7. Transport in plants
A section of Biology, 9700
Listing 10 of 457 questions
Water and mineral ions are transported up the stem of a plant to the leaves within xylem vessels. Some water and mineral ions can pass out of xylem vessel elements to supply parenchyma tissue in the stem. is a plan diagram of a section through a stem. Identify one location where xylem tissue occurs in the stem by drawing a label line and the letter X on . Explain how hydrogen bonding between water molecules contributes to the movement of water within xylem vessels up the stem to the leaves. is a diagram of a photomicrograph showing three adjacent parenchyma cells in the stem. These parenchyma cells can be described as typical plant cells. The arrows show the direction of movement of water between the cells. A B C Describe and explain the movement of water shown in . Only some of the structures visible using the light microscope have been included in . List the features that can be seen using the high power of a light microscope that help identify a parenchyma cell as a plant cell and not as an animal cell.
9700_s20_qp_23
THEORY
2020
Paper 2, Variant 3
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The transport tissues of plants are phloem and xylem. The role of xylem is the transport of water and mineral ions from the soil solution to the different parts of the plant body. The role of phloem is the translocation of assimilates and other substances from sources to sinks. The source of mineral ions for the plant is the soil solution. These mineral ions are transported from the roots in the xylem. Mineral ions are also found in the phloem sap within phloem sieve tubes. Suggest why mineral ions are found within phloem sieve tubes and state how they are transported within phloem sieve tubes. Phloem tissue consists of different cell types. Complete the passage using the most appropriate terms to summarise some of the features of phloem tissue. The end walls of sieve tube elements are modified to allow efficient flow of phloem sap by the formation of . These structures also prevent the cells from bursting under pressure. The cytoplasm of sieve tube elements is very much reduced and is found at the of the cells. Most of the organelles in the cell are absent. Adjacent to sieve tube elements are cells that carry out the metabolic processes of the missing organelles, allowing the sieve tube elements to function. The boundaries and names shown, the designations used and the presentation of material on any maps contained in this question paper/insert do not imply official endorsement or acceptance by Cambridge Assessment International Education concerning the legal status of any country, territory, or area or any of its authorities, or of the delimitation of its frontiers or boundaries.
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THEORY
2022
Paper 2, Variant 2
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Phloem and xylem are specialised tissues involved in the transport of water, ions and assimilates in plants. A photomicrograph of a transverse section of a dicotyledonous stem is shown in . Use label lines and labels to identify the phloem tissue and xylem tissue in . Describe how sucrose is transported in phloem sieve tubes from photosynthesising leaves to other parts of the plant. Cyanide ions (CN–) inhibit the activity of an enzyme involved in respiration. Suggest why the treatment of photosynthesising leaves with CN– results in less sucrose being transported into phloem sieve tubes. A student was asked to carry out semi-quantitative Benedict’s tests on two solutions. • Solution A was extracted from the cytoplasm of cells in the mesophyll tissue of photosynthesising leaves. • Solution B was extracted from the phloem sap in phloem sieve tubes. The solutions were taken from the same plant, and other variables were standardised. For each solution, the student measured the time taken for the first colour change to appear. Suggest which of the two solutions, A or B, would change colour in the shortest time. Explain your answer.
9700_s23_qp_23
THEORY
2023
Paper 2, Variant 3
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Use shows an electron micrograph of some xylem vessels in tobacco leaf fragments in a cigarette. magnification = × 395 Describe and explain two features of the xylem vessels, visible in , that are adaptations for the transport of water in a plant. feature explanation feature explanation Explain the mechanisms that cause movement of water in xylem vessels. Examiner’s Use When tobacco leaf fragments in cigarettes are burnt, substances that are hazardous to health are released. Name three of these hazardous substances and for each describe one effect on the body. substance effect substance effect substance effect
9700_w07_qp_2
THEORY
2007
Paper 2, Variant 0
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Questions Discovered
457