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PLANTS Chapter 22-24 What are plants? Plants… Eukaryotic (have a nucleus) Have cell walls made of cellulose Carry out photosynthesis using the pigment chlorophyll a and chlorophyll b Belong to the kingdom Plantae Types of plants 1) Green Algae 2) Bryophytes (Mosses and others) 3) Ferns 4) Gymnosperms -------------- 5) Angiosperms Green Algae Mostly aquatic Found in fresh water, seawater, and moist areas Absorb nutrients from surroundings Many form colonies Spirogyra Volvox Bryophytes Bryophytes Life Cycle Nonvascular plants ( No xylem to conduct water or Phloem to conduct nutrients) Need water to transfer sperm to egg needs water for germination. 3 Types of Bryophytes Mosses Liverworts Hornworts Moss life cycle pg 642 Seedless Vascular Plants (Ferns) Characteristics: Have vascular tissue for conducting nutrients and water throughout the plant. Produce Spores (not seeds) – need water for fertilization Vascular Tissue - Move fluids against water Xylem Carries Water Phloem Caries Nutrients Gymnosperms – cone bearing plants First seed plants – allows the plant to Reproduce without water Protect the embryo in a seed Provide nutrients to the embryo Reproduction occurs through pollination Pollen (the male gametophyte) is transferred to the female cone Gymnospserm lifecycle Angiosperms – flowering plants Reproduce sexually through flowers Ovaries in flowers develop into fruits to help disperse seeds Flowers attract pollinators and reproduction is more efficient than the wind pollination of gymnosperms Monocot vs. dicot Annuals, biennials, perennials What do plants need to survive Sunlight Make food through photosynthesis Gas Exchange (CO2 and O2) Water and Minerals PHOTOSYNTHESIS 6 CO2 + 6 H2O 6 O2 → C6H12O6 + Carbon dioxide + Water + Light energy → Glucose + Oxygen Plant Structure and Function Plants have tissues and organs too!!!!! TISSUES = dermal, vascular and ground ORGANS = Roots, stems and leaves Types of tissue – Dermal Tissue Dermal tissue = the protective outer covering in a plant Epidermis – outer layer of cells Cuticle – waxy covering Vascular Tissue Vascular tissue = supports the body and transports water and nutrients Xylem – transports water Tracheids (lignin in cell wall to give structure)and vessel elements Phloem Sieve – transports nutrients tube elements and companion cells Ground Tissue Ground tissue = produces and stores sugars and contributes to the support of the plant Parenchyma = thin cell walls, contain a large vacuole, in leaves have chloroplasts Collenchyma = thicker cell walls (make up “strings” of celery Sclerenchyma = thickest cell walls – nutshells, seed coats Plant growth Where do plants grow???? Meristems = regions of cells in which mitosis produces new cells that are ready for differentiation Apical meristem = rapidly growing regions at the tip of the stem and roots Roots Root Function Support a plant Anchor it to the ground Store food Absorb water from the soil Absorb nutrients from the soil Roots cont. Types of roots Taproot – carrots, beets, dandelions Fibrous root - grasses Root pressure – roots actively pump nutrients into the root. Water moves in by osmosis. This causes a pressure that causes water to move up the plant into the stem Stems Functions of stems Produce leaves, branches and flowers Hold up the leaves to the sun Transport substances throughout the plant Formation of wood and tree rings Leaves (pg.681) Anatomy of a Leaf Stomata (next slide) Mesophyll – where Photosynthesis occurs Cuticle – waxy cover to protect/prevent water loss Leaves are optimized to absorb light and carry out photosynthesis Leaves – stomata Stomata – openings in the leaf that allow CO2, water, and O2 to diffuse in and out of the leaf Guard cells = cells that surround the stomata and regulate their opening and closing Homeostasis and stomata Plants keep stomata open just enough so that gas exchange can occur for photosynthesis but not so much that they lose too much water When water is abundant water flows into the leaf. This increases water pressure in the guard cells and opens them. When water is scarce, pressure decreases and the stomata close Water transport in plants Transpiration = water loss from a plant through its leaves Water leaves through open stomata Dry cell walls pull water from deeper in the leaf and pulls water from the roots, stem and leaf through xylem Water “sticks” to water (cohesion) and other molecules (adhesion) Even small trees can lose 100L of water/day What conditions increase transpiration??? Hot Dry Wind How does water move up the plant? Capillary action – the tendency of water to rise in a thin tube 24.1 Reproduction in flowering plants Parts of a flower Sepals = enclose the flower before the bud opens and protects the flower Petals = attract pollinators to the flower often brightly colored inside the sepals Parts of a flower (cont.) Parts of a flower Stamen = male parts of the flower Anther – produce pollen Filament – a stalk that holds up the anther Carpels Stigma (pistil) = female parts of the flower – sticky structure designed to capture pollen Style – a stalk that holds up the stigma Angiosperm gamete production Angiosperm lifecycle Fruit and seed development Fruit = a thickened ovary wall that encloses seeds Seed Dispersal = Animals = seeds with tough coats are encased in a sweet fleshy fruit Apples, grapes Wind = lightweight fruits that allow them to be carried in the air Dandelions Water = buoyant fruits that allow them to float coconuts Seed Dormancy and Germination Dormancy = the embryo is alive but not growing Germination = growth of the plant embryo following dormancy Advantages of Dormancy Allows for long distance dispersal Allows seeds to germinate in ideal growth conditions Some seeds only germinate under extreme conditions Some pine cones remain sealed until the high temps generated by forest fires cause the cones to open Plant Hormones Hormones = chemical signals produced by an organism that affect the growth, activity, and development of cells and tissues Auxin – stimulate cell elongation and growth of roots Produced in the shoot apical meristem and transported When light hits a part of a plant, auxins build up in the shaded region, causing the plant to bend toward the light Growth of lateral buds is inhibited by auxin (if you cut off the top of a plant, the lateral buds grow more quickly. Cytokinins Cytokinins = hormones produced in the growing roots and developing fruits and seeds. Often produce effects opposite of auxins Stimulate cell division Interact with auxins to balance root and shoot growth Stimulate regeneration of tissues damaged by injury Giberellin, abscisic acid, ethylene Giberellins Found in meristems of shoot, root, and seed embryo Stimulate growth, promote germination Abscisic Acid Found in terminal buds and seeds Inhibits cell division Promotes seed dormancy Ethylene Found in fruit tissues and aging leaves and flowers Stimulates fruits to ripen Causes plants to seal off and drop leaves Tropisms Tropism = plants response to environmental stimuli Phototropism – tendency of a plant to grow toward light Gravitropism – response of a plant to gravity Thigmotropism – response of a plant to touch Rapid responses Some plants can also adjust quickly to their environment Venus fly trap Mimosa (folds leaflets in a few seconds when touched) Response to seasons How do plants know when to flower, drop leaves, etc? Photoperiod = the number of hours of light/dark a plant receives (pigment phytochrome) Winter Dormancy Deciduous plants turn off photosynthetic pathways Transport materials from leaves to roots Seal off leaves Chlorophyll breaks down allowing other pigments to be seen (brown, yellow, etc.)