Pollen grain ultrastructure comparative of two species belonging to Calochortus Pursh (Liliaceae).

Pollen morphology of two genera of Calochortus was studied under transmission electron microscopy (TEM). The shape of caput in Calochortus is oblate spheroidal, flattened-spheroidal, rectangular that similar to caput of columella in other genera in Liliales. Absent endexine of Calochortus is advanced features in Liliales order, as well as monocotyledon plants. Also Calochortus has three layers intine, which consists of exintine, mesintine and endexine. The microreliefs on the surface of the muri in studied species Calochortus are smooth. The tectum to foot layer ratio (T/F) in studied species Calochortus is 1.6–2.6. This species was different from each other by shape and thickness of caput, length and width of columella and T/F ratio. The minimal thickness foot layer was in the pollen grain C. albus Douglas ex Benth The elliptical (oblate-spheroidal) caput form is in C. eurycarpus Wats, but from the caput in C. albus is spheroidal to indeterminate. In additional to sporoderm feature in Calochortus was similar to some species of genera Tulipa and Fritillaria.