Plant Hormones & Growth Flashcards
All 7 cards in this deck
Where in a plant shoot is auxin produced?
In the tip of the shoot. It then moves down the shoot to the region where cells elongate.
What are the steps that make a shoot bend towards light?
e.g. a shoot lit from the left only
- Auxin from the shoot tip moves to the shaded side — here, the right side.
- Auxin makes those cells elongate more — the right-side cells get longer.
- The shoot bends towards the light — it bends to the left (positive phototropism).
What are the steps that make a root grow downwards?
e.g. a seedling laid on its side
- Auxin collects on the lower side of the root.
- In roots auxin inhibits cell elongation, so the lower cells stay short and the upper cells elongate.
- The root bends downwards, in the direction of gravity (positive gravitropism).
A shoot tip is cut off and the shoot stops growing; when the tip is placed back on, the shoot grows again. What conclusion can be made?
Auxin (the substance that causes shoot growth) is produced in the tip of the shoot, and the tip controls growth.
True or false? On a graph of auxin concentration against growth, the more auxin there is, the more a plant grows.
False. Growth increases up to an optimum concentration; higher concentrations slow or inhibit growth, and very high concentrations (as in weedkillers) kill the plant.
In an investigation where several shoots are each lit from one side, name two variables that must be controlled.
Same light intensity (lamp at the same distance) for each shoot, and same temperature.
Also accept same volume of water, same species/age of shoot.True or false? Repeating an investigation into shoot growth using more shoots makes the results more reliable.
True. A mean can be calculated and anomalous results identified.