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 Multiple Choice QuestionsMultiple Choice Questions

1.

In CAM plants

  • stomata open in day and close at night

  • stomata remain open in day and night both

  • stomata remain closed in day and night both

  • stomata open at night and close in day


D.

stomata open at night and close in day

CAM is found in members of the family Crassulaceae (e.g., Kalanchoe), family Cactaceae (e.g., Opuntia, Cereus), and some members of Liliaceae, Orchidaceae, Bromeliaceae, Euphorbia sp. All CAM plants are not succulent and stomata open at night.


2.

In photosynthesis what occurs in PS-II?

  • It takes longer wavelength of light and e- from H2O

  • It takes shorter wavelength of light and e- from H2O

  • It takes longer wavelength of light and e- from NADP

  • It takes shorter wavelength of light and e- from NADP


B.

It takes shorter wavelength of light and e- from H2O

Green plants and algae use two type of photo-system called Photosystem- I (PS-I) and Photosystem- II (PS -II).

In PS-I, chlorophyll absorb maximum at 700 nm wavelength of light thus reaction centre is P700 and PS-II absorb maximum at 680 nm wavelength of light thus reaction centre is P680. P680 (PS-II) extracts an electron from water, returning to its unexcited state because hydrolysis of H2O occurs in PS-II. So, O2 evolved in PS-II come from water.


3.

Energy transfer in photosynthesis occurs as

  • Phycoerythrin Phycocyanin Carotenoid Chlorophyll a

  • Chlorophyll b Carotenoid Phycoerythrin Chlorophyll a

  • Phycocyanin Phycoerythrin Carotenoid Chlorophyll a

  • Chlorophyll b Carotenoid Phycocyanin Chlorophyll a


A.

Phycoerythrin Phycocyanin Carotenoid Chlorophyll a

Chlorophyll is the principal pigment involved in photosynthesis. Chlorophyll a is the major pigment involved in trapping light energy and converting it into electrical and chemical energy. Chlorophyll b molecules also acts as accessory pigment.

Other accessory pigments are phycoerythrinphycocyanin, carotenoids etc. The accessory pigment and reaction centre together form photo-system.


4.

In photosythesis action and absorption spectrum were related by

  • Von Helmont

  • Engelmann

  • Emerson

  • Lavosier


B.

Engelmann

Engelmann studied the effect of different region of the visible spectrum on the rate of photosynthesis of different algae. The amount of oxygen (O2 ) released was found to be maximum in blue and red absorption bands of chlorophyll.


5.

In C4 plants, CO, fixation is done by

  • mesophyll cells

  • guard cells

  • sclerenchyma

  • chlorenchyma and hypodermis


A.

mesophyll cells

In C4 plants, CO2 is picked up by phosphoenol pyruvate (PEP) in the cytoplasm of mesophyll cells.


6.

Stomatal opening in plants occurs due to influx of

  • Na

  • K

  • ABA

  • Auxins


B.

K

Opening of stomata is an energy consuming process whereas closing of stomata is not. The turgidity of guard cells is usually controlled by K+, Cl- and H+. The opening of stomata is initiated by excretion of H+ by guard cells, intake of K+ and Cl- and closing is controlled by abscisic acid.


7.

In Hatch and Slack type plants CO2 acceptor is

  • malate

  • pyruvate

  • phosphoenol pyruvate

  • aspartate


B.

pyruvate

In Hatch and Slack cycle CO, acceptor is phosphoenol pyruvic acid and first product is oxaloacetic acid, (a 4-C compound). Therefore it is popularly termed as C4 cycle.


8.

In C4 plants, CO2 combines with

  • phosphoglyceric acid

  • ribulose diphosphate

  • phosphoenol pyruvate

  • phosphoglyceraldehyde


C.

phosphoenol pyruvate

In C4 plants, CO2 is picked up by a 3-carbon compound Phosphoenol pyruvate (PEP) to form 4-carbon compound Oxaloacetic acid. This reaction is catalysed by PEP carboxylase and it takes place in the cytoplasm of mesophyll cells.


9.

Photorespiration is favoured by

  • high O2 and low CO2

  • high CO2 and low O2

  • high temperature and low O2

  • high humidity and temperature


A.

high O2 and low CO2

Photorespiration is a respiratory process in many higher plants by which they take up oxygen in the light and give out some carbon- dioxide.

Oxygen is a competitive inhibitor of CO2 fixation. Increase in O2 concentration would favour the uptake of oxygen by Rubisco leading to increase in photorespiration.


10.

The true statement about 'green-house effect' is that it is

  • caused only by CO2

  • caused by CO2, CFCs, CHand NO2 gases

  • caused by combination of many gases

  • none of the above


B.

caused by CO2, CFCs, CHand NO2 gases

A Greenhouse gas is a gas that absorbs and emits radiant energy within the thermal infrared range. It causes the greenhouse effect. Green-house effect is caused by CO2, CFCs, CH4 and NO2.