Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
Neha studies bundles on three slides. Slide P is from a young stem: a strip of cells that can divide lies between the xylem and the phloem, and the phloem is only on the outer side. Slide Q is from a grass stem: there is no such strip. Slide R is from a root: the xylem and the phloem are in separate patches, and the first-formed vessels are at the outer edge. (a) Is the bundle on slide P open or closed, and which class of plant is it from? (b) Is slide Q open or closed? (c) What are the bundle arrangement and the xylem type on slide R?
Epidermal tissue system: epidermis with cuticle (cutin, absent in roots), stomata (bean-shaped guard cells in dicots, dumb-bell in grasses; thick inner wall, thin outer wall; subsidiary cells; the stomatal apparatus), root hairs (unicellular) and trichomes (multicellular, on stems). Ground tissue system: all but epidermis and vascular bundles; cortex, pericycle, medullary rays, pith; mesophyll in leaves. Vascular tissue system: xylem and phloem; open bundles (cambium, dicot stem) and closed (monocot stem); conjoint (stems, leaves) and radial (roots); collateral and bicollateral; endarch xylem in stems, exarch in roots.
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. Slide P. The dividing strip is the cambium, so the bundle is open. A conjoint, collateral, open bundle belongs to a dicot stem.
Step 2. Slide Q. A grass is a monocot. With no cambium, its bundle is closed.
Step 3. Slide R. Xylem and phloem on different radii are radial. Protoxylem at the outer edge is exarch xylem.
Answer: (a) open, from a dicot; (b) closed; (c) a radial bundle with exarch xylem.
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