Tag: kingdom plantae

Bryophytes are an informal group consisting of three divisions of non-vascular land plants: the liverworts, hornworts and mosses. They are characteristically limited in size and prefer moist habitats although they can survive in drier environments. A bryophyte spore germinates and produces an often algal-like mat, called a protonema (plural protonemata) and the leafy or thalloid stage of the gametophyte develops from the protonemal stage. The protonemata are almost always ephemeral but there are exceptions. Amongst the mosses there is a small number of species in which the protonemata are persistent and the leafy plants are ephemeral. The spore was haploid and so are the resulting protonema and the ensuing leafy or thalloid stages.

Most of the algae have dominant gametophyte generations. But in some species, the gametophytes and sporophytes are morphologically similar. An independent sporophyte is a dominant form in all clubmosses, horsetails, ferns, gymnosperms, and angiosperms that have survived to the present day. The gametophyte is dominant in the mosses, liverworts & hornworts only. In mosses, the gametophyte feeds its small attached offspring sporophyte. The mature sporophyte is composed of a "foot" that remains stuck in the gametophyte moss carpet. The sporophyte stands above the moss mat as a long stalk and a capsule that looks like a salt shaker at the tip.
The sporophyte is dominant in all other plants: the ferns, club mosses, horsetails, the gymnosperm (conifers, cycads, ginkgo), and the angiosperm.
In gymnosperm and angiosperm, the entire gametophyte generation is miniature and contained in the cones or the flowers.

Fern phloem lacks companion cells. Placenta in fern is the place of attachment of sporangia.
Companion cells occur only in angiosperms.
Companion cell is any of a number of specialized parenchyma cells adjacent to a sieve tube in the phloem of flowering plants, believed to regulate the flow of nutrients through the tube.

Pteridophyta is the primitive vascular plants. They are also called as vascular cryptogams. They are flowerless, seedless, spore-bearing vascular plants. In pteridophytes, the xylem mainly consists of tracheids and xylem parenchyma. Generally, vessels are absent but some primitive types of vessels are present in some of the species.

Ramenta is one of the thin, chaff like scales covering the shoots or leaves of certain ferns. Young leaves of fern are protected by ramenta.
Therefore, the correct answer is option B.

Pteridophytes:
1. Members of this group are most primitive living vascular plants.
2. The main plant body is a sporophyte. It is differentiated into root, stem and leaves.
3. Plants (sporophyte) reproduce by spores formed in sporangia. Sporangia develop either on the ventral surface or in the axil of leaves.
4. Plants may be homosporous or heterosporous. The development of sporangium may be of eusporangiate (when developing from a group of initials) or leptosporangiate. (When developing from a single initial) type.
5. Spores develop into a multi-cellular gametophytic body called prothallus- a thalloid structure. It is independent and chlorophyllous. It bears male reproductive organs called antheridia and female reproductive organs called archegonia. Reproductive organs are multicellular and jacketed.
6. Water is essential to effect fertilization as male reproductive units are flagellated and motile.
7. Seed formation never takes place in living pteridophytes.
8. An embryo develops in situ after fertilization and the sporophyte remains attached to the gametophyte till the development of root.
9. Plants show clear alternation of generations. The sporophyte and gametophyte are independent of each other.

Pteridophytes or Pteridophyta are vascular plants meaning that they contain vascular systems for the transport of water and food material.These vascular systems are xylem and phloem. They reproduce bt spores. They are flowerless and seedless plants and hence they are also called as vascular cryptogams. 

Pteridophytes are vascular plants which have leaves (known as fronds), roots and sometimes true stems, and tree ferns have full trunks. For example, ferns, horsetails and clubmosses. Fronds in the largest species of ferns can reach some six meters in length. Many ferns from tropical rain forests are epiphytes, which means they only grow on other plant species. Their water comes from the damp air or from rainfall running down branches and tree trunks. There are also some purely aquatic ferns such as water fern or water velvet (Salvinia molesta) and mosquito ferns (Azolla species).