Question

In angiosperms, transport of food and water is more efficient than gymnosperms and pteridophytes. In angiosperms longitudinally arranged sieve elements and vessels with perforated end walls are present.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

The Correct Option is A

Vessels are much elongated tubes which are closed at either end and are formed by the union of several short, wide and thickened cells called vessel elements. The end walls of vessel elements are transverse or oblique. They are often completely dissolved. The condition is called simple perforation plate. In a few cases the end walls remain intact and possess several pores in reticulate, scalariform or forminate forms. Such an end wall is called multiple perforation plate. Sieve tubes are elongated tubular conducting channels of phloem formed of several cells called sieve tube elements or members or sieve tube cells. Sieve tube members are placed end to end. The end walls are generally bulged out. They may be transverse or oblique. They have many small pores or sieve pits. Due to the presence of sieve pits the end walls are commonly called sieve plates. In some cases the end walls of sieve elements possess more than one porous area. Such an end wall is called compound sieve plate. Gymnosperms & pteridophytes lack these two vascular structures i.e. vessels and sieve elements. In angiosperms presence of vessels & sieve elements in addition to all other vascular tissues make their food & water transport more efficient.