plant organs

Organs

Structure and Function

Plant

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Plant Organs Organs: tissues that act together to serve a specific function.

DermalVascularGround

DermalVascularGround

DermalVascularGround

Stems

Roots

Leaves

Plant Organs

Plant Organs – Organs composed of

one or more tissues.– Three major types:

• Roots• Stems• leaves

– Flowers and fruits evolved from stems and leaves

Function of Plant Organs

ROOTS – Function Anchorage Absorption Storage Conduction

STEMS –Function Suppor Transport.

LEAVES – Function Photosynthesis

ROOTS “the hidden half” Functions of roots:

Anchorage Absorption of water &

dissolved minerals Storage (surplus sugars,

starch) Conduction water/nutrients

ROOT

Structure of RootsLongitudinal section of roots Root cap

Zone of cell division Zone of cell elongation Zone of maturation

Cross section of root Vascular bundle (Stele)

contains xylem and phloem Cortex Epidermis Root hairs

Absorb water and minerals

Types of Roots– Fibrous, multibranched roots (e.g. lettuce)

– Dominant tap root

– Adventitious roots• root-like structures arising from stems or leaves• e.g. prop roots (corn) and holdfasts

– Tuberous roots • Swollen structure on fibrous root used to store

carbohydrates (e.g. sweet potato)

• Tap roots used to absorb water deep in soil• Some tap roots used to store carbohydrates (e.g. carrots)

Fibrous roots Tap root

Adventitious roots Tuberous roots

Types of Roots

STEMS Above-ground organs.

(usually)

Support leaves and fruits.

Conduct water and sugars throughout plant.

STEM STRUCTURES

Nodes: location of leaves on stem Internodes: stem between leaves Buds: undeveloped leaves or flowers

– Terminal (apical)– axillary (lateral)– Apical dominance is growth inhibition caused by

apical bud

Stem Structure

Function of Stems Support leaves, flowers, fruits. Transport of water (xylem) and

products of photosynthesis (phloem). Storage of carbohydrates

Tubers - swollen underground stems that store carbohydrates (e.g. potato).

Corm - swollen base of stem covered in papery leaves. Bulb - cluster of fleshy leaves attached to short, thick stem with basal roots (e.g. onion).

Bulbils - tiny bulbs arising in leaf axils. Rhizome - horizontal stem below ground

that produces roots and shoots at each node.

Stems Stems used only for asexual reproduction. Stolon (or runner) - horizontal stem that arises

from leaf axel and runs above ground (e.g. spider plant) When tip of solon hits ground a new plant

forms

Spur - stem with short internodes growing from a larger branch of woody plant.

Waterspout - stem that arises from latent buds in branches of woody plants.

Sucker - stem arising from root tissue, often from cut woody plant.

Types of modified stems

Types of Stems

Tendrils - twining stems used to secure climbing plants to vertical surfaces (e.g. peas, grapes).

Prickles - tiny, pointed projections of epidermis tissues of stems (e.g. blackberry).

Thorns - long, pointed projections produced in leaf axils (e.g. Hawthorn).

Cladophylls - stems modified for photosynthesis (e.g. cacti, asparagus).

Types of Stems Types of modified stems

Types of modified stems

Types of modified stems

LEAVES

Most leaves are thin and flat An adaptation that helps them capture sunlight for

photosynthesis.  Although this structure may be typical, it is certainly

not universal.  Leaves are extremely variable. This variability represents adaptations to

environmental conditions.

Blade - Flat expanded area

Petiole - stalk that connects leaf blade to stem, and transports materials

Pair of stipules

Leaf parts

Leaves structure

Leaf epidermis Is transparent – so that sun light can go through. Waxy cuticle protects against drying out Lower epidermis: stomata with guard cells – for gas

exchange (CO2, H2O in; O2 out)

A. CuticleB. Upper epidermisC. Palisade layer D. Spongy LayerE. Lower epidermis

Leaves functions

Leaves

Carry out photosynthesis in order to make glucose.

Composed of epidermal, vascular and ground tissue.

Flower A flower is the reproductive organ of angiosperms. Flowering plants reproduce by pollination.

Flower To Fruit

A fruit is defined as a ripened ovary that contains angiosperm seeds.

The function of a fruit is to hold and protect the seeds.

Fruits

Each kernel of corn on a cob is actually an individual fruit

In peaches, the fruits are soft and fleshy and contain a single, stony seed.

Legumes like beans and peas produce a fruit called a pod that contains many seeds.

The End

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