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Plant Test Review

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CAS BI 107
Sean Mullen

Plants: • Key Traits: o Alternation of Generations (Sporophytes-Gametophytes-Sporophytes)  Part of the plant body which produces haploid male and female spores is called a sporophyte  The spores divide to produce more cells, which together are called the gametophyte (female and male gametophytes, produce sperm and eggs)  Fusion of egg and sperm spawns sporophyte again for next generation o Multicellular, dependent embryo  Embryo depends on parent plant to survive/lives in it o Apical meristems  Dividing cells at the tip of shoots and roots  Cells formed from apical meristems are what form entire plant (i.e. branches, leaves, roots)  Allow plants to grow above and below ground • Cuticle: a protective layer on stems and leaves that prevents loss of water from cells • Synthesis of diverse secondary compounds: afford protection to plant from herbivores, pathogens, harmful effects of UV light • Symbiosis between ancient land-plants and fungi may have helped plants gain nutrients o Endophytes: fungi that live inside of a plant (spaces outside of plant cells) • Diversification of Plants: o Nonvascular Plants:  No true xylem or phloem  Haploid o Vascular Plants:  Ploem: sugar-conducting tissue  Xylem: water-conducting tissue  Diploid o Seedless plants produce spores o Seed Plants:  Gymnosperms (naked seed plants): • Seed not enclosed in fruit  Angiosperms (covered seed plants): • Seed enclosed inside fruit • Flowering Plants (Angiosperms): o Main Types:  Parenchyma: Thin-walled cells. Spherical or polyhedral, generally loosely packed, with lots of intercellular spaces. Can have chloroplasts, starch granules, oil droplets. Acts as storage (stems, roots) or photosynthetic (leaf, stems) tissue, not support tissue.  Collenchyma: Support tissue. Strength + flexibility to plant parts that can bend. Cell walls thickened at corners, or unevenly.  Sclerenchyma: Support tissue, but more rigid. Cell walls are thickened throughout the surface (cells are really thick). Cells are often dead at maturity. Major Cell Types: o Fibres: long, tapered cells, form length-wise bundles o Sclereids: very thick, stone-like cell walls  Xylem (water-conducting tissue): • Vessels: wide tubes with thin walls  Phloem (sugar-conducting tissue): • Sieve Tubes: carry sugar solution throughout the plant, allow exchange of material, no nucleus • Companion Cell: controls function of sieve tube, has a nucleus • Vascular Bundle: xylem and phloem form it, vascular bundles form network • Leaf Structure and Function: o Main function: photosynthesis o Internal Structure:  Epidermis (outer skin): • Upper and lower epidermis: cells are thin-walled and transparent to allow sunlight in, lack chloroplasts • Cuticle: prevents water loss, allows sunlight to come in • Stomata: tiny openings between pairs of guard cells, allow exchange of gases with atmosphere, more stomata on lower epidermis o Transpiration: loss of water vapor through stomata o **stomata takes in CO2, without it photosynthesis could not occur (cuticle doesn't let anything in) • Guard Cells: regulate the opening and closing of stomata  Mesophyll (middle of leaf): • Photosynthetic tissue between epidermal layers, thin-walled cells with chloroplasts • Chlorophyll: traps sunlight for photosynthesis • Mesophyll cells become turgid (taut) when filled with water, flaccid when water is lost • In Dicots, mesophyll consists of: o Palisade layer(s): tightly packed, columnar cells, lots of chloroplasts. Main site of photosynthesis o Spongy layer(s): loosely arranged cells, allowing gas exchange. Also photosynthetic.  Vascular Bundles • Bundle Sheath: surrounds xylem and phloem, x+p are
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