1 thought on “How are bryophytes are better adapted to living on land than are green algae?”
gardengallivant
Survival on land, out of water, requires an ability to resist and repair damage from drying that agal species do not face. Protection from desiccation came with a shift in plant’s surfaces.
These plants add the sporopollenin to protect spores (In algae it prevented desiccation of zygotes only.) This is an important reuse of a function for the transition to land.
Gametangia are multicellular with a protective jacket of sterile cells to house gamete producing cells.
Embryo, easily protected by the female gametophyte, develops from the fertilized egg with differentiating cells in a regulated progression.
Botanists refer to the moss leaf-like structures as phyllids. The phyllids are only one-cell thick and have a midline of hydroid & leptoid cells. Moss leaves are never lobed, are all the same size, and arrange in a spiral along the stem. Moss leaves are analogous to true leaves in photosynthetic function but have no vascular structure so are not ‘true’ leaves. Moss leaves are thin sheets of cells that increase the photosynthetic area as long as water keeps them turgid. Mosses have hydroid cells that are slightly more permeable with thinner cell walls to permit easier water conduction by osmosis to the phyllids, so these cells function as a protoxylem.
Survival on land, out of water, requires an ability to resist and repair damage from drying that agal species do not face. Protection from desiccation came with a shift in plant’s surfaces.
Moss has an epidermis (unicellular external layer) and a waxy cuticle able to resist water loss and yet allow light transmission for photosynthesis. Some liverworts have simple leaf pores but mosses & hornworts have true regulated stomata in the epidermal layer to regulate the exchange of gases for photosynthesis and control the loss of water.
http://www.palaeos.com/Plants/Bryophyta/Bryophyta.html
Moss stomata are less specialized and not present in both life phases. The stomata are found in mosses & hornworts only in their sporophyte phase. Liverwort lack stomata but have pores.
"Stomatal Function"
http://books.google.com/books?id=mp-aAAAAIAAJ&pg=PA37&lpg=PA37&dq=moss+stomata&source=bl&ots=T4e4o35g9k&sig=_yVymhmTPUpjXRZXmBc1AYCipvs&hl=en&ei=OX8zTPLBBdyxnAfttKWLBA&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCAQ6AEwAg#v=onepage&q=moss%20stomata&f=false
Moss Characteristics
http://science.jrank.org/pages/4456/Moss-Moss-characteristics.html
These plants add the sporopollenin to protect spores (In algae it prevented desiccation of zygotes only.) This is an important reuse of a function for the transition to land.
Gametangia are multicellular with a protective jacket of sterile cells to house gamete producing cells.
Embryo, easily protected by the female gametophyte, develops from the fertilized egg with differentiating cells in a regulated progression.
Botanists refer to the moss leaf-like structures as phyllids. The phyllids are only one-cell thick and have a midline of hydroid & leptoid cells. Moss leaves are never lobed, are all the same size, and arrange in a spiral along the stem. Moss leaves are analogous to true leaves in photosynthetic function but have no vascular structure so are not ‘true’ leaves. Moss leaves are thin sheets of cells that increase the photosynthetic area as long as water keeps them turgid. Mosses have hydroid cells that are slightly more permeable with thinner cell walls to permit easier water conduction by osmosis to the phyllids, so these cells function as a protoxylem.