Ch 29 Plant Diversity 1 Algal Ancestry Plants and chlorophytes share many common features o They are multicellular and photosynthesize o Chloroplasts with chlorophyll a and b o Cell walls with cellulose o Storage molecule is starch Charophytes are the closest algal relatives to plants o Several cell level synapomorphies shared derived characteristics Peroxisomes cytokinesis see book Many charophytes live in ponds that dry out o Zygotes survive in the dry air by a protected coat of sporopollenin 29 3 o Similar conditions may have led to the first plants There is one common ancestor for all plants o It was most similar to today s bryophyte and arose around 475 mya o Plant lineages are marked by key adaptations to land life Adaptations to land life Alternation of Generations o Found in some algae but not in charophytes o It multiplies the number of unique offspring per fertilization Walled haploid spores o Allows for dispersal through air o Sporopellenin prevents desiccation o Made with in the multicellular sporangia Multicellular gametangia o Protecting sperm with in the antheridium o Protecting egg with in the archegonium Embryos enclosed with in the female gametophyte o Nourished through placental transfer cells Cuticle o A waxy coat around the leaves that stops desiccation o Stomata present in most plants are pores needed to allow for gas exchange Apical Meristems o Meristems just keep dividing o Continual growth toward resources directional growth Mycorrhizae o Mutualism with fungi that helps with water and mineral absorption o Date back to early land plants before roots Secondary compounds o Chemicals that protect plants from competitors herbivores and parasites o Caffeine latex rubber tannins Diversification of Plants Kingdom Plantae is monophyletic Major lineages linked to key adaptations Table 29 1 Bryophytes Non vascular Plants Liverwarts Hepatophyta Mosses Bryophyta Hornworts Anthoerophyta Common features o Haploid gametophyte is dominant independent form in the life cycle Lacks supportive and vascular tissue Most are small low growing in moist areas o Body size restricted because they are dependent on diffusion o Very thin body o Have rhizoids for attachment and anchoring but they are not true roots o Diploid sporophyte depends on gametophyte for food and water Develops from the zygote within the archegonium Sporangium makes haploid spores Moss life cycle o Spores n are produced and dispersed in the air need water when they land o If they find water the start to grown and photosynthesize a bud becomes a full male or female gametophyte o Gametophytes make gametes in the archegonium or antheridium o Sperm swims to the egg for fertilization o Goes through mitosis to form a dependent sporophyte o Sporophyte goes through meiosis to make spores Ecological Importance o Major producers in cold high regions or places with bad soil o Sphagnum peat moss 29 11 bird migration and wetlands fuel source gardening Early Seedless Vascular Plants Evolution of a larger sporophyte Dichotomous branching led to multiple sporangia More spores lead to more offspring Independence of the gametophyte began with photosynthesis in stems Vascular tissue supports taller stems o Xylem carries water and minerals Tracheido strengthened by lignin in most vascular plants gives lots of support o Phloem carries sugar and other products of photosynthesis Roots evolved from underground stems o Anchor larger plants o Absorb water and minerals o Mycorrihzae Taller growth improves access to light Evolution of leaves o Microphylls first single vein Only present in lycophytes today o Magaphylls later ex fern Larger with branched veins In pterophytes and seed plants o Sporophylls are leaves that bear sporangia Sori are a cluster of sporangia Strobius are on lycophytes and are cone like groups of sprophyls o Sparophytes can be huge Tree size in the Carboniferious swamps Phylum lycophyta Relicit group o Closest group to the ancestral vascular plants o All very small o Have microphyllys and strobili cone like structures o Include club mosses quillwort and spike mosses o Little ecological importance Phylum pterophyta Whisk ferns o Dichotomous branching o No true leaves or roots Horse tails o Jjointed stems and tiny leaves stobili Ferns o Most widespread and diverse pterophytes o Mostly understory epiphytes grow on something but not a parasite o There are some tree sized ones today o Have large megaphylls o Sporophylls with sori on the undersides The fern life cycle is almost the same as the moss lifecycle