Tag: blackman's principle of limiting factors

Questions Related to blackman's principle of limiting factors

Active $K^{+}$ ion exchange mechanism of opening and closing of stomata was given by

blackman's principle of limiting factors photosynthesis in higher plants biology

  1. Khorana

  2. Scarth

  3. Levitt

  4. Kohli

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Correct Option: C
Explanation:

Potassium is an important macronutrient for plants. Potassium ions cause turgor movement of guard cells. 

Gain of potassium ions by guard cells causes a decrease in water potential of guard cells which leads to inflow of water into the guard cells. This makes guard cells turgid and they swell. Increase in turgidity of guard cells opens the stomatal pore. 
Movement of potassium ions out from guard cells results in an increase in water potential, they lose water due to exosmosis, become flaccid and stomatal pore closes. 
This mechanism of stomatal opening and closing was first stated by Levitt.

Active $K^+- H^+$ exchange theory explains

blackman's principle of limiting factors photosynthesis in higher plants biology

  1. Ascent of sap

  2. Phloem conduction

  3. Ion absorption

  4. Stomatal movement

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Correct Option: D
Explanation:

Transpiration occurs through stomata. The opening and closing of stomatal pore depends on the turgidity of guard cells. When guard cells become turgid the stomata open and when guard cells become flaccid the stomata close. 

According to the most widely accepted theory of 'Active $K^+$−$H^+$ exchange' the guard cells become turgid or flaccid in response to entry and exit of potassium ions. The entry and exit of potassium ions is balanced by the entry and exit of protons to maintain electrical neutrality.

The conversion of starch to organic acid is essential for stomatal

blackman's principle of limiting factors photosynthesis in higher plants biology

  1. Closure

  2. Growth

  3. Intitiation

  4. Opening

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Correct Option: D
Explanation:

During stomatal opening starch gets converted to organic acids, like malic acid. The dissociation of organic acid increases proton concentration. The protons move out of guard cells and to maintain electrical neutrality potassium ions move into the guard cells. The inflow of potassium ions results in a drop in water potential in guard cells, due to which water moves into guard cells making them turgid and stomata open.

Which of the following one function as primary osmotic substance in opening and dosing of stomata _______________.

blackman's principle of limiting factors photosynthesis in higher plants biology

  1. Water

  2. Starch

  3. Sugar

  4. K - malate

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Correct Option: D

Which ion is accumulated in the guard cells before opening of stomata?

blackman's principle of limiting factors photosynthesis in higher plants biology

  1. $PO _4$

  2. $K^+$

  3. $Mg^{++}$

  4. $Na^+$

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Correct Option: B
Explanation:

According to the most widely accepted theory of stomatal opening and closing, potassium ions are involved in turgor movement of guard cells. Inflow of potassium ions decreases water potential in guard cells, which leads to inflow of water. Consequently guard cells swell and stomatal pore opens. When potassium ions move out, these events are reversed and stomatal pore closes.

Guard cells control

blackman's principle of limiting factors photosynthesis in higher plants biology

  1. Intensity of light entering

  2. Photosynthesis

  3. Closing and opening of stomata

  4. Change in green colour

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Correct Option: C
Explanation:

Transpiration is the process of loss of water, in vapour form, through stomata. The process depends on the turgidity of guard cell. An increase in turgidity of guard cells opens stomatal pore, whereas a decrease in turgidity of guard cells closes stomatal pore. The change in turgidity of guard cells is brought about by reversible influx and efflux of potassium ions.

Conversion of starch to organic acid is essential for

blackman's principle of limiting factors photosynthesis in higher plants biology

  1. Stomatal closure

  2. Stomatal opening

  3. Stomatal initiation

  4. Stomatal growth

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Correct Option: B
Explanation:

Starch is osmotically inactive and does not contribute to decrease in water potential. Conversion of starch to organic acids like malic acid promotes uptake of ions like potassium. This decreases water potential and helps in uptake of water. Thus making guard cells turgid and opening of stomata.

Stomata in angiosperms open and close due to

blackman's principle of limiting factors photosynthesis in higher plants biology

  1. Their genetic constitution

  2. Effect of hormones

  3. Change of turgor pressure in guards cells

  4. Pressure of gases inside the leaves

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Correct Option: C
Explanation:

Changes in turgidity of guard cells, regulate the opening and closing of stomata. When guard cells are turgid, stomatal pore opens and when guard cells are flaccid stomatal pore closes.

The metal ion involved in the stomatal regulation is or Stomata will open, if there is accumulation of the following elements in the guards cells

blackman's principle of limiting factors photosynthesis in higher plants biology

  1. Iron

  2. Magnesium

  3. Zinc

  4. Potassium

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Correct Option: D
Explanation:

Potassium ions movement into and out of guard cells is related to the turgidity and consequent opening and closing of stomatal pore.

Stomata open because of

blackman's principle of limiting factors photosynthesis in higher plants biology

  1. Oxygen in the air

  2. Increased turgidity of the guard cells brought about by exposure to light

  3. Vacuoles in guard cells

  4. All of the above

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Correct Option: B
Explanation:

Guard cells have chloroplast, on exposure to light, there is synthesis of sugar in guard cells. The increase in sugar concentration causes water to move in from surrounding cells, thus making guard cells turgid. Increase in turgidity of guard cells leads to stomatal opening.