Plant Reproduction

Most plants reproduce sexually, combining genetic material from two parents to produce offspring. In flowering plants, the male part is the stamen, which produces pollen containing sperm cells. The female part is the pistil, which contains an ovary with eggs. Pollination is the transfer of pollen from stamen to pistil, often facilitated by wind, water, insects, birds, or bats. Once pollen reaches an egg and fertilization occurs, the ovule develops into a seed and the surrounding tissue often develops into a fruit.

Flowers and fruits are evolutionary inventions that opened up new possibilities for plant reproduction. Flowers attract specific pollinators, often through colors, scents, and rewards like nectar and pollen. Fruits package seeds with food and incentives for animals to eat them, dispersing the seeds in the process. Many plants and pollinators have co-evolved to the point that they depend on each other. The fig and its specialized wasp, the yucca and its specific moth, and many orchids and their bee partners are striking examples.

Many plants also reproduce asexually, producing genetically identical copies of themselves. Strawberry plants send out runners that root and become new plants. Aspens send up new shoots from underground roots, sometimes covering acres with genetically identical clones. Asexual reproduction allows fast spread when conditions are good but reduces genetic diversity, leaving clones vulnerable to disease. Most plants combine both strategies, switching between them depending on conditions.

Flowering plants, called angiosperms, are by far the most diverse group of plants today, with about 295,000 known species. Their dominance over earlier plant groups like ferns and conifers is largely due to the evolutionary success of the flower-fruit-seed strategy. Every apple, every almond, every grain of wheat is a product of this reproductive system at work.