Pollen morphology of seven wild species of Acacia in Saudi Arabia

Pollen micromorphological characters such as pollen size, shape, number of associated monads, colpi and ornamentation of the tectum surface, of seven species of Acacia belonging to the family Mimosaceae were studied, using light microscope (LM) and scanning electron microscope (SEM). The study showed that the pollen size range from 42.1 to 69.4 µm, pollen shape is round to semi- round, the number of associated monads is 16 or 32, and the colpus is Y - H shaped. The tectum surface ornamentation among the species is variable, it is foveolate in Acacia ehrenbergiana; psilate-foveolate in Acacia nilotica, Acacia laeta and Acacia negrii; and micro-reticulate in Acacia farnesiana, Acacia oerfota and Acacia tortilis ssp. raddiana. An artificial key based on micromorphological characters is provided. Key words: Mimosaceae, Acacia, pollen morphological characters, Saudi Arabia.