The Reproductive Biology of the Liverwort Blasia Pusilla L

Document Type

Note

Publication Date

1-1-1993

Description

Following sex organ production and fertilization in the late spring, the sporophytes of Blasia develop during the summer months. By the early autumn cell division in the seta is complete and the cells are packed with amylochloroplasts, whilst the capsule contains monoplastidic sporocytes at meiotic prophase with abundant protein bodies. The parent gametophytes die and the immature sporophytes overwinter in the dead tissues. The spores mature the following spring and seta elongation is associated with depletion of its starch reserves. A survey of a range of hepatics reveals that premature death of entire sporophyte-bearing gametophytes appears to be unique to Blasia although young sporophytes of Calypogeia and Goebelobryum overwinter in marsupia that die in the autumn. Daylength probably controls the initiation of sex organ formation in the spring and autumnal dormancy of the immature sporophytes whereas the sporophyte maturation process is almost certainly triggered by higher temperatures. Physiological independence of the sporophyte prior to spore maturation may have been a key step in the evolution of the fully independent dominant sporophyte generation of pteridophytes.Whereas the stellate gemmae of Blasia are short-lived and packed with starch, the ellipsoidal gemmae contain abundant lipid droplets and protein reserves and retain their viability for several months. Production of two kinds of morphologically and physiologically distinct vegetative propagule appears to be unique to Blasia in the Hepaticae but parallels the development of protonemal and rhizoidal gemmae in some mosses.

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