Ch 3Kingdom Plantae — Class 11 Biology, concept-first.

Having already studied the general principles of classification, this chapter looks at how Kingdom Plantae itself is split into smaller groups.

The three groups discussed under Cryptogamae — Thallophyta, Bryophyta and Pteridophyta — share the basic feature of reproducing by spores rather than seeds, but they differ enormously in body organisa…

Thallophyta, commonly called algae, are a highly diverse group whose defining feature is a thalloid body — the plant is not differentiated into true root, stem and leaves.

Chlorophyceae, the green algae, are named for the dominance of chlorophyll a and b in their chloroplasts, which gives them their characteristic green colour.

Phaeophyceae, the brown algae, owe their colour to the accessory pigment fucoxanthin masking their chlorophyll.

Rhodophyceae, the red algae, take their colour from the pigment phycoerythrin.

Bryophyta takes its name from the Greek bryon (moss) and phyton (plant). The group comprises approximately 960 genera and about 25,000 species.

Liverworts (Hepaticeae) are considered the most primitive members of Bryophyta.

Mosses (Musci) are considered the more advanced members of Bryophyta, distinguished by an erect plant body.

Pteridophyta takes its name from the Greek pteron (feather) and phyton (plant), reflecting the feather-like (pinnate) form of many of its leaves.

Phanerogamae, the seed-bearing plants, are divided into two major groups on the basis of whether the seed is naked or enclosed: Gymnospermae and Angiospermae.

Gymnospermae takes its name from the Greek gymnos (naked) and sperma (seed), reflecting the fact that its seeds are not enclosed within a fruit.

Angiospermae takes its name from the Greek angios (enclosed vessel) and sperma (seed) — in this group the seeds develop enclosed within a fruit, i.e. within the ovary.

Dicotyledonae are the class of Angiosperms whose embryo carries two cotyledons.

Monocotyledonae are the class of Angiosperms whose embryo carries a single cotyledon.

A plant's life cycle unfolds across two alternating generations: the diploid sporophyte (2n) and the haploid gametophyte (n).