$$$2 \quad \mathrm{P} 1$$$ is a slide of a stained transverse section through a plant leaf. Fig. 2.1 is a photomicrograph of a transverse section through a leaf of a different species of plant. (i) Identify three observable features, other than colour, that are different between the leaf in Fig. 2.1 and the leaf on P1. Record the differences between these three observable features in Table 2.1. (ii) The leaf section shown in Fig. 2.1 is from a plant that is adapted to live in water. State one feature visible in Fig. 2.1 that adapts the plant to live in water. Suggest the function of this feature. feature ........................................................................................................................... function .......................................................................................................................... ....................................................................................................................................... .

Biology

IGCSE&ALevel

CAIE

Exam No：9700_m24_qp_33 Year：2024 Question No：2(b)

Answer:

Knowledge points:

7.1.1 draw plan diagrams of transverse sections of stems, roots and leaves of herbaceous dicotyledonous plants from microscope slides and photomicrographs

7.1.2 describe the distribution of xylem and phloem in transverse sections of stems, roots and leaves of herbaceous dicotyledonous plants

7.1.3 draw and label xylem vessel elements, phloem sieve tube elements and companion cells from microscope slides, photomicrographs and electron micrographs

7.1.4 relate the structure of xylem vessel elements, phloem sieve tube elements and companion cells to their functions

7.2.1 state that some mineral ions and organic compounds can be transported within plants dissolved in water

7.2.2.1 apoplast pathway, including reference to lignin and cellulose

7.2.2.2 symplast pathway, including reference to the endodermis, Casparian strip and suberin

7.2.3 explain that transpiration involves the evaporation of water from the internal surfaces of leaves followed by diffusion of water vapour to the atmosphere

7.2.4 explain how hydrogen bonding of water molecules is involved with movement of water in the xylem by cohesion-tension in transpiration pull and by adhesion to cellulose in cell walls

7.2.5 make annotated drawings of transverse sections of leaves from xerophytic plants to explain how they are adapted to reduce water loss by transpiration

7.2.6 state that assimilates dissolved in water, such as sucrose and amino acids, move from sources to sinks in phloem sieve tubes

7.2.7 explain how companion cells transfer assimilates to phloem sieve tubes, with reference to proton pumps and cotransporter proteins

7.2.8 explain mass flow in phloem sieve tubes down a hydrostatic pressure gradient from source to sink

Answer:

Knowledge points:

Solution:

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