- Which of the following statements is not true for stomatal
apparatus?
(a) Guard cells invariably possess chloroplasts and
mitochondria.
(b) Guard cells are always surrounded by subsidiary cells.
(c) Stomata are involved in gaseous exchange.
(d) Inner wall of guard cells are thick.
(NEET - Karnataka 2013)
Assertion & Reason
The following questions consist of two statements each :
assertion (A) and reason (R). To answer these questions,
mark the correct alternative as directed below :
(a) If both A and R are true and R is the correct explanation
of A.
(b) If both A and R are true but R is not the correct
explanation of A.
(c) If A is true but R is false.
(d) If both A and R are false.
Assertion : Exudation of sap from cut or injured parts
of plants is called bleeding.
Reason : Bleeding occurs due to root pressure, phloem
pressure and local pressure in xylem.
Assertion : Loss of water in the form of liquid droplets
from leaves of plants is called transpiration.
Reason : Transpiration takes place through special
structures called hydathodes.
Assertion : (^) Xylem transport is unidirectional.
Reason : Phloem transport is bi-directional.
Assertion : Transpiration is an unavoidable evil.
Reason : Plants cannot regulate transpiration.
- Assertion : Guttation drops are restricted to tips or
margins of leaves while dew drops are found all over
the plant.
Reason : Both dew drops and guttated water are pure
water.
Short Answer Type Questions - Read the following statements and fill in the blanks with
correct words/terms.
(i) Rate of transpiration is when relative humidity
is .
(ii) and are antitranspirants which reduce
transpiration by reducing the stomatal opening for
a period of few weeks, without influencing other
metabolic activities.
(iii) The movement of ions from soil to interior of root
requires _____.
(iv) Mineral elements pass up xylem in both _____ and
_____ form.
(v) In_____ there is no external symptom, but mesophyll
cells lose sufficient water due to transpiration being
higher than the availability of water.- How do surface films check transpiration?
- What adaptations are found in xerophytic plants to
reduce the rate of transpiration?
Answer Key
New MCQs- (d) 2. (d) 3. (b) 4. (c) 5. (d)
- (b) 7. (c) 8. (c) 9. (a) 10. (b)
- (d) 12. (c) 13. (b) 14. (b) 15. (a)
- (d) 17. (a) 18. (b) 19. (a) 20. (d)
Exam Section- (a) 2. (c) 3. (a) 4. (a) 5. (b)
- (c) 7. (a) 8. (c) 9. (b) 10. (d)
- (c) 12. (a) 13. (b) 14. (a) 15. (d)
- (d) 17. (c) 18. (d) 19. (b) 20. (d)
- (a) 22. (d) 23. (b) 24. (b) 25. (b)
Assertion & Reason - (a) 2. (d) 3. (b) 4. (c) 5. (c)
Short Answer Type Questions- (i) higher/lower, lower/higher
(ii) Phenyl mercuric acetate, ABA
(iii) active transport
(iv) inorganic, organic
(v) incipient wilting - Film forming chemicals check transpiration by forming a
thin film on the transpiring surface. They are sufficiently
permeable to carbon dioxide and oxygen and allow
photosynthesis and respiration but prevent movement
of water vapours through them. - The sunken (deep seated) stomata and leaf modifications
such as formation of prickles, leaf spines, phyllodes
etc., are some adaptations in xerophytes which help in
reducing the rate of transpiration.
nn