12th biology chapter 7 MCQs ( Plant Growth and Mineral Nutrition )

Multiple choice questions.

1. Which of the hormones can replace vernalization?
    a. Auxin
    b. Cytokinin
    c. Gibberellins
    d. Ethylene

Answer : Gibberellins
Explanation : Gibberellin is a hormone that replaces vernalisation. Vernalization is a period of cold treatment for plants, usually perennials or trees.


2. The principle pathway of water translocation in angiosperms is ..........
    a. Sieve cells
    b. Sieve tube elements
    c. Xylem
    d. Xylem and phloem

Answer : Xylem
Explanation : The principal pathway of water translocation in angiosperms is xylem vessel system. The sap (i.e., water with dissolved minerals) is absorbed mainly by roots and is moved upward to all the parts of plants via stem.


3. Abscisic acid controls ..................
    a. cell division
    b. leaf fall and dormancy
    c. shoot elongation
    d. cell elongation and wall formation

Answer : leaf fall and dormancy 
Explanation : Abscisic acid a plant hormone that plays important role abscission of leave. It inhibits stem elongation by inhibiting gibberellic acid. It prevents loss of dormancy in seeds. 





4. Which is employed for artificial ripening of banana fruits?
    a. Auxin
    b. Ethylene
    c. Cytokinin
    d. Gibberellin

Answer : Ethylene 


5. Which of the following is required for stimulation of flowering in the plants?
    a. Adequate oxygen
    b. Definite photoperiod
    c. Adequate water
    d. Water and minerals

Answer : Definite photoperiod
Explanation : According to the phenomenon of photoperiodism, all plants are having an optimum amount of light to be lit on them for their flowering to be induced. Thus, the plants have been classified into long day plants, short day plants and neutral day plants. This shows that they have a definite photoperiod for inducing flowering



6. For short day plants, the critical period is .................
    a. light
    b. dark/ night
    c. uv rays
    d. both a and c

Answer : light
Explanation :  Short Day Plants (SDP)



7. Which of the following is day neutral plant?
    a. Tomato
    b. Cotton
    c. Sunflower
    d. Soybean

Answer : Tomato 
Explanation: Short day plants require long period of darkness and short period of light to flower. Long day plants will flower when they are exposed to short period of darkness and long period of light. Long day plants flower in summer and short day plants flower in spring. Day neutral plants do not depend upon the amount of darkness or daylight hours. Examples of day neutral plants are sunflower and tomato. Examples of short day plants are rice, tobacco, cotton. Examples of long day plants are lettuce, spinach, potato.


8. Essential macro elements are ............
    a. manufactured during photosynthesis
    b. produced by enzymes
    c. absorbed from soil
    d. produced by growth hormones

Answer : Absorbed from soil


9. Function of Zinc is ................
    a. closing of stomata
    b. biosynthesis of 3-IAA
    c. synthesis of chlorophyll
    d. oxidation of carbohydrates

Answer : Oxidation of carbohydrates



10. Necrosis means ...............
    a. yellow spots on the leaves
    b. death of tissue
    c. darkening of green colour in leaves
    d. wilting of leaves

Answer : Death of tissue



11. Conversion of nitrates to nitrogen is called .....................
    a. ammonification
    b. nitrification
    c. nitrogen fixation
    d. denitrification

Answer : denitrification
Explanation : Denitrification is the process that converts nitrate to nitrogen gas, thus removing bioavailable nitrogen and returning it to the atmosphere.


12. How many molecules of ATP are required to fix one molecule of nitrogen?
    a. 12
    b. 20
    c. 6
    d. 16

Answer : 16
Explanation : For fixing of nitrogen molecule 16 molecules of ATP are required.