Such changes in the hereditary material are called mutations and organisms that display them are called mutants . The term wild type describes in a very general manner those phenotypes of a species that are most common in nature. Mutations are contrasted by modifications . The term describes changes in the phenotype that are caused by environmental influences. This example illustrates that the expression of a phenotype can be influenced by environmental factors like temperature.
Modifications are very common, especially in plants.
Among the better known textbook examples is the flower colour of a certain variety of Primula sinensis that is red at room temperature and white at increased temperatures. Mutants that can be distinguished only at increased temperatures are also called temperature-sensitive . Alpine plants and plants in general that grown under intense radiation, are usually stout. Plants from lowlands and such plants that got just little amounts of sunlight during growth, show an unmistakable elongation growth. It is known that the development of plants is, much more than that of animals, influenced by external factors.