Plant physiology is a subdiscipline of botany concerned with the functioning of plants. There are around 14,500 species of flowering plants and trees. Butterflies are important as pollinators for some species of plants. The monocots are one of the major divisions of the flowering plants or angiosperms. Pesticides kill insects, plants and fungi. Additionally, there four invasive flowering plants on the list. It hosts over 20,000 species of aquatic plants and animals. Isoflavones are closely related to flavonoids found in other plants, vegetables and flowers. Hydroponics refers to the technique of growing plants without soil. They are one of the most economically important ornamental plants. Water buffaloes thrive on many aquatic plants. Another important area of symbiosis between carnivorous plants and insects is pollination. The caterpillars of a number of species of Lepidoptera feed on strawberry plants. These include bacteria, fungi, other plants, and animals. Many mites are parasitic on plants and animals.