Mira counts the stomata on a guava leaf…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Mira counts the stomata on a guava leaf. The lower surface has about nine times as many stomata as the upper surface. (a) What kind of leaf is this, dorsiventral or isobilateral? (b) Name the two layers of mesophyll in it and say which lies on the upper side. (c) Give a reason why most stomata face downwards.
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 kind of leaf. It is a dicot leaf, so it is dorsiventral.
Step 2. The mesophyll. Palisade parenchyma lies on the upper side. Spongy parenchyma lies on the lower side.
Step 3. The reason. The lower face is away from the sun and stays cooler. Pores there lose less water vapour.
Answer: (a) dorsiventral; (b) palisade (upper) and spongy (lower) parenchyma; (c) the lower face is cooler and in shade, so fewer water molecules escape.
Discussion (0)
Log in to join the discussion.
Loading…