HardBiologyHigh School (11–12)Tissues and Organs › Anatomy of Flowering PlantsConceptualA-LevelIBNEET
On a hot afternoon, a farmer sees the leaf blades of her maize plants rolling inwards…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
On a hot afternoon, a farmer sees the leaf blades of her maize plants rolling inwards. By evening, they are flat again. (a) Which cells cause the rolling, and where do they lie? (b) What happens to them when the plant is short of water? (c) Why does the rolling help the plant? (d) Is the maize leaf dorsiventral or isobilateral, and how are its stomata placed?
Need a reminder? The key ideaShow
Dicot leaf (dorsiventral): adaxial and abaxial epidermis with cuticle, more stomata on the abaxial face; mesophyll of palisade parenchyma (upper, long cells, many chloroplasts) and spongy parenchyma (lower, loose, air cavities); reticulate venation; xylem towards the upper side and phloem towards the lower side of a bundle with a bundle sheath. Monocot leaf (isobilateral): stomata on both faces, mesophyll not differentiated, parallel venation, bundles nearly equal; bulliform cells on the upper epidermis help the leaf to curl in dry weather.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The cells. They are the bulliform cells, large empty cells in rows along the veins of the upper epidermis.
Step 2. In dry weather. They lose water and become limp.
Step 3. The gain. The leaf curls inwards and shows less surface to the air. So less water is lost.
Step 4. The leaf type. Maize is a monocot, with an isobilateral leaf. Its stomata are on both faces.
Answer: (a) bulliform cells, on the upper epidermis along the veins; (b) they lose water and go limp; (c) the leaf curls and loses less water; (d) isobilateral, with stomata on both faces.
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