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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
Division Bryophyta: Mosses
– 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
Division Bryophyta: Mosses
• 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
Division Bryophyta: Mosses
– 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
Division Bryophyta: Mosses
• 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
Divison Hepatophyta: Liverworts
– 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
Divison Hepatophyta: Liverworts
• Gametophyte Generation
– Spore germinates into a small proonematal structure– Small rhizoids on undersurface– Can be either uni or bisexual (Marchantia unisexual)
» Male - Antheridiophores
Divison Hepatophyta: Liverworts
» Female - archegoniophores
Divison Hepatophyta: Liverworts
• Sporophyte
Divison Hepatophyta: Liverworts
– 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
Division Anthocerotophyta: Hornworts
Division Anthocerotophyta: Hornworts
– Sporophyte