Pollen morphology of the subfamily Aurantioideae (Rutaceae)

The Aurantioideae is one of seven subfamilies of the Rutaceae consisting of two tribes. the Clauseneae, containing five genera, and the Citreae, with 28 genera. Each tribe contains three subtribes. The pollen morphology of the subfamily Aurantioideae is described;Ind illustrated for the first time based on light and scanning electron microscopy. Five pollen types have been recognised in the subfamily, based mainly on aperture number and exine ornamentation. The pollen grains show a high degree of intergeneric variation. Pollen grains of Clauseneae are 3-colporate, microstriate or microstriato-reticulate, whereas pollen grains of Citreae are almost always 4/5 colporate with exines varying from microperforate to coarsely reticulate. Congruence between pollen types and the currently accepted classification is discussed, as well as the systematic implications of pollen morphology for the subfamily.