Pollen and anther characters in monocot systematics

Pollen and anther characters are potentially informative in higher-level sy stematics of monocotyledons. Several characters of monocot pollen and anthe rs (tapetum type, microsporogenesis type and inaperturate pollen) are revie wed here in relation to recent phylogenetic concepts of the group, and new data are presented for some critical taxa. The first-branching monocotyledo n, Acorus, has a secretory tapetum but most other early branching taxa (i.e ., most Alismatales, except Tofieldia) are plasmodial. The lilioid orders, Pandanales, Dioscoreales, Liliales and Asparagales are almost uniformly sec retory. The tapetum is more diverse within the commelinoid clade. Successiv e microsporogenesis predominates in the monocotyledons although the simulta neous type is of systematic significance within some orders, such as Diosco reales, Asparagales and Poales. Inaperturate pollen (either "functionally m onoaperturate" or "omniaperturate") occurs in every major monocot group. It predominates in Alismatales and Zingiberales, and is a synapomorphy for so me Liliales and Asparagales.