Flowering Plants: Reproduction and Development The process of meiosis and fertilization occur in the flower, a plant structure specialized for sexual reproduction.

Flower Structure: The flower may contain both the male reproductive organ, the stamen, and female reproductive organ, the pistil. Flowers with both reproductive organs are called perfect or complete flowers, while those with only one or the other are called imperfect or incomplete flowers. Petals and sepals may also be present.

The stamen is composed of an anther and a filament The stamen is composed of an anther and a filament. As a result of meiosis, the diploid cells of the anther produce pollen grains which contain monoploid nuclei (n). The pistil is composed of the stigma, style, and the ovary. As a result of meiosis, ovule(s), developing within the ovary, contain the monoploid egg nucleus (n).

Pollination Pollination is the transfer of pollen grains from the anther to the stigma. Pollination may be accomplished by wind, insects, and birds. In some instances, the colored petals act as a visual attractant for insects while nectar acts as a chemical attractant. After pollination, the pollen grain forms a pollen tube which extends to the ovule and moves the sperm nuclei to the ovule.

Two Types of Pollination Self-pollination – the transfer of pollen from anther to stigma of the same flower or to stigma of another flower on same plant. Cross-pollination – transfer of pollen from an anther on one flower to a stigma of a flower on a different plant. * Enhances variation (increases variety). The pollen grain may be thick in dry climates to prevent dehydration.

Fertilization and Embryo Development The union (fusion) of male and female nuclei in the ovule results in a zygote. The zygote undergoes development resulting in the formation of the embryo. The ripened ovule, containing the embryo develops into the seed. A seed consists of a seed coat, which develops from the outer covering of the ovule, and an embryo. The ripened ovary develops into the fruit.

Three Parts of a Plant Embryo Hypocotyl – develops into root and lower stem portion Epicotyl – develops into leaves and upper portions of stem. Cotyledon – contains stored food which provides nutrients for germinating plant. A – hypocotyl B – epicotyl C – seed coat D - cotyledon

Germination In flowering plants, seeds develop inside a fruit. Fruits are specialized structures which aid in seed dispersal. Under suitable environmental conditions, the dispersed seeds germinate. For most seeds these conditions include: Sufficient moisture Proper temperature Sufficient oxygen The development of a seed into a mature plant, which is capable of reproduction, involves cell division, differentiation, and growth.

Growth in higher plants is restricted largely to specific regions known as meristems. Apical meristems are found in the tips of roots and stems and are responsible for the growth in the length of the plant.. Some plants also contain an active lateral meristem region, the cambium, located between the xylem and phloem. This is responsible for the growth in diameter of roots and stems. Mitosis