O-LevelBiologyTransport in Plants5090/22 · May/June 2023 · Q515 Marks

Fig. 5.1 is a photomicrograph of the centre of a plant root. [Figure 5.1]

(a)(i)Identify each of the tissues labelled J and K. J K[2]
(a)(ii)State the term used to describe the group of tissues labelled L.[1]
(a)(iii)State two ways in which the structure of a cell in tissue K will differ from a cell in tissue J. 1 2[2]
(a)(iv)Outline the function of tissue J.[4]
(b)(i)Name the type of response shown by a plant root when it grows down into soil after the seed has germinated.[2]
(b)(ii)Explain how this response shown by the plant root is necessary for the leaves to grow and to appear green.[4]

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Mark scheme

Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.

[2] (J) phloem ; (K) xylem;
[1] vascular bundle / organ ;
[2] K xylem / ORA J phloem: thick wall; thin wall; lignin / lignified; no lignin; no + cell contents /organelles / named organelles; cell + contents / organelles / named organelles; no + end wall / cross wall / sieve plates; sieve plates; no + companion cell; companion cell;
[4] 1 translocation; 2 (transport) sucrose ; 3 (transport) amino acids ; 4 from where produced / source + where used / to sink ; 5 bidirectional AW flow;
[2] gravitropism; positive + (gravitropism);
[4] 1 absorbs/ take up water; 2 absorb / take up + ions / named ion / minerals ; 3 water + cell elongation AW ; 4 photosynthesis ; 5 magnesium + chlorophyll ; 6 nitrates + amino acids / proteins;

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