Tag: photosynthesis in higher plants

Questions Related to photosynthesis in higher plants

Conversion of starch to organic acids is required for 

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

  1. Stomatal opening

  2. Stomatal closing

  3. Stomatal formation

  4. Stomatal activity

Show answer
Correct Option: A
Explanation:

According to Lloyd the stomatal movement is regulated by interconversion of starch and organic acids. When starch is converted into organic acid in the presence of enzymes and light, guard cells get turgidity and eventually causes the opening of stomata.

For keeping stomata open, besides $K^+$ ions the guard cells require a constant supply of

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

  1. ABA

  2. ATP

  3. Organic acids

  4. Protons

Show answer
Correct Option: B
Explanation:
Guard cells help to regulate the rate of transpiration by opening and closing the stomata. When the guard cells are turgid/swollen, then this turgidity is caused by the accumulation of K ions in guard cells. As K ion level increases, the water potential of guard cells drops and water enters the guard cells and for diffusion of water and activity of guard cells, it requires energy which is utilized from ATP form of energy. Thus this requires a constant supply of ATP.
So the correct answer is 'ATP'.

Latest explanation for closure of stomata is 

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

  1. Starch glucose theory

  2. Active $K^+$ ions theory

  3. ABA theory

  4. None of the above

Show answer
Correct Option: C
Explanation:
There are many theories regarding the closure of stomata. The latest explanation is ABA theory according to which ABA (abscisic acid) blocks the uptake of potassium ions by guard cells on dark. It also prevents efflux of hydrogen ions from the guard cells. ABA helps in lowering the pH in guard cells and making the acidic medium. This helps in the closing of the stomata.
So, the correct answer is 'ABA theory'.

Identify the correct statements and find out the correct combination?
1. Accumulation of $K^+$ ions in guard cell does not require energy.
2. A high pH favors stomatal opening.
3. Movement of chloride ions into guard cells is in response to electrical differential created by $K^+$ ions.
4. With the entry of several $K^+$ ions and chloride ions, the water potential of guard cells increases.

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

  1. 1 and 3

  2. 1 and 2

  3. 2 and 3

  4. 3 and 4

Show answer
Correct Option: C
Explanation:

The opening and closing of stomata are controlled by many factors such as light, pH, amount of water and solute and the osmotic pressure.

So, the correct answer is '2 and 3'.

Starch of guard cells is converted into PEP through

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

  1. Hydrolysis

  2. Oxidation

  3. Dephosphorylation

  4. Decarboxylation

Show answer
Correct Option: A
Explanation:

(A) Hydrolysis is the breaking of the bond due to reaction with water. Starch in plants is converted into PEP through the breaking of bonds as it reacts with water.

(B) Oxidation is the process of gaining electrons.
(C) Dephosphorylation is the removal of a phosphate group by hydrolysis.
(D) Decarboxylation is the process of removal of the carboxyl group.
So, the correct answer is 'Hydrolysis'.

Stomata open during the day due to 

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

  1. Accumulation of $K^+$ ion and sugar

  2. High pH

  3. Osmotic effect of ions present in guard cells

  4. None of the above

Show answer
Correct Option: A
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 favours the closing of stomata.
So, the correct answer is 'Accumulation of K+ ion and sugar'.

Enzyme connected to stomatal opening is

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

  1. Hexokinase

  2. Cytochrome oxidase

  3. PEP carboxylase

  4. RuBisCo

Show answer
Correct Option: C
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'.

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

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

  1. True

  2. False

Show answer
Correct Option: B
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'.

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

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

  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.

Show answer
Correct Option: D

What causes opening of stomata?

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

  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.

Show answer
Correct Option: D
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.'