brno
Key words
Dracaena, Dracaena draco, Dracaena cinnabari, population, germination, seeds, statistical analysis, biometric dimensions, age structure, anatomical structure, climatic data
Abstract
Dracaena draco (Macaronesia) and Dracaena cinnabari (Socotra) are taxonomicaly related species. D. draco is extremly rare in original populations. The development of the populations of D. cinnabari under environmental pressure of pasture does not offer an optimistic look in to the future.
The germinating ability of seeds of D. draco may in optimal conditions reach at least 77 %. In case of this species the germination was significantly higher if the experiment was started with entire fruits.
D. cinnabari germinated in soil conditions by only 5% after preparation in H3C-COOH. The germination was increased to 22 % using 1% H2O2.
Statistical analysis of biometric dimensions in two populations of D. cinnabari are presented. Fractile functions for each mesured dimension and locality were found. The probable age structure of both populations is discussed.
D. draco has in 95 % cases and with 95% statistical certainty the diameter of seed between 6.60 mm and 8.81 mm. The same percentage of seeds with the same statistical certainty have by D. cinnabari the diameter between 4.13 mm and 4.98 mm. Fractile functions for seeds diameter of both species are included.
There are anatomical differences between the part of the stem, which originates from primary meristems of the terminal bud and the part formed by special cambial tissue.
One-year period of processed climatic data from Socotra (Firmihin 440 m) can be found in this work. A theoretical annual course of weather for lower parts of Firmihin (440 m) is described.
Summary
The germinating ability of seeds of Dracaena draco may in optimal conditions reach at least 77 %. In case of this species the germination was significantly higher if the experiment was started with entire fruits.
Dracaena cinnabari germinated in soil conditions by only 5% after preparation in H3C-COOH. The germination was increased to 22 % using 1% H2O2.
The variances of heights of trees and lenghts of stems are significantly higher in Methar (1310 m) than in Firmihin (440 m). The average value of the height of tree in Methar does not differ from this value in Firmihin. The average value of the lenght of stem in Methar is significantly smaller then in Firmihin. Fractile functions for each mesured dimension and locality is also available. The probable age structure of both populations were discussed.
Dracaena draco has in 95% cases and with 95% statistical certainty the diameter of seed between 6.60 mm and 8.81 mm. The same percentage of seeds with the same statistical certainty have by Dracaena cinnabari the diameter between 4.13 mm and 4.98 mm. Fractile functions for seeds diameter of both species are included.
There are anatomical differences between the part of the stem, which originates from primary meristems of the terminal bud and the part formed by special cambial tissue. Stems of Dracaena species contain exclusively tracheids, however in leaves and roots also vessels are present.
It seems, that precipitations in higher areas of Socotra are possible during each of the monsoons. In lower altitude of southern Socotra the precipitations occur in most of cases from August to early October (summer monsoon). On the other hand the precipitations in lower parts of nothern Socotra are to be expected from November to January (winter monsson). This distribution of precipitations is a consequence of drier phenomenon caused by the orographic ridge of Haghier mountains.