This process is sometimes called cloning because every new plant is exactly like the parent. One type of cloning uses cuttings --parts of plants that grow into new plants.
Both stems and leaves can be used as cuttings. Another kind of cloning is grafting --the joining together of two plants into one. Gardeners grow plants from cuttings. They do this by snipping a young shoot off a plant, dipping it in rooting hormone and placing the cutting in a mixture of sand and potting mix. The cutting soon grows roots and can be transferred outdoors. Grafting and budding are two ways to make new plants. This video, Grafting and budding , demonstrates these two techniques.
Fruit tree breeders often use grafting to make new plants. Grafting allows them to have large plantings of the same fruit variety with exactly the same genetic material. Grafting uses the rootstock of a plant that grows well in the soil and joins it to the plant the breeder wishes to produce.
Although we think of science as always advancing at a steady pace, techniques like cutting and grafting have been around for thousands of years. Science has helped us understand how these techniques work and improve them with advances like rooting hormones and breeding new plant cultivars. As the language used may be too complex for younger students, consider muting the audio and providing your own simpler narration. Scientists divide plants into two main groups depending on whether they reproduce by seeds or spores.
Seed plants have special structures on them where male and female cells join together through a process called fertilisation. After fertilisation, a tiny plant called an embryo is formed inside a seed. The seed protects the embryo and stores food for it. The parent plant disperses or releases the seed. If the seed lands where the conditions are right, the embryo germinates and grows into a new plant. Scientists divide seed plants into two main groups: plants with flowers and plants with cones.
They also have special names for these groups. Plants that have flowers are called angiosperms. Plants that hold their seeds in cones are called gymnosperms. Angiosperms have flowers. The flowers are special structures for reproduction. Organisms use spores as a means of asexual reproduction. Spores are also formed in bacteria , however, bacterial spores are not typically involved in reproduction.
These spores are dormant and serve a protective role by safeguarding bacteria from extreme environmental conditions. Some bacteria form spores called endospores as a means to combat extreme conditions in the environment that threaten their survival. These conditions include high temperatures, dryness, the presence of toxic enzymes or chemicals, and lack of food. Spore-forming bacteria develop a thick cell wall that is waterproof and protects bacterial DNA from desiccation and damage.
Endospores can survive for long periods of time until conditions change and become suitable for germination. Examples of bacteria that are capable of forming endospores include Clostridium and Bacillus. Algae produce spores as a means of asexual reproduction. These spores may be non-motile aplanospores or they may be motile zoospores and move from one place to another using flagella. Some algae can reproduce either asexually or sexually. When conditions are favorable, the mature algae divide and produce spores that develop into new individuals.
The spores are haploid and are produced by mitosis. During times when conditions are unfavorable for development, the algae undergo sexual reproduction to produce gametes. These sex cells fuse to become a diploid zygospore. The zygospore will remain dormant until conditions become favorable once again. At such time, the zygospore will undergo meiosis to produce haploid spores. Some algae have a life cycle that alternates between distinct periods of asexual and sexual reproduction.
This type of life cycle is called alternation of generations and it consists of a haploid phase and a diploid phase.
In the haploid phase, a structure called a gametophyte produces male and female gametes. The fusion of these gametes forms a zygote. In the diploid phase, the zygote develops into a diploid structure called a sporophyte.
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