Frugivore - Plant Mechanisms To Delay or Deter Frugivory

Plant Mechanisms To Delay or Deter Frugivory

Further information: Plant defense against herbivory

Plants invest energy into the production of fruits. Plants have evolved to encourage mutualist frugivores to consume their fruit for seed dispersal but also evolved mechanisms to decrease consumption of fruits when unripe and from non-seed dispersing predators. Predators and parasites of fruit include seed predators, insects and microbial frugivores. Plants have chemical and physical adaptations.

Physical deterrents

• Cryptic coloration (e.g. green fruits blend in with the plant leaves)
• Unpalatable textures (e.g. thick skins made of anti-nutritive substances)
• Resins and saps (e.g. prevent animals from swallowing)
• Repellent substances, hard outer coats, spines, thorns

Chemical deterrents

• Chemical deterrents in plants are called secondary metabolites. Secondary metabolites are compounds produced by the plant that are not essential for the primary processes such as growth and reproduction. Toxins might have evolved to prevent consumption by animals that disperse seeds into unsuitable habitats, to prevent too many fruits from being eaten per feeding bout by preventing too many seeds being deposited in one site, or to prevent digestion of the seeds in the gut of the animal. Secondary chemical defenses are divided into three categories: nitrogen based, carbon based terpenes, and carbon based phenolics.

Examples of secondary chemical defenses in fruit:

• Capsaicin is a carbon based phenolic compound only found in plant genus Capsicum (chili and bell peppers). Capsaicin is responsible for the pungent, “hot” flavor of peppers and inhibits growth of microbes and invertebrates.
• Cyanogenic glycosides are nitrogen based compounds and are found in 130 plant families but not necessarily in the fruit of all the plants. It is specifically found in the red berries of the genus Ilex (Holly, an evergreen woody plant). It can inhibit electron transport, cellular respiration, induce vomiting, diarrhea, and mild narcosis in animals.
• Emodin is a carbon based phenolic compound in plants like rhubarb. Emodin can be cathartic or act as a laxative in humans, kills dipteran larvae, inhibits growth of bacteria and fungi and deters consumption by birds and mice.