level ii horticulture course week 2 – plant science tuesday, 28 th october 2014 graeme cross,...
TRANSCRIPT
Level II Horticulture CourseWeek 2 – Plant Science
Tuesday, 28th October 2014Graeme 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)
LEAVESThe home of photosynthesis: the means by
which energy is captured from sunlight for plant growth and storage
Carbon dioxide + water = sugar + oxygenCO2 + H20 = C6H12O6 +
O2
Carbon dioxide + water = sugar + oxygenCO2 + 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’.
SHOOTSThese 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 + O2
=> CO2 + 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?
ROOTSA 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.
TRANSPIRATIONThe 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
FLOWERA specialist
structure which allows the transfer of pollination
between plants and creates seed for the
next generation.
POLLINATIONThe transfer of pollination between male and
female reproductive parts of flower(s) which leads to fertilisation.
How is pollen transferred between flowers?
FERTILISATIONThe fusion of the two gametes (the pollen from male
and the ovum from female)
within the flower, to form a new
seed
SEEDS / FRUITS / NUTSThe structures which allow the germination of a
new generation of plants (= embryo plants + food reserve)
PLANT HORMONESSpecific 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
AuxinsCytokinins
GibberrellinsEthylene (Ethene)
Abscisic acid
AUXINSIndole-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”)
GIBERRELINSInvolved 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 /
seedling3. Young plant /
vegetative phase
4. Established flowering plant
5. Mature / Harvest plant
CROP GROWTH STAGES IN CEREALS
1 Seedling development (leaves).2 Tillering. 3 Stem elongation.4 Booting (developing head inside sheath).5 Heading (ear emerging).6 Flowering (anthers visible).7 Milk (grains soft and milky).8 Dough (grains firm and doughy)9 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