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Chapters 22-25:Plant Notes Ferns Conebearing plants Flowers; Seeds Enclosed in Fruit Mosses Seeds Water-Conducting (Vascular) Tissue Green algae ancestor Flowering plants Plant Characteristics: • • • • • photosynthetic multicellular eukaryotic cell wall made of cellulose sexual (seeds and spores) and asexual (vegetative propagation) reproduction • common ancestor was green algae (a protist) • 2 Categories of Plants: Vascular and Nonvascular (vascular tissue- is specialized tissue for the transport of water and solutes through a plant) Plant Classification • 10 Major Divisions in the Plant Kingdom • 4 Main Divisions are: – Bryophyta – Mosses (Nonvascular) • 23,000 living species • Lack vascular tissue – Need moist environment-water is absorbed from cell to cell • Lack true roots – have rhizoids • Reproduce by spores – Pterophyta – Ferns (Vascular) • 12,000 living species • Can inhabit drier areas • Reproduce by spores – NO seeds Comparison of Moss with Flowering Plant Division of Plants Continued – Gymnosperms : Conifers • 550 living species • Produce naked seeds in cones – Angiosperms : flowering plants • 235,000 living species • Produce seeds in flowers (protected in fruit) Two Groups: Monocots and Dicots Features of Seed Plants Comparing Comparing Features Features of of Seed Seed Plants Plants Feature Feature Gymnosperms Angiosperms Seeds Seeds Bear their seeds on cones Bear their seeds within flowers Reproduction Reproduction Can reproduce without water; male gametophytes are contained in pollen grains; fertilization occurs by pollination Can reproduce without water; male gametophytes are contained in pollen grains; fertilization occurs by pollination Examples Examples Conifers, cycads, ginkgoes, gnetophytes Grasses, flowering trees and shrubs, wildflowers, cultivated flowers Comparison of Monocots and Dicots Vascular Plants • vascular plants make up over 90% of all plants • ferns (seedless), gymnosperms (cone bearing), and angiosperms (flowering plants) • xylem and phloem make up vascular tissue – xylem- tissue that carries water and minerals upward in a plant – phloem- tissue that carries sugars (from photosynthesis) upward and downward in a plant • have roots – to absorb water, anchor the plant in the ground, protect the plant from bacteria and fungi – two types of roots • taproot- enlarged primary root; grows deep to reach water deep below the surface (carrot) • fibrous- numerous, extensively branched roots; grow near the surface and help prevent topsoil from being washed away by heavy rains (grass) Vascular Tissue Xylem Cells Phloem Cells Carry water Carry Food More on Vascular plants….. • have stems – holds leaves up to sunlight and transport water and food between roots and leaves • have leaves – collect light for photosynthesis – have stomas- pores in epidermis of leaf for carbon dioxide, water vapor, and oxygen to be exchanged • reproduce by seeds and spores – ferns- have spores, no seeds (sperm and egg) – gymnosperms- seeds in cones (pine tree) – angiosperms- seeds in flowers (deciduous trees, flowers, bushes) Nonvascular Plants- Bryophytes • Mosses, Liverworts, and Hornworts • lack vascular tissue for long distance transport of water and solutes • more dependent on water, need to live in moist environments • lack true roots, stems, and leaves • have rhizoids- long, thin cells that anchor them to the ground and absorb water and minerals • need water for sexual reproduction- sperm swim to egg Nonvascular Plants Plant Life Cycle-Alternation of Generation • plants have two alternating phases in their lifecycle • a diploid (2N) phase – sporophyte (makes spores by meiosis) • a haploid (N) phase – gametophyte (makes gametes by mitosis) haploid diploid Spores Gametophyte Sporophyte mosses Gametophyte Sporophyte sperm fertilization eggs ferns seed plants Alternation of Generations in Ferns Fern Life Cycle Alternation of Generations in Conifers Alternation of Generations in Angiosperms Comparison Flower Structure A Perfect Flower stigma filament anther petal ovary style sepal • • • • • • A perfect flower is one that contains both male and female reproductive structures. The male reproductive structures are collectively called the stamen. The stamen consists of the filaments and anthers. The female structures are collectively called the pistil. The pistil consists of the ovary, style and stigma. The sepals and the petals are called sterile structures since they are not part of the reproductive system. stigma filament anther petal ovary style sepal • • • • • • • • • Sepals- usually green surrounding the flower and protect the flower while it is developing Petals- which are often brightly colored and attract insects and other pollinators to the flower Stamen- anther and filament Filament- long, thin stalk that supports the anther Anther- oval sac where pollen is made (male gametophyte) Carpels- (pistils) produces the female gametophyte Ovary- contains ovules (female gametophyte) Style- stalk to carpel Stigma- top sticky portion of the carpel, this is where pollen lands Plant Adaptations • Cuticle covering outside of land plants to conserve water • Lignin makes cell walls harder which enables trees and woody plant to grow taller and spread branches and leaves for catching sunlight • Lose leaves (deciduous) to cope with drought and become dormant Leaf Structure Parts of a Leaf 3. 4. 5. 6. • • • • • • 3.cuticle 4. epidermis 5. mesophyll 6. vein (phloem and xylem) 7. stoma 8. guard cells 7. 8 •Mesophyll- ground tissue where photosynthesis takes place •Guard Cell- specialized cells in the epidermis that controls the opening and closing of the stomata •Cuticle- waxy coating on leaf to reduce water loss •Epidermis- outer layer of the leaf - Protection •Xylem- cells that carry water upward from the roots •Phloem- cells the transport sugar throughout the plant •Stoma- pore-like openings in the underside of the leaf that allow CO2 and O2 to diffuse in and out of the leaf Adaptations: • Plants regulate the opening and Guard cells closing of their stomata to balance stoma water loss with rates of photosynthesis Stomata open stoma Guard cells Stomata closed Plant Structures • Roots – absorb water and minerals • root hairs-extensions of epidermis –greatly increase surface area for absorption – anchor plant in soil – Store food – Two Types of roots – taproot-enlarged primary root • Grow deep reaching water deep below surface – Fibrous –numerous branched roots • Grow near surface Root Types Tap Root Fibrous Root Plant Structures Continued • Stems – Hold leaves up to sunlight and transport water and food between roots and leaves – Produce flowers for reproduction Cross-section of a tree trunk Cambium = growth Wood Bark Cork- contains old nonfunctioning phloem Xylem: Heartwood- Cork Cambium- produces cork contains old xylem provides the tree with support Phloem wood Vascular Cambium- produces new xylem Xylem: Sapwood- contains active xylem Plant Response • Phototropism- tendency of a plant to grow towards a source of light • Geotropism- response of a plant to the force of gravity (why plants grow up) • Photoperiodism- response of plants to periods of light and darkness Vegetative Propagation Producing new plants from roots, stems or leaves of an existing plant –(Asexual) • • • • Bulbs –short underground stem with thick fleshy leaves containing stored food Tubers – fleshy portion of an underground stem with has buds (“eyes”) Runners – an over ground stem that produces new roots and upright stems at various points Rhizomes – an under ground stem that produces new roots and upright stems at various points Plant Hormones Chemical Messengers molecules produced at specific locations. Occur in low concentrations. Cause altered processes in target cells at other locations. General plant hormones Auxins Gibberellins Cytokinins Abscisic acid Ethylene Auxin Auxins are produced in the apical meristem and are transported downward into the rest of the plant. Stimulate cell elongation Other Effects of Auxin • • • • Apical dominance Prevents leaf abscission Involved in growth tropisms Enhances fruit growth – Auxin from the developing seeds results in fruit growth Apical Dominance Fig. 28-5 Auxin associated with phototropism Growth movement Loosening of cell wall Gravitropism (Geotropism) Auxin as a weed killer • 2,4-D – 2,4 dichlorophenoxy acetic acid • Causes a plant to grow itself to death • More readily absorbed by broad-leaved plants • Most often the “weed” of ‘Weed and Feed’ lawn fertilizers Gibberellin Produced in the shoot apex of leaf buds and root system Stimulates cell division and elongation Discovered in association with Foolish disease of rice (Gibberella fujikuroi) uninfected infected Effects of Gibberellins Produce dramatic increases in size, particularly in stems and fruit. General cell elongation. Breaking of dormancy. Promotion of flowering. Transport is non-polar, bidirectional producing general responses. Fig. 28-19 Cytokinins Function of Cytokinins Promotes cell division. Morphogenesis. Lateral bud development. Delay of senescence. Stomatal opening. Rapid transport in xylem stream. Abscisic acid Made by the leaves Widespread in plant body-moves readily through the plant Functions of abscisic acid General growth inhibitor – counteracts the growth promoting effects of auxins and gibberellins Causes stomatal closure. Readily translocated. Produced in response to stress. Ethylene H H \ / C = C / \ H H Functions of ethylene Gaseous in form. Rapid diffusion. Affects adjacent individuals. Fruit ripening. Senescence and abscission. Interference with auxin transport. Initiation of stem elongation and bud development.