Lecture 2 Flashcards
What is agronomy
the application of science and technology from the fields of biology, chemistry, economics, ecology, soil science, water science, pest management and genetics to the improvement and management of the major food crops of the world.
Major Agronomic cereal crops
wheat, barley, oats, rye; rice, corn, millet
Major Agronomic break crops
pulses (field beans/peas), oilseed rape
Major Agronomic horticultural crops
potatoes, field vegetables
Major Agronomic protected crops
salads, tomatoes, peppers, berries
Major Agronomic forage crops
maize, legumes (clover, beans), root crops (turnip, swede, beets)
Name the external (environmental) facts that affect plant growth and development
• Light (quantity and quality)
• CO2
• O2
• Temperature
• Water
• Minerals (macro and micro)
• pH
Name the internal factors that affect plant growth and development
• Photosynthesis
• Photoperiod
• Transpiration
• Respiration
Who is responsible for the law of the minimum
Justice von Liebig
Name the limiting factors for plant growth and development
• Light (quantity and quality)
• CO2
• O2
• Temperature
• Water
• Minerals (macro and micro)
What is absence of light known as
Etiolation
Low intensity light (mostly red wavelengths)
Causes long spindly growth
High intensity light (mostly UV wavelengths)
Causes plant dwarfing
What is photosynthetically active radiation in nm
400-700nm
What does PAR stand for
photosynthetically active radiation
What does photoperiod regulate
Time of flowering
Cessation of vegetative growth
Seed germination
Elongation of seedlings
Fruiting in some species
How is photoperiodism regulated
By phytochromes (photoreceptor pigments) that detect red and far red light
When does chrysanthemums form flower buds
When day length is <14.5 hours
When does further development into open flower occur in chrysanthemums
When day length is <13 hours
All plants that respond to daylength contain what pigment
Phytochrome C
Loss of Phytochrome C resulted in how many day delay in wheat flowering under long days
108 days
Functions of stomata
Photosynthesis
CO2 uptake
Evaporative cooling
Resistance to phytotoxic gases
Contribution of CO2-induced reduction in stomatal transpiration to global run-off since when
1960
Increase CO2 means what for terrestrial
Increased runoff ,erosion and nutrient leaching
Increased CO2 means what for aquatic area
Increased eutrophication , anoxia and toxicity
Why can concentration of CO2 temporarily fall outdoors
if planting is too dense, so photosynthesis stops
CO2 falls dramatically under cover especially when plants are actively growing how can this be rectified
By ventilating, or in cold weather, leave glasshouse closed and pump in up to 3 times the normal atmospheric concentration of CO2
What is oxygen required for
aerobic respiration
cell repair
reproduction
growth
What effect does decreasing O2 have
decreases respiration
<15% [O2] means what for reproduction
It is reduced
<2.5% [O2] means what for reproduction
It fails
0% [O2] causes what to take place
Anaerobic respiration
Anaerobic conditions in flooded soil can lead to what in plant roots
Ethanol toxicity (alcohol poisoning)
What is temperature important for in plants
cell structure and function and in regulating rate of transport within the plant
Plant enzymes operative best at what temperature
at ~25 degrees Celsius
Too low of a temperature has what affect
membranes not fluid, affecting transporters
Too high of a temperature has what affect
Membranes disintegrate and plant dies
Activity for the photosynthesis cycle (Calvin Cycle) increase between what temperature
0 and 36 degrees Celcius
Why is temperature control in glasshouses critical
To avoid thermal damage
Name the most important compound in the biological world
Water
Water has the greatest single influence on what in climate
Heat sink and source
Precipitation
Rising sea levels
What is the role of water in plants
• Essential component in photosynthesis
• Responsible for turgor pressure in cells:controls growth (internal skeleton)
• Solvent for minerals and CHO movement
• Controls stomatal opening and closing
• Cools leaves via latent heat of vaporisation
Under drought conditions do plants open or close their stomata
Close it
Disadvantages of drought conditions
• No CO2 intake so photosynthesis stops
• No minerals brought in
via roots up through plant so so biochemical processes
cannot proceed
• Plant cannot regulate temperature so thermal damage occurs
What causes viscosity of water to vary
Temperature
When temperature INCREASES what happens to viscosity
It decreases
Viscosity of H20 is how many times more great at 0 degrees as it is at 25 degrees
Twice as great
Why does Cold water taken up by the plant in spring move more slowly in the vascular system than it does in summer / early autumn
Due to higher viscosity
The problem is when air is warm and windy
What causes leaf scorch
when the soil is cold and the evaporating power of the atmosphere is high (because it contains warm dry air)
When may leaf scorch occur
Early spring
Name the central atom of Chlorphyll
Magnesium
Name the MACRO nutrients
N, P, K, S, Ca, Mg
(NO PAUL KILLED SEAN CIAN MICHAEL)
Name the MICRO nutrients
Fe, Mn, B, Cu, Zn, Mo, Cl, Ni
(FUNNY MAN BUYS COKE ZEBRAS MILK CAKE NAPPIES )
