If a metabolic inhibitor prevents the active accumulation of solutes in the guard cells of a grass leaf during the day, what will be the shape of these guard cells, and how will it affect the stomatal pore?
In grasses, the guard cells are characteristically dumb-bell shaped. When active solute accumulation is blocked, guard cells cannot become turgid to open the stomata. Thus, they retain their default dumb-bell shape, and the stomatal pore remains closed.
Question 2 of 115
📘 CLASS XI
If the thick inner walls of dicot guard cells were to lose their rigidity and become as thin and elastic as their outer walls, what would occur when the cells become highly turgid?
Normally, the outer walls of guard cells are thin and elastic, while the inner walls facing the pore are highly thickened. When turgor increases, the outer walls stretch outward, pulling the thick, rigid inner walls into a crescent shape to open the pore. If the inner walls were equally elastic, they would stretch symmetrically, and no opening pull would be generated.
Question 3 of 115
📘 CLASS XI
A researcher treats a seedling with a chemical that completely blocks the development of multicellular appendages on the shoot while leaving unicellular epidermal appendages unaffected. What structural observations will be made on the roots and stems?
According to NCERT, root hairs are unicellular elongations of epidermal cells. On the stem, the epidermal hairs are called trichomes and are usually multicellular. Blocking multicellular appendages will eliminate shoot trichomes while leaving the unicellular root hairs functional.
Question 4 of 115
📘 CLASS XI
What is the physiological consequence of a mutant plant failing to develop trichomes on its aerial shoot system in an arid environment?
Trichomes on the shoot system can be branched/unbranched, soft/stiff, or even secretory. Their primary physiological role is to help in preventing water loss due to transpiration. Without them, the plant will suffer from high transpirational water loss in arid conditions.
Question 5 of 115
📘 CLASS XI
Why is the waxy cuticle layer present on the epidermis of leaves and stems but completely absent on the epiblema of primary roots?
The cuticle is a waxy, thick layer that prevents the loss of water. While this is essential for aerial parts like leaves and stems to reduce transpiration, roots must absorb water and minerals. A waterproof cuticle on roots would act as a barrier to absorption, which is why cuticle is absent in roots.
Question 6 of 115
📘 CLASS XI
In a stomatal apparatus, if the subsidiary cells are selectively destroyed while keeping the guard cells intact, what is the most likely functional outcome?
Subsidiary cells are specialized epidermal cells located in the immediate vicinity of the guard cells. Together with the guard cells and stomatal pore, they form the stomatal apparatus. They assist the guard cells by acting as water reservoirs during rapid turgor pressure adjustments; their destruction impairs the smooth opening/closing mechanism.
Question 7 of 115
📘 CLASS XI
Which of the following statements represents a true structural difference between the cells of the general epidermis and the guard cells?
General epidermal cells are parenchymatous with a small amount of cytoplasm and a large vacuole, but they do not typically have chloroplasts. In contrast, the guard cells possess chloroplasts which allow them to regulate stomatal movements.
Question 8 of 115
📘 CLASS XI
If you observe an epidermal tissue system under a microscope and find both multicellular branched trichomes and stomata with bean-shaped guard cells, what can you definitively conclude about the specimen?
Dicotyledonous plants have bean-shaped guard cells, and multicellular trichomes are characteristic of the shoot system (stems/leaves). Roots do not have trichomes (they have root hairs) or stomata. Thus, the specimen must be a dicot shoot/leaf.
Question 9 of 115
📘 CLASS XI
Why are epidermal cells described as having a small amount of cytoplasm lining the cell wall despite occupying a large volume?
NCERT states that epidermal cells are parenchymatous with a small amount of cytoplasm lining the cell wall and a large vacuole. The massive vacuole occupies the center of the cell, restricting the cytoplasm to a thin peripheral layer.
Question 10 of 115
📘 CLASS XI
How does the ground tissue of a dorsiventral leaf differ fundamentally from the ground tissue of a primary dicotyledonous stem?
In stems and roots, the ground tissue is divided into distinct zones like cortex, pericycle, pith, and medullary rays. However, in leaves, the ground tissue is undifferentiated into these zones and instead consists of thin-walled chloroplast-containing cells called mesophyll.
