Hormonal influence on root growth
For a plant a good set of roots is of great importance. Not surprising, lots of hormones have a stake in organizing this. Now a group of international researchers show that one of those hormones, cytokinin, is regulating the production of another, ethylene.
A plant regulates the growth of its roots with help of multiple hormones, which you can think of as managers. They regulate the different processes of root growth, and influence each other. Lots is already known about this, still researchers don’t know everything yet. Like how the interaction between cytokinin and ethylene influences root growth.
The researchers of the study noticed that plants that produce extra cytokinin have shorter roots and smaller root-growth centres. But that when researchers by these plants the production of ethylene blocked, that these plants do produce longer roots. Suggesting that the amount of ethylene determines the root length, and that cytokinin is influencing the amount of ethylene.
Cytokinin causes the roots to produce more ethylene
Subsequently the researchers found out hoe cytokinin does this. They discovered that cytokinin not only activate the genes of ethylene precursor ACC, but also those needed for the converting of ACC in ethylene. When a root is producing ethylene, then this ethylene is making sure its production stays stable.
That cytokinin indeed influences root growth via ethylene, that, the researchers confirmed when they treated plants that don’t produce any ethylene with cytokinin. Under normal circumstances those ethylene free plants have longer roots. But while by ethylene producing plants the root growth is reduced when treated with cytokinin, that was not the case by those that did not produce any ethylene.
The presence of cytokinin causes the roots to produce more ethylene. Depending on the location in the root, this might result in more cell divisions or less cell elongations. Which in turn influences how long the roots get.
Literature
Yamoune A. et al., (2024) Cytokinins regulate spatially-specific ethylene production to control root growth in Arabidopsis. Plant Commun. https://doi.org/10.1016/j.xplc.2024.101013
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