Question

Gymnosperms generally lack:
A. Xylem tracheids and sieve tubes in phloem
B. Xylem vessels and sieve tubes in phloem
C. Xylem vessels and companion cells in phloem
D. Xylem tracheids and companion cells in phloem

Answer 1

Hint: Gymnosperms are plants having seeds and in which the seeds remain open over the surface of the megasporophylls because they are not folded to form pistils. Gymnosperms are a smaller group of seed plants that are represented by only 900 living species. They are more ancient than the angiosperms. They used to be the dominant vegetation on earth around 200 million years ago in the mesozoic era.

Complete answer:
Xylem is the water conducting tissue found in vascular plants. There are two types of cells that perform the process viz. tracheids and vessel elements. The vessel elements are the building blocks of vessels that form these vessels, which is responsible for the major role of the water conducting system in the plants in which they occur. Vessels form an elaborate system for transporting water and necessary minerals from the root to the leaves and other parts of the plant.
The phloem distributes the sugars, amino acids, and organic nutrients synthesized in the leaves to the non-photosynthetic tissues of the plant. Vascular tissues are arranged systematically into vascular bundles just like angiosperms except for a few cells that are absent in gymnosperms. Vascular bundles of stem are open-type so that secondary growth is quite common.
a) Gymnosperms like Gnetales species have the presence of xylem tracheids and sieve tubes in phloem in their vascular system.
b) While Xylem vessels are absent in Gymnosperms, they still have sieve tubes in their phloem part of the vascular system.
c) Gymnosperms lack flowers, this trait distinguishes them from angiosperms; They also lack xylem vessel elements and companion cells in their phloem. Instead, these have albuminous cells in the place of companion cells for the conduction of food throughout the length of the plant.
d) Although the gymnosperms have xylem tracheids, they still don’t have companion cells like the angiosperms. They lack vessels except the Gnetum species but possess tracheids. Infact, tracheids constitute 90−95% of wood in gymnosperms.

So, the correct answer is option (C) Xylem vessels and companion cells.

Note:
All gymnosperms grow in all the seasons and are woody in texture. They form either small bushes or large trees. Some of these are massive and live for thousands of years, e.g., Sequoia species (tallest gymnosperm) and the Zamia species is the smallest. Flowers are absent in these plants. The two types of sporophylls that are: microsporophylls and megasporo­phylls are usually present in a cluster to form distinct cones known as strobili that bear pollen cones i.e., male cones and seed cones i.e., female cones, respectively.