Most accepted theory for ascent of sap is from Biology Transport

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 Multiple Choice QuestionsMultiple Choice Questions

31.

In plants, water supply is due to

  • osmosis

  • imbibition

  • guttation

  • adhesion force


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32.

Most accepted theory for ascent of sap is

  • capillary theory

  • root pressure theory

  • pulsation theory

  • transpiration pull


D.

transpiration pull

Transpiration pull or the suction force is the force which aids in drawing the water upward from roots to leaves. In leaves, some amount of water is used for photsynthesis and excess of water is released into atmosphere through openings called as stomata.

Root Pressure Theory is the transverse osmotic pressure within the cells of a root system that causes sap to rise through a plant stem to the leaves.

Pulsation theory or Vital force theory was not accepted because living cells are not involved in the ascent of sap as water continue to rise upwards in the plant.

Capillarity Theory is the capillarity movement of water due to adhesion and cohesion forces balanced by downward pull of gravity.


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33.

Which of the following theory gives the latest explanation for the closure of stomata?

  • ABA theory

  • Munch Theory

  • Starch glucose theory

  • Active K+ transport theory


34.

Root hair absorbs water from soil through

  • turgor pressure

  • ion exchange

  • osmosis

  • DPD


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35.

Who said that 'transpiration is a necessary evil'

  • Curtis

  • Andersen

  • Steward

  • J.C. Bose


36.

Transpiration would be lowest when

  • wind velocity is high

  • enough water is in the soil

  • atmospheric RH is high

  • high temperature and light


37.

Which of the following exhibits a direct porportionality to transpiration

  • Light and RH

  • Temperature and RH

  • Temperature and wind

  • RH and wind


38.

Water in plants is transported by

  • cambium

  • phloem

  • xylem

  • epidermis


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39.

The most important force which pulls water up in tall trees is

  • imbibition force

  • osmotic force

  • cohesive force

  • electromagnetic force


40.

The light phase of photosynthesis is called

  • Hill reaction

  • photo action

  • pigment action

  • chlorophyllous process


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