Question

Consider the following statements and choose the correct option.
(i) The thread like cytoplasmic strands, running from one companion cell to a sieve cell is called as plasmodesmata.
(ii) Fibres are absent in both xylem and phloem in a dicotyledonous leaf.
(iii) The first form xylem elements are described as metaxylem.
(iv) Radial vascular bundles are mainly found in the leaves.

• A. (i) is true, but (ii), (iii) and (iv) are wrong.
• B. (ii) is true, but (i), (iii) and (iv) are wrong.
• C. (iii) is true, but (i), (ii) and (iv) are wrong.
• D. (iv) is true, but (i), (ii) and (iii) are wrong.
• E. (i) and (ii) are true, but (iii) and (iv) are wrong.

Answer 1

The correct option is E (i) and (ii) are true, but (iii) and (iv) are wrong.

The sieve tube cells are alive but lack nuclei and other organelles. Phloem sieve tube elements can live for years. This ability is provided by adjacent companion cells as the companion cells have complex cytoplasm with mature organelles and provide the metabolic and homeostatic needs of the sieve tube elements through plasmodesmata. Plasmodesmata is the small channel that connects the cytoplasm of two cells.
In a dicot leaf, phloem is towards lower epidermis, xylem is towards upper epidermis, with metaxylem facing phloem. Fibres are absent in both xylem and phloem. When different type of vascular bundle meets in the same plane is called as radial vascular bundle found in roots of monocot and dicot.
Thus, the correct answer is option A.