Plant Reproduction and Photosynthesis Explained

Plant Anatomy and Reproduction

The flower, which is responsible for reproduction, has a female part: the carpel, and a male part: the stamen. The female gametes (ovules) are produced in the ovary inside the carpel, while the male gametes are called pollen grains. Petals attract animals and protect the flower, while sepals cover and protect the other parts of the flower.

As a result of fertilization, a seed develops, which is responsible for the survival and dispersal of the plant.

3. Reproduction in Plants

Aquatic organisms often use water as a medium for transporting their gametes and for fertilization. On land, the vast majority of plants have developed mechanisms of reproduction that make their fertilization independent of water. Plants can reproduce asexually (when a separate fragment of a plant develops into a new individual) or sexually (by means of reproductive cells, or gametes). Asexual reproduction is also called vegetative reproduction.

3.1. Flowering Plant Reproduction

Plant reproduction begins in flowers. The male sex cells, called pollen grains, fertilize the female sex cells, called ovules. After fertilization, seeds develop and are then dispersed by the plant.

Flowering plant reproduction involves several steps:

• Pollination: Pollen is transferred from the male stamen to the female stigma. Pollen is carried by insects or the wind.
• Fertilization: When pollen lands on a stigma of the same species, the pollen grain grows a tube to join with the female sex cell or gamete: the ovule.
• Seed dispersal: After fertilization, the flower's petals fall off and a fruit usually forms from the ovary, while the fertilized ovules form seeds. The seeds are dispersed by wind or animals.
• Seed germination: Seeds start to grow when the temperature, air, and water conditions are right.

4. Green Plants

Green plants are able to make food by the process of photosynthesis. They use a green pigment in their leaves called chlorophyll that absorbs light, which is found in the chloroplasts of plant cells. They also need sunlight, water, and carbon dioxide to make food. Sunlight is absorbed by the leaves, and carbon dioxide is taken in by pores in the back of the leaves called stomata. Water is absorbed by the roots and travels through the stem to the leaves, where photosynthesis takes place.

4.1. Photosynthesis: The Equation

Photosynthesis is a chemical reaction which takes place in green plants to produce food. The formula for photosynthesis is:

CO2 + H2O + mineral salts + sunlight → glucose + O2

During photosynthesis, water and carbon dioxide are taken in, and glucose and oxygen are produced. In order to create enough glucose to grow, a tree has thousands of leaves, which produce food through photosynthesis continuously throughout the hours of daylight.

Photosynthesis is vital to life on Earth. Plants not only provide food for animals but also produce oxygen, which is needed for respiration.