Studies of Pollen Characteristics in Plants of Fruitless Tecomella undulata (Sm.) Seem. (Bignoniaceae) in Golparaki Region of Jiroft City, Iran

Abstract

Tecomella undulata is valued for beautiful flowers, resistance against extreme temperature and drought, stabilizing shifting sand dunes, medicinal properties and wood production. In spite of massive flowering, the species is seedless. The present study examines the causes of its sterility indicating on pollen characteristics. Flowers were hand pollinated by pollen of either self- or outcross pollen. Some flowers were tagged as open pollination treatment. Pollen structure, in situ and in vitro pollen germination and pollen tube growth were analyzed. Mature pollen grains are heteromorphic, mostly heterogeneous sized as small and large. Both pollen grains types are prolate and tricolpate with rugulate–reticulate sculpture. Flowers are protandrous and have long stylus; a nectariferous tissue secreting abundant nectar exists in the ovary base. No effective pollinator visited flowers during the observation period. No pollen germination and pollen tube growth were observed in self- and cross-pollinated styles and under in vitro condition. It seems that pollen heterogeneity, lack of pollinators and pollen limitation, the failure of autogamy due to protandry or long styli as well as self-incompatibility resulted in pollen sterility and seedlessness. In addition, probably polyploidy and cytomixis affect infertility too that needs to be studied in detail in the future.