MediumBiologyHigh School (11–12)Tissues and Organs › Anatomy of Flowering PlantsConceptualA-LevelIBNEET
Hira is given two unlabelled stem slides…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Hira is given two unlabelled stem slides. Slide 1 shows scattered vascular bundles, each in a sheath of sclerenchyma, and a rim of sclerenchyma under the epidermis. Slide 2 shows eight bundles in a ring, a wide pith and bands of cells between the bundles. (a) Which slide is a monocot stem, and which is a dicot stem? (b) What is the layer under the epidermis in each? (c) Name the bands between the bundles on slide 2.
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 classes. Scattered, closed bundles with sheaths mean a monocot stem: slide 1. A ring of bundles round a pith means a dicot stem: slide 2.
Step 2. The hypodermis. In slide 1 it is sclerenchyma. In slide 2 it is collenchyma.
Step 3. The bands. The radial bands of parenchyma between the bundles are the medullary rays.
Answer: (a) slide 1 is the monocot stem and slide 2 is the dicot stem; (b) sclerenchyma in slide 1 and collenchyma in slide 2; (c) medullary rays.
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