Topic 5 - Water Flashcards
What do ressurection plants do?
They are able to recover from drought. Tissues can dry out/dessicate, but they recover once wetted. Example: mosses and some ferns.
What is an epiphyte?
A plant that grows on another plant for support (not parasitic)
What is a xerophyte?
A plant adapted physiologically to dry conditions, so that it remains metabolically active rather than going dormant..
Give two features of xerophytes.
Leaves orientated vertically.
Small leaves to minimise water loss.
Stomata protected to minimise water loss.
Give three example of physiological drough (ie. when water is present but can’t be used)
Saline
Clay
Water-logged
What is the equation for water potential?
ψ = P − π – m
Water potential =
Hydrostatic pressure
less Osmotic pressure
less Matric pressure
What is Turgor?
Turgor is a type of pressure. It is the act of cell membrane pressing against the cell wall, ie. it stops them expanding infinitely.
What is the difference between a secretion and an excretion?
Both are substances that pass from a cell into its external environment, but:
- secretion is produced by the cell to serve a useful purpose once outside
- excretion is a waste product ejected from the cell.
What is cavitation?
It is when an embolism forms in a plant stem - an air bubble caused by lack of water.
What does ABA stand for and what does it do?
ABA = abscisic acid. It is a plant growth regulator (hormone).
What is a hormone?
It is a chemical that conveys messages from one cell to another, often in different parts of an organism.
They are produced/released in response to a trigger.
What is the difference between positive and negative hormone signals? Give an example of each.
Positive signals are triggered by the presence of a hormone. Example - ABA (abscisic acid).
Negative signals are triggered by the absence of a hormone. Example - cytokinin.
What is basal respiration?
Minimal amount of energy needed to keep an organism alive, by maintaining essential processes and repairing any damaged cells.
What is the compensation point?
It is when energy coming in from sun is equal to that required for basal respiration.
