Flower and stamen structures of male-fertile and male-sterile chestnut (Castanea sativa Mill.) cultivars

The flower and stamen structures of four male-fertile ('Firdola', 'Karamehmet', 'Sariaslama', and 'Haciomer') and two male-sterile ('Osmanoglu' and Wakit Kestanesi') chestnut cultivars were evaluated using scanning electron and light microscopes. Anther dimensions and pollen production capabilities were also determined. Stamens of the male-fertile cultivars showed more distinct flowering habit than male-sterile cultivars, which failed to show visible flowering due to shorter stamens. Flower clusters on the catkins had six to seven flowers while the mean number of stamens per flower varied from 9.50 to 11.95 among the cultivars, except for 'Osmanoglu' with 2.60 stamens per flower. Some 'Osmanoglu' flowers had no stamens or abnormal stamens (e.g., lacking anthers) or abortive anthers. Stamens of the male-sterile cultivar Vakit Kestanesi had short filaments and small anthers with few or no pollen. The pollen number per anther was significantly lower in the male-sterile than in the male-fertile cultivars. Three different kinds of anther surface morphologies were determined among the cultivars. The surface structure of male-fertile cultivars consisted of polygonal epidermis cells. Male-sterile 'Osmanoglu' had long polygonal epidermis cells, which had a thread-like surface appearance. Male-sterile Wakit Kestanesi' had epidermis cells with hollow middles and swollen edges. In male-sterile cultivars the length of the anthers was significantly less than that of the male-fertile cultivars. The anther wall of the male-fertile cultivars consisted of three clearly different cell layers. However, the anther walls of the male-sterile cultivars were not complete in all cases, and the number of layers varied from one to three