Anatomy of the Isobilateral (Monocotyledonous) Leaf
The isobilateral leaf is the monocot counterpart of the dorsiventral leaf, and its anatomy is organised around a striking symmetry: the upper and lower surfaces are anatomically interchangeable. This quiz tests the defining features of that leaf — stomata on both epidermises, mesophyll that is not differentiated into palisade and spongy parenchyma, the remarkable bulliform cells of grasses, and the way parallel venation is reflected in near similar vascular bundle sizes.
You will also be tested on the chapter summary: the three tissue systems, and the differences between monocotyledonous and dicotyledonous plants in the type, number and location of vascular bundles, together with where secondary growth occurs.
Before you begin
- Read each question carefully — several options are close distractors.
- Recall that turgid bulliform cells expose the leaf surface, while flaccid ones make the leaf curl inwards.
- All questions are answerable from the lesson material alone.
Fifteen questions, medium difficulty. Take your time and check each answer against the explanation provided.
Q1. In an isobilateral (monocotyledonous) leaf, where are the stomata present?
The lesson states that in an isobilateral leaf the stomata are present on both the surfaces of the epidermis, unlike the dorsiventral leaf where they are concentrated on the lower epidermis.
Q2. Which feature of the mesophyll distinguishes an isobilateral leaf from a dorsiventral leaf?
In an isobilateral leaf the mesophyll is not differentiated into palisade and spongy parenchyma, whereas the dorsiventral leaf shows this differentiation.
Q3. Bulliform cells are modified from which cells?
In grasses, certain adaxial epidermal cells along the veins modify themselves into bulliform cells.
Q4. Which description best matches bulliform cells?
Bulliform cells are described as large, empty and colourless cells.
Q5. What happens when the bulliform cells of a grass leaf absorb water and become turgid?
When bulliform cells have absorbed water and are turgid, the leaf surface is exposed.
Q6. What is the effect of flaccid bulliform cells on a grass leaf?
When bulliform cells are flaccid due to water stress, they make the leaves curl inwards.
Q7. Why is inward curling of the leaf, caused by flaccid bulliform cells, advantageous to the plant?
The lesson states that curling inwards occurs to minimise water loss under water stress.
Q8. The parallel venation of monocot leaves is reflected in which anatomical feature seen in vertical sections?
The parallel venation in monocot leaves is reflected in the near similar sizes of vascular bundles, except in the main veins.
Q9. Which structural feature is common to BOTH isobilateral and dorsiventral leaves?
Both isobilateral and dorsiventral leaves contain vascular bundles (veins) running through the mesophyll. Stomata restricted to the lower epidermis and palisade/spongy differentiation are features of dorsiventral leaves, while bulliform cells are characteristic of many grasses with isobilateral leaves.
Q10. Which three types of tissue systems are described in the chapter summary?
The summary states there are three types of tissue systems: epidermal, ground and vascular.
Q11. According to the summary, the ground tissue system is divided into which three zones?
The ground tissue system forms the main bulk of the plant and is divided into three zones: cortex, pericycle and pith.
Q12. The epidermal tissue system is made up of which components?
The summary states that the epidermal tissue system is made of epidermal cells, stomata and the epidermal appendages.
Q13. Monocotyledonous and dicotyledonous plants differ in their internal structures with respect to which features of vascular bundles?
The summary states that monocots and dicots differ in the type, number and location of vascular bundles.
Q14. In which of the following does secondary growth occur, according to the chapter summary?
The summary states that secondary growth occurs in most of the dicotyledonous roots and stems.
Q15. Which statement about the isobilateral leaf is correct?
The lesson states that the anatomy of the isobilateral leaf is similar to that of the dorsiventral leaf in many ways, but it differs in having stomata on both surfaces and mesophyll not differentiated into palisade and spongy parenchyma.