Sample 1Easy
In grasses, the guard cells of the stomata are
- A
bean-shaped
- B
dumb-bell shaped
- C
spherical
- D
cuboidal
Show the answer
The answer is B.Each stoma is bordered by two guard cells. In grasses the guard cells are dumb-bell shaped, while in other plants they are bean-shaped.
- A.
Bean-shaped guard cells are found in most plants other than grasses.
- C.
Guard cells are not described as spherical in any plant.
- D.
Guard cells are not cuboidal.
NCERT: Class 11 Biology, Chapter 6 (Anatomy of Flowering Plants), The Tissue System, Epidermal Tissue System
Sample 2Medium
A figure shows a transverse section of a young plant organ, from outside inwards. A is an outer layer of cells, many with unicellular hairs. B is several layers of thin-walled parenchyma. C is a single layer of barrel-shaped cells whose radial and tangential walls carry suberin bands. D is a few layers of thick-walled parenchyma just inside C. Inside D, two to four patches of xylem alternate with patches of phloem on different radii. Which labelled layer initiates lateral roots and the vascular cambium during secondary growth?
- A
A, the epiblema
- B
D, the pericycle
- C
B, the cortex
- D
C, the endodermis
Show the answer
The answer is B.The section is of a dicot root: epiblema, cortex, endodermis with Casparian strips, then the pericycle, with radial vascular bundles. Lateral roots and the vascular cambium of secondary growth are initiated in the pericycle.
- A.
A is the epiblema, the outer layer that bears root hairs. It does not initiate lateral roots.
- C.
B is the cortex, made of thin-walled parenchyma with intercellular spaces. It does not give rise to lateral roots.
- D.
C is the endodermis, whose Casparian strips make it impermeable to water. Lateral roots arise from the layer just inside it.
NCERT: Class 11 Biology, Chapter 6
Sample 3NEET level
Assertion (A): The vascular bundles of a monocotyledonous stem are conjoint and closed. Reason (R): In a monocotyledonous stem the vascular bundles are scattered and each is surrounded by a sclerenchymatous bundle sheath. Choose the correct answer from the options given below.
- A
Both A and R are true and R is the correct explanation of A
- B
Both A and R are true but R is not the correct explanation of A
- C
A is true but R is false
- D
A is false but R is true
Show the answer
The answer is B.Monocot stem bundles are conjoint (xylem and phloem on the same radius) and closed because they have no cambium between xylem and phloem. They are also scattered and sheathed by sclerenchyma, which is true but is not why they are closed.
- A.
The bundles are closed because cambium is absent, not because they are scattered or sheathed.
- C.
R is true: monocot stem bundles are scattered, each with a sclerenchymatous bundle sheath.
- D.
A is true: monocot stem bundles are conjoint and closed.
NCERT: Class 11 Biology, Chapter 6 (Anatomy of Flowering Plants), Monocotyledonous Stem