Transcript Plants
Plants Magnet: Chapter 24, only parts of 2528 (Mader text) Honors: Ch 21 and 23? What is a plant? • Multicellular, autotrophic, eukaryotes • Plants are adapted for terrestrial life •Waxy cuticle •Stomata & guard cells •Root systems & shoot systems •Vascular tissue (xylem & phloem) •Eventually, the advent of the seed! Alga vs. Plant Leaf structure Alternation of Generations • Plant life cycle Four Main Groups of Land Plants • Bryophytes •nonvascular plants •Pteridophytes •seedless vascular plants •Gymnosperms •vascular plants with naked seeds (no flowers) •Angiosperms •vascular flowering plants Plants can reproduce with spores and seeds • Spore and seeds both grow into adult plants • Seeds are the result of fertilization, and are therefore diploid • Spores are haploid cells that can grow up into haploid adults, without participating in fertilization Plants Exhibit an Alternation of Generations Bryophytes • The nonvascular plants • Ex: mosses • Have flagellated sperm which must swim in order to reach the egg • The dominant generation of the mosses is the gametophyte; the sporophyte cannot survive independently Pteridophytes • • • • The seedless vascular plant Have true roots with vascular tissue; fronds Sporophyte is the dominant generation In order to complete their life cycle, they must be in a moist environment, since swimming sperm must swim through water to reach the egg • Ex-Ferns Gymnosperms • Seeds do not develop within ovaries, but on the surfaces of specialized leaves • Produce seeds, but no flowers or fruits • Huge advantage; pollen! •Pollen is the male gametophyte (only 2 cells), and therefore produces the male gamete – the sperm •No longer are the sperm restricted to aquatic environments to swim to the egg! •Evergreens, conifers Angiosperms • • • • Flowering plants Parts of the flower- KNOW! Fruit – a mature ovary; function – seed dispersal Male gametophyte is contained within pollen grains • Ovules within the ovary contain the female gametophyte, which produces the female gamete, the egg • Pollination vs. fertilization Life Cycle of an Angiosperm Two Groups of Angiosperms •Although all angiosperms have a number of features in common, two plants groups, the monocots and dicots, differ in many anatomical details. Comparison of monocots and dicots Plant growth • Annuals • Perennials • Roots From flower to fruit to seed Plant Responses • Plant hormones help coordinate growth, development, and responses to stimuli • Hormones – Are chemical signals that coordinate the different parts of an organism. Made in one place and transported to another The Discovery of Plant Hormones • Any growth response: – That results in curvatures of whole plant organs toward or away from a stimulus is called a tropism. – Is often caused by hormones (ex- auxins, gibberlins (sp), ethylene, cytokinins….EOCT only) – If plant grows toward stimulus- positive tropism (away from stimulus is negative) – Examples of tropisms-1- phototropism (growth toward light source; 2- gravitropism (positive: downward growth of root; negative- upward growth of stem away from gravity; 3- Thigmotropism- Mechanical- growth toward point of contact (like a vine around fence or tree) Additional info • Complete flower vs. incomplete • Perfect vs. Imperfect flower – A flower can be perfect, but incomplete. How? • Growth rings in stems – How can you tell if it was a rainy season vs a drought? **Tubers and bulbs are underground stems for food storage; Strawberries are runners (horizontal to ground). Form roots when “touch” ground **FRUIT- reproductive (anything with seeds); VEGETABLE- no reproductive parts (no seeds)