Structure of Flowering Plants

Miss Rochford

Sixth Year Biology

In this topic:

• Tissue in flowering plants

• Structure of a flowering plant

• Monocotyledons and dicotyledons

Types of Tissue in Flowering Plants

Tissue in Flowering Plants

• Also known as ‘meristem’

• Found in:

– Shoot tips

– Root tips

– Buds

Meristematic tissue: Unspecialised cells that are continuously dividing by mitosis

Tissue in Flowering Plants

Tissue Location Function

Dermal tissue Outer covering • Protection

Ground tissue Between dermal and vascular tissues

• Photosynthesis • Storage of food and

wastes • Strength • Support

Vascular tissue • Xylem: transport water & minerals • Phloem: transport food

Vascular Tissue: Xylem

• It is a dead tissue

• Cells lose their cytoplasm early in development and become hollow

• Transports water and dissolved minerals

• Two types of xylem:

1. Vessels

2. Tracheids

Vascular Tissue: Xylem

• Cells join to make a continuous, hollow tube

• Pits in walls let water pass from one vessel to another

• Lignin in walls make them strong

• More efficient than tracheids

• Found in most flowering plants

1. Xylem Vessels

Vascular Tissue: Xylem

1. Xylem Vessels

Vascular Tissue: Xylem

• Long, sloping or tapering cells

• Hollow inside

• They overlap and allow water to pass from tracheid to tracheid via pits

• More basic than vessels

• Found in coniferous trees

2. Xylem Tracheids

Vascular Tissue: Xylem

2. Xylem Tracheids

Vascular Tissue: Xylem

Vascular Tissue: Phloem

• Transports food

• Mainly made of two elements:

1. Sieve Tubes

2. Companion Cells

• Companion cells are alive so phloem is a living tissue

Vascular Tissue: Phloem

• Long and tubular, with end walls

• End walls have pores to allow passage of materials

• End walls = sieve plates

• Have cytoplasm but no nuclei

• Walls made of cellulose

• No lignin

1. Sieve Tubes

Vascular Tissue: Phloem

• Each sieve tube has an accompanying companion cell

• Each has a nucleus and dense cytoplasm

• They maintain the sieve tube cells

2. Companion Cells

Differences between Xylem and Phloem

Xylem Phloem

Carries water and minerals Carries food

Dead Living

Has lignin No lignin

No companion cells Companion cells

Structure of Flowering Plant

ROOTS

Root Functions

• Anchor & support plant

• Take in water & minerals from soil

• Transport water and minerals

• Some store food in roots.

– Carrots

– Beetroot

– Radishes

• Plumule: will form the shoot

• Radicle: will form the roots

Remember from the Junior Cert:

Broad bean seed

Root Types 3 main types of root

1. Tap roots • Main root develops from the radicle • Also called the primary root • Many smaller roots grow from the tap root • Found in most dicotyledons Dandelion Carrot

Root Types

2. Fibrous roots

• Radicle withers and dies • A group of equally sized roots left behind • These emerge from the base of the stem • Found in monocotyledons Grasses Marigold

Root Types

3. Adventitious roots

• Related to fibrous roots • Grow from unusual places on a plant • Can come from anywhere on a stem or branches,

depending on the plant • Examples: Ivy Banyan tree

Root structure • All roots have the same general structure

Zone Function

Zone of protection A root cap protects meristematic tissue as it pushes through soil

Meristematic zone Meristem that undergoes rapid mitosis for root growth

Zone of elongation Newly produced cells increase in size

Zone of differentiation

Cells specialise into a specific plant tissue type

Root Structure

Root: Transverse Section

Root: Transverse Section

STEMS

Stem functions

• Support leaves & flowers

• Transport:

– water & minerals from roots to leaves

– food from leaves to roots

• If green: photosynthesis

• Some store food.

– Potato

– Asparagus

Stem Structure

Stem Structure

Nodes: points on the stem where new branches and leaves develop

Internodes: regions between nodes where no branching occurs

Stem Structure

Lenticels: small pores on a stem that function in gas exchange

Stem Structure

Stem Structure

Part Location Function Apical Bud

(or terminal bud) Tip of the stem

Causes the stem tip to grow

Axillary bud (or lateral bud)

Between a leaf and stem

Produce new branches or flowers

Stem: Transverse Section

Stem: Longitudinal and Transverse Sections

LEAVES

Leaf functions

• Photosynthesis

• Gas exchange

• Transpiration

• Some store food.

– Cabbage

– Spinach

Leaf Structure

• Leaves attach to the stem at nodes

Leaf Structure

• Petiole = stalk of the leaf

• Leaves without a petiole are known as sessile

Long petioles in rhubarb Sessile leaves on speedwell

Leaf Structure

• Leaf veins are xylem and phloem vessels

• Xylem is always on the top side of the leaf

• Phloem is always below the xylem

Leaf Venation

• Veins run in parallel • Found in most monocots

Grasses Daffodils

Parallel Venation

• Veins form a branching network

• Found in dicots Rose Horse chestnut

Net/Reticulate Venation

Leaf: Transverse Section

MONOCOTYLEDONS & DICOTYLEDONS

Monocotyledons

• Often referred to as ‘Monocots’

• Examples:

Cotyledon: the first leaf that develops in a seed

Daffodils Grasses Cereals Tulips

Dicotyledons

• Often referred to as ‘Dicots’

• Examples:

Beans Sunflowers Oak trees Roses

Monocots and Dicots: Differences

Chapter 24: Structure of Flowering Plants

DONE!!