In modern agriculture, more and more attention is paid not only to the size of the harvested crop, but to its quality. For this purpose, in addition to pesticides, a number of preparations qualified as plant growth biostimulators and bioregulators, bacterial vaccines or algae extracts are used.
Plant growth bioregulators and biostimulators – what is the difference?
The purpose of biostimulators is to control and accelerate life processes, increase the resistance of plants to stress conditions and stimulate root and leaf development, etc. Due to the way they work, they are safe for humans, animals and the environment. According to the Polish Plant Protection Act of 18 December 2003 (§ 14, art. 2), “agents that affect plant life processes in a manner other than as a nutrient, including growth regulators” are classified as plant protection products, in the group: Plant development regulators.
Plant growth regulators are preparations consisting of phytohormones (auxins, gibberellins, cytokinins, abscisic acid, ethylene) and other specific substances of plant origin such as: phenols, polyamines, salicylic acid, which by participating in physiological and biochemical processes change the natural behavior and development of plants. Plant resistance stimulators, otherwise known as biostimulators or phytostimulators, are most often synthetic preparations. They do not take part directly in the regulation of physiological processes, but by affecting the metabolism, they support and stimulate life processes. The action of phytohormones, bioregulators and other groups of active substances, ultimately affects the stimulation of plant growth and their productivity, so the term biostimulators is often used for this entire group, especially in the colloquial sense.
Who discovered plant growth biostimulants and when?
The history of plant growth regulators dates back to prehistoric times, when it was common practice in the Middle East to sprinkle figs with olive oil to stimulate growth. It is now known that with time and heat, the oil then broke down, releasing ethylene, resulting in better fig growth and development.
In 1893, in the Azores Islands, the use of smoke to initiate the growth of pineapple flowers was discovered quite by accident. A carpenter while working in a greenhouse accidentally set fire to a pile of wood chips. As a result of the smoke in the greenhouse after a small fire, to the surprise of the grower, the pineapple flowers growing in the greenhouse, instead of being destroyed, were stimulated to grow.
Thus, until 1920, it was believed that the flowering of the pineapple could be stimulated by smoke from the fire, for example, during the occurrence of low air temperature, inhibiting the growth of this plant. It was also claimed that such an effect was due to the presence of unsaturated gases in the smoke, such as ethylene. Ethylene was observed to have an effect on plant growth, but no one at the time thought that the plants themselves produced this gas.
In the years that followed, it turned out to be a natural hormone that regulates many processes in the plant, occurring as a gas. Today, ethylene is still the simplest plant hormone known to date, used as a growth regulator.
What is the role of plant growth biostimulators and bioregulators?
One of the main tasks of development regulators and biostimulators is to protect plants from stress and to facilitate their recovery and vigor after the impact of adverse stress factors, such as: drought, frost and cold, stress after the use of herbicides, environmental pollution with toxic substances or heavy metals. It works by stimulating leaf, stem and root development. Biostimulator applied at a time when the plants are still healthy, should change the metabolism in such a way that it becomes stronger and more resistant to attack by pathogens or drought, for example.
The protective effect of plant extracts is that after their application, plants are able to resist pathogens or pests by structurally strengthening the plant or by increasing resistance to pathogen mycelium penetration, or by causing more luxuriant growth. Biostimulants are typically used for preventative or intervention treatments.