7.1. Structure of transport tissues
A subsection of Biology, 9700, through 7. Transport in plants
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When water molecules enter a plant through the roots, the molecules cross the cortex and enter the xylem tissue to be transported to other parts of the plant. There are two pathways that water can take when crossing the root to the xylem tissue. Complete Table 5.1 with information about the two pathways. Table 5.1 name of pathway outline of pathway movement of water from cell to cell through plasmodesmata is a photomicrograph of a transverse section through the stem of a flowering plant. On , draw a label line and the letter T to identify xylem tissue. Scientists have studied the process of cell death that occurs during the development of the cells that become mature xylem vessel elements. During this development, the tonoplast ruptures and releases hydrolytic enzymes contained in the vacuole into the cytoplasm. Name an organelle found in animal cells that has a similar function to the vacuole in the developing xylem vessel elements. The rupture of the tonoplast during development of xylem vessel elements is due to changes in permeability of the tonoplast. Suggest how the permeability of the tonoplast changes and explain how this change could result in the rupture of the tonoplast. During development of the xylem vessel elements the pH of the cytoplasm decreases. This change in pH activates enzymes in the cytoplasm that cause organelles to swell. Suggest how a change in pH of the cytoplasm can activate enzymes. Some insects are vectors of disease. When an insect feeds on the xylem fluid it can act as a vector of plant diseases such as Pierce’s disease. This bacterial disease affects many fruit trees causing the leaves to turn brown and drop from the plant, resulting in much less fruit being produced. Explain why Pierce’s disease can be described as an infectious disease. Malaria is another infectious disease that also involves an insect vector. State the type of organism that causes malaria and name one organism that causes malaria in humans. type of organism name
9700_w22_qp_21
THEORY
2022
Paper 2, Variant 1
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