MONOPLASTIDIC MEIOSIS IN DUMORTIERA HIRSUTA (BRYOPHYTA; MARCHANTIALES)

Abstract

  The early sporocyte of Dumortiera hirsuta contains a single large plastid. Plastid division occurs in advance of nuclear division and the four resultant plastids migrate to the future spore domains. In many cases, the four daughter plastids continued to divide before nuclear division. The cytoplasm becomes shallowly lobed around the four domains and each domain contains at least one plastid. Positioning of plastids and cytoplasmic lobing seem to establish the meiotic division planes before nuclear division. Monoplastidic meiosis, which can be considered to be a symplesiomorphic character, is typical of mosses and hornworts but is known only sporadically in isolated taxa of liverworts. Meiosis of Dumortiera seems to represent an evolutionary stage that is transitional between monoplastidic and polyplastidic meiosis.