A student made an impression of the lower surface of a leaf by painting on clear nail varnish, letting it dry and peeling off the film. She mounted the impr...
Question 1 Report
A student made an impression of the lower surface of a leaf by painting on clear nail varnish, letting it dry and peeling off the film. She mounted the impression on a slide and viewed it under a microscope. Fig. 2.1 shows the circular field of view, with the small stomata visible as pores in the surface, beside a scale bar. Counting the stomata in a known area allows the stomatal density of the leaf to be worked out. She kept the microscope on the same magnification throughout.
(a) Measure, using Fig. 2.1, the number of stomata visible in the field of view. [1]
(b) Measure, using the scale bar, the diameter of the field of view. [1]
(c) Name the cells that open and close each stoma. [1]
(d) Describe how the student made the impression of the leaf surface. [3]
Answer Details
This question tests counting a microscopic feature, reading a scale bar, and describing the nail-varnish impression technique.
(a) Counting the pores visible in the field of view gives 12 stomata (accept 11 to 13) [1].
(b) Reading the field of view against the scale bar, its diameter is about 1.0 mm (accept 0.9 to 1.1) [1].
(c) The cells that open and close each stoma are the guard cells [1].
(d) To make the impression, the student painted clear nail varnish onto the lower leaf surface [1], allowed it to dry [1], then peeled off the dried film and mounted it on a slide [1]. [3]
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