There are several vitamins that act as plant biostimulants, but the most popular ones are B1, B2, B3 and B6 because of their positive effect on the metabolism of the plant. Many microorganisms produce B-vitamins as natural byproducts, but yeast extracts contain the highest concentrations. B-vitamins work at the cellular level, and they are commonly found as additives in cloning gels and cloning solutions, rockwool conditioning solution, and most commercial plant biostimulant products.
Chemical reactions in plant cells are dependant on enzymes, large organic molecules that act as catalysts. Enzymes allow chemical reactions to take place many times faster and more efficiently than under normal conditions. Since the enzymes are not consumed in the chemical reaction itself, the same enzymes can be used over and over in the cell, sometimes performing thousands of chemical reactions per second!
Many enzymes, however, are inactive until turned on by a co-enzyme. B-vitamin derivatives form many of these important co-enzymes. For example, niacin is a component of the co-enzyme NAD, an extremely important cofactor in energy metabolism. Another important cofactor is FAD, derived from the B-vitamin riboflavin. Much of the energy from photosynthesis is ultimately transferred to NAD and FAD to activate and energize countless chemical reactions. Plants cannot take up large enzymes through the roots, but small co-enzymes such as B-vitamins are easily absorbed, and it only takes microscopic amounts to activate thousands of enzymes.
Under normal conditions, plants produce all of the vitamins that they need, but under stress conditions, plant cells at the growing tips tend to shut down to conserve energy. Therefore, under drought stress, heat stress and salt stress, growth rates are greatly impaired. Adding a few drops of B-vitamins directly to the nutrient solution helps the plant recover from stress much faster, stimulating the plant to keep growing instead of going semi-dormant.
One of the best applications for B-vitamins is to help plants recover from transplant shock. When a plant is transplanted, the microscopic root hairs are often damaged, making it difficult for the plant to take up enough water and minerals. Adding B-vitamins to the irrigation water gives the plants a needed boost, often reducing transplant shock from weeks to a matter of days. B-vitamins are also beneficial when transplanting from soil to hydroponics. Simply soak the plant roots in a bucket of luke-warm water with a few drops of B-vitamins added. Gently remove as much of the soil as possible, then transplant to a hydroponic system. Once the plant recovers, it will usually thrive!