Plants produce a wide variety of factors that decrease their nutritional quality or make their nutrients unavailable when they are released during feeding by herbivores. Thiaminase, which breaks down the B vitamin thiamin, occurs in the ferns bracken and nardoo. Protease inhibitors, such as the Kunitz inhibitor, occur in soybean and many other seeds. Tannins are also antinutritional factors, because they bind to proteins and make them more difficult to digest. Go back to question 4 or go on to question 5 .
Oxalates serve to protect plant tissues from herbivores.
They are stored in vacuoles as crystals or solubilized. The crystals may act as spears and physically damage cells. Go back to question 7a or go on to question 7b . The cuticle is a waxy covering over plant surfaces, especially leaves. It is made up mainly of long chain, hydrophobic alcohols and fatty acids which may be linked together as esters.