Tarun cuts across a thin palm trunk and across a thick mango branch…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Tarun cuts across a thin palm trunk and across a thick mango branch. The mango branch shows rings of wood. The palm trunk does not.
- Which of the two plants is a dicot?
- Why does the branch show rings of wood, and the palm trunk does not?
- How does the palm trunk grow, if it grows only upwards?
Need a reminder? The key ideaShow
Secondary growth makes dicot stems and roots thicker. It is done by the vascular cambium and the cork cambium. A dicot vascular bundle is open, with fascicular cambium between the xylem and the phloem. Interfascicular cambium forms from cells of the medullary rays, and the two join into a ring. The cambium cuts off secondary xylem inward and secondary phloem outward, and makes much more xylem than phloem. Monocot bundles are closed and have no cambium. In a dicot root the cambium arises from conjunctive tissue and the pericycle.
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) The mango is a dicot. The palm is a monocot.
Step 2. (b) The mango branch has open bundles with cambium, so the cambium cuts off new xylem and phloem each year. The palm has closed bundles with no cambium, so it makes no new wood.
Step 3. (c) A palm trunk gets taller through its apical meristem. This is primary growth.
Answer: (a) mango; (b) cambium in the mango, none in the palm; (c) by primary growth at the tip.
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