AChapter 27: The Plant Kingdom : Seedless Plants Plant Constitution/Adaption Cuticle- important adaption- covers aerial portion of plant, minimizes desiccation (drying out). Moist habitat= thin cuticle. Drier environment= thicker cuticle. Negligible area for gas exchange. Stomata- in almost all plants- facilitate gas exchange. On leaves/stems of plant. Gametangia- sex organs of multicellular plants. Each organs has sterile cells that protect gametes (egg/sperm cells). Fertilized egg develops into multicellular embryo in female. Charophytes/Stoneworts- green algae- plant probably arose from these. Ferns & other vascular plants: Xylem- conduct water/dissolved material. Phloem- conduct dissolved sugar. Lignin- strengthens cell wall, support conduction, maximum light reception (causes stiffness). Alternation of Generation Plants spend part of life in haploid gametophyte generation and other part in diploid sporophyte generation. Gametophyte generation- Produces haploid gametes via mitosis in antheridia (male gametangia, make sperm cells) and archegonia (female, produce eggs) Gametes fuse to form diploid zygote. Sporophyte generation- zygote develops within archegonium into multicellular embryo. Embryo → mature sporophyte plant--> sporogenous cells--> spores (first stage of gametophyte generation and after sporogenous cells meiosis). All plants= spores by meiosis. Algae/Fungi= spores by mitosis/meiosis. Seeded Vascular Plants (General)- Gymnosperms & Angiosperms (flowering plants) Gymnosperms- naked seeds- seeds borne unprotected in a cone. Angiosperms- most recent- seeds enclosed & protected within a fruit. The Bryophytes- Seedless General: Non vascular, lack conduction system thus small size, rely on diffusion & osmosis, disperse via haploid spores, earliest plants to colonize land, lack xylem/phloem, only plants with dominant gametophyte generation. Sporophytes dependent on gametophyte for nutrition so they are attached. Moss-Phylum Bryophyta- gametophytes grow from protonema. Rhizoids anchor to soil. Lack true leaves, roots, & stems. Sphanum- commercial moss- soil conditioner. Spanish moss-misnomer- angiosperm. Apparent Alternation of Generation: Gametophyte bears gametangia at apex. Zygote(egg + sperm in archegonium) + mitosis→ Embryo → moss sporophyte attached to gametophyte. Gametophyte has a foot, seta, and a capsule with sporogenous cells. Meiosis in capsule results in haploid spores. Spore germinates in to protonema. Protonema → Buds → gametophytes. Liverworts- Phylum Hepatophyta- gametophytes flattened, lobed thalli, others leafy. Asexual reproduction- 1)involved gemmae that disperse via raindrops/animals. 2) Thallus branching. Hornwort- Phylum Anthocerophyta- thalloid gametophytes. Gametangia embedded in thallus. Seedless Vascular Plants- has vascular tissues (xylem & phloem), dominant sporophyte generation, depends on
