Protection of Plants against Toxic Substances
Plants produce several toxic substances themselves and may also encounter the ones produced by other plants or present in the environment. Toxic effects of these substances is prevented by confining them in some part of the plant's organs (e.g., seeds, roots and leaves), tissues (e.g., epidermal layer and the spongy mesophyll), organelles (e.g., vacuoles and chloroplasts) or extra cytoplasmic space (cell wall etc.). The enzymes involved in degradation of these substances are also concentrated in these parts. Usually autogenous (self-produced) toxins are stored as their non-toxic derivative.
The enzymes that modify self-toxins can also detoxify toxins of foreign origin. Plants have evolved a huge arsenal of enzymes catalysing chemical modification of such toxic compounds. In some cases, a small number of enzymes with each one targeted towards a broad group of chemicals is produced. Both these kinds of enzymes have been found in plants.