How Plants Reproduce
Plants create more of their own species by sexual reproduction or by asexual reproduction. With sexual reproduction, a male sperm cell joins with a female egg cell to produce a new plant, hereditary information from both plants is passed to the new plant. Asexual reproduction often involves the division of one plant into one or more parts that become new plants, this type of asexual reproduction is called vegetative propagation and genetic material is passed to the offspring by the single parent plant. Many plants can reproduce both sexually and by vegetative propagation.

Sexual reproduction in plants happens with the complex cycle we call alternation of generations. During one phase of the life cycle, the plant is a gametophyte which produces gametes (sperm and egg cells). It may produce one or the other or both, depending on the plant species. Fertilization occurs when the sperm and egg cell unite and the egg develops into the second phase of the plant's life cycle where the plant is called a sporophyte or spore-bearing plant. This spore-bearing part of the plants life is typically what people see and recognize as a plant. Sporophytes produce tiny structures called spores through a process of cell division called meiosis. The spores form in capsules called sporangia. Gametophytes develop from the spores, and the life cycle begins again.

With seed plants, which include flowering and cone-bearing plants, alternation of generations involves a series of complicated steps. With these plants, only the sporophyte generation can be seen with the unaided eye. Spores are produced in both male and female reproductive organs. The spores grow into gametophytes and remain inside the plant's reproductive organs.

Flowering plants house their reproductive parts in flowers. The stamens are its male reproductive organs and the pistil is the plant's female reproductive organ. Each stamen has an enlarged tip called an anther. The ovary, which forms the round base of the pistil, contains the ovules. The anthers consist of microsporangia, and the ovules megasporangia. Cell divisions in the microsporangia and megasporangia results in the production of spores. Typically, one spore in each ovule grows into a microscopic female gametophyte and produces one egg cell. In the anther, the spores, called pollen grains, contain microscopic male gametophytes and each pollen grain produces two sperm cells. Pollination occurs when a pollen grain is transferred from the anther to the pistil. When this process happens on one plant, it's called self-pollination. Cross-pollination happens from one plant to another plant.

In conifers, the reproductive parts are housed within the cones. A conifer has two kinds of cones, the pollen, or male, cone is the small and soft. Seed, or female, cones are the larger, hard cones. A pollen cone has many tiny sporangia that produce pollen grains. Each of the scales that make up a seed cone has two ovules. Every ovule produces a spore that grows into a female gametophyte and this tiny plant produces egg cells.

The wind usually delivers the pollen grains from the pollen cone to the seed cone, this is the yellow haze often seen in the spring in coniferous forest areas. A pollen grain sticks to the cone near an ovule and usually enters the pollen chamber of the ovule through an opening called the micropyle. The pollen grain then forms a pollen tube where two sperm cells develop. After the pollen tube reaches the egg cell, one sperm cell fertilizes the egg and the other that does not reach the egg disintegrates. The fertilized egg develops into a sporophyte embryo, the ovule containing the embryo becomes a seed, the seed falls to the ground and, if conditions are right or the seed is not eaten, a new sporophyte begins to grow.

In ferns and mosses, the sporophyte and gametophyte generations are represented by two greatly different plants. The ferns sporophytes have leaves which are much larger than the gametophytes and clusters of sporangia, where the spores develop, called sori form on the edges or underside of each leaf. After the spores ripen, they fall to the ground and grow into gametophytes. A fern gametophyte produces both male and female sex cells, and if enough moisture is present, a sperm cell swims to an egg cell and unites with it. Once fertilized, the egg grows into an adult sporophyte.

Among mosses, a sporophyte consists of a long, rigid stalk with a spore-producing container at the end, extending from the top of a soft, leafy, green gametophyte. The sporophyte depends on the gametophyte for food and water. When we think of the green carpet of mosses, it is the gametophyte we are seeing.

Vegetative propagation is the process of reproduction by which a part of a plant may grow into a complete new plant. Any part of a plant, whether a root, stem, leaf, or flower may be propagated into a new plant. A new plant can even grow from a single cell of another plant.

Vegetative propagation occurs most often in plants where the stem grows just below or along the ground surface. These runners, send out roots at points where they touch the ground and in turn produce plantlets (new leaves and stems) and are part of the parent plant. A new plant is formed only when the plantlets are separated from the parent plant. Ferns, irises, many kinds of grasses, and some species of trees propagate from underground stems. They can also sprout plantlets where a branch has come in contact with the ground.

Farmers and gardeners use vegetative propagation to raise many plants and food crops. Gardeners use this method for reproducing plants including gladioli, irises, lilies, and tulips. Farmers plant apples, bananas, oranges, and white potatoes this way. If you cut up potatoes, being careful to leave one eye per piece, you will quickly be able to grow a crop of nice potato plants.

Vegetative propagation usually happens one of three ways when practiced in farming or gardening. Cuttage involves the use of parts of plants taken from growing plants. Most cuttings are stems that develop roots when placed in water or moist soil then grows into a new plant. In the case of African Violets, removing a healthy leaf and placing it in moist soil will produce a new plant. Grafting also involves cuttings but instead of placing the plant part in water or soil, it is grafted directly onto another living plant that provides an already developed root system.