2.81 Phototropism

• Phototrpoism means photo is light and tropism is growth in response to this light, and the positive is a growth towards the light.
• So we considered this in stem so, let take the tip of the stem and draw that with a simple structure like this and uniform light coming from all directions it would grow forwards and upwards.
• However, if we present the same stem tip with light from the side so, the lateral light source what happens is that the plant bends in the growth towards that light band.
• So, this is an example of positive phototropism growth of the stem towards the light.
• The understand of this the light on this side causes the movement to the opposite side of a compound known as "Auxin" which is a plant hormones which causes more gorwth and on this side and this side causes more bending.