Chapter 10 Plant Kingdom

Chapter 10 : Plant Kingdom Characteristics of the Plant Kingdom : 1) contain chlorophyll a and b 2) store carbohydrate as starch 3) have a cellulose cell wall 4) usually terrestrial (growing on land) : waxy cuticle (reduces water loss) stomata in leaf to allow gas exchange 5) alternation of generations : a haploid gametophyte produces gametes that fuse to form a diploid sporophyte. The sporophyte, in turn, produces haploid spores by meiosis which grow into another haploid gametophyte. Trends in plant evolution : From : gametophyte dominant To : sporophyte dominant From : need water for reproduction To : no water needed There are three main phyla of spore plants that lack vascular tissue. These are the non-vascular plants: Liverworts, Hornworts and Mosses 1) Phylum Bryophyta ( Mosses ) 20,000 species. Mosses lack vascular tissue to carry water, so they are small and low growing. Gametophyte dominant. Mosses need water to reproduce : antheridia produce sperm. and archegonia produce eggs. Spores are wind dispersed : some species have peristome teeth around the capsule to release spores in dry weather. Mosses and liverworts The haploid spores grow into a long thin protonemawhich eventually forms the haploid gametophyte. After the sperm swims to the egg, the diploid sporophyte grows out of the top of the gametophyte, and often gets food directly from the photosynthetic gametophyte.Animation Mosses are very desiccation tolerant. Rhizoids anchor the plant. example : Sphagnum peat moss ( used commercially for holding moisture in the soil. Sphagnum can hold 20 times its own weight of water). It stores water in dead cells and creates acid conditions in peat bogs. Bog bodies Bog snorkelling could be the next Olympic sport! Bog snorkelling Sphagnum moss releases its spores in an explosive burst. 2) Phylum Anthocerophyta (Hornworts) Only about 100 species. Hornwort Probably one of the oldest land plants, although very few fossils exist. Usually have only one chloroplast per cell, and often contain nitrogen-fixing bacteria. The sporophyte is a small, rod-shaped green plant, with numerous stomata. The sporophyte grows upwards due to a meristem at its base. The tip of the sporophyte splits, releasing spores that will grow into a new gametophyte. Example: Anthoceros 3) Phylum Hepaticophyta (Liverworts) 6,000 species. Liverworts are restricted to wet areas : lack cuticle, and lack vascular tissue. Gametophyte dominant (like bryophyta and hornworts). Asexual reproduction by gemmae, which are dispersed by rain. Sporangium may have elaters to shoot out the spores. The sporophyte is totally dependent on the gametophyte for food. example : Marchantia the gametophytes are dioecious (separate males and females ) Sexual reproduction : antheridia are on round topped stalks. archegonia are on palm tree like stalks ( with lobes instead of a circular disc on the top).