Question

The number of stomata and epidermal cells in 1 $m{m}^2$ area of abaxial surface of leaves a, b, c and d are :

Plant	Number of Stomata	Number of Epidermal cells
a	40	730
b	60	510
c	70	450
d	30	620

Identify two plants having least stomatal index

• A. b and c
• B. a and d
• C. a and c
• D. a and b

Answer 1

The correct option is B a and d

Stomatal index is the percentage which the number of stomata forms to the total number of epidermal cells, both per unit area of concern. Stomatal index can be calculated using the equation: SI % = (S / (S+E)) * 100 where,

S = No. of stomata per unit area,

E = No. of epidermal cells in the same unit area.

From the question, it is given that

Plant a : S = 40,

E = 730,

SI % = (40 / (40+730)) * 100 = (40 / 770) * 100 = 0.0519 * 100 = 5.19

Plant b : S = 60,

E = 510,

SI % = (60 / (60+510)) * 100 = (60 / 570) * 100 = 0.105 * 100 = 10.5

Plant c : S = 70,

E = 450,

SI % = (70 / (70+450)) * 100 = (70 / 520) * 100 = 0.134 * 100 = 13.4

Plant d : S = 30,

E = 620,

SI % = (30 / (30+620)) * 100 = (30 / 650) * 100 = 0.0461 * 100 = 4.61

Therefore, two plants having least stomatal index is 4.61 and 5.19 i.e, plant d and plant a.

So, the correct answer is option B.