Tag: blackman's principle of limiting factors

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

Enzyme connected to stomatal opening is

  1. Hexokinase

  2. Cytochrome oxidase

  3. PEP carboxylase

  4. RuBisCo
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

(A) Hexokinase is the enzyme catalysing the production of fructose from glucose.

(B) Cytochrome oxidase catalyses the electron transfer for the formation of molecular oxygen.
(C) PEP Carboxylase stimulates the stomatal opening.
(D) RuBisCo is the enzyme catalysing the carbon fixation.
So, the correct answer is 'PEP Carboxylase'.

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

Role of Na$^+$ in stomatal opening is now universally accepted.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
The opening and closing of stomata are governed by the increase and decrease of solute concentration in guard cell, causing the using or losing the water. Generally, the stomatal opening is affected by the light.
So, the answer is 'False'.
Multiple choice blackman's principle of limiting factors photosynthesis in higher plants biology

According to Steward's starch hydrolysis theory which one of the following is the principal reason for the opening of stomata during daytime

  1. Influx of K$^+$ ions into guard cells under influence of ABA hormone.

  2. Conversion of sugar into starch in guard cells.
  3. Efflux of K$^+$ ions from guard cells under influence of ABA hormone.
  4. Photosynthetic utilisation of CO$ _2$ in guard cells.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Steward's theory posits that the photosynthetic utilization of CO2 in guard cells during the day increases the pH, which activates phosphorylase to convert starch into sugar, thereby increasing osmotic pressure.

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

What causes opening of stomata?

  1. Thin wall of guard cell facing stomatal pore is stretched more, curves in and the pore opens.

  2. Thin wall of guard cell facing stomatal pore is stretched more, moves in and the pore opens.

  3. As thin wall of guard cell is stretched less, the guard cell wall facing the stomatal pore moves in and pore opens.

  4. Thick wall of guard cell facing the stomatal pore is stretched less, moves in and the pore opens.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Stomata are the structure present in the leaf which meant for exchange of gases and loss of water. Opening and closing of stomata are regulated by guard cells. Lloyd found that in daytime starch gets converted into sugar which accumulates in guard cells.

Fujino found that in the presence of light there is the influx of potassium ion in guard cells which causes the opening of stomata.
High pH favors the closing of stomata.
So, the correct answer is 'Thick wall of guard cell facing the stomatal pore is stretched less, moves in and the pores opens.'

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

Which of the following scientists is credited with the mechanism of opening and closing of stomata related to $K^+$ exchange?

  1. Levitt

  2. Sayre

  3. Scarth

  4. Lloyd
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

  • Stomata are the structure present in the leaf which meant for exchange of gases and loss of water. 
  • Opening and closing of stomata are regulated by guard cells. 
  • Levitt found that in daytime starch gets converted into sugar which accumulates in guard cells.
  • Fujino found that in the presence of light there is the influx of potassium ion in guard cells which causes the opening of stomata.
  • High pH favours the closing of stomata.
So, the correct answer is 'Levitt'.

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

The effect of accumulation of $K^+$ ions in guard cells

  1. Solute potential increases

  2. Water potential decreases

  3. Water potential increases

  4. Both A and B
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The opening and closing of stomata are controlled by the accumulation of potassium ion. Potassium ion is found in the guard cell of the plant. The increase in the solute potential and a decrease in water potential is affected by potassium ion in the plant.

So, the correct answer is 'Both A and B'.

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

Find the correct pair of statements :
(i)  The influx of Cl into guard cells during stomatal opening is active.
(ii) Entry of sucrose from companion cells into sieve tubes at source involves the expenditure of energy.
(iii) At the sinks, sucrose moves out of phloem by passive transport.
(iv) Efflux of K$^+$ from guard cells during stomatal closure does not involve energy expenditure.

  1. ii, iv

  2. ii, iii

  3. i, iii

  4. iii, iv
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The influx of $K^+$ into guard cells during stomatal opening is active.

Movement of Sucrose from companion cells to sieve tubes is against its concentration gradient so protons are transported along with it in the opposite direction which involves the use of energy.
At the sink, the sugar moves out of the phloem tube into the cells by active transport.
Efflux of $K^+$ from guard cells does not involve the expense of energy as it is along the concentration gradient.
So the correct answer is 'ii, iv'.

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

Accumulation of which one of the following acids results in closure of stomata 

  1. Malic acid

  2. Aspertic acid

  3. PEP

  4. OAA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Accumulation of maleic acid in stomata causes its closure. 

This causes an efflux of potassium ions too. Then exosmosis occurs and the cells become flaccid.
So the correct answer is 'Malic acid'.

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

Accumulation of which one of the following acids results in closure of stomata?

  1. Malic acid

  2. Aspartic acid

  3. PEP

  4. OAA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When there is the rise in pH it causes hydrolysis of starch into sugar which accumulates in guard cells which results in the opening of cells. For this mechanism, cytokinins, malic acid, and cAMP are required.

Abscisic acid is the stress hormone which results in the closing of stomata.
So, the correct answer is 'Malic Acid'.

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

When turgidity is lost in guard cells, the stomatal pore

  1. Remains unchanged

  2. Gets plasmolysed

  3. Closes

  4. Opens fully
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Guard cells get swollen up or turgid due to absorption of water so the stomatal pore is opened up.

When the turgidity is lost they lose their shape and cause the closing of the stomatal pore.
Plasmolysis occurs when cells are placed in hypertonic solutions.
So the correct answer is 'Closes'.