Biology Today — December 2017

• Sporophyte consists of foot, seta and capsule. In some members, however, the sporophyte is represented either only by capsule
  or by foot and capsule.


• Sporogonium produces haploid meiospores inside its capsule. On germination, each spore produces a gametophyte either directly
  or through a juvenile stage called protonema.


• Bryophytes show heteromorphic or heterologous alternation of generations.

Classification of Bryophytes

Table: Characteristics of different classes of bryophytes

Features Hepaticopsida Anthoceropsida Bryopsida

Common name Liverworts Hornworts Mosses

Gametophytic plant

body

May be thallose or foliose,

unicellular and unbranched,

smooth walled and

tuberculated rhizoids.

Thallose, unicellular,

unbranched, smooth

walled and rhizoids.

Gametophyte has two growth stages:

thalloid protonema stage and leafy

gametophore stage. Rhizoids are

multicellular, branched with oblique

septae.

Sex organs Present on dorsal surface of

thallus.

Present on dorsal surface

of thallus.

Develop from the superficial cells at the

apex of leafy gametophore.

Sporophyte

or sporogonium

Simple, represented by

capsule only e.g., Riccia or

differentiated into foot, seta

and capsule, e.g., Marchantia.

Differentiated into a

bulbous foot, small

meristematic seta and

long cylindrical capsule.

Differentiated into foot, seta and capsule.

Elaters Generally present, absent in

some like Riccia.

Pseudoelaters are present

in the capsule.

Absent.

Sporogenous cells Develop from endothecium. Develop from

amphithecium whereas

endothecium forms sterile

columella.

Develops from inner fertile layer of

amphithecium, whereas endothecium

forms sterile columella.

Examples Riccia, Marchantia,

Sphaerocarpos, etc.

Anthoceros, Notothylas,

Megaceros, etc.

Sphagnum, Polytrichum, Funaria, etc.

Economic Importance of Bryophytes

Prevention of soil erosion

Mosses form dense mats over the soil and

prevent soil erosion by running water.

Soil formation

They make an important link in ecological succession on rocky areas by taking part in soil formation

in rocky crevices, formed by lichens. For example, growth of Sphagnum fills ponds and lakes with soil.

Peat

Sphagnum often grows in acidic marshes where there is little decay. The dead parts

of moss and other marshy plants slowly get carbonised, compressed and fossilised

over thousands of years to produce a dark spongy mass called peat. It is dried,

compressed and cut to form blocks. Peat is used as good manure to overcome soil

alkalinity and it increases water retention as well as aeration of soil.

Water retention

Some bryophytes or mosses can absorb water such as

Sphagnum which can retain or absorb 18-26 times water

of its weight. This water retention capability is employed

by gardeners to keep seedlings and cut plants moist

during transportation and propagation.

Economic Importance