Phytotoxicity describes any adverse effects on plant growth, Plant physiology, or metabolism caused by a chemical substance, such as high levels of fertilizers, herbicides, heavy metals, or .
Fertilizers
High concentrations of mineral salts in solution within the plant growing medium can result in phytotoxicity, commonly caused by excessive application of
.
For example,
urea is used in agriculture as a nitrogenous fertilizer. However, if too much is applied, phytotoxic effects can result from urea toxicity directly or ammonia production from
hydrolysis of urea.
Organic fertilizers, such as
compost, also have the potential to be phytotoxic if not sufficiently
Humification, as intermediate products of this process are harmful to plant growth.
Herbicides
are designed and used to control unwanted plants such as agricultural weeds. However, the use of herbicides can cause phytotoxic effects on non-targeted plants through wind-blown
spray drift or from the use of herbicide-contaminated material (such as straw or manure) being applied to the soil.
Herbicides can also cause phytotoxicity in crops if applied incorrectly, in the wrong stage of crop growth, or in excess.
The phytotoxic effects of herbicides are an important subject of study in the field of
ecotoxicology.
Heavy Metals
Heavy metals are high-density metallic compounds which are poisonous to plants at low concentrations, although toxicity depends on plant species, specific metal and its chemical form, and soil properties.
The most relevant heavy metals contributing to phytotoxicity in crops are
silver (Ag),
arsenic (As),
cadmium (Cd),
cobalt (Co),
chromium (Cr),
iron (Fe),
nickel (Ni),
lead (Pb), and
zinc (Zn). Of these, Co, Cu, Fe, Ni, and Zn are trace elements required in small amounts for enzyme and
Redox essential in plant development.
However, past a certain threshold they become toxic. The other heavy metals listed are considered toxic at any concentration and can
Bioaccumulation, posing a health hazard to humans if consumed.
Heavy metal contamination occurs from both natural and anthropogenic sources. The most notable natural source of heavy metals is rock outcroppings, although volcanic eruptions can release large amounts of toxic material.
Nanoparticles
Nanotechnology is a rapidly growing industry with many applications, including
drug delivery,
, and electronics.
As a result, manufactured nanoparticles, with sizes less than 100 nm, are released into the environment.
Plant uptake and bioaccumulation of these nanoparticles can cause plant growth enhancement or phytotoxic effects, depending on plant species and nanoparticle concentration.
