CYTOKININS AND PLANT HORMONES
In this article we dive right into the intricate world of plant hormones. Not everything was going to be to put a little water to a plant, some compost and to work (or yes?). Within plant biochemistry, we can “play” with the hormones that the plant produces directly at various stages of its life. There are a few (and they are sold), although today we will talk about cytokinins and their importance.
STARTING FROM SCRATCH. WHAT ARE CYTOKININS?
You don’t have to overheat your head, we are going to include them in the world of plant hormones. We are not talking about “cycling” a plant or introducing something unnatural to it, since these hormones are produced automatically in the plant, particularly in specific areas where you want them to produce a particular physiological effect. These cytokinins cannot be found artificially. Its extraction is simple. You simply have to look for this hormone in areas where cell division is taking place (seeds, fruits, roots, etc.).
The history of cytokinins is relatively recent, as the main investigations began in 1950, with Miller and Skoog as a precursor .
They found that certain plant extracts were powerful activators of cell division. When wondering about this fact, what they did was pull biochemistry and laboratory and isolate this component, cytokinin .
Depending on which plants we can find different cytokinins. The first of them, zeatin , was extracted from the cultivation of corn ( Zea mays), one of the most active plant hormones of this nature, although currently different hormones have been obtained from different plants.
EFFECTS OF CYTOKININS IN PLANTS
- Promote cell differentiation.
- Stimulate cell division (as do auxins).
- Revert apical dominance (activate lateral bud growth).
- Activation of adventitious buds.
- Intervene in the development and size of the fruit.
- Induction of parthenocarpy (formation of fruits without previous fertilization) in fruits.
- Delaying the senescence of the leaves (opposite effect to ethylene ).
For example, if you have been given by growing potatoes , cytokinin induces the formation of new organs, such as tubers.
Its effects are closely related to those of auxins. In fact, depending on the concentration of one or another hormone in the cells, it will produce one effect or another. Very curious.
- Concentration of cytokinins and auxins alike: callus (large number of cells without differentiation.
- Higher concentration of cytokinins versus auxins: stem formation is promoted .
- Higher concentration of auxins compared to cytokinins: promotes the elongation of roots.
TRANSPORT OF CYTOKININS IN THE PLANT
In the specific case of this plant hormone, its transport takes place from the root to the aerial part (acropetic movement). Therefore, the movement it makes through the conductive vessels is from the xylem (upward flow) to the phloem (downward flow). From there it is distributed to all parts of the plant, including the leaves.
Once the leaf is fully developed and has reached its maximum size, these cytokinins continue their journey to other parts of the plant where they are needed, via phloem (descending).
FACTORS INFLUENCING CYTOKININ PRODUCTION
If we have already seen what these plant hormones produce on the plant, we also have to know the climatic or biotic effects caused by their lack of synthesis in the plant. Some of them are the following:
Interestingly, the lower the ambient temperature, the greater the movement of cytokinins from the root to the top. We remember that this was the movement of the xylematic conducting vessel (acropet).
At the end of dormancy (when the plants stop their growth and winter), the production and synthesis of cytokinins is accelerated, stimulating the emergence of shoots, cell division, etc. That is to say, everything that we have mentioned before that favors plant growth .
Potassium nitrate, a fertilizer we have already talked about , when we apply it via irrigation (fertigation or blanket) stimulates the production of cytokinins, which later travel to the leaves and fruits.
Phosphoric fertilization is very interesting, since its lack or lack of application reduces the synthesis of this plant hormone by the plant.
Situations of environmental or biotic stress
When the plant enters a stress situation, either due to adverse climatic effects (strong wind, frost, excess heat, drought, pH, salinity, etc.) or biotic (attack by pathogens), the production of cytokinins stops, and with it, part of its new production of organs and stems.
That is why it is very interesting to avoid, as far as we can, all these situations that cause stress in the plant and reduce production significantly.
Of course, we do not forget other plant hormones such as auxins , gibberellin , ethylene , etc., to which we will dedicate future articles. 🙂