Keywords :
Seed; Dry Dipterocarp Forest
บทคัดย่อ :
The relationship of seed moisture content (fresh weight basis) to germination, and the effect on viability of various storage conditions were examined for five species of the tropical forest tree genus Dipterocarpus. It was shown that seeds fall into two groups with regard to desiccation tolerance. Firstly, D. obtusifolius and D. turbinatus cannot be dried below about 45% moisture content without damage; a sigmoid curve was found to fit the relationship between germination and moisture content for the latter species. Secondly, D. intricatus, D. tuberculatus and D. alatus can be safely dried to lo%, 12% and 17% moisture contents respectively, but desiccation to near 7% moisture content reduced viability by at least a half. Storage studies showed that seed of D. intricatus and D. tuberculatus possessed increased longevity as moisture contents were reduced within the range 6-20%. It was concluded that seeds in the first group are recalcitrant and that those in the second group are orthodox in their storage physiology, according to the categories described by Roberts (1973). Wide differences between species in seed desiccation rates were observed. In 15% relative humidity D. intricatus dried to 7% moisture content within a week, whilst D. obtusijolius retained 30% moisture content even after 5 wk; other species had intermediate desiccation rates. Seed size and structure may partly account for the differences observed. Correlations were observed between seed storage physiology and other factors which were investigated. Orthodox seeds had quicker desiccation rates, were derived from drier habitats, and had smaller embryos than those of recalcitrant seeds. Orthodox seeds, with the possible exception of D. alatus, should be kept at 0-3(degrees)C with about 12% moisture content in the short term and, provided less than 10% germination is lost on freezing, at - 18(degrees)C with about 8% moisture content in the long term. Recalcitrant seeds should be stored in ventilated containers at 21(degrees)C and with moisture contents above 45-50%.
เอกสารอ้างอิง :
Tompsett, P. (1987). Desiccation and storage studies on Dipterocarpm seeds. Annals of Applied Biology, 110(2), 371-379.
