nonvascular plants - Mount Saint Mary...

Nonvascular Plants

• Believed to have evolved from green-algae

– Chlorophylls a & b and cartenoids

– Store starch within chloroplasts

– Cell wall made up mostly of cellulose

• Major adaptations in going from water to land

– A protective sterile jacket to protect reproductive structures, antheridia and archegonia

– Development of a waxy cuticle

– Development of stomata for gas exchange on sporophytes

Nonvascular Plants

• Classification – three major divisions – grouped together because of several similarities

– Gametophyte nutritionally independent from the sporophyte, but the sporophyte is permanently attached to the gametophyte

– The gametophyte is the the conspicuous generation

– Possess rhizoids for anchoring but not absorption

– Sperm requires water to swim to the egg

– Possess a venter (surrounds the egg), neck canal cells that disintegrate and form a tube for sperm to follow to fertilize the egg

Nonvascular Plants

– Antheridium surrounded by a one cell layer thick sterile jacket

– Spermatogenous cells form biflagellated sperm– Zygote developes within the archegonium

– Archegonium expands to form a calyptra

Division Bryophyta: Mosses

• Gametophyte Generation

– Leafy, upright, leaves arranged in a spiral fashion

– Possess multicellular rhizoids for anchoring

– Leaves, gametophores, usually one cell thick – not true leaves nor ancestors of true leaves


– Stems

• Very little in the way of differentiation

• possess a central area of conducting cells composed of hydroidsand leptoids

– hydroids – tracheid like cells, dead, empty, carry water and nutrients– leptoids – like sieve tubes, transport sugars, lack nuclei, many

plasmodesmata

– Antheridia frequently found in splash cups

– Gametes are produced either in leaf axils or at the tips


• Sporophyte

– Can take up 6 – 18 months to develop

– Associated with the gametophyte

– Sporangia typically associated with a stalk, seta

– Possess stomates with only one guard cell

– When young are photosynthetic but lose this


– Spore dispersal

• Calyptra (archegonial tissue) dies, dries, and falls off, taking with it the operculum

• Loss of opercululum exposes the periostome, which change shape depending upon humidity, gradually releasing spores

• Each capsule up to 50 million spores


• Metabolism and Ecology

– Very prone to desiccation – several adaptations have evolved to accommodate for this

• Grow in very moist habitats or dry areas with microhabitats, no need for vascular tissues

• Can become dormant during dry spells• Frequently grow in dense clumps to trap moisture

– Some can thrive at very low temperatures

– Can grow on very hard, dense surfaces, not roots

– Play a role in soil production because of acids produced

Divison Hepatophyta: Liverworts

• 8500 species• Diverse• Inconspicuous, but may form large mats• Some consider them the simplest of the plants because

they have:– Conducting tissue– A cuticle– Stomates

• In most the gametophyte is formed by the germination of a spore

• Divided into two groups


– Thallose Liverworts

• Moist, cool, shaded environments

• Thallus multicellular with upper cells containing chlorophyll, lower cells colorless

• Upper surface lacks stomates but does have pores

• Marchantia – very common

– Dichotomously branching gametophyte

– Gametangia located on gametophores

– Gametophytes are unisexual, easily seen


• Gametophyte Generation

– Spore germinates into a small proonematal structure– Small rhizoids on undersurface– Can be either uni or bisexual (Marchantia unisexual)

» Male - Antheridiophores


» Female - archegoniophores


• Sporophyte


– Leafy Liverworts

• About 6000 species

• Found in tropics and subtropics (warm and wet)

• Branched forms form mats

• Leaves only one cell thick, usually forming two rows on each side and one colorless one on underside

Division Anthocerotophyta: Hornworts

• Small group, only 6 genera

• Most common genus, Anthoceros

– Only one chloroplast– Each chloroplast has a pyrenoid– Gametophyte appears as a rosette

• Multicellular with mucilage between cells

• Within this mucilage can be found the cyanobacteria, Nostoc, which is nitrogen fixing

• Can be bi or unisexual

– Archegonia found sunken on the dorsal surface

– Antheridia clustered within chambers


– Sporophyte

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