SEED MASS AND NUTRIENT CONTENT IN NUTRIENT-STARVED TROPICAL RAIN-FOREST IN VENEZUELA

Mean seed dry mass values were determined for 27 species of trees and shrubs in Amazonian caatinga (a forest-type especially short of nitrog en) and for 11 species in adjacent much taller forest on less poor soi l. The tall trees (>15 m) of caatinga have smaller seeds than the tall trees in adjacent forest on less infertile soil (both overall and in six taxonomically controlled comparisons), and than the tall trees in lowland rainforests elsewhere. The smaller seed size is interpreted in terms of a major advantage of keeping up seed number outweighing the marginal advantages of larger seed size. For trees of caatinga and adj acent forest considered together, there is a significantly greater con centration of P and Mg, and almost significantly greater concentration of N, in the embryo-cum-endosperm fraction of smaller-seeded species, but the content per seed of N, P and Mg is smaller in smaller seeds. The mean contribution of the seed coat (including endocarp for pyrenes ) was 17% for dry mass, 3% for content of P, 10% for N and Mg, 15% for K, and 30% for Ca.