In this chapter of AS/A-level Biology, we will learn about auxin and phototropism.
Auxins
In AS/A-level Biology, auxins (such as IAA) are produced at the apex. Auxin stimulates shoot growth by causing cell elongation – process is called acid growth hypothesis.
Phototropism
In a phototropic response, a shoot bends towards a light source. This happens between the shaded side elongates faster than the illuminated side, which pushes the end of the shoot towards the light.
The role of hormones in leaf loss in deciduous plants
In AS/A-level Biology, cytokinins stop the leaves of deciduous trees senescing (ageing) by making sure the leaf acts as a sink for phloem transport – this means the leaf is guaranteed a good supply of nutrients. However, if cytokinin production drops, that supply of nutrients dwindles and senescence begins.
This is the end of this topic!