Plant & zo
The science of plants and more
Light makes plants move
Light, the most important energy source for a plant. It is not always easily accessible. Anchored in the ground, plants can not step out of the shadow and into the light. But that is not to say that they don’t try to reach for the light. They do. By moving their leaves upwards. In this way plants tilt their leaves above those of their neighbours, receiving more light themselves.
Light is so important, that plants constantly measure how much there is. For this they have specific photoreceptors. Shade, caused by other plants, changes the amount of red vs far-red light photoreceptors receive. The shadow causing leaves absorb the red light for their own photosynthesis. But not the far-red light. Letting the plant know it is in the shade.
Researchers for Utrecht studied the effect of receiving more far-red than red light. After exposing a leave-tip to far-red light they noticed that the plant tilts the leave higher. Also, after exposing the leave-tip to far-red light, the production of the plant hormone auxin increased. Checking if auxin is needed for the response, they applied auxin on the leave-tip. The plant moved the leave higher. Indicating that the local production of auxin is required for this response.
Auxin moves, with help of the auxin transporter PIN3, specifically from the leave-tip to the abaxial side, the underside, of the leafstalk. In the leafstalk, the researchers noticed, auxin activates the expression of gibberellin synthesis genes. It is the combination of auxin and gibberellin that causes cells at the abaxial side of the leafstalk to stretch. Resulting in shorter cells at the top and longer cells at the underside, curling the leafstalk upwards. Moving the leave above the shadow.
Küpers, J.J., Snoek, B.L., Oskam, L., Pantazopoulou C.K., Matton, S.E.A., Reinen, E., Liao, C.-Y., Eggermont, E.D.C., Weekamp, H., Kohlen, W., Weijers, D., Pierik, R. (2022) Local light signalling at the leaf tip drives remote differential petiole growth through auxin-gibberellin dynamics. bioRxiv 2022.02.25.481815; doi: https://doi.org/10.1101/2022.02.25.481815