Download leaf structure transpiration translocation - aiss-biology-11

Leaves
• Tissues of leaves and their function
• Palisade mesophyll – consists of densely
packed cylindrical cells with many
chloroplast. This is the main
photosynthetic tissue and is positioned
near the upper surface where the light
intensity is highest
• Upper epidermis – a continuous layer of
cells covered by a thick waxy cuticle.
Prevents water loss from the upper
surface even when heated by sunlight.
Lower epidermis is in a cooler position and
has a less thick waxy covering
• Note stomata on
epidermis. The stomata
is a pore that allow
carbon dioxide for
photosynthesis to diffuse
in and oxygen out
• Xylem – brings water to replace losses
due to transpiration
• Phloem – transports products of
photosynthesis out of leaf.
• Both xylem and phloem are called the
vascular system of plants. The vein is
centrally located to be close to all cells.
phloem
Transport in phloem
• Phloem is located inside leaves. Used to
transport sugars, amino acids, and other
organic compounds from photosynthesis.
• Structures called sieve tubes do the
transporting.
• This is an active process requiring ATP
• High concentration in sieve tubes of solute
cause water to move in by osmosis
• This creates a high enough pressure for
movement where ever the plant needs
these products.
• The transport of any biochemical (includes
sprayed on chemicals) in phloem is called
translocation.
• Sugar Transport in Plants
Transpiration
• Flow of water from the roots, through the
stems to the leaves of plants
(transpiration)
• Starts with evaporation of water from the
cell walls of spongy mesophyll.
• Water is replaced with water from the
xylem
Xylem and transport of water
• Google Image Result for
http://www.phschool.com/science/biology_
place/labbench/lab9/images/xylem.gif
Structure of xylem
Factors which affect transpiration
• Light – closed guard cells in stomata in darkness
• Temperature high temp increase rate of diffusion
through air spaces in spongy mesophyll
• Humidity – movement by osmosis requires water
potential gradient. Low humidity increases
transpiration
• Wind blows saturated air away from leaf thus
increasing transpiration
Food storage in plants
The excess products of photosynthesis may
be stored in storage area called tubers.
Roots
• Roots absorb mineral ions and water from
the soil
• Anchor the plant and are sometimes used
for food storage
• Plants: Transport and Nutrition - Water
Movement
Mineral uptake by roots
• Plants absorb potassium, nitrate and other
mineral ions
• Concentration is lower than inside roots
• = active transport
• Root hairs provide surface area for ion
uptake