Ch. 35 Plant Structure, Growth, and Development Feb 3­12:31 PM 1 Essential Question: How is the structure of the plant related to its function? Feb 3­12:32 PM 2 Tissue = a group of cells with a common function, structure or both Organ = several types of tissues that carry out a particular function Three basic plant organs = roots, stems and leaves Apr 12­7:49 AM 3 Feb 5­9:22 AM 4 The Body of a Plant A. Root system root = organ that anchors a vascular plant, absorbs minerals and water, and can store organic nutrients Two types of roots 1. taproot system ­ one vertical root that develops from embryonic root ­lateral roots (branch roots) come off of taproot ­found in eudicots (many flowering plants that have two cotyledons)and gymnosperms Feb 3­12:33 PM 5 tap roots ­go deep into ground Ex. carrots, turnips, sugar beets Mar 11­9:28 AM 6 2. Fibrous root system ­ a mat of thin roots that spread just below soil surface, with no main root ­found in seedless vascular plants and most monocots (ex. grasses) embryonic root dies, roots grow from stem each root has lateral roots these roots are adventitious ­ a part of a plant that grows in an unusual location prevent soil erosion http://www.botany.uwc.ac.za/ecotree/root/roottypes.htm root hair­ extension of a root epidermal cell ­ increase surface area Feb 3­12:45 PM 7 Other modified roots: • prop roots ­ aerial roots, Ex corn storage roots ­ store food Ex. beets Apr 12­8:19 AM 8 • strangling aerial roots ­ plants that germinate in branches of tall trees and send aerial roots to ground • buttress roots ­ aerial roots that look like buttresses Apr 12­8:25 AM 9 • pneumatophores ­ air roots Ex. mangroves Apr 12­8:27 AM 10 B. stem = an organ made of an alternating system of nodes (points where leaves attach) and internodes (segment in between nodes) axillary bud­ found in the angle formed by stem and leaf a structure that has the of potential of forming a lateral shoot most are dormant terminal bud (apical bud)­ young shoot located near shoot apex ­has compact nodes and internodes apical dominance­ when a plant puts its resources to elongating the plant ­increases ability to get light if terminal bud can't work, axillary buds will then come out of dormancy ­ result = more lateral shoots Feb 3­12:52 PM 11 Axillary and terminal buds Feb 5­9:32 AM 12 Modified stems: Rhizomes ­ horizontal shoot that grows just below surface of ground Apr 12­8:29 AM 13 Bulbs: ­ vertical underground shoots consisting of the enlarged bases of leaves that store food Apr 12­8:31 AM 14 Stolons: ­ horizontal shoots that grow along the surface of ground ­ "runners" Apr 12­8:32 AM 15 tubers ­ enlarged ends of rhizomes or stolons specialized for storing food Apr 12­8:34 AM 16 C. Leaves­ photosynthetic organ of plant (stems can also do photosynthesis) blade veins components: blade ­flattened part of leaf petiole­ joins leaf to node of stem some plants lack this (ex. grasses) veins­ vascular tissue of leaf petiole monocots have parallel veins, length of blade eudicots ­ multibranched with a network of veins Feb 3­1:00 PM 17 can classify by shape simple ­ single undivided ,vein compound­ blade has many leaflets double compound­ each leaflet is divided into smaller leaflets Feb 5­9:35 AM 18 Leaf modifications tendrils­ fasten plant, support (peas) spines­ to conserve water (cactus), protection storage leaves­ hold water (succulents) Bracts ­ leaves that surround a flower red leaves of poinsettia, attract pollinators reproductive leaves­ make plantlets Feb 3­1:09 PM 19 leaves, stems and roots are made of three tissue systems Feb 3­1:13 PM 20 a. dermal tissue system­ outer protective layer ­first line of defense ­called epidermis in non woody plants ­ tightly packed cells ­called periderm in woody plants­ replace older regions of roots and stems ­some have cuticle to prevent water loss ­ waxy coating b. Vascular tissue system­ long­distance transport of materials between roots and shoots xylem, phloem stele­ vascular tissue of a root or stem arrangement of stele depends on species and organ ­ angiosperms ­ root has vascular cylinder, stems and leaves have vascular bundles (both xylem and phloem) Feb 5­9:37 AM 21 xylem phloem Feb 5­9:38 AM 22 c. Ground tissue system­tissue that isn't dermal or vascular pith­ground tissue that is internal to vascular tissue in stem cortex­ ground tissue external to vascular tissue functions: storage, photosynthesis and support http://www.backyardnature.net/woodtwi2.htm Feb 3­1:20 PM 23 Types of plant cells Feb 5­9:44 AM 24 1. parenchyma ­ primary wall ­ thin, flexible ­lack secondary wall ­large vacuole when mature ­typical plant cell ­ function ­ perform most metabolic functions of plant ­phototsynthesis, storage of starch ­ can divide 2. Collenchyma ­ function: help support young parts of plant shoot ­thicker primary walls ­lack secondary wall ­ex strings in celery stalk Feb 3­1:24 PM 25 3. Sclerenchyma ­support plants, rigid ­have secondary walls ­ thick (lignin) ­in part of plant not growing two types: a. sclerids ­ short, irregular shape, give hardness to nut shells, gritty texture of pears support and strengthening b. fibers ­ long, slender, tapered threads ex: hemp fibers for rope flax fibers for linen Feb 3­1:28 PM 26 4. Water conducting cells ­dead at maturity a. tracheids ­found in xylem of all vascular plants ­dead, tubular, long cells ­water moves cell to cell through pits b. vessel elements ­ wider, shorter, thinner walled cells ­attached end to end, making long pipes ­end walls have perforations to let water flow freely Feb 3­1:33 PM 27 5. Sugar conducting cells of phloem ­alive at maturity, but lack organelles ­sieve cells ­long narrow cells that transport sugar ­sieve tube members ­ chains of sieve cells ­sieve plates ­ end walls between sieve tube members ­have pores Feb 3­1:37 PM 28 companion cells ­ plant cell that is connected to a sieve tube member by many plasmodesmata and whose nucleus and ribosomes may serve one or more adjacent sieve tube members ­ some plants these are loading areas into the sieve tube members Mar 11­9:33 AM 29 Growth of plants indeterminate growth ­ growth occurring throughout live of plant determinate growth ­ stop growing after reaching certain size Ex. leaves, thorns and flowers Length of life cycle: Annuals ­ complete life cycle in single year Ex. legumes, grains Biennials ­ require two growing seasons to complete life cycle Ex. radishes, carrots Perennials ­ live many years Ex. trees, shrubs, some grasses Feb 3­1:45 PM 30 Indeterminate growth ­plant has embryonic, developing and mature at same time ­can do this due to meristems ­ embryonic tissue ­initials = "stem cells" of plant ­derivatives = specialized cells a. apical meristems­ tips of roots, buds of shoots ­have primary growth ­ growing in length ­ in herbaceous plants (non woody) ­ makes all of plant body ­ in woody plants ­ secondary growth caused by lateral meristems (growth in thickness) b. lateral meristems (vascular cambium and cork cambium) Apr 12­8:45 AM 31 vascular cambium ­ adds layers of vascular tissue called secondary xylem (wood) and secondary phloem cork cambium = replaces epidermis with periderm Mar 11­9:34 AM 32 Three years' growth Mar 16­9:20 AM 33 How do roots grow? root cap­ protects meristem pushed through soil secretes polysaccharide (lubrication) zone of cell division ­ primary meristems quiescent center ­ area of slow growth in apical meristem protoderm ­ will become dermal layer procambium­ will become vascular layer ground meristem ­ will become ground tissue layer zone of elongation ­ cells elongate zone of maturation (zone of differentiation)­cells become mature and distinct cell types Feb 3­1:56 PM 34 root structure Apr 12­8:59 PM 35 Root with xylem and phloem in center ­ (typical of eudicots) Mar 16­9:22 AM 36 xylem and phloem of eudicot in root Mar 16­9:23 AM 37 Root with parenchyma in the center( typical of monocots) Mar 16­9:25 AM 38 Lateral roots grow from pericycle ­ outermost layer in vascular cylinder, pushes through cortex and epidermis ­grows from center because its vascular system must be continuous with center vascular cylinder Apr 12­9:33 AM 39 How do shoots grow? ­shoot apical meristem ­ dome­shaped mass of dividing cells at shoot tip ­ in a bud ­ leaves form from leaf primordia on sides of apical meristem ­shoot elongation is due to internodes that lengthen Feb 3­2:06 PM 40 The shoot tip Apr 12­9:02 PM 41 Vascular bundles Organization of primary tissues in young stems Feb 3­2:11 PM 42 Review of leaf anatomy Feb 3­2:13 PM 43 Mar 16­9:29 AM 44 Mar 16­9:30 AM 45 Stomata ­ pores for gas exchange ­regulate CO2 uptake for photosynthesis ­regulate water loss ­flanked by two guard cells ­ regulate opening of stomata mesophyll­ parenchyma cells for photosynthesis palasade mesophyll spongy mesophyll Veins = leaf's vaxcular bundles Apr 12­8:46 PM 46 Primary growth ­ occurs in apical meristems and involves production and elongation of roots, stems and leaves Secondary growth ­ growth in diameter ­produced by vascular cambium and cork cambium ­happens in all gymnosperms, in dicot angiosperms ­not in monocot angiosperms ­thickens stems and roots Feb 3­2:15 PM 47 Vascular cambium ­ function to add secondary xylem to inside of cambium and secondary phloem to outside of cambium Cork cambium produces cork Apr 12­9:14 PM 48 Secondary growth of a stem 1. primary growth forms vascular cambium 2.