Plant structure and leaf structure adaptations that help!
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of biology notes on PHOTOSYNTHESIS
(3) Plant structure and photosynthesis - leaf
structure adaptations that help!
area is provided by having broad leaves, beneath the apparently flat
surface of a leaf is quite a porous layer of air spaces between the outer
layers of cells - particularly on the underside of leaves - quite often the
lower surface of a leaves feel rougher and 'roughness' means a more
disrupted surface of a larger surface area.
side of a leaf is smoother and greener - richer in chloroplasts to
capture the sunlight
side of a leaf is rougher - more 'porous' for efficient gas exchange
and the veins more prominent
The palisade cells contain the chloroplasts
containing the green pigment chlorophyll to absorb light.
Plants look so green because they contain a relatively high
concentration of chlorophyll.
The upper epidermis is transparent to visible light
so it can get through to the palisade layer.
The stomata (tiny holes in the
leaf surface) facilitate gas
exchange (carbon dioxide, oxygen and water vapour)
Xylem and phloem networks of
cells, transport substances
around the plant e.g. sugars like sucrose and glucose from photosynthesis, and
through the roots minerals (e.g. magnesium) and water for
The tissues of leaves are adapted for gas
The lower epidermis contains lots of stomata
(plural of stoma, pores) which let
carbon dioxide directly diffuse into the leaf for photosynthesis and
oxygen to diffuse out of the leaves - the gas exchange system.
Leaves also have a network of veins which convey water to
the leaf cells and in return transport the glucose made in photosynthesis.
The spongy mesophyll tissue also contains
air spaces that help increase the rate of diffusion of gases in and out of
In the outer epidermis
layer guard cells are adapted to open
and close the pores of the stomata (stomatal pores) which allows gas exchange and water evaporation
eg for photosynthesis carbon dioxide in and oxygen out.
helps regulate transpiration and respiration and all
connected with photosynthesis.
transport in plants more on plant
structure, function including gas exchange and leaf adaptations
The epidermal tissues are covered with a
waxy cuticle which helps reduce the loss of water by evaporation.
All of the above structures
mentioned must be 'connected' for the 'system to function' in a
It should be mentioned
that a large percentage of the Earth's photosynthesis occurs
in oceans in phytoplankton.
A summary of some particular
adaptations of leaves that aid photosynthesis
transparent waxy cuticle
through for photosynthesis
cells arranged in end-on, near the upper surface, maximises
chloroplasts at the top of the cells
maximum amount of light to be absorbed for photosynthesis
shaped cells creating air spaces
surface are for diffusion: CO2 in, O2 out -
increases efficiency of gas exchange
Leaf structure, diffusion
Carbon dioxide diffuses into the leaves
through the stomata and is depleted through photosynthesis.
Therefore as photosynthesis proceeds, the
internal carbon dioxide concentration in the leaf is much lower than in the
surrounding air, so carbon dioxide will diffuse into the leaf down this
The rate of diffusion of the carbon
dioxide (and any other gas) is increased by:
Increasing the surface area of the
leaf - always the broadest part of any plant.
The smaller the distance the
molecules have to travel as they diffuse - thin leaves with an even
thinner mesophyll layer.
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