Answer:Phloem is a type of plant tissue that is responsible for the transportation of organic nutrients and other substances, such as hormones, from the leaves to the other parts of the plant, including the roots, stems, and developing organs.
Phloem carries organic nutrients such as sugars, amino acids, and other substances produced during photosynthesis and metabolism in the leaves.
Sieve tubes are elongated cells that form the main conducting tubes of the phloem. They are associated with companion cells, which are specialized cells that provide metabolic support to the sieve tubes, such as by synthesizing and transporting proteins and other molecules required for phloem transport.
Translocation is the process of transporting organic nutrients and other substances through the phloem from the source (usually the leaves) to the sink (the part of the plant that needs the nutrients).
Pressure and water potential play a crucial role in translocation. Pressure flow theory explains that the phloem sap moves from source to sink due to differences in hydrostatic pressure gradients between the two regions. This process is aided by the active transport of solutes into the sieve tubes, which results in the creation of a high concentration gradient and a decrease in water potential, thus drawing water into the phloem.
Aphid stylets can be used to measure phloem transport rates by inserting the stylets into the phloem and measuring the rate of sap flow using electrical sensors.
Radioactively-labelled CO2 can be used to measure phloem transport rates by exposing a leaf to a small amount of radioactive CO2, which is then fixed into organic compounds and transported through the phloem to other parts of the plant. The rate of radioactive CO2 uptake can be measured to determine the rate of phloem transport.
Meristems are regions of undifferentiated cells in plants that are responsible for growth and development.
Apical meristems are meristematic regions located at the tips of roots and shoots, which are responsible for primary growth, or the increase in length of the plant.
These regions are important because they are responsible for the continuous production of new cells that differentiate into specialized cells required for plant growth and development.
Cell division, or mitosis, causes the growth of new plant tissue.
Tropism refers to the directional growth of plants in response to external stimuli, such as light or gravity.
Two tropisms are phototropism, which is the growth of plants in response to light, and gravitropism, which is the growth of plants in response to gravity. In phototropism, plants grow towards a source of light, while in gravitropism, plants grow in the direction of gravity, either towards or away from it.
The main group of plant hormones are auxins, gibberellins, cytokinins, abscisic acid, and ethylene.
The main functions of plant hormones include regulating growth and development, mediating responses to environmental stimuli, and coordinating physiological processes such as seed germination, flowering, and fruit ripening.
Auxin influences gene expression by binding to specific receptors in the cytoplasm of target cells, which triggers a signal transduction cascade that activates or represses the expression of certain genes.
Micropropagation is a plant propagation technique that involves the aseptic culture of plant tissue, such as shoot tips or nodal segments, on a nutrient medium containing plant hormones, to produce genetically identical plantlets.
Micropropagation is done to produce large numbers of genetically identical plants quickly and efficiently, for purposes such as crop improvement, conservation of rare or endangered species, or the production of ornamental plants
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