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How does the calyptra protect a developing bryophyte sporophyte?
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bryophyte
Bryophyte moss growing on oak trees.
In bryophytes, the calyptra serves as a protective sheath for the developing embryonic sporophyte.1
Following fertilization, the resulting zygote remains within the archegonium, the female sex organ. As the zygote undergoes mitotic cell divisions to develop into an embryo, the lower cells of the archegonium also divide to form the calyptra. This structure effectively covers and shields the growing sporophyte embryo as it begins to enlarge and establish its connection to the gametophyte for water, minerals, and nutrients.1