Plant Physiology: II. Plant Nutrition

21. Nitrogen is taken by plants in the form of : [Jharkhand P.C.S. (Pre) 2021]

(a) Oxide
(b) Nitrate
(c) Nitric acid
(d) Chloride

Correct Answer: (b) Nitrate

Solution:Nitrogen is one of the most essential nutrients for plant growth. Although nitrogen gas in the atmosphere represents the largest quantity of the nutrient in the environment, it is unavailable to most plants as a direct source. Nitrogen is normally absorbed by plants from soil in the form of nitrate (NO₃⁻) ions, although in acid environments such as boreal forests, where nitrification is less likely to occur, ammonium (NH₄⁺) is more likely to be the dominant source of nitrogen.

22. Which of the following nutrient is necessary for 'Nodule Formation' in legumes? [U.P. B.E.O. (Pre) 2019]

(a) Nitrogen
(b) Silicon
(c) Boron
(d) None of the above

Correct Answer: (c) Boron

Solution:Boron is an essential micronutrient for plants. It is essential for development and growth of new cells in plant meristem. It is necessary for 'Nodule Formation' in legumes. It is associated with translocation of sugars, starches, nitrogen and phosphorus.

23. Identify parasite in the following? [R.A.S./R.T.S. (Pre) 1997]

(a) Pitcher plant
(b) Cuscuta
(c) Sunflower
(d) Bladderwort

Correct Answer: (b) Cuscuta

Solution:Cuscuta (dodder) is a genus of about 100–170 species of yellow, orange or red parasitic plant. Dodder can be identified by its thin stems-appearing leafless, with the leaves reduced to minute scales. The Dodder produces haustoria. It is used in traditional medicine as a purgative and to treat disorders of the liver, spleen and urinary tract.

24. Consider the following statements : [U.P. R.O./A.R.O. (Pre) 2016]

Assertion (A) : Cuscuta (Amarbel) is an example of parasitic angiosperm.
Reason (R) : It gets its nutrition from the leaves of the host plant.

Choose your answer from the code 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) Assertion (A) is false, but (R) is true.
(d) Assertion (A) is true, but (R) is false.

Correct Answer: (d) Assertion (A) is true, but (R) is false.

Solution:Cuscuta is a rootless, yellow coloured plant with a slender stem which twines around the stem of the host. It is an example of parasitic angiosperm. It develops haustoria which enter the host plant forming contact with xylem and phloem of the host. It absorbs the prepared food, water and minerals from the host plant.

25. Crop logging is a method of - [U.P.P.C.S. (Pre) 2006]

(a) Soil fertility evaluation
(b) Plant analysis for assessing the requirement of nutrients for crop production
(c) Assessing of crop damage
(d) Testing suitability of fertilizers

Correct Answer: (b) Plant analysis for assessing the requirement of nutrients for crop production

Solution:Crop-logging may be of great help to determine the adequate levels of different nutrients for good plant growth and high yield. The concept of crop-logging was developed by Clements of USA for the growing of sugarcane in Hawaii, where the fertilizer requirements of this crop are greatly influenced by weather and climate. Crop-logging is a method of plant analysis for assessing the requirement of nutrients for crop production.