Plant Structure and Growth - Mrs. Boyle's Biology Website

Plant Structure and Growth - Mrs. Boyle's Biology Website

Chapter 35 Plant Structure, Growth and Development Plants

Are very plastic in their body forms. They cant move, so they adapt the growth and structure of their bodies instead. Case in Point

Chapter focus Plant structure and growth Warning many terms or vocabulary words Warning many diagrams Focus structure, function, located next to .

Question ? What heading can be given to the following groups of words?

--------Lettuce Peas Beans ---------Rhubarb Apples Oranges

Question ? What is a vegetable? What is a fruit? Vegetables Lettuce Rhubarb

Fruits Peas Beans Apples Oranges Point

Plants have tissues and organs too, just like animals. Asexual organs (vegetables) Sexual organs (fruits) Asexual Organs 1. Stem

2. Leaf 3. Root Stem The main body of the portion above ground of a tree, shrub or herb. The ascending plant axis.

Have buds. Stem Functions Support of other plant organs. Ps. Storage (water and food).

Modified Stems 1. Rhizomes 2. Stolons 3. Tubers 4. Tendrils Rhizome

An elongated underground horizontal stem.

Ex: Iris, many grasses Stolon

An elongated above-ground horizontal stem. Ex: Strawberries Airplane Plant Tuber

A muchenlarged, short, fleshy underground stem tip.

Ex: Dahlia, Potato Leaf

Lateral outgrowths of the stem axis. Primary photosynthetic organs. Function: Photosynthesis Storage

Leaf Modifications 1. Tendrils: for support Ex: Peas 2. Bulbs: for food storage Ex: Onion

3. Insect Catching Ex: Carnivorous Plants 4. Flowers: thought to be modified leaves. Other Modifications of Leaves

Tendrils Succulent Leaves Spines Bracts

Root The descending axis of a plant, normally below ground. Functions:

Anchorage. Absorption of water and minerals. Storage. Root Types

Taproot - one main root. Ex: carrot Fibrous Roots - many small

roots of equal size. Ex: grass roots Other Root Types Sexual Organs

1. Flowers 2. Fruits 3. Seeds Flowers Modified leaves grouped together on a stem. Sexual reproductive organs.

Function: Sexual Reproduction Fruit

A mature ovary, sometimes including other floral parts. Function: Seed dispersal

Seed protection Fruits Seed Mature ovule containing the embryo and nutrient tissues. Function:

Dispersal unit in sexual reproduction. Plant Cell Types

Differentiated by the type and thickness of the cell wall. 1. Parenchyma (soft tissue) 2. Collenchyma (glue tissue) 3. Sclerenchyma (hard tissue) Parenchyma Cells

Primary wall only. Thin cell wall.

Alive when mature, typical" plant cell. Functions Ps Storage

"Filler" cells Cell division (mitosis) Collenchyma

Primary wall only. Wall is thickened, especially in the corners. Alive when mature.

Function Support of non-woody plant parts. Ex: veins, stems. Sclerenchyma

Secondary wall present. Wall

strengthened with lignin. Dead when mature. Sclerenchyma Types 1. Fibers 2. Sclereids

3. Tracheids 4. Vessel Elements Fibers

Elongated thin cells used for support. Ex: Hemp fibers Sclereids

Used for hard dense areas and support. Ex: Nut shells, seed coats

Tracheids Spindle shaped cells with pits in the

cell walls. Used for water transportation. Vessel Fiber

Vessel Elements Wide stocky cells with pits in the side

walls; lack end walls. Used for water transportation. Plant Tissues

Can be named by several methods: Ex: Cell Location Cell Origin Cell Function

Point The same cell can have several tissue names depending on the criteria for naming.

Main Tissue Systems 1. Dermal 2. Vascular 3. Ground Dermal Tissue Epidermis or "skin" of the plant.

Often has a cuticle, a waxy coating to prevent water loss. Functions: Prevent water loss. Water absorption (root hairs).

Vascular Tissue Made of Xylem and Phloem. Functions: Transport

and support Xylem - Water Phloem - Food Xylem Phloem

Phloem Sieve Cell alive when functioning, but lacks a nucleus. Companion Cell alive, controls itself and the sieve cell.

Ground Tissue Tissue between the dermal and the vascular tissues. Functions: "Filler" tissue

Ps storage support Question ?

How does plant growth and animal growth differ ? Animals Whole organism increases in size. Determinant Growth: grow to a certain size, then stop.

Plants Growth in specialized areas only. Indeterminant Growth: grow as long as they live because the specialized areas remain

embryonic. Plant Meristems

Perpetual embryonic regions. Zones for cell division. Meristem Types 1. Apical growth in

length. Primary growth. 2. Lateral/Cambiums growth in diameter. Secondary growth. Comment

Some tissues like Xylem may be Primary or Secondary depending on which meristem produced the cell.

Ex: Primary xylem Secondary xylem Apical Meristem Types 1. RAM Root Apical Meristem: primary growth of roots.

2. SAM Shoot Apical Meristem: primary growth of shoots. RAM

Located at the tip of each growing root. Protected from the soil by the Root Cap. RAM

Root Cap Protects RAM. Secrets a polysaccharide lubricant for root growth. Primary Root Zones

1. Cell Division - cells small and embryonic. 2. Cell Elongation - cells elongate and start to mature. 3. Cell Differentiation - cells mature into final cell types. Root Hairs

Extensions of the epidermis to increase surface area for water absorption. Not a true tissue. Comment - root hairs are very delicate and must be continually replaced.

Root Hairs RAM - Primary Tissues 1. Protoderm 2. Procambium 3. Ground Meristem

Protoderm Will mature into the epidermis and root hairs. Procambium Stele

Matures into the vascular tissues of the stele: Xylem Phloem Pericycle site of branch roots

Ground Meristem Matures into the ground tissues: Cortex

storage tissue Endodermis second skin around the stele that controls the movement of materials into the stele. Epidermis Cortex

Stele Endodermis Pericycle Xylem Phloem Branch Roots

Originate from the pericycle. Burst their way to the

outside. SAM Produces 1. Protoderm 2. Procambium 3. Ground Meristem Comment these tissues mature into the same things

as seen in RAM. SAM Differences No "root" cap. Produces leaves as stem out-growths at the nodes. Has buds.

Buds Apical Meristems protected by

modified leaves or bud scales. Axillary Buds Branch Stems

Develop from axillary meristems or axillary buds. "External" development.

Leaves Stem outgrowths for Ps. Leaf Morphology: 1. Gross 2. Fine

Gross Morphology Blade - the flattened portion of a leaf. Petiole - stalk of a leaf. Axillary Buds

Blade Petiole Blade/Leaf Types Simple - 1 blade. Compound - Several blades.

Nodes and Internodes Node - stem area where a leaf and bud are attached. Internode - stem area between nodes.

Nodes } Internode Fine Morphology The tissues within a leaf.

1. Upper Epidermis 2. Mesophyll 3. Lower Epidermis 4. Veins Upper Epidermis Cuticle present.

Usually 1 cell layer thick. Cells w/o chloroplasts . Function: protects the mesophyll. Mesophyll 1. Palisade

upright cells. 2. Spongy loosely organized cells with air spaces. Function: major sites for Ps.

Epidermis Epidermis Lower Epidermis Cuticle present. Usually 1 cell layer. Cells w/o chloroplasts.

Stomata present for gas exchange. Stomata (mouth) Regulated by

Guard Cells which have chloroplasts. Vein Structure Xylem: dorsal Phloem: ventral Often surrounded by bundle

sheath cells for support. Xylem Phloem Bundle Sheath Cells

Collenchyma Stem Vascular Tissue Eudicots vascular bundles join together to make a ring. Often have secondary growth. Monocots vascular bundles are scattered. No true

secondary growth. Secondary Growth Growth in diameter. Growth from lateral meristems or cambiums.

Cambium Types 1. Vascular produces xylem and phloem. 2. Cork produces cork. Vascular Cambium Location: between primary

xylem and phloem. Produces: secondary xylem and phloem. Fibers Phloem Vascular Cambium

Xylem Fibers Vascular Cambium: Cell Maturation Internal xylem External phloem The VC pushes the xylem and

phloem apart from each other. Result Newest xylem is next to the cambium. Oldest xylem is in the center

of stem. Result Newest phloem is next to cambium. Oldest phloem is under the epidermis.

Result Xylem accumulates over time. Phloem is destroyed by the outward growth and must be replaced yearly.

Cork Cambium Location: Cortex (external to the VC). Produces: Cork Comment commercial cork is harvested from a Cork Oak.

Cork Cells Produced "outwardly" only. Covered with suberin and are dead when mature. Function insulation and protection.

Epidermis Cork Cambium Cortex Phloem Vascular

Cambium Xylem Fibers Bark All tissues external to the VC. Includes:

Phloem (1 degree and 2 degree) Cork Cortex Epidermis Fiber cells

Wood Xylem tissue of a dicot stem. Comment monocots dont have VC and technically dont produce true wood.

Xylem Growth Springwood - Large cells Rapid growth Summerwood - Small cells Slow growth Annual Rings

Formed by the growth difference between springwood and summerwood. Usually one produced per year. Comment Ring size varies by climate

and growing conditions. Rings can be used to date wooden structures. Summer Wood Spring Wood One Years Growth

Angiosperms Divided into two main types: 1. Eudicotyledons or Eudicots 2. Monocotyledons or Monocots Cotyledons = seed leaves

Monocots vs. Eudicots 1. Seeds and embryos 2. Leaves 3. Stems 4. Roots 5. Pollen 6. Flowers

Seeds and Embryos Eudicots - no endosperm. - 2 cotyledons. Monocots - endosperm - 1 cotyledon Leaves

Eudicots netted veins. Monocots - parallel veins. Stems Eudicots - ring pattern

- vascular cambium Monocots - scattered pattern - no vascular cambium Roots Eudicots - taproot.

- xylem centermost tissue. Monocots - fibrous roots. - pith centermost tissue. Pollen Eudicots 3 openings

Monocots 1 opening Flowers Eudicots parts in 4's or 5's. Monocots parts in 3's.

How do plants make their bodies different? By changes in growth, morphogenesis and differentiation.

Growth Meristems give information to new cells on how they should develop. Plane

and symmetry of cell division Orientation of cell elongation Plane of Cell Division Cell Expansion

Mophogenesis How cells organize into tissues and organs. Determined by: Positional

information Homeotic genes Cell Differentiation Regulation of transcription and translation to make specific proteins. Often keyed by positional

information. Cell Differentiation Example - Flowering Flowering is a phase change from indeterminate growth to

determinate growth. Triggered by environmental or internal signals. ABC model of organ identity genes. ABC Model

The 4 flower parts are controlled by interaction of genes A, B and C in 4 layers of cells. Model

Sepals Gene A only in the outermost or 4th layer Petals Genes A and B in the 3rd

layer. Stamens Genes B and C in the 2nd layer. Carpels Gene C only in the centermost layer. Model

Mutants ABC model African Violet Mutants ABC active in 2nd layer A only mutant Summary

Know the main organs of plants and their functions. Know the main cell types or tissues in plants and their functions. Summary

Know the structural organization of stems, roots, and leaves. Know the differences between eudicots and monocots.

Summary Know about meristems and how plants grow. Know about growth, morphogenesis and differentiation in plant bodies.

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