“Some plants have specific “pests,” such as insects, that have adapted to be resistant to that plant’s toxins, but if the plant and its predator are to survive, there has to be a balance between the plant tissue’s digestibility and its toxicity. Injury of a plant stimulates it to make increased amounts of its defensive chemicals.
A particular plant will have a variety of defensive chemicals, with specific functions. Underground, the plant’s roots and tubers are susceptible to attack by fungi and nematodes. The leaves, stems, and seeds are susceptible to attack by insects, birds, and grazing animals. Since the plant’s seeds are of unique importance to the plant, and contain a high concentration of nutrients, they must have special protection. Sometimes this consists of a hard shell, and sometimes of chemicals that inhibit the animal’s digestive enzymes. Many plants have evolved fruits that provide concentrated food for animals, and that serve to distribute the seeds widely, as when a bird eats a berry, and excretes the undigested seed at a great distance. If the fruit were poisonous, it wouldn’t serve the plant’s purpose so well. In general, the plant’s most intense toxins are in its seeds, and the fruits, when mature, generally contain practically no toxins. Roots contain chemicals that inhibit microorganisms, but because they aren’t easily accessible by grazing animals and insects, they don’t contain the digestive inhibitors that are more concentrated in the above-ground organs of the plant.
The toxins of plants include phenols, tannins, lectins/agglutinins, and trypsin-inhibitors, besides innumerable more specific metabolic inhibitors, including “anti-vitamins.” Unsaturated fats themselves are important defenses, since they inhibit trypsin and other proteolytic enzymes, preventing the assimilation of the proteins that are present in seeds and leaves, and disrupting all biological processes that depend on protein breakdown, such as the formation of thyroid hormone and the removal of blood clots.
Generally, fruits, roots, and tubers provide a high concentration of nutrients along with low concentrations of toxic antimetabolic substances.” Raymond Peat, PhD., Vegetables, etc.—Who Defines Food?
“Plant defense against herbivory or host-plant resistance (HPR) describes a range of adaptations evolved by plants which improve their survival and reproduction by reducing the impact of herbivores. Plants can sense being touched, and they can use several strategies to defend against damage caused by herbivores. Many plants produce secondary metabolites, known as allelochemicals, that influence the behavior, growth, or survival of herbivores. These chemical defenses can act as repellents or toxins to herbivores, or reduce plant digestibility.” Plant defense against herbivory
“I think far too little attention is being given to the effects of abnormal and stressful growth conditions on the plants’ natural defense systems. Plants normally synthesize some toxins and inhibitors of digestive enzymes to discourage attacks by bacteria, fungi, insects, and other predators. When a plant is injured or otherwise stressed, it produces more of the defensive substances, and very often they communicate their stress to other plants, and the resulting physiological changes can cause changes in seeds that affect the resistance of the progeny. (Agrawal, 2001).” Raymond Peat, PhD., Milk in context: allergies, ecology, and some myths
“Natural rubber latex immunoglobulin E-mediated hypersensitivity is probably one of the most relevant challenges that has been faced in the treatment of allergies during recent years. Additionally, allergen cross-reactivity has arisen as another very important problem, in the difficulty in diagnosing it and in its clinical implications. It is clear that some latex allergens cross-react with plant-derived food allergens, the so-called latex-fruit syndrome, with evident clinical consequences. Although the foods most frequently involved are banana, avocado, kiwi, and chestnut, several others are also implicated. Investigations point to a group of defense-related plant proteins, class I chitinases, which cross-react with a major latex allergen, hevein, as the panallergens responsible for the syndrome. This review focuses on our current understanding of the latex-fruit syndrome.” Latex-fruit syndrome. (2003)
“Latex allergy is an increasing hazard to people who frequently come into contact with latex products. Of interest concerning this immediate-type allergy is the cross-reactivity to various vegetable foods and pollen. Despite its high prevalence, no adequate explanation has been provided for the cross-reactive antigens.” Plant defense-related enzymes as latex antigens. (1998)
“Natural rubber latex is used in the manufacture of many products in the United States. As natural rubber latex allergy becomes of increasing concern, dietitians need to have an understanding of this allergy and how it relates to workplace safety, employee health, and patient feeding and counseling. Natural rubber latex contains more than 35 proteins that may be related to Type I, Ig-E-mediated allergy in numerous segments of the population, including health care workers and patients. Many foods, especially chestnut, banana, and avocado, have the potential to cross-react with natural rubber latex. Chitinase enzymes, related to plant defense, are believed to be involved in this cross-reaction. A strong connection between food allergy and natural rubber latex allergy is recognized and described in this review.” The latex and food allergy connection. (2000)
“Approximately 30-50% of individuals who are allergic to natural rubber latex (NRL) show an associated hypersensitivity to some plant-derived foods, especially freshly consumed fruits. This association of latex allergy and allergy to plant-derived foods is called latex-fruit syndrome. An increasing number of plant sources, such as avocado, banana, chestnut, kiwi, peach, tomato, potato and bell pepper, have been associated with this syndrome. The prevailing hypothesis is that allergen cross-reactivity is due to IgE antibodies that recognize structurally similar epitopes on different proteins that are phylogenetically closely related or represent evolutionarily conserved structures. Several types of proteins have been identified to be involved in the latex-fruit syndrome. Two of these are plant defence proteins. Class I chitinases containing an N-terminal hevein-like domain cross-react with hevein (Hev b 6.02), a major IgE-binding allergen for patients allergic to NRL. A beta-1,3-glucanase was identified as an important latex allergen which shows cross-reactivity with proteins of bell pepper. Another important NRL allergen, Hev b 7, is a patatin-like protein that shows cross-reactivity with its analogous protein in potato. Furthermore, patients with allergy to plant-derived foods and associated pollinosis show a high frequency of IgE reactivity to the pan-allergen profilin, which may cause positive serum IgE determinations to NRL. Although there is much information about the plant-derived foods and some data about the allergens involved in the latex-fruit syndrome, it is not always clear whether latex sensitization precedes or follows the onset of food allergy.” The latex-fruit syndrome. (2002)
“Latex allergy represents an increasing occupational problem, mainly among healthcare workers. An association between latex allergy and hypersensitivity to some plant foods, particularly fruits (the latex-fruit syndrome), has been established. Class I chitinases with an N-terminal hevein-like domain from avocado, chestnut, banana and other foods, and latex hevein seem to be the allergens responsible for the cross-reactions involved in the latex-fruit syndrome. The potential role of other latex allergens, such as profilin, Hev b 5, Hev b 7 and beta-1,3-glucanases, in the co-sensitization to latex and plant foods is also discussed.” The role of plant panallergens in sensitization to natural rubber latex. (2001)
“Herbivory has many effects on plants, ranging from shifts in primary processes such as photosynthesis, growth, and phenology to effects on defense against subsequent herbivores and other species interactions. In this study, I investigated the effects of herbivory on seed and seedling characteristics of several families of wild radish (Raphanus raphanistrum) to test the hypothesis that herbivory may affect the quality of offspring and the resistance of offspring to plant parasites. Transgenerational effects of herbivory may represent adaptive maternal effects or factors that constrain or amplify natural selection on progeny. Caterpillar (Pieris rapae) herbivory to greenhouse-grown plants caused plants in some families to produce smaller seeds and those in other families to produce larger seeds compared with undamaged controls. Seed mass was positively associated with probability of emergence in the field. The number of setose trichomes, a putative plant defense, was higher in the progeny of damaged plants in some families and lower in the progeny of damaged plants in other families. In a field experiment, plant families varied in their resistance to several herbivores and pathogens as well as in growth rate and time to flowering. Seeds from damaged parent plants were more likely to become infested with a plant virus. Although herbivory on maternal plants did not directly affect interactions of offspring with other plant parasites, seed mass influenced plant resistance to several attackers. Thus, herbivory affected seed characters, which mediated interactions between plants and their parasites. Finally, irrespective of seed mass, herbivory on maternal plants influenced components of progeny fitness, which was dependent on plant family. Natural selection may act on plant responses to herbivory that affect seedling-parasite interactions and, ultimately, fitness.” Transgenerational consequences of plant responses to herbivory: an adaptive maternal effect? (2001)