Plant nutrition
the study of the
chemical elements and compounds
necessary for plant growth and
reproduction, plant metabolism and
their external supply.
Introduction to leaves
Main functions of leaves:
•photosynthesis
•storage
• gas exchange
External structure of a leaf
From the book
Internal structure of the leaf
Upper epidermis
the Cells are tightly packed together.
it is covered by the cuticle which is secreted by the cells.
the cuticle is thin transparent and water-proof.
the cuticle stops water vapours from exiting the leaf.
photomicrograph of upper epidermis
spongy mesophyll
the cells in this layer contain less amounts of chloroplast.
the cells have air spaces between them.
the air spaces allow oxygen and carbon dioxide to diffuse into the
cells in the leaf.
photomicrograph of spongy mesophyll layer
vascular bundle
this consists of xylem and phloem vessels.
they carry different substances to and from the leaves.
they also form the veins in the leaf
lower epidermis
the cells are tightly packed together.
it is covered by the cuticle.
it has tiny openings called stomata.
the stomata allows carbon-dioxide particles to enter and oxygen particles
to leave the leaf
plisade mesophyll
the cells in this later contain
the most chloroplast.
They are not as tightly packed
as the upper epidermis.
chlorophyll
it captures energy from the
sunlight.
this energy is used in the process
of photosynthesis.
photosynthesis
It is the process by which a plant synthesises
carbon dioxide and raw material using
energy from the sunlight.
carbon dioxide + water
6Co₂ + 6H₂O
sunlight
and
chlorophyl
Glucose + oxygen
C₆H₁₂O₆ + 6O₂
uses of glucose in plants
making amino acids, to make proteins
Collecting nitrate ions
to make proteins
Chains of Amino-Acids
making cellulose, to build cell walls.
Photomicrograph
of a cell Wall
Fibres criss-crossed
in a Cell wall
making nectar to attract pollinators
making sucrose, for transport
Photomicrograph
of phloem tubes
Birds feeding on
nectar
releasing useful energy
storing,to use later
Energy is used for
various activities ,such
as respiration or for the
transportation of mineral ions
Photomicrograph
of starch
Factors affecting Photosynthesis
•the supply of the raw materials
•the quantity of sunlight
•the temperature
Controls
• A standard sample that is used as a comparison,to find the effect of a
changing variable.
Experiment to investigate the
necessity for light for photosynthesis
Limiting Factors
•Light Intensity
•Carbon dioxide
•Temperature
•Stomata
B
B
A
C
High Carbon dioxide
concentration
Low Carbon dioxide
concentration
A
•A-B:Light is a Limiting Factor
•B-C:Light is no longer a Limiting Factor