Transcript Plant Leaves Stems Tissues

Plants
Tissues part 2
Stem
Leaf
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 of
cell wall
Phloem
Companion cells
• Living cells at functional maturity
– Transport sugars
– cell membrane, cytoplasm
• control of diffusion
– lose their nucleus, ribosomes & vacuole
Sieve plates
• 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
Ground tissue
• Makes up the bulk of plant organs.
• Functions: Metabolism, storage and support.
Root
Stem
Leaf
Plant Organs
• Roots
Dermal
Vascular
Ground
• Stems
Dermal
Vascular
Ground
• Leaves
Dermal
Vascular
Ground
Root Ground tissue
• In roots, ground tissue (a.k.a. cortex)
provides support, and
often 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.