Temperature and Chilling Flashcards
Describe circadian rhythm.
Phases of growth and activity appearing in regular/ 24hr cycles allowing plants to anticipate environmental cycles and coordinate activity. These occur even under constant conditions.
Name 5 plant functions controlled through circadian rhythm and endogenous timing mechanisms.
Gene regulation, Enzyme activity, Leaf movements, Flower opening, Stomatal opening.
Which two processes interact to control major biological processes?
Circadian rhythm and photoperiodism.
Name 7 plant growth processes influenced by temperature.
Photosynthesis, Respiration, Transpiration, Breaking of seed dormancy, Seed germination, Protein synthesis, Translocation.
What (usually) happens to enzyme activity and chemical reactions when the temperature rises?
They increase.
What happens to the translocation of photosynthate at higher temps.?
It is faster, so plants mature earlier.
State 2 facts about optimum flowering temperature.
Progress towards flowering increases linearly with temperature up to an optimum, above which flowering can be delayed.
The optimum flowering temperature is not always the same as the optimum leaf size or stem length temperature.
What happens when a plant is too hot?
Enzymes denature and metabolism is damaged,
Excess transpiration causes water deficit,
Stomata close to preserve water at the expense of evaporative cooling.
What happens to plants in extreme cold?
Water is less mobile and can not be absorbed as easily,
Water freezing and expanding inside a plant causes cell walls to rupture.
When would a plant need chilling?
Some biennial crops require prolonged cool periods to initiate flowering,
Low temperatures accelerate flowering in some plants.
What is vernalisation?
The acquisition or acceleration of the ability to flower following a chilling treatment.
What is bolting?
Premature flowering is called bolting.
This can cause substantial yield loss.
This is particularly true for crops that require little cold exposure, like heat-tolerant Chinese cabbage, Endive.
What are chill units?
A chilling unit in agriculture is a metric of a plant’s exposure to chilling temperatures. One chilling unit, in the simplest models, is equal to one hour’s exposure to the chilling temperature; these units are summed up for a whole season.
