B3.2.6 Flashcards
What is a tropism
Plants detect stimuli in their environment and can respond to it by growing in a particular direction. This is called a tropism.
What happens if a plant grows towards a stimulus
It’s a positive tropism whereas if it grows away from it, it’s a negative tropism.
What is phototropism
As the plant can grow towards the light the plant can photosynthesise more. This means it can grow more and faster. Increases the chance of the plant’s survival.
What is gravitropism
Growing in the same direction as gravity. It’s important for the root to grow downwards as growing deeper into the soil helps to provide anchorage.
Where are AUXINS made and how do they affect plants responses to stimulus
Auxin is made in cells near the tops of plant shoots or roots. The response to a stimulus occurs because of uneven distribution of AUXIN. Causes unequal growth rate as AUXINS elongate cells.
What do AUXINS cause
AUXINS cause growth in stems but inhibit it in root cells.
How do AUXINS cause phototropism
AUXINS move to the dark side when light hits it. Causes AUXINS to move to that side leading to increased concentration. Elongating the cells on that side of the shoot, so the shoot bends towards the light.
When light falls evenly what happens
The AUXINS are distributed throughout the tip so it grows straight.
How do AUXINS cause gravitropism
AUXINS respond to gravity as well they go to the same side as gravity, however they inhibit growth in roots so it causes the roots to bend down.
