Between-tree and floral variations in pollen viability and pollen tube growth in obeche ( Triplochiton scleroxylon)

Abstract

Pollen from 60 flowers obtained from three different obeche trees ( Triplochiton scleroxylon K. Schum.) located in Ibadan (7°17′N and 3°30′E) were studied for variability in viability and tube growth. Pollen viability differed significantly between the flowers from the three sources. The number of flowers with viable pollen grains ranged from 5 (25%) in the sample from tree II to a maximum of 13 (65%) in the sample from tree III. The mean number of viable pollen grains per sample ranged from 1 in tree II to a maximum of 4 in tree III. Among the flowers with viable pollen grains, the mean number of viable pollen grains per flower ranged from 1 to 4 in tree II to a maximum of 17 in trees I and III. There were significant differences in pollen tube growth between the flowers from each of the trees. Apart from the effects of pests and diseases, variation in pollen viability between trees and from flower to flower may also contribute to the low seed-set in this species.