Question

In a dorsiventral leaf, what is true regarding the position of xylem?
A) Xylem is towards adaxial epidermis.
B) Xylem is towards abaxial epidermis.
C) Xylem surrounds phloem.
D) Xylem is surrounded by phloem.

Answer 1

Xylem is a transport tissue present in vascular plants.The xylem is responsible for keeping a plant hydrated by transporting water from roots to stems and leaves.

Complete answer:
The leaf is the primary photosynthetic organ of the plant. It is an outgrowth from the stem of a vascular plant and has a flattened structure. Free exchange of nutrients, water, and end products of photosynthesis can be carried to various parts through the leaf. Major leaf tissues include epidermis, mesophyll and vascular tissue. The internal structure of the leaf is covered by the leaf epidermis, which is continuous with the stem epidermis. Epidermis is a waxy cuticle, impermeable to water and protects the plant by acting as a boundary separating the plant’s inner cells from the external world. The mesophyll consists of soft-walled, unspecialized parenchyma cells. One-fifth of the mesophyll consists of chlorophyll-containing chloroplasts. In most flowering plants, the mesophyll is divided into a palisade layer and a spongy layer.
The vascular tissue is a conducting tissue formed of more than one type of cell, and is found in vascular plants. Its primary components are xylem and phloem which transport fluid and nutrients internally. They are long and slender cells and are connected end to end forming vascular bundles. In stem, xylem lies close to the interior of the stem and phloem to the exterior. During the secondary growth in plants, the activity of xylem and phloem is controlled by the cambium to form annual rings.In leaves, the vascular bundles are located among the spongy mesophyll. The xylem lies towards the adaxial surface of the leaf (usually the upper side) and phloem is on the abaxial surface of the leaf.

Hence, the correct option is A, ‘xylem is towards the adaxial epidermis ’.

Note: The dorsiventral leaf is a structure that has a distinct dorsal (upper) and ventral (lower) surface found in dicots.Here xylem lies toward the upper epidermis or the adaxial epidermis (facing towards the stem of a plant).