7.1. Structure of transport tissues
A subsection of Biology, 9700, through 7. Transport in plants
Listing 10 of 147 questions
Explain the need for transport systems in multicellular plants and animals. In mammals, the role of the heart is to pump blood around the body. The events that occur during one heart beat are known as the cardiac cycle. The timing for one cardiac cycle is shown in . V X P Q W Y Z 0.8 0.7 0.6 0.5 0.4 seconds 0.3 0.2 0.1 P and Q represent the two types of heart chambers. V, W, X , Y and Z represent the systolic or diastolic state of the relevant heart chambers. In the spaces provided on , identify chambers P and Q. Complete the table by writing the letters V, W, X, Y and Z in the appropriate box to indicate the state of the heart chambers during the cardiac cycle as shown in . systole diastole In plants, assimilates are transported in phloem sieve tube elements by a process known as translocation. Explain how assimilates that arrive in the phloem sieve tubes from mesophyll cells can be translocated to other parts of the plant.
9700_s14_qp_22
THEORY
2014
Paper 2, Variant 2
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Meristematic tissue is found in the growing regions of plants, such as shoot tips. Meristematic cells have a similar role to stem cells in animals. shows some of the stages in the formation of a mature phloem sieve tube element and companion cells from a meristematic cell. meristematic cell mature sieve tube element and companion cells F G H J E Cells E and F in are daughter cells produced when the meristematic cell divides in the shoot tip. Explain why it is important that one of the daughter cells (cell E) is a meristematic cell. Complete Table 4.1 to describe the changes that are shown in between stages: • F and G • G and H • H and J. Table 4.1 stages description F and G G and H H and J Explain how the structure of a mature sieve tube element is related to its function. Describe the functions of companion cells in transport in the phloem.
9700_s19_qp_21
THEORY
2019
Paper 2, Variant 1
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Questions Discovered
147