Bio 1B Fall ’05 Lecture Land Plant Adaptations, Professor Thomas Carlson <[email protected]> 1 Bryophytes, Pteridophytes & Adaptations of Land Plants Bio 1B Fall ’05 Professor: Thomas Carlson Bio 1B Fall ’05 Lecture Land Plant Adaptations, Professor Thomas Carlson <[email protected]> 2 Land Plants Bio 1B Fall ’05 Lecture Land Plant Adaptations, Professor Thomas Carlson <[email protected]> 3 Land Plants 460 million years ago: - land plants evolved from aquatic green algae - the green algae were probably from fresh water 400 million years ago: - first vascular tissue, stomata, & roots 380 million years ago: first wood 360 million years ago: first seeds 260 million years ago: first vessels in vascular system 125 million years ago: first flowers Bio 1B Fall ’05 Lecture Land Plant Adaptations, Professor Thomas Carlson <[email protected]> 4 Green Algae (Charophyta) (Figs 29.4, 29.7) - progenitor to Green Land Plants Green Land Plants - cellulose cell wall - chlorophyll a and b - starch storage product in chloroplast - embryo protected by tissue of parent plant - alternation of generationsBio 1B Fall ’05 Lecture Land Plant Adaptations, Professor Thomas Carlson <[email protected]> 5 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 Bio 1B Fall ’05 Lecture Land Plant Adaptations, Professor Thomas Carlson <[email protected]> 6 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 Bio 1B Fall ’05 Lecture Land Plant Adaptations, Professor Thomas Carlson <[email protected]> 7 Adaptations to Life on Land Vascular Tissue: - 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 Bio 1B Fall ’05 Lecture Land Plant Adaptations, Professor Thomas Carlson <[email protected]> 8 Bryophytes = Non-tracheophyte plants (Table 29.1, Figs 29.7, 29.8, 29.9, 29.10) Earliest land plants Most are only a few cm high or long Grow in dense mats in moist habitats Alternation of generations Dominant haploid gametophyte Sporophytes are dependent & attached to gametophyteBio 1B Fall ’05 Lecture Land Plant Adaptations, Professor Thomas Carlson <[email protected]> 9 Bryophytes = Non-tracheophyte plants Liverworts (Marchantia) (Fig 29.9) - flat thallus with dichotomous branching Hornworts (Fig 29.9) - stomata development Mosses (Polytrichum, Funaria) (Fig 29.9) - apical cell division - hydroids: primitive vascular tissue - green leaf bearing structure is the gametophyte Bio 1B Fall ’05 Lecture Land Plant Adaptations, Professor Thomas Carlson <[email protected]> 10 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 - diaper rashes - athelete’s foot - to dress wounds Bio 1B Fall ’05 Lecture Land Plant Adaptations, Professor Thomas Carlson <[email protected]> 11 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 Bio 1B Fall ’05 Lecture Land Plant Adaptations, Professor Thomas Carlson <[email protected]> 12 Tracheophytes Contain tracheids which are the principal water conducting element of the xylem - water & mineral transport - rigid structural support Dominant and independent sporophyte phase Non-seed tracheophytes: pteridophytes Seed containing tracheophytes: gymnosperms & angiospermsBio 1B Fall ’05 Lecture Land Plant Adaptations, Professor
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