Pollen vigour and composition in relation to andromonoecy in cashew (Anacardium occidentale L.: Anacardiaceae)

Summary Cashew trees produce four types of pollen from the large and small stamens of the hermaphrodite and male flower (HL, HS, ML, MS). Comparative studies were made of the grain number, structure, viability, vigour, and sugar and amino acid composition of the four pollen types. Anther and pollen grain numbers and dimensions of the four pollen types were similar, as were pollen structure and staining characteristics. The fluorescein diacetate test showed that the HL pollen had the highest percent fluorescence, and viability of all pollen types had declined by 48 h after anthesis. Following controlled hand pollination, the ML pollen had the highest capacity to germinate on the stigma and penetrate the ovule, followed by the MS, HL, and HS pollens. Glucose and fructose and 19 free amino acids were present in all pollen types, with higher levels in the hermaphrodite than in the male flower pollen. The results indicate that the pollen of the male flower is specialised for pollination and fruit set, whereas that of the hermaphrodite flower may be specialised for insect attraction.