Citric acid is a natural product of citrus fruits such as lemons, limes, oranges and tangerines. A small amount is also present in berries, particularly blackberries and raspberries. In the environment, citric acid does not only affect humans, animals and aquatic life, but affects plants as well. Some studies show that citric acid, when used in smaller doses may be beneficial to plants; however, large and repeated doses may be harmful.
Plants make adenosine tripohosphate (ATP) during photosynthesis by releasing energy from glucose and other stored sugar. During aerobic respiration, the cell uses oxygen to burn molecules and release energy. This reaction, which is the opposite of photosynthesis, takes place over the course of three major reaction pathways: glycolysis, Krebs cycle and electron transport phosphorylation (ETP).
Citric acid is a main component of Krebs cycle, also known as citric acid cycle, which is a series of complicated chemical reactions as part of respiration of all oxygen-utilizing cells including those found in plants. Disturbing or distorting the citric acid cycle will hamper the glucose transformation and impair the plant's energy.
An article on homeopathy written by V.D. Kaviraj, a Dutch homeopath, author, researcher and pioneer in agrohomeopathy, explains how citric acid and other closely related acids can have an allelopathic effect on plants. V.D. Kaviraj mentions that allelopathy is the inhibition of growth of a plant due to biomolecules (allelochemicals) released by another. Repeated dosage of citric acid on healthy plants can cause the plants to die, which is why citric acid is useful as a weed remover.
Promotes Rooting Ex Vitro
The International Society for Horticultural Science (ISHS) published a research study on the effect of ascorbic acid and citric acid on ex vitro (plants grown naturally) rooting and acclimatization of Prunus avium L. (sweet cherry) microshoots. The ISHS study indicates that applying low doses of ascorbic acid and citric acid to the sweet cherry microshoots can promote rooting and survival.
Coqui frogs (Eleutherodactylus coqui and E. planirostris), otherwise known as Caribbean tree frogs, can affect Hawaii's floriculture industry because of quarantine measures implemented by the Hawaiian islands on infested plants. Prompting growing concerns from greenhouse growers, the United States Department of Agriculture performed a series of experiments on orchids and other plants using low doses of citric acid.
Research showed that dermal application of 16 percent citric acid was effective in controlling frogs due to its phytotoxic (poisonous) effects on plants without damaging the leaves. The study indicates that citric acid can be an effective quarantine treatment for plants.