Question

Which of the following features makes leaves of gymnosperms anatomically unique?
(a) Mesarch condition
(b) Collateral closed vascular bundles
(c) Transfusion tissue
(d) All of the above

Answer 1

Hint Gymnosperms are the plants in which seeds are naked. They are also called conifers that grow in cold climatic conditions. They have various industrial uses. They are used in making paper, resin and gums. They are also used for making perfumes.

Complete answer
In mesarch condition, the development of the protoxylem of the primary xylem first occurs from the middle of the stand centrifugally and centripetally i.e. in both directions. The metaxylem is present at the centre and the periphery while the protoxylem is present in between the metaxylem. This type of mesarch development is seen in the leaves and stems of most of the ferns.
In the stem of monocots, collateral and closed vascular bundles are present. Collateral closed vascular bundles means phloem is external to xylem i.e. xylem is inside, there is no cambium between the vascular bundles. The xylem and phloem are on the same line (collateral).
Transfusion tissue helps in the lateral conduction of water. The presence of transfusion tissue in the leaves of gymnosperms makes it anatomically unique. It surrounds the vascular bundles of gymnosperms. Both living and non-living cells are present in transfusion tissue. As lateral veins are absent in gymnosperms, it compensates for the absence of these veins by conducting water laterally.

Thus the answer of the above question is (C) transfusion tissue, as it is an anatomically unique character found in the leaves of gymnosperms only. From the above explanation, it is clear that mesarch condition and collateral closed vascular bundles are absent in the leaves of gymnosperms.

Note: As gymnosperms grow in very cool climatic conditions, they have needle-like leaves to drop the fallen ice. They are evergreen plants in which the leaves do not fall during a particular time of the year. Examples of gymnosperms include Cycas, Pinus, and Ginkgo etc.