HardBiologyHigh School (11–12)Tissues and Organs › Anatomy of Flowering PlantsTissues and Organs › Plant TissuesConceptualA-LevelIB
Ravi looks at a primary xylem strand under a microscope…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Ravi looks at a primary xylem strand under a microscope. The narrow cells of the protoxylem are near the outside, and the wide cells of the metaxylem are near the centre.
- Which organ is it from, a stem or a root?
- What name is given to this arrangement?
- Which kind of xylem forms first, the protoxylem or the metaxylem?
Need a reminder? The key ideaShow
Xylem carries water and minerals: tracheids, vessels, xylem fibres (dead) and xylem parenchyma (living). Phloem carries food: sieve tube elements, companion cells, phloem parenchyma (living) and phloem fibres (dead). In a stem the protoxylem lies towards the centre (endarch); in a root it lies towards the outside (exarch).
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. (a) In a stem the protoxylem is towards the centre. Here it is towards the outside, so the organ is a root.
Step 2. (b) This is exarch xylem.
Step 3. (c) The protoxylem forms first. The metaxylem forms later.
Answer: (a) a root; (b) exarch; (c) the protoxylem.
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