Phototoxic Effect

Definition - What does Phototoxic Effect mean?

Phototoxicity is a term used to describe light sensitivity. It’s most commonly applied to skin irritation in mammals due to a combination of exposure to chemicals and light. However, it also applies to plants. Many types of plants are phototoxic or photosensitive and can experience phototoxicity in certain situations.

Phototoxic effects are those that stem from chemical exposure by plants, in addition to the presence of light. Many plants are phototoxic to specific chemical formulations and even individual components in those formulations. Understanding phototoxic effects can help prevent the application of chemical pesticides, fungicides, herbicides, and other treatments to sensitive plants.

MaximumYield explains Phototoxic Effect

Copper is one of the most common elements that creates phototoxic effects in plants. Stone fruits are particularly sensitive to copper, and applying Bordeaux mix to apple trees, plum trees, and even watermelon or cantaloupe plants can cause a number of problems, including stunted growth, browning or dead leaves, and more.

Zinc is another element that can create phototoxic effects in plants, particularly in fruit trees. No fruit tree should ever be sprayed with an application that contains zinc sulfate, or it can result in significant defoliation (leaf death).

Sulfur can also cause phototoxic effects. This is particularly true for delicate ornamental plants, such as roses, but also crop plants, including cucumbers and squash.

Finally, both herbicides and insecticides can cause burning of the leaves and leaf malformation/deformation when applied under bright, hot sunlight, or applied to the wrong type of plants. Foliage burn can be severe enough to kill the plant in many cases.

Conversely, phototoxic effects can be caused by specific plants when they come into contact with unprotected human skin. Dill, fennel, parsley and coriander are just some of the plants that can cause skin irritation.

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