- Slides: 26
Plants (short version) Magnet: Chapter 24, only parts of 2528 (Mader text)
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- *see Ch 7 *Remember: Parenchyma=mesophyll
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
Alternation of Generations • Plant life cycle
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
Groups of Bryophytes • Mosses and their relatives are called bryophytes, or nonvascular plants • They do not have vascular tissues, tissues or specialized tissues that conduct water and nutrients.
Capsule Structure of a Moss Plant Sporophyte Stalk Stem like structure Leaf like structure *Rhizoid is the holdfast Rhizoid Gametophyte
Pteridophytes (*formerly called Tracheophytes) • Seedless, vascular • True roots with vascular tissue; leaves called fronds • Sporophyte (diploid) is the dominant generation (gametophyte is underground and inconspicuous) • Sporophyte is “what you see” (above the ground). Diploid sporangia produce haploid spores on back side of frond. • In order to complete their life cycle, they need a moist environment, since flagellated sperm must swim thru water to reach egg • Ex- ferns
Life Cycle of Ferns and other vascular plants have a life cycle in which the diploid sporophyte is the dominant stage.
Life Cycle of Ferns • Fern sporophytes develop haploid spores on the underside of their fronds in structures called sporangia • Sporangia are grouped into clusters called sori.
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
Gymnosperms—Cone Bearers –Conifers • Conifers are the most common gymnosperms, with more than 500 known species. Sometimes called evergreens • Conifers include pines, spruces, firs, cedars, sequoias, redwoods, junipers, and yews.
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
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
Angiosperm Life Cycle DOUBLE FERTILIZATION: 1 -Zygote (2 N) and 2 -endosperm (3 N)
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 – Two of the most common: Auxin (stem elongation); Ethylene (fruit ripening and apoptosis)
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) – If plant grows toward stimulus- positive tropism (away from stimulus is negative) – Examples of tropisms-1 - phototropism (positive: growth toward light source); 2 - gravitropism (positive: downward growth of root; negative- upward growth of stem away from gravity; 3 - Thigmotropism(Mechanical)- pos. -growth toward point of contact (like a vine around fence or tree)
Additional info to know • 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)
Questions to also Know: Ch 27 • Differentiate between xylem and tracheid. • Explain transpiration, in terms of processes such as cohesion, adhesion, capillary action. • Explain these in terms of photosynthesis: stomata, guard cells, mesophyll (chloroplasts). • What is found in a leaf vein? • *Remember leaf structure and the general equation (and process) of photosynthesis