Plants

Tissues part 2StemLeaf

Plant TISSUES

• Dermal– Epidermis (“skin” of plant)– single layer of tightly packed

cells that covers & protects plant

• Ground– bulk of plant tissue – Photosynthetic – Storage

• Vascular– transport system in

shoots & roots – xylem & phloem

Dermal tissue• Epidermis • In stems and leaves has cuticle,

a waxy layer that prevents water loss.

• Some have trichomes (hairs)• Root epidermis has root hairs

Vascular tissue• Transports water and organic materials (sugars)

Xylem – transports water and dissolved ions from the root to the stem and leaves.

• Phloem – carries dissolved sugars from leaves to rest of the plant

Xylem cells

• Xylem cells are dead!• They are hollow cells

and consist only ofcell wall

Phloem• Living cells at functional maturity

– Transport sugars– cell membrane, cytoplasm

• control of diffusion

– lose their nucleus, ribosomes & vacuole• more room for specialized transport of

liquid food (sucrose)

• Cells – sieve tubes

• sieve plates — end walls — have pores to facilitate flow of fluid between cells

– companion cells• nucleated cells connected to the sieve-tube • help sieve tubes loading material

Companion cells

Sieve plates

Ground tissue• Makes up the bulk of plant organs. • Functions: Metabolism, storage and support.

Root Stem Leaf

Plant Organs

• Roots

• Stems

• Leaves

DermalVascularGround

DermalVascularGround

DermalVascularGround

Root Ground tissue• In roots, ground tissue (a.k.a. cortex)

provides support, andoften stores sugars and starch (for example: yams, sweet potato, etc.)

cortex

Root cortex: Casparian strip• The Casparian strip is a water-impermeable

strip of waxy material found in the endodermis (innermost layer of the cortex).

• Helps to control the uptake of minerals into the xylem

Tissues of the Leaf (Epidermis)

• Cuticle– Waxy substance that

covers the leaves & stems

– Waterproof layer that keeps water in plants

Tissues of the Leaf (Epidermis)

• Stomata– Openings in the

epidermis mainly located on the underside of leaves

– Exchange of gases

Tissues of the Leaf (Epidermis)

• Guard Cells– Two cells located on

each side of stomata– Open and closes

stomata

Tissues of the Leaf(Mesophyll Layer)

• Palisade mesophyll– Primary site of photosynthesis

• Spongy mesophyll– Contains air & chloroplasts– Site of photosynthesis and gas exchange

Stems

• Functions– Movement of materials• Water & minerals from roots to leaves• Manufactured food from leaves to roots

– Support leaves & reproductive structures– Food storage

Internal Stem Structure

• Xylem– The tissue that transports water & nutrients up from roots

to stems & leaves.• Phloem– Tissue that transports food down from leaves to roots.

• Cambium– Thin, green, actively growing tissue located between bark

& wood and produces all new stems cells.