Ovules are the parts of flowers that develop into seeds. Ovules exist in female plants and flowers, and reside in the ovaries. They form the reproductive system of plants, along with many other organs, enabling the growth and development of new offspring.
The work of ovules begins with pollination. Pollination occurs when grains land on the flowers of receptive species. These grains then stimulate the growth of pollen tubes, which connect with ovules in the ovaries. This connection facilitates the passage of male gametes into the ovaries. There, male gametes fertilize eggs, and the process of fertilization completes. Upon fertilization, seeds develop from the ovules and eventually turn into fruit.
Ovules exist in many types of plants, flowers and trees, but vary in location and shape depending on the species. In gymnosperms, which include conifers and cone-bearing relatives, ovules exist on the scales of cones, exposed to the environment. In angiosperms, or flowering plants, ovules attach to stalk bases and derive protection from surrounding outer shells. In addition to affording seeds protection with outer shells, ovules support growth and provide nutrition. One or two external seed coats supply germinating seeds with food, along with a layer of food tissue. Ovules in some plants stand vertically, while others lean sideways or backwards, which helps identify the plant species.