Question

The following diagrams show the types of secondary thickening in the xylem vessels. Identify the types labelled from a to f. Choose the correct option from those given.

• A. a = Annular, b = Spiral, c = Scalariform, d = Reticulate, e = Pitted, simple, f = Pitted with border.
• B. a = Spiral, b = Annular, c = Scalariform, d = Reticulate e = Pitted with border, f = Pitted, simple
• C. a = Spiral, b = Annular, c = Reticulate, d = Scalariform, e = Pitted with border, f = Pitted, simple
• D. a = Annular, b = Spiral, c = Scalariform, d = Reticulate e = Pitted with border, f = Pitted, simple

Answer 1

Answer: (D)

a = Annular, b = Spiral, c = Scalariform, d = Reticulate e = Pitted with border, f = Pitted, simple

a) Annular thickening: These are ring like thickening present on the inner side of primary wall.

b) Spiral or helical thickening: These are spiral or helical thickening of secondary wall materials.

c) Scalariform thickening: The thickenings appear as parallel transverse bands like the rungs of a ladder.

d) Reticulate thickening: The secondary wall appears as a network as the meshes remain thin.

e) Bordered pit: In these pits, the pit cavity is partly enclosed by over-arching of the secondary cell wall.

f) Simple pit: A pit is said to be simple where the secondary wall does not arch over the pit chamber and so the rim of the pit aperture contains no border.

So, the correct answer is 'a = Annular, b = Spiral, c = Scalariform, d = Reticulate e = Pitted with border, f = Pitted, simple.'