Level II Horticulture Course
Week 2 – Plant Science
Tuesday, 28th October 2014
Graeme Cross, CAFRE
Tonight’s Course Content:
• Plant Structures
• Plant Processes
• Plant Development
Plant Structures
• Scientists like to classify and name things!
• What are the parts of a plant?
• Leaves, stems/shoots, roots, flowers, seeds,
fruits
• Why are these plant parts significant?
• All have different roles / functions
Plant Structures & Functions
Leaf:photosynthesis &
transpiration
Stem/shoot: support &
water movement
Root: support/anchorage
& water/nutrient
uptake
Flower: pollination
(reproduction)
Seed (fruit/nut): new
generation (reproduction)
LEAVES
The home of photosynthesis: the means by
which energy is captured from sunlight for
plant growth and storage
Carbon dioxide + water = sugar + oxygen
CO2
+
H20 =
C6H12O6 +
O2
Carbon dioxide + water = sugar + oxygen
CO2
+
H20 = C6H12O6 + O2
LEAF COMPLEXITY
A simple leaf
Compound
Leaves
LEAF AREA INDEX (L.A.I.)
A calculation (measurement) of the total
coverage that plant foliage creates for the
interception (capture) of available light.
Of all the energy emitted from the sun, we can only
see what is called the “visible spectrum”. This is
also the range in which plants absorb energy
through photosynthesis.
Different pigments in plants (e.g chlorophyll)
absorb different wavelengths of light.
FACTORS INFLUENCING PHOTOSYNTHESIS
•
•
•
•
•
Carbon dioxide
Light
Temperature
Water (opening & closing of stomata)
Health of the leaves - nutrition
A NOTE ON LEAF HEALTH (NUTRITION)
Mineral deficiencies (shortage of essential
nutrients) can lead to poor colour of the leaf
(pigmentation) and so reduce ‘performance’.
SHOOTS
These structural
supports are formed
from strong, fibrous
tissues arranged in
bundles to carry
weight and resist
damage from wind
and animal feeding.
They also contain the
transport system for
the plant
WHAT IS RESPIRATION?
This process of respiration is
the reverse to
photosynthesis i.e. It is the
conversion of sugars into
energy for life (growth,
reproduction, etc.)
Sugar + oxygen
=> Carbon dioxide + water
C6H12O6
=> CO2
+
+
O2
H20
RESPIRATION : KEY POINTS
• Occurs all the time (and not dependent on
light levels)
• Takes place in every living cell (inc. roots)
• Requires oxygen, so anaerobic conditions are
bad!
•  temperature =  respiration =  growth
rate
• High respiration in stores is not recommended
Why is this?
ROOTS
A network of specialist tissues for the
anchorage of plants in the soil or medium on
which they grow.
Roots also act to uptake water and dissolved
nutrients.
TRANSPIRATION
The movement of
water from soil
through root
tips to the leaf
and hence
through the
whole body of
the plant
Mature tree may
lose 70-100 l/hr
in daylight
FLOWER
A specialist
structure which
allows the
transfer of
pollination
between plants
and creates
seed for the
next
generation.
POLLINATION
The transfer of pollination between male and
female reproductive parts of flower(s) which
leads to fertilisation.
How is pollen transferred between flowers?
FERTILISATION
The fusion of the
two gametes (the
pollen from male
and the ovum
from female)
within the flower,
to form a new
seed
SEEDS / FRUITS / NUTS
The structures which allow the germination of a
new generation of plants
(= embryo plants + food reserve)
PLANT HORMONES
Specific chemical compounds which are
produced naturally within the plant’s own
tissues to regulate the growth of new organs
and parts.
Some Named Plant Hormones
Auxins
Cytokinins
Gibberrellins
Ethylene (Ethene)
Abscisic acid
AUXINS
Indole-acetic acid (IAA),
Napthyl acetic acid (NAA)
Used in Rooting Powder
Auxins encourage roots and discourage shoots
CYTOKININS
Work in
combination
with auxins to
control the
extent and
direction of
shoot (stem)
growth
(“Apical
Dominance”)
GIBERRELINS
Involved in a range of growth responses such as
flower and fruit formation, seed development
EHTHYLENE (ETHENE)
A simple gas (C2H4) which controls the
maturation of fruits and the aging process in
fruits and flowers
ABSCISIC ACID (ABA)
A single carbon compound which triggers a
range of responses such as dormancy,
maturation, leaf fall, cell division.
1. Seed (sown)
2. Germination /
seedling
3. Young plant /
vegetative
phase
4. Established
flowering
plant
5. Mature /
Harvest plant
CROP GROWTH STAGES IN CEREALS
1
2
3
4
5
6
7
8
9
Seedling development (leaves).
Tillering.
Stem elongation.
Booting (developing head inside sheath).
Heading (ear emerging).
Flowering (anthers visible).
Milk (grains soft and milky).
Dough (grains firm and doughy)
Ripening (grains hard).
Zadok’s Cereal Growth Stages
Potato Growth Stages
IDENTIFY THE GROWTH STAGES
Seedling /
Young Plant
Established/
Flowering
plant
Mature /
harvest /
senescent
plant