Plant FormChapter 36

The World of Plants

• Video Clip

• Parts of a Flowering Plant

• Transpiration

• Transpiration in Plants

• Monitoring Water in Plants

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Plant Body OrganizationA vascular plant consists of:

1. Root system, which is underground

-Anchors the plant, and is

used to absorb water and minerals

2. Shoot system, which is above ground

-Consists of supporting stems, photosynthetic leaves and reproductive flowers

Each has an apex that extends growth

Roots, shoots and leaves contain three basic tissue systems:-Dermal tissue – For protection (Wax and bark)-Ground tissue – For storage, photosynthesis and secretion-Vascular tissue – For conduction

-Xylem – Water and dissolved minerals-Phloem – Nutrient-containing solution

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Plant CellsPlant cell walls consist of cellulose

-Primary cell wall

-Found in all cells

-Cellulose fibers parallel to microtubules

-Secondary cell wall

-Found in some cells

-Additional layers of cellulose and lignin

-Increase mechanical strength of wall

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Plant Stem Cells

Meristems are clumps of small cells with dense cytoplasm and large nuclei They act as stem cells do in animals

-One cell divides producing a differentiating cell and another that remains meristematic

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The Primary Plant BodyApical meristems are located at the tips of stems and roots

-Give rise to primary tissues which are collectively called the primary plant body

-Three primary meristems (that come from apical meristem)

Epidermis,1o vascular tissue, Ground tissue

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Secondary Plant Body (increases girth)Lateral meristems are found in

plants that exhibit secondary growth

-Give rise to secondary tissues which are collectively called the secondary plant body

-Woody plants have two types

-Cork cambium Outer bark

-Vascular cambium 2o vascular tissue

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Plant Tissues

As mentioned earlier, plants contain three main types of tissue

-Dermal

-Ground

-Vascular

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Dermal Tissue*Forms the epidermis, which is usually one cell layer

thick & is outer protective covering*Covered with a fatty cutin layer constituting the

cuticle (prevents water loss)*Contains special cells, including guard cells,

trichomes and root hairs

Guard cells are paired sausage-shaped cells-Flank a stoma, which is the passageway for oxygen and carbon dioxide...and is the epidermal opening between 2 guard cells

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Dermal Special Cells ContinuedTrichomes are cellular or multicellular hairlike

outgrowths of the epidermis

-Keep leaf surfaces cool and reduce evaporation by covering stomatal openings

-Some are glandular, secreting substances that deter herbivory

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Roots hairs are tubular extensions of individual epidermal cells in growing roots

-Greatly increase the root’s surface area and efficiency of absorption...of water and minerals

Dermal Special Cells Continued

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Ground Tissue

Parenchyma cells - most common plant cell-storage,photosynthesis,secretion-chloroplasts-chlorenchyma

Collenchyma cells - support for organs, bend but don’t break

Sclerenchyma cells - tough thick walls...usually haveSecondary cell walls with lignin (polymer seen in wood)

A tissue that functions in food, water storage, photosynthesis and secretion...Consist of 3 types of cells

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Vascular TissueXylem -Constitutes the main water-and mineral-conducting tissue...Water goes in a stream from rootsto shoots and out of the leaves via transpiration

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Vascular Tissue

Xylem

-Also conducts inorganic ions such as nitrates, and supports the plant body

-Typically includes parenchyma cells

-Function in lateral conduction and food storage

Note: The diffusion of water vapor from a plant is termed transpiration

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Vascular TissuePhloem

-Constitutes the main food-conducting tissue in vascular plants-Contains an elongated living cell with no nuclei called sieve tube members

Phloem transports sucrose, hormones, and amino acids

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Roots

Root cap-Contains types of cells that are formed continuously by the root apical meristem

Zone of elongation

-Roots lengthen because cells become several times longer than wide

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Prop roots Aerial roots

Pneumatophores Water storage roots Buttress roots

Keep plant

upright

Obtain water from air

Oxygen uptake Weigh over 60 pounds Stability

Modified Roots

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Stems

Leaves may be arranged in one of three ways

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External Stem Structure

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External Stem Structure

Node = Point of attachment of leaf to stem Internode = Area of stem between two nodesBlade = Flattened part of leafPetiole = Stalk of leafAxil = Angle between petiole/blade and stemAxillary bud = Develops into branches with

leaves or may form flowersTerminal bud = Extends the shoot system

during the growing season

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Internal Stem StructureVascular tissue arrangement is directly related to the stem’s ability for secondary growth-In eudicots, a vascular cambium develops between the primary xylem and phloem

-In monocots, there is no vascular cambium-Therefore, no secondary growth

Aging a Tree

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Scots Pine ( Pinus sylvestris ) x3 .Transverse section represents 30 years of even growth.  Note that the summerwood (White)and spring wood (green)have different relative thickness' depending  upon weather conditions that year.  Note excess production of resin which bleeds into the ring structure as seen above right side.

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Modified Stems

Resemble leaves

Used for climbing

Swollen tip of rhizome

Grow along groundUnderground

stems

Bulbous

Undergroundstem with fleshy leaves

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Leaves Leaves are the main site of photosynthesis -They are

determinate structures whose growth stops at maturity

A leaf-blade has veins which consist of xylem and phloem

-Monocot leaves have parallel veins

-Eudicot leaves have netted or reticulate veins

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Leaves

Simple – undivided blades Pinnate - paired leaflets

Palmate - center axis

of leaflets

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Basic Leaf Histology

The mesophyll is the tissue between the upper and lower epidermis

Epidermis has a waxy cuticle

-The lower epidermis contains numerous

mouth-shaped stomata flanked by guard cells

Evergreen vs. Deciduous

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Male vs Female Cones

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What is Pollen?

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Catkins