Land Plants Bryophytes Pteridophytes Adaptations of Land Plants Professor Thomas Carlson Bio 1B Fall 06 1 2 Green Algae Charophyta Land Plants Figs 29 4 29 7 460 million years ago progenitor to Green Land Plants land plants evolved from aquatic green algae the green algae were probably from fresh water Green Land Plants 400 million years ago first vascular tissue stomata roots 380 million years ago 360 million years ago 260 million years ago system 125 million years ago first wood first seeds first vessels in vascular first flowers cellulose cell wall chlorophyll a and b starch storage product in chloroplast embryo protected by tissue of parent plant alternation of generations 3 4 5 6 Adaptations to Life on Land Apical Meristems of Shoots Roots Fig 29 5 Cuticle waxy covering that retards desiccation drying Stomata developed for gas exchange Pigments that protect plant against UV radiation Land Plants Optimize Photosynthesis CO2 from atmosphere is more available on land LIGHT from sun is more available on land 7 8 9 10 Vascular tissue enables transport of water against gravity from tissues in contact with wet soil to tissues in contact with air Hydroids tiny channel through which water travels in mosses Tracheids specialized conducting cells in pteridophytes gymnosperms Vessels specialized conducting cells in angiosperms Lignin strengthens cell walls of vascular conducting xylem and provides rigid structural support so plant does not fall over in response to gravity or wind 11 12 Adaptations to Life on Land Fig 29 5 Thick spore walls that prevent desiccation resist decay Gametangia enclose plant gametes prevent them from drying Archegonia encloses eggs Antheridia encloses sperms Embryos young sporophytes contained within protective structure Adaptations to Life on Land Vascular Tissue Bryophytes Non tracheophyte plants Bryophytes Non tracheophyte plants Table 29 1 Figs 29 7 29 8 29 9 29 10 Liverworts Marchantia Fig 29 9 Earliest land plants flat thallus with dichotomous branching Most are only a few cm high or long Hornworts Fig 29 9 Grow in dense mats in moist habitats stomata development Alternation of generations Mosses Polytrichum Funaria Fig 29 9 apical cell division hydroids primitive vascular tissue green leaf bearing structure is the gametophyte Dominant haploid gametophyte Sporophytes are dependent attached to gametophyte 13 14 Bryophytes Non tracheophyte plants Sphagnum moss common name is peat moss Very abundant widespread in wetland bogs in northern latitudes Peat partially decomposed plant material resulting from rapidly growing upper layers of Sphagnum that compress deeper lying layers Fig 29 10 Sphagnum moss contains acidic compounds that are antiseptic is used to treat 15 diaper rashes athelete s foot to dress wounds 16 Bryophytes mosses non tracheophytes sporophyte is small and depends on the gametophyte for nutrition Pteridophytes ferns seedless tracheophytes Figs 29 12 29 14 Sporophytes are much larger than gametophytes Both sporophytes and gametophytes produce their own food through photosynthesis Mature gametophyte lives independently of mature sporophyte 17 18 Seedless Tracheophytes Pteridophytes Tracheophytes Contain tracheids which are the principal water conducting element of the xylem water mineral transport rigid structural support Rhyniopsida only known from fossils Lycopods Lycophyta simple leaves in spiral Horsetails Anthrophyta simple leaves in whorl Dominant and independent sporophyte phase Non seed tracheophytes pteridophytes Seed containing tracheophytes gymnosperms angiosperms Table 29 1 Figs 29 7 29 12 29 14 Equisetum is genus name rich deposits of silicon in cell walls used to scour pans tea used as a diuretic Whiskferns Psilotophyta Ferns Pterophyta 19 20 21 22 Seedless Tracheophytes Pteridophytes Haploid diploid generations independent at maturity Mature Sporophyte dominant independent Reproduce by single celled spores Homospory in terrestrial ferns Small gametophytes 1 2 cm long short lived Require aqueous environment for motile flagellated sperm to fertilize 23 24 Ferns Pterophyta Figs 29 12 29 14 Frond fern leaf Fig 29 12 large complex leaves branching vascular strand roots leaves stems require water for transfer of male gametes to female gametes sori clusters of sporangia under leaf surfaces moist terrestrial environments most ferns Size a few centimeters to over 10 meters tree ferns some ferns are aquatic epiphytic or live on rocky cliffs Developing frond crozier or fiddlehead fiddleheads of some species consumed as delicacy Sporophyll frond that produces spores Sporangia spore producing structures that are often aggregated under the leaf into patches called sori Haploid spores develop into gametophytes 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 Seedless Tracheophytes Pteridophytes Homosporous terrestrial pteridophytes Heterosporous aquatic ferns e g Azolla Marsilea Homospory plants in which sporophyte produces single type of spore that develops into a bisexual gametophyte with both male female organs Heterospory plants in which sporophyte produces two kinds of spores that develop into unisexual female or male gametophytes megaspores produce female megagametophytes microspores produce male microgametophytes 47 48 Azolla aquatic fern Floating water fern with a symbiotic relationship with cyanobacteria which live in leaf cavities Cyanobacteria Photosynthetic oxygen producing Fix nitrogen into ammonia which is converted by the fern into amino acids other organic compounds Azolla is commonly grown in rice paddies in Asia especially Vietnam and Asia Grows very quickly provides nitrogen fertilizer for the cultivation of rice that feeds 49 millions of people 50 51 52 53 54 tcarlson berkeley edu 11 11 03 Bryophytes Pteridophytes Alternation of Generations X X Haploid Dominant X X Sporophyte dependent on gametophyte Water required for fertilization X Diploid Dominant Tracheids or vessels Gametophyte dependent on sporophyte Wind or animal fertilization Pollen Seeds Flowers Fruits Double Fertilization Triploid Endosperm X 56 57 58 Angiosperms X X X Independent sporophyte gametophyte Heterosporous Gymnosperms 55 X X X tracheids Aquatic ferns X X tracheids vessels X X vessels tracheids X X X X X mainly wind X X X animals wind X X X X 59
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