This document is designed to help students with leaves and photosynthesis topics this topic is a quite tricky topic and there is mostly always a question in the exam paper of them so it is better to learn the key points. And it has exam-style questions too.
The wax cuticle
layer is there to
protect the leaf
without
blocking out
sunlight
The above diagram shows the specialised cells in a green leaf – you should know
how to label a diagram like the one above. These cells are adapted to do certain
jobs:
Cell Adaption Purpose
The outer epidermis is transparent They allow light to reach the palisade
because it lacks chloroplast (and as layer; they do not act as an obstacle
such chlorophyll which is a green to light
pigment)
Upper palisade layer contains most Because this is where most of the light
of the leafs chloroplasts from the sun will be received, it allows
the plant to absorb all of this light
The spongy mesophyll cells are 1) This allows the diffusion of
loosely packed (there’s lots of air gases between the cells and the
space) atmosphere to happen
2) It also creates a large surface
area to volume ratio – this
means that large amounts of
gases can enter and exit the
cells
Leaf adaptations for Photosynthesis:
Leaves are adapted so that photosynthesis is VERY efficient.
, Photosynthesis and Leaves – Revision Pack
Leaf Adaption Purpose
Broad To maximise surface area so they can
get as much light as possible
Thin 1) So that gases (like CO2) can
diffuse through easily
2) So that light can get to ALL cells
Contain a variety of pigments (e.g. This allows the plant to absorb light
chlorophyll a, b, carotene etc.) from a broad range of the light
spectrum
They have loads of vascular bundles This allows support and transport of
(or veins) chemicals like water and glucose
Specialist guard cells These control the opening and closing
(see below) of the stomata, thus regulating the
flow of carbon dioxide, oxygen and
water loss
When the stoma is open, the
guard cells are full of water
and are turgid.
When the stoma is closed, the
guard cells lose water and
become flaccid. They would
normally only close when it is
dark when no carbon dioxide
is needed for photosynthesis.
NOTE – Through having a variety of pigments (these being: chlorophyll a,
chlorophyll b, carotene and xanthophylls), the plants cells can maximise the use
of the suns energy. Each of these pigments absorbs light of different
wavelengths.
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