The period for which seed can remain viable without germinating is greatly affected by its quality at the time of collection, its treatment between collection and storage and the conditions in which it is stored. According to Harrington (1972) one of the two main factors influencing seed longevity is seed moisture content. Seeds are hygroscopic and their moisture contents come into equilibrium with those of the atmosphere. Nevertheless, seed longevity varies enormously from species to species even if they are given identical treatment and storage conditions. Ewart (1908) divided seeds into three biological classes according to the time for which they are capable of retaining viability under “good” storage conditions:
• Microbiotic: seed life span not exceeding 3 years
• Mesobiotic: seed life span from 3 to 15 years
• Macrobiotic: seed life span from 15 to over 100 years.
Although Ewart's classes were useful in drawing attention to the differences in natural longevity of seeds of different species, his classification is too rigid to fit …show more content…
Attack by fungi and insects is most rapid on the forest floor, so collection from the ground should be carried out as soon after fruit fall as possible. Fungicidal treatment cannot be generally recommended since it can be harmful to seeds (Magini 1962); many fungicides are only effective when dissolved in water and are inappropriate for dry storage. Insects are usually killed if seeds are dried at temperatures above 40° – 42° C. For seeds which cannot be dried, other measures may be needed (FAO, 1985, Willan, 1985). For example seeds of Quercus are fumigated with serafume or other chemicals or heated in warm water for control of weevils (Belcher 1966, Olson 1957), while methyl bromide or carbon bisulphide are also commonly used to kill insects (Boland et al.