In fragmentation, an entire colony rather than just a polyp branches off to form a new colony. This may happen, for example, if a larger colony is broken off from the main colony during a storm or boat grounding. In terms of sexual reproduction, some coral species, such as Brain and Star coral, produce both sperm and eggs at the same time.
For other corals, such as Elkhorn and Boulder corals, all of the polyps in a single colony produce only sperm and all of the polyps in another colony produce only eggs. Coral larvae are either fertilized within the body of a polyp or in the water, through a process called spawning.
Subsequent cell-to-cell and nuclear fusion results in the formation of the zygote. The nascent zygote then re-enters the mitotic cell cycle, giving rise to its first diploid bud. Zygotes will appear dumbbell shaped cells, either with or without a bud. You might be wondering how haploids are produced in the first place. The answer is simple: meiosis. You probably already know that, following an initial chromosomal duplication, meiosis.
When yeast are under environmentally stressful conditions a form of meiosis takes place, known as sporulation. During sporulation, haploid spores are produced for each mating type and are contained in a tough membranous structure called an ascus, as indicated here with yellow circles. When environmental conditions improve, spores are released from the ascus. From there, they further develop into Mat a and Mat alpha haploid cells and go through the sexual reproduction cycle once again.
Understanding yeast reproduction is integral in genetic experiments, for example, generating yeast strains with multiple mutations. In this video, you can see the mixing of two different haploid strains, Mat a and Mat alpha, on an agar plate, and the subsequent incubation to allow for mating and diploid formation. They are then replica plated onto selective media that will only permit diploid growth.
The diploids can then be sporulated in nutrient deficient media, the resulting haploid spores dissected with a micromanipulator, and seeded onto an agar plate in a matrix pattern.
The haploid genotypes can be confirmed by PCR or growth on selective media. Aging studies can also be carried out by examining the replicative lifespan of yeast cells. The replicative life span is the number of buddings a cell goes through in its lifetime. A single yeast cell can produce 30 or so buds before dying. Here, you can see that a micromanipulator is used to separate a daughter cell from the mother cell in order to analyze the yeast life span over time.
The raw data produced by a replicative lifespan experiment is a list of numbers corresponding to daughter cells produced by each mother cell at each age point. The development of cell morphology as a function of cellular processes, such as protein concentration, can be studied in budding yeast.
Over here you see the preparation of cells for microcopy to visualize specific phenotype-specific defects. In this time-lapse video, multi- buds form, indicating that cells fail to separate from each other, suggesting a defect in cell division.
In this video, we talked about the yeast cell cycle and touched base on the asexual and sexual reproduction life cycles of this specie. Subscription Required. Please recommend JoVE to your librarian. Biology I: yeast, Drosophila and C. Yeast Reproduction. To learn more about our GDPR policies click here. If you want more info regarding data storage, please contact gdpr jove.
Your access has now expired. Provide feedback to your librarian. If you have any questions, please do not hesitate to reach out to our customer success team. The plant part often gives rise to an undifferentiated mass, known as a callus, from which, after a period of time, individual plantlets begin to grow. These can be separated; they are first grown under greenhouse conditions before they are moved to field conditions. The life cycles and life spans of plants vary and are affected by environmental and genetic factors.
The length of time from the beginning of development to the death of a plant is called its life span. The life cycle, on the other hand, is the sequence of stages a plant goes through from seed germination to seed production of the mature plant. Some plants, such as annuals, only need a few weeks to grow, produce seeds, and die. Other plants, such as the bristlecone pine, live for thousands of years.
Some bristlecone pines have a documented age of 4, years. Even as some parts of a plant, such as regions containing meristematic tissue the area of active plant growth consisting of undifferentiated cells capable of cell division continue to grow, some parts undergo programmed cell death apoptosis.
The cork found on stems and the water-conducting tissue of the xylem, for example, are composed of dead cells. Plant life spans : The bristlecone pine, shown here in the Ancient Bristlecone Pine Forest in the White Mountains of eastern California, has been known to live for 4, years. Plant species that complete their life cycle in one season are known as annuals, an example of which is Arabidopsis , or mouse-ear cress. Biennials, such as carrots, complete their life cycle in two seasons.
Commercial growers harvest the carrot roots after the first year of growth and do not allow the plants to flower. Perennials, such as the magnolia, complete their life cycle in two years or more. In another classification based on flowering frequency, monocarpic plants flower only once in their lifetime; examples of monocarpic plants include bamboo and yucca.
During the vegetative period of their life cycle which may be as long as years in some bamboo species , these plants may reproduce asexually, accumulating a great deal of food material that will be required during their once-in-a-lifetime flowering and setting of seed after fertilization. Soon after flowering, these plants die. Polycarpic plants form flowers many times during their lifetime. Fruit trees, such as apple and orange trees, are polycarpic; they flower every year.
Other polycarpic species, such as perennials, flower several times during their life span, but not each year. By this method, the plant does not require all its nutrients to be channeled towards flowering each year. As is the case with all living organisms, genetics and environmental conditions have a role to play in determining how long a plant will live.
Susceptibility to disease, changing environmental conditions, drought, cold, and competition for nutrients are some of the factors that determine the survival of a plant. Plants continue to grow, despite the presence of dead tissue, such as cork.
Individual parts of plants, such as flowers and leaves, have different rates of survival. In many trees, the older leaves turn yellow and eventually fall from the tree. Leaf fall is triggered by factors such as a decrease in photosynthetic efficiency due to shading by upper leaves or oxidative damage incurred as a result of photosynthetic reactions.
The components of the part to be shed are recycled by the plant for use in other processes, such as development of seed and storage. This process is known as nutrient recycling. However, the complex pathways of nutrient recycling within a plant are not well understood. The aging of a plant and all the associated processes is known as senescence, which is marked by several complex biochemical changes.
One of the characteristics of senescence is the breakdown of chloroplasts, which is characterized by the yellowing of leaves. The chloroplasts contain components of photosynthetic machinery, such as membranes and proteins. Chloroplasts also contain DNA. The proteins, lipids, and nucleic acids are broken down by specific enzymes into smaller molecules and salvaged by the plant to support the growth of other plant tissues.
Hormones are known to play a role in senescence. Applications of cytokinins and ethylene delay or prevent senescence; in contrast, abscissic acid causes premature onset of senescence. Plant senescence : The autumn color of these Oregon Grape leaves is an example of programmed plant senescence. Privacy Policy. Skip to main content.
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