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Q.
Unifacial leaves are found in
NTA AbhyasNTA Abhyas 2020
Solution:
There are three main leaf types based on their adaxial–abaxial faces:-
(i) bifacial, (ii) unifacial, and (iii) equifacial.
(i) Bifacial leaf :- the term is usually used as dorsoventral leaf and found in dicots. The adaxial surface of the leaf consists of an epidermis with a relatively thick cuticle and densely packed palisade mesophyll cells, which optimise light capture.
The abaxial (lower) surface of this leaf consists of an epidermis with abundant stomata and spongy mesophyll cells, which function in gas exchange and the regulation of transpiration. In this type of leaves, the leaf vasculature is also aligned along the adaxial–abaxial axis, with xylem tissue differentiating adaxially and the phloem abaxially. This adaxial–abaxial development of xylem and phloem in the leaf vasculature is a reflection of the inner–outer orientation of xylem and phloem in the vascular trace emanating from the shoot axis.
(ii) Unifacial leaves term is used for isobilateral leaves that form tubes, as in the case of onion (Allium cepa) and rushes (Juncus glaucus), have no upper or lower sides, and appear to be derived entirely from abaxial tissues. This type of leaf develops from one side of the leaf primordium.
(iii) Equifacial leaves may be flattened, as in the case of the Satureja, but have adaxial tissue (palisade parenchyma) on both upper and lower sides.