PLANT KINGDOM DIVERSITY The Green Planet

KINGDOM PLANTAE  Plantae are multicellular organisms which produce food by the process of photosynthesis. All plants are multicellular and eukaryotic.  One of the characteristic features of plants is the presence of pigments (like chlorophyll a and b and carotenoids) which aid to convert sunlight into chemical energy by the process of photosynthesis.

Green Algae (Plant-like organisms)  Photosynthetic Eukaryotes Contain chloroplast w/ chlorophyll and other pigments Likely endosymbiosis: a heterotrophic eukaryotic cell engulfed a photosynthetic prokaryote that eventually evolved into an organelle  Require water for reproduction and survival Sperm are flagellated; swim through water to fertilize eggs No cuticle to avoid desiccation; no vascular tissues to move water

Bryophytes (Non-vascular Plants)  The first line of Embryophytes (land plants) Developed cuticle to avoid desiccation on land Must live close to water in order to reproduce  Do not have true vascular tissue (xylem & phloem) so only grow close to ground  Ex: Hornworts, Liverworts, and Mosses

Seedless Vascular Plants  Contain vascular tissue (xylem & phloem)  Reproduce by spores instead of seeds and/or flowers Depend on water during fertilization, therefore are generally found in moist environments  Ex: Lycophytes- Club & Spike Mosses  Ex: Pterophytes- Horsetails and Ferns

Spermatophytes (Seed Plants)  Evolution of seeds & pollen allows reproduction without water  Seeds remain dormant until growth conditions are favorable. Seeds have protective coat to avoid desiccation Seeds have storage tissue to sustain growth  Pollen allows dispersal of gametes across large distances Protected from desiccation; can reach ovary without need for water  Two clades (monophyletic groups):  Gymnosperms & Angiosperms

Gymnosperms 350 MYA  Conifers are the largest living group (630 species) Conifers dominate cold climates near the poles Generally evergreen; have long thin needle-like leaves Seeds develop inside a protective cone Conifers exhibit secondary growth (development of wood)  Cycads (300 sp.), Gnetophytes (80 sp.), and Gingko (1 sp.) Cycads dominant during dinosaur time; found in tropics today

Angiosperms 140 MYA  Most diverse and numerous embryophytes (land plants)  Characterized by flowers; seeds are contained in fruits Species-specific breeding  faster speciation/adaptation to niches  Reduction of gametophyte size (pollen & embryo sac) Shortens time between pollination and fertilization  Flowers enlist animals in developing mutualistic relationships to increase reproduction

Growth in Plants  Primary Growth: (all plants)  exhibited when stems/roots lengthen Cell division (mitosis) in apical meristems at root or shoot tip Enables plants to continuously seek water (roots) or sunlight (shoots)  Secondary Growth: (woody plants)  exhibited when stem gets thicker Cell division (mitosis) in lateral meristems: Vascular cambium- form secondary vascular cells Cork cambium- produces cork cells (bark)