Phytotoxic

Phytotoxic is an adjective used to describe substances, organisms, or conditions that are toxic to plants. Phytotoxic agents can impair germination, growth, photosynthesis, or survival, and may cause symptoms such as chlorosis, necrosis, wilting, or stunted development.

Sources of phytotoxicity are diverse. They include natural allelopathic compounds produced by plants themselves, toxins produced by plant pathogens (fungi and bacteria), and synthetic chemicals such as herbicides and other pollutants. Metal ions and environmental contaminants can also exhibit phytotoxic effects at certain concentrations. Phytotoxicity can influence plant-plant interactions in ecosystems and affect crop yields in agriculture.

Mechanisms of phytotoxic action vary widely. Some agents disrupt cell membranes or photosynthetic processes, others inhibit enzyme function or interfere with nutrient uptake. Many cause oxidative stress, leading to cellular damage and growth inhibition. The specific signs and severity depend on the agent, the plant species, and exposure conditions.

Assessment of phytotoxicity often involves simple bioassays, such as seed germination tests and root elongation measurements, as well as more complex analyses of photosynthetic performance or tissue damage. These evaluations are used in weed management, pesticide risk assessment, and ecological research, as well as in studies of plant-plant interactions and allelopathy.

Examples of well-known phytotoxic contexts include juglone, a toxin produced by black walnut trees that can inhibit neighboring plants, and various herbicides such as paraquat that intentionally exert phytotoxic effects to control unwanted vegetation.