What kind of reproduction produces seeds

After some time, roots will appear; this portion of the plant can be removed and transplanted into a separate pot. Layering : In layering, a part of the stem is buried so that it forms a new plant. Micropropagation also called plant tissue culture is a method of propagating a large number of plants from a single plant in a short time under laboratory conditions. This method allows propagation of rare, endangered species that may be difficult to grow under natural conditions, are economically important, or are in demand as disease-free plants.

To start plant tissue culture, a part of the plant such as a stem, leaf, embryo, anther, or seed can be used. The plant material is thoroughly sterilized using a combination of chemical treatments standardized for that species. Under sterile conditions, the plant material is placed on a plant tissue culture medium that contains all the minerals, vitamins, and hormones required by the plant.

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.

After the female gametes are fertilised by male gametes from the pollen, the female cones produce seeds, which are then scattered away from the plant by wind or animals. Most gymnosperms are trees. There are about 20 native gymnosperms in New Zealand, including our tallest tree, the kahikatea Dacrycarpus dacrydioides , white pine.

Ferns, mosses, liverworts and green algae are all plants that have spores. Spore plants have a different life cycle. A parent plant sends out tiny spores containing special sets of chromosomes. These spores do not contain an embryo or food stores. Fertilisation of the spores takes place away from the parent, usually in a damp place. An embryo is formed and a new plant grows from it.

For more information, view the Fern life cycle interactive. New Zealand has about species of ferns and over species of moss. Classification helps us put order into the world around us. Scientists start with very big categories like plants and animals and continue to divide the groups based on shared characteristics — like methods of reproduction. Take a bag of thawed frozen broad beans to school and hand a few to each student.

Students can remove the seed coat and split the bean to reveal the embryo inside. Use magnifying glasses to examine the embryos. How plants form their seeds. Retrieved November 10, from www. They explain the genetic control mechanisms underlying the The 'how and when' of this evolutionary step has, until now, remained unknown. Plant biologists have Plants react sensitively to changes in their surroundings and possess the ability to adapt to them. They use the photoreceptor Similar to animals, plants have evolved small ScienceDaily shares links with sites in the TrendMD network and earns revenue from third-party advertisers, where indicated.

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