Egeria (plant) Egeria (plant) Egeria is a genus of three species of aquatic plants in the family Hydrocharitaceae described as a genus in 1849. native to warm-temperate South America. The genus was formerly included in the related genus "Elodea", from which it differs in having the leaves in whorls of four or more, not three, and in having more conspicuous flowers with larger (particularly broader) petals. "Egeria" is found in many temperate and subtropical regions throughout the world as an introduced, or "alien", species, meaning a species that does not originate from the area in which it is found. In many places,
Plant defense against herbivory reproduction. Many models have been proposed to explore how and why some plants make this investment in defenses against herbivores. The optimal defense hypothesis attempts to explain how the kinds of defenses a particular plant might use reflect the threats each individual plant faces. This model considers three main factors, namely: risk of attack, value of the plant part, and the cost of defense. The first factor determining optimal defense is risk: how likely is it that a plant or certain plant parts will be attacked? This is also related to the "plant apparency hypothesis", which states that a plant