Light conveyed by the signal transmitting molecule sucrose controls
growth of plant roots

Date:
May 30, 2023
Source:
University of Freiburg
Summary:
Researchers shows how information about the quantity of absorbed
light passes from the leaves to the roots. Photosynthetic sucrose
not only supplies roots with carbohydrates but also acts as a
signal transmitter for light-dependent root architecture.


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FULL STORY ========================================================================== Researchers shows how information about the quantity of absorbed light
passes from the leaves to the roots. Photosynthetic sucrose not only
supplies roots with carbohydrates but also acts as a signal transmitter
for light-dependent root architecture.

Plant growth is driven by light and supplied with energy through
photosynthesis by green leaves. It is the same for roots that grow in
the dark -- they receive the products of photosynthesis, in particular
sucrose, i.e. sugar, via the central transportation pathways of
phloem. Dr. Stefan Kircher and Prof. Dr.

Peter Schopfer from the University of Freiburg's Faculty of Biology have
now shown in experiments using the model plant Arabidopsis thaliana (thale cress) that the sucrose not only guarantees the supply of carbohydrates
to the roots, it also acts as a signal transmitter for the formation of light-dependent root architecture. It does this in two ways: firstly,
sucrose directly guides elongation of the primary root. Secondly, the
sucrose that is transported to the tip of the root then regulates the production of the plant hormone auxin.

This hormone drives the rate of formation of new lateral roots, which
along with elongation of the primary root is synchronised by the joint
signal transmitter.

"This enables the root growth to adapt to the current photosynthesis performance of the leaves as light and other environmental conditions
change, for example on the change from day to night," says Kircher.

Experimental evidence To demonstrate that the sucrose produced through photosynthesis is the decisive signal transmitter, Kircher and Schopfer
placed the plants in a room with light but with no carbon dioxide (CO2)
in the air, thus making photosynthesis impossible. The outcome was that
no more lateral roots were formed. This result was confirmed by another experiment in which the two biologists treated either the leaves or
the roots in the dark with a solution of sucrose. In both approaches,
lateral roots developed the same as in control plants which were exposed
to light. "These results show that the production of sucrose in leaves
is necessary for the formation of lateral roots. And it confirms the
hypothesis that sucrose acts as a signal transmitter for light stimuli,"
says Kircher.

Activation of auxin biosynthesis by sucrose signal In earlier studies, researchers had already shown that the auxin produced in the roots
from the amino acid tryptophan drives the rate of development of new
lateral roots. Kircher and Schopfer have now shown how sucrose triggers
this process. To do this, they placed the plants in a dark room for two
days and carried out various experiments to discover their influence on
the formation of lateral roots. Administering tryptophan to the roots
at the same time as treating the leaves with sucrose had the greatest
effect. By contrast, tryptophan had little effect if it was applied to
the leaves or without sucrose at the roots. "These observations confirm
that the sucrose produced through photosynthesis serves as a trigger
for the synthesis of auxin," says Kircher.

* RELATED_TOPICS
o Plants_&_Animals
# Endangered_Plants # Botany # Food_and_Agriculture
# Nature
o Earth_&_Climate
# Global_Warming # Sustainability # Environmental_Issues
# Air_Quality
* RELATED_TERMS
o Root_vegetable o Ginger o Nicotine o Pupil o Leaf o Herbal_tea
o Chlorophyll o Ultraviolet

========================================================================== Story Source: Materials provided by University_of_Freiburg. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Stefan Kircher, Peter Schopfer. Photosynthetic sucrose drives
the lateral
root clock in Arabidopsis seedlings. Current Biology, 2023; DOI:
10.1016/ j.cub.2023.04.061 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/05/230530174307.htm

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