Question

An angiosperm lacking vessels is
A. Trochodendron
B. Acacia
C. Salix
D. Dendrocalamus

Answer 1

Xylem is the chief conducting tissue of vascular plants responsible for conduction of water and inorganic solutes. The term xylem was introduced by Nageli. The xylem is composed of four components- Xylem tracheid, xylem vessels, xylem fibres and xylem parenchyma.

Complete answer: The xylem vessels designates a long tube containing a series of drum-shaped cells placed one above the other with their end walls perforated or dissolved. The vessels are thus syncytia formed by the fusion of cells. Each cell appears circular, oval or sometimes polygonal in cross-section with a very wide lumen. They become dead and lose their protoplasm due to deposition of the lignified secondary wall.
Vessels of primary xylem develop from procambium whereas those of secondary xylem develop from vascular cambium. They can also be derived by dissolution of end walls or pit membrane. Each cell is short but due to cell fusion, the tubes become much longer and reach about 10 cm length but in some cases like in Quercus, it may reach upto 2m.
Vessels possess various types of wall thickenings. The most common one are scalariform, reticulate and pitted. The protoxylem vessels possess annular and spiral thickening s which later on becomes scalariform and reticulate due to deposition of more thickening materials. The metaxylem vessels generally possess simple pits,
The vessels of the secondary xylem possess scalariform reticulate and pitted thickenings. The pits may be simple or bordered.
Generally all angiosperms have xylem vessels but genus Trochodendron is an exception. It lacks xylem vessels.
So, the correct answer is “Option A”.

Note: Vessels are chief conducting tissue of vascular plants, particularly in angiosperms. They translocate water and dissolved mineral nutrients from roots to the leaves. They also provide mechanical support to the plant.