MediumBiologyHigh School (11–12)Tissues and Organs › Anatomy of Flowering PlantsConceptualA-LevelIBNEET
A root takes up water and dissolved minerals from the soil…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A root takes up water and dissolved minerals from the soil. Between the cortex and the vascular tissue there is a layer whose cells carry waxy strips on their radial and inner walls. (a) Name the layer and the waxy material. (b) Why can water not move between the cells of this layer? (c) What does this force the water to do, and why is that useful?
Need a reminder? The key ideaShow
Dicot root: epidermis with root hairs, cortex, endodermis with Casparian strips of suberin, pericycle (lateral roots), radial bundles with two to four xylem strands (tetrarch), conjunctive tissue, small pith. Monocot root: same plan, more than six xylem strands (polyarch), large pith, no secondary growth. Dicot stem: epidermis with cuticle and trichomes, collenchymatous hypodermis, parenchymatous cortex, starch sheath endodermis, sclerenchymatous pericycle patches, medullary rays, a ring of conjoint open endarch bundles, a large pith. Monocot stem: sclerenchymatous hypodermis, ground tissue with no pith, scattered conjoint closed bundles with sheaths, smaller bundles near the edge, water-containing cavities.
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 layer. It is the endodermis. The waxy material is suberin, in the Casparian strips.
Step 2. The block. Suberin does not let water through. So water cannot squeeze through the walls between the cells.
Step 3. The result. The water must pass through the living cells of the endodermis. The cells can then control which minerals enter the xylem.
Answer: (a) the endodermis, with suberin in the Casparian strips; (b) the waxy strips are watertight; (c) water must pass through the living cells, so the root controls what reaches the xylem.
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