Non Vascular Plants: Mosses,Liverworts and Hornworts (Division Hepatophyta…
Non Vascular Plants: Mosses,Liverworts and Hornworts
Classification of Non Vascular plants
Division Bryophyta: Mosses
the gametophyte generation
the leafy stems are gametophytes
the moss gametophores grow from an apical meristem that contains a prominent apical meristem
derivative cells subdivide producing the tissues if the stem and the leaves.
in some family of mosses innermost cortex is composed of cells called hydroids that conduct water and dissolve minerals
species that have hydroids also have leptoids which acts as a function of sieve cells.
majority of mosses lack lack hydroids and leptoids : water is conducted along the exterior of their stems by capillary action.
growth of gametophore begins when spore germinate and sends out a long, slender chlorophyllus cell.
this cells undergoes mitosis and produce potonema
potonema organize a apical meristem and grow upright as a stem which is called a gametophore.
gametophore produce gametogonia. sperm produced in icrogametogonia and eggs are produced in magagametogonia.
after sperm cells mature, antheridium breaks and liberates sperm cells. sperm cells swim towards eggs. after meeting fertilization occurs.
the sporophyte generation
A sporophyte is a multicellular diploid generation found in moss
It produces haploid spores that develop into a gametophyte.
The gametophyte then makes gametes that fuse and grow into a sporophyte
Metabolism and Ecology
the small size and lack of conductng tissues are two critical factors in the metabolism and ecology of mosses
many species of mosses grow permanently in moist habitats such as rain forests. this helps to compensate the inability o them to retain water.
sme mosses are tolerant o dessication
Division Hepatophyta: Lverworts
The Gametophyte Generation
gametophytes are divided into two basi groups: leafy liverworts and thallose liverworts.
gametophyte stage is initiated when spores germinate and establish a small, temporary protonemal phase. An apical cell is established and growth o gametophore begins
gametophore of leafy liverworts greatly resembles to that of moss. however, liverworts typically have two lobes with no midrib and no conducting tissue
thallosee gametophytes show less resemblance to that of mosses. they are not leafy rather they are flat.
bodies of thallose livewort are more startified
liverworts gametophyte may be either bisexual or unisexual
The Sporophyte Generation
The sporophyte generation develops from this diploid embryo and forms a sporangium at its apex
Spores are released when the sporangium ruptures, marking the start of a new gametophytic generation.
Division Anthocerotophyta: Hornworts
The gametophyte Generation
three or four protonema cells are produced before the gametophore phase.
the gametophyte is parenchymatous
internally, hornworts gametophytes have many chambers.
gametangium development in hornworts is disttintive
antheridia are formed from special mucilus chambers while archaegonia are ormed from superficial cells.
the sporophyte of horwort is different than that of mossses and livverworts.
he zygote becomes the sporophyte, which is the part of the plant that will produce haploid spores.
The sporophyte is the reason a hornwort is called a hornwort. spores look like horn.
the spores released by the sporophyte will later develop into gametophyte plants.