Nonvascular Plants: Mosses, Liverworts, and Hornworts

Characters of Nonvascular Plants

Classifications of Nonvascular Plants

Division Bryophyta: Mosses

Sporophyte Generation

Metabolism and Ecology

Gametophyte Generation

Division Anthocerotophyta: Hornworts

Gametophyte Generation

Sporophyte Generation

embryophytes that do not have vascular tissue

have multicellular sporangia and gametangia

bodies composed of true parenchyma

all mosses and many liverworts

have leafy stems

almost exclusively terrestrial

have cuticle over much of their bodies

many have stomata

life cycle

alternation of heteromorphic generations

can never grow to be really large

thrive in microhabitats

microhabitats that have too little water or soil]

not known how closely related mosses, liverworts, and hornworts are

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treated as 3 distinct divisions

Hepatophyta #

Bryophyta #

Anthocerotophyta #

liverworts

mosses

hornworts

Division Hepatophyta: Liverworts

Gametophyte Generation

Sporophyte Generation

all groups together are called "nonvascular plants" #

Liverworts

moss

hornwort

Morphology

gametophores

all moss stems have leaves

leafy stems

grow close together

stems

little tissue differentiation

tissue called cortex\

Water Transport

hydroids

cells that make up innermost cortex

they conduct water & dissolved minerals

leptoids

cells that resemble sieve cells

majority of mosses lack leptoids and hydroids

instead water is conducted along exterior of their stems

by capillary actions

rhizoids

located at base of stem]

small, multicellular trichome-like structures

only anchor the stem, do not conduct water and minerals

Development

growth begins when a spore germinates

this cell undergoes mitosis

then produces a branched system of similar cells

prootonema #

the entire network

Reproduction

produces gametangia

all mosses are oogamous

antheridia

the sperm

archegonia

the eggs

shaped like a vase

a short stalk

zygote of a moss undergoes a division

foot

the basal cell, develops into a small bulbous tissue

capsule

upper cell grows into a simple apical sporangium

seta

a narrow stalk

located between the foot and sporangium

operculum

apex of the sporangium differentiates as a caplike lid

separates from the rest of the sporangium as cells are torn apart

peristome teeth

cells breaking into 1 or 2 rows of complec teeth

calyptra

layer of cells derived from then neck of the archegonium

covers the apex of the sporangium

leaves on moss gametophores

have only a thin, incomplete cuticle

if exposed to dry air for even a few minutes

plant would dry out

this is due to the lack of vascular tissue

many mosses live in moist microhabitats

mosses are important in later establishments of other species

their sporophyte is even less conspicuous than in mosses

they are also dependent on the gametophyte

hepatic gametophytes are divided into 2 groups

leafy liverworts

thallose liverworts

their leaves typically have 2 rounded lobes w no midrib

no conducting tissues

leaves are arranged in 3 rows

thallus

the body

a body without roots, stems, and leaves

air pores

large air chambers that open to the exterior

not stomata

no guard cells and cannot be closed

antheridiophore

male gametophore

umbrella shaped outgrowth

archegoniophores

stalked, but apex is a set of radiating fingers

project outwards

elaters

single, elongate cells with spring-shaped walls ]

some cells do not undergo meiosis

development is distinctive

special mucilage chamber forms near the upper surface

cells lining the chamber grow into it and become antheridia

as sperm cells mature, antheridia transform their chloroplast

have a foot embedded in gametophore tissue

above the foot is a meristem that continuously produces new sporangium tissue

as cells are pushed upward

they grow, differentiate, mature and then die