14.2. Homeostasis in plants
A subsection of Biology, 9700, through 14. Homeostasis
Listing 10 of 36 questions
shows a section through part of a dicotyledonous leaf of the tea plant Camellia sinensis. On , use label lines and letters to label each of the following parts: X – xylem tissue P – palisade mesophyll tissue. The leaves of C. sinensis have a large surface area and are thin. Explain how each of these two features help the leaf to carry out photosynthesis. The lower epidermis contains stomata. State one structural difference between a guard cell and other lower epidermal cells. Abscisic acid has an important role in the closure of a stoma. It promotes the loss of potassium ions from guard cells. Outline how the loss of potassium ions from guard cells will lead to the closure of a stoma.
9700_s15_qp_41
THEORY
2015
Paper 4, Variant 1
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shows a section through part of a dicotyledonous leaf of the tea plant Camellia sinensis. On , use label lines and letters to label each of the following parts: X – xylem tissue P – palisade mesophyll tissue. The leaves of C. sinensis have a large surface area and are thin. Explain how each of these two features help the leaf to carry out photosynthesis. The lower epidermis contains stomata. State one structural difference between a guard cell and other lower epidermal cells. Abscisic acid has an important role in the closure of a stoma. It promotes the loss of potassium ions from guard cells. Outline how the loss of potassium ions from guard cells will lead to the closure of a stoma.
9700_s15_qp_43
THEORY
2015
Paper 4, Variant 3
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Nerium oleander is a xerophytic plant. A photomicrograph of a section through the leaf of N. oleander is shown in . palisade mesophyll cell vein The leaf shown in has a number of adaptations to reduce water loss by transpiration. Two of these adaptations are: • a multilayered epidermis • stomata only found in depressions, known as stomatal crypts, on the lower surface of the leaf. Explain how a multilayered epidermis and stomatal crypts will help to reduce water loss in N. oleander. multilayered epidermis stomatal crypts Sucrose, amino acids and other assimilates synthesised in palisade mesophyll cells of N. oleander pass to the vein, where they can be transported within specialised cells from the source to the sink. Name the cells specialised for the transport of assimilates in N. oleander. Explain the difference between a source and a sink. One of the enzymes involved in the synthesis of sucrose in the cytoplasm of palisade mesophyll cells is known as cyFBPase. The gene coding for this enzyme is cyFBP. The importance of cyFBPase in plant growth can be investigated using plants with a mutation in gene cyFBP. These plants cannot synthesise cyFBPase. State what is meant by a gene mutation. Suggest one way in which the mutation of cyFBP prevents the synthesis of cyFBPase. Monoclonal antibody can be produced that is specific to cyFBPase. This antibody is used by investigators to check that the plants with the cyFBP mutation do not synthesise this enzyme. In monoclonal antibody production, a small mammal is inoculated with cyFBPase and several weeks later cells are removed from the spleen. Some of these cells are required for the production process. Describe the events occurring within the body of the small mammal that lead to the formation of the cells needed for monoclonal antibody production. Anti-cyFBPase monoclonal antibody is added to extracts taken from the leaves of the plants with the cyFBP mutation. State the expected results following addition of the monoclonal antibody that would confirm the absence of cyFBPase in the leaf extracts. Investigations have shown that plants with the cyFBP mutation grow to a much smaller height and have proportionately far less starch stored in their roots than normal plants. Suggest why plants with the cyFBP mutation will store less starch in their roots.
9700_s18_qp_23
THEORY
2018
Paper 2, Variant 3
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Questions Discovered
36