PLANTSSTRUCTURE

AND GROWTH

FRUIT an organ that contains seeds, protecting

these as they develop and often aiding in their dispersal.

derived from ovaries, and other flower parts. Ovary walls thicken to form pericarp

Can be composed of up to 3 layers Exocarp Mesocarp Endocarp

TYPES OF FRUIT Simple fruits – form from a simple ovary of a

single carpel, or from a compound ovary of several fused carpels Dry fruits

Achenes – close fitting pericarp around single seed Sunflowers

Grains – pericarp is fused to a single seed Wheat, corn

Nuts - thick woody pericarp fused to a single seed Walnuts, hazelnuts, acorns

Legumes - Pod that splits along two opposite sides Beans, peas, peanuts

TYPES OF FRUIT CONT’D Simple fruits – cont’d

Fleshy Fruits – mesocarp forms flesh Drupes – 1 or 2 seeds, stony endocarp

Plum, peach Berries – 1 to many seeds, no stony endocarp

Tomatoes,, grapes, all citrus

TYPES OF FRUIT CONT’D Compound/Aggregate Fruits

Develop from several individual ovaries of one flower Raspberries Strawberries...the inside is not actually fruit, but

flesh formed from the receptacle

Multiple fruits Formed from the fusion of many carpels belonging to

separate flowers pineapple

FRUIT STRUCTURE AND FUNCTION FIG 10.8

SEEDS AND YOUNG SHOOTS Germination occurs when conditions are

favorable Need: water, warmth, and oxygen

Many seeds remain dormant until certain conditions are met Inhibitors prevent germination, stimulators

trigger it High moisture levels, period of cold weather, fire

etc...

SEEDS AND YOUNG SHOOTS Initial leaves to appear are the cotyledons

In dicots the cotyledons provide initial nutrition in monocots endosperm fills this role

First root to appear is the radical.

FIG. 10.9AND 10.10

PLANTS STRUCTURE All plant tissue develops from meristems

Specialized regions where cell division occurs

Apical Meristems are responsible for increased length Root Apical Meristem (RAM) Shoot Apical Meristem (SAM)

Protoderm develops epidermal tissue

Ground Meristem produces ground tissue

Procambrium develops vascular tissue

FIG. 9.11B

EPIDERMAL TISSUE Surrounds entire body of herbaceous and

young woody plants “Bark” develops after first year of growth

Bark is only a small portion of the new outer layer called periderm

Closely packed cells, designed to protect, and minimize water loss.

EPIDERMAL TISSUE – CONT`D Specialized epidermal cells:

Root Hairs – Long projections from epidermal cells to increase surface area

Trichomes – hairs on stems, leaves and reproductive organs to protect against moisture loss

Guard Cells – surround microscopic holes on underside of leaves, able to open and close for gas exchange.

FIG. 9.4A

GROUND TISSUE Forms the bulk of the plant

3 main cell types Parenchyma

Most abundant, look like ‘typical’ plant cell Least specialized, often contain plastids that store

products of photosynthesis.

GROUND TISSUE CONT’D Collenchyma

Thickened cell wall, provide flexible support Strands in celery

Sclerenchyma Have thick secondary cell walls, mostly non-living,

provide support and structure Fibres – hemp, flax Sclerids – stones in peaches, grittyness of pears.

GROUND TISSUE CONT’D

VASCULAR TISSUE Located in

Vascular cylindar in roots Vascular bundles in stems Veins in leaves

Two primary tissues Xylem and Phloem

VASCULAR TISSUE Xylem

Water and minerals from roots to leaves Two cell types, both non-living at maturity

Tracheids , Vessel elements FIG 9.6

VASCULAR TISSUE Phloem

Sugar and other organic compounds, including - hormones, usually from leaves to roots

Two cell types Sieve tube members – have holes between to form

continuous tube, no nucleus Companion cells have nucleus, controls and maintains

life of both cells.

FIG 9.7

LEAVES Photosynthetic organs of plants

Structure generally a flattened blade and a petiole that attaches to stem Simple leaves – single blade Compound leaves – many blades on one petiole

Adaptations Shade plants – broader leaves, darker in colour Xerophytes – no moisture, small needle-like leaves Tendrils to attach to objects Catch insects

LEAF STRUCTUREFIG 9.8

LEAF STRUCTURE Cuticle (upper and lower)

Waxy layer prevents moisture loss

Epidermis (upper and lower) Outer layer of cells, provides structural support,

generally no chloroplasts

LEAF STRUCTURE CONT’D Pallisade Mesophyll

Brick like cells, stacked on end Primary site of photosynthesis

Spongy Mesophyll Irregular cells, Loosely packed, lots of air space

Promotes gas exchange Veins are held within this layer

Veins Vascular tissue surrounded by bundle sheath cells

LEAF STRUCTURE CONT’D Stomata

lower epidermis, regulates gas exchange and water levels

Opening surrounded on each side by two large guard cells. Water levels control opening and closing

absorb water swell stomata opens. lose water relax stomata close

During the heat of the day, water levels decrease, stoma stay closed Helps to decrease water loss

At night, water levels are able to rise, stoma open allowing leaves to release excess water, exchange Carbon Dioxide and Oxygen.

FIG 9. 23