CHLOROPLAST DEVELOPMENT DURING SPOROGENESIS IN SIX SPECIES OF MOSSES

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Abstract
Chloroplast development during sporogenesis in Mnium cuspidatum, M. medium, M. rostratum, Aulacomnium heterostichum, Bartramia pomiformis, and Timmia megapolitana is as follows: During the early mitotic divisions in the sporogenous area of the capsule the number of plastids is reduced from many to one cup‐shaped plastid per sporogenous cell. This single plastid divides during the early spore‐mother‐cell stage. A second division of plastids produces four plastids within each spore‐mother‐cell. A massive accumulation of starch occurs within each of the four plastids. Following meiosis, the single plastid allocated to each spore produces distinct lobes that are “blebbed” off as proplastids. A photosynthetic membrane system is established within the many proplastids as each spore matures.