The calyptra is a cap of maternal gametophyte tissue that covers the apex of the offspring sporophyte during development. My research shows that in the calyptra has a waxy cuticle that develops early and prevents water loss from the underlying sporophyte tissues. I think about this as the maternal gametophyte investing in these protective layers to keep the sporophyte safe from the harsh conditions of drying out as it grows taller and taller.
An additional interpretation is presented by Haig. He views the waxy layers on the calyptra as slowing down or preventing the sporophyte from pulling up more water and potentially nutrients from the maternal plant.
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These differing interpretations of the same phenomenon are not mutually exclusive. One is not right and the other is wrong. As Haig mentions, both maternal protection and restraint are likely to be occurring at the same time. This relationship between mothers and their offspring is a phenomenon that is seen across the plant and animal kingdoms.![]()
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| This figure illustrates the maternal gametophyte calyptra and its location across the stages of sporophyte development. |
An additional interpretation is presented by Haig. He views the waxy layers on the calyptra as slowing down or preventing the sporophyte from pulling up more water and potentially nutrients from the maternal plant.
Haig, D. (2012). Filial mistletoes: the functional morphology of moss sporophytes Annals of Botany, 111 (3), 337-345 DOI: 10.1093/aob/mcs295
These differing interpretations of the same phenomenon are not mutually exclusive. One is not right and the other is wrong. As Haig mentions, both maternal protection and restraint are likely to be occurring at the same time. This relationship between mothers and their offspring is a phenomenon that is seen across the plant and animal kingdoms.