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. secondary xylem and phloem form 3. initials give rise to vascular rays 4. cork cambium forms cork

Feb 5­9:52 AM 49 Production of secondary xylem and phloem

Feb 5­9:50 AM 50 stems­ due to vascular cambium and secondary vascular tissue made ray initials ­ cambium cells that produce radial parenchyma cells fusiform initials ­ make new vascular tissue (secondary) periderm = cork + cork cambium bark­ all tissues external to the vascular cambium (phloem + periderm) can look at tree rings for secondary growth

Apr 12­9:10 PM 51 Dendrochronology = study of tree ring growth

­rings vary in thickness depending on seasonal growth

Three year old stem

Feb 5­9:53 AM 52 heartwood = older layers of secondary xylem that no longer transport water and minerals sapwood = newest, outer layers of xylem that transport sap lenticels = small, raised areas of periderm; space between cork cells so living cells can live ­ some gas exchange

Apr 12­8:53 PM 53 Mar 16­9:38 AM 54 Wawona Sequioa in Yosemite national Park ­ cut in 1881 ­ lived another 88 years

*tree do not need heartwood to survive

Mar 16­9:39 AM 55 Plant growth, morphogenesis and differentiation

Plant growth ­ involves cell division and expansion plane and symmetry of cell division can influence form

Feb 3­2:27 PM 56 asymmetrical cell division ­ where one daughter cell receives more cytoplasm than other cell ex. to make guard cells ­plane of cell division is laid down in late interphase ­ is called the preprophase band ­disappears before metaphase cell expansion adds length of cells ­ usually due to extra water ­grows in plane perpendicular to microfibrils

Feb 3­2:32 PM 57 plane of symmetry

preprophase band and plane of cell division

Apr 12­9:29 PM 58 Orientation of plant cell expansion

­usually due to water uptake

­cell enzymes weaken cross­links of cell wall which allow it to expand

Feb 5­9:56 AM 59 morphogenesis­ organization into tissues and organs called pattern formation ­depends on positional information ­ signals in embryonic tissue A. wild­type B. fass mutant seedling ­ex. polarity ­ root and shoot ends C. Mature fass mutant happens in first division of zygote genes are important A.

B. C.

Feb 3­2:40 PM 60 differentiation ­occurs throughout plant's life ­depends on genes expression too phase changes ­ a. vegetative growth from juvenile state to mature state ex. change in leaf structure

Feb 3­2:45 PM 61 regular expression of gene

over expression of gene

Apr 12­9:35 PM 62 b. vegetative shoot tip to floral meristem triggers: day length, hormones ­meristem identity genes get turned on to make floral meristem ­organ identity genes also promote change to a particular organ ex. stamen

phase change in shoot system of Eucalyptus

Feb 5­9:58 AM 63 ABC model of flower formation identifies how three classes of genes direct the formation of four types of floral organs each class of organ identity genes is switched on in two specific whorls of the floral meristem

Apr 12­9:41 PM 64 What would happen if had mutant lacking A and B?

Feb 5­9:58 AM 65 So, How is the structure of the plant related to its function?

Apr 13­8:57 AM 66