Tag: photosynthesis in higher plants

Quizzes (15) Questions (239)

Questions Related to photosynthesis in higher plants

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

Stomatal mechanism operates in response to

  1. Temperature

  2. Light

  3. Soil moisture

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Stomatal movement are influenced by many environmental factors like temperature, light humidity, water availability (moist soil), CO$ _2$ concentration, growth hormones, minerals and pH.

Therefore, the correct answer is option D.  

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

Opening and closing of stomata is due to the : -

  1. Hormonal change in guard cells

  2. Change in Turgor pressure of guard cells

  3. Gaseous exchange

  4. Respiration
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Stomata take in C02 required for the photosynthetic activity during the day.  They give out excess water released in the process of respiration during the night along with CO2. Opening and closing of stomata are controlled by the concentration of solutes in guard cells. Opening and closing of stomata take place due to turgor changes in guard cells.

  • Opening of Stomata
Solutes from neighbouring epidermal and mesophyll cell enter the guard cell lowering it osmotic potential and water potential. This lowered water potential and osmotic potential will allow movement of water in guard cells from neighbouring cells. Guard cell becomes turgid and swells in size resulting in the stomata opening due to water accumulation in them.
  • Closing of stomata
As the stomata open the solute concentration is reduced. This makes the water from the guard cell to move away into the neighbouring cell and making them flaccid with no water. They collapse against each other and results in the closing of stomata.

So, the correct answer is 'Change in Turgor pressure of guard cells'.

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

Which ion accumulates in the guard cells at the time of opening of stomata?

  1. P

  2. K

  3. Mg

  4. Ca
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

It is generally well accepted that stomata opens, when guard cells become turgid due to entry of water. The water enters the guard cells from the surrounding cells, when the guard cells accumulate ions, which causes a decrease in water potential. It has been established that the ion, which accumulates in guard cells is the potassium ion. When plants are exposed to light, the guard cells accumulate large amounts of $K^+$. Light appears to stimulate active movement of $K^+$ ions from surrounding cells into the vacuoles of the guard cells. In guard cells, osmotic and hence, water potentials become very negative due to the presence of KCI, potassium malate or dipotassium malate or both. A water potential gradient is established from the accessory water movement, increased turgidity and stomatal opening.

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

The most abundant intracellular cation is

  1. $Ca^{++}$
  2. $H^+$
  3. $K^+$
  4. $Na^+$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Sodium ion is the most abundant extracellular cation, while potassium ion is the most abundant intracellular cation. Both maintain osmotic balance, both involved in nerve conduction and maintainance of membrane potential in animals, while potassium alone is involved in guard cell movements and many other plant movements. Living cells operate sodium potassium pump to regularly throw out sodium and take in potassium ions.
So, the correct answer is '$K^+$'
Multiple choice blackman's principle of limiting factors photosynthesis in higher plants biology

Match the column.

Column I Column II
A Alcohol dehydrogenase (i) Magnesium
B Opening and closing of stomata (ii) Potassium
C PEP-case and RuBisCO (iii) Sulphur
D Thiamine (iv) Zink

  1. A-(i), B-(iv), C-(ii), D-(iii)

  2. A-(i), B-(ii), C-(iii), D-(iv)

  3. A-(iii), B-(ii), C-(iv), D-(i)

  4. A-(iv), B-(ii), C-(i), D-(ii)
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice blackman's principle of limiting factors photosynthesis in higher plants biology

Read the following statements and choose the correct option:
Statement -A : Potassium pump theory explains that during opening of stomata in light, ion exchange is an active process.
Statement -B : Poaceous stomata are ellipsoidal in shape.

  1. Only statement B is correct.

  2. Only statement B is incorrect.

  3. Both statement are incorrect.

  4. Both statement are correct.
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice blackman's principle of limiting factors photosynthesis in higher plants biology

Which is the latest explanation for the closure of stomata?

  1. Starch glucose theory
  2. Active $K^+$ ion theory

  3. ABA theory

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  • K+ ion theory was proposed by Levitt in 1974. K ions are balanced by malate ions present in guard cells and also by taking in some Cl ions. 
  • This ion exchange occurs through the expenditure of ATP energy.
  • Plant hormone ABA acts on guard cells, which interfere with the exchange of K+ H+ ions in guard cells, results in a reverse of the reaction of the opening of stomata, hence stomata closed.
  •  Hence, Active K+ ion theory is the latest explanation for the closure of stomata.
  • So, the correct answer is  'Active K+ ion theory'.
Multiple choice blackman's principle of limiting factors photosynthesis in higher plants biology

Which of the following theory of stomatal opening and closing is given by Levitt?

  1. Theory of starch - glucose transformation
  2. Theory of active $K^+$ transport

  3. Theory of starch - sugar interconversion

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

There are three main theories about the mechanism of stomatal movement.

  1. 'Guard Cell Photosynthesis' (proposed by Schwendener, 1881).
  2. 'Starch Hydrolysis' and Starch sugar interconversion theory (proposed by Sayre, 1923 and 1926 and other contributions were made by Lloyd and Steward)
  3. Malate or potassium ion pump hypothesis (proposed by Levitt, 1974). 
According to the potassium ion pump theory, rise in pH of guard cells (due to photosynthesis and consequent decrease of carbon dioxide) causes hydrolysis of starch to form phospho enol pyruvate (PEP). PEP combines with carbon dioxide to form organic acids, like oxalic acid. The organic acids get ionised and the proton passes out of guard cells and potassium ion is actively absorbed and accumulated. This results in absorption of water from adjacent cells,  guard cells become turgid and stomata open.

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

Who proposed the theory of starch sugar inter conversion for opening and closing of the stomata?

  1. Steward

  2. Yin and Tung

  3. Sayre

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

Starch hydrolysis theory is the classical theory for stomatal opening and closing. It was originally proposed by Sayre, 1923. According to this theory, guard cells contain starch, which is hydrolysed to form glucose under high pH caused due to reduced carbon dioxide concentration. The carbon dioxide concentration is reduced due to the process of photosynthesis Glucose increases the osmotic concentration and hence, DPD of guard cells. The later absorb water from epidermal cells, swell up and open the stomatal pore. Major contributors to this theory were Lloyd, 1908, who proposed starch sugar interconversions; Sayre, proposed that starch hydrolysis occurs with rise of pH and Steward, suggested that closing movement requires ATP.

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

Which of the following conditions help in opening of stomata?

  1. Darkness, pH 5, high $CO _2$ concentration
  2. pH 7, low $CO _2$ concentration and light
  3. pH 5, low $CO _2$ concentration and light
  4. High $CO _2$ concentration, low $K^+$ ion concentration in guard cells
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Malate or potassium ion pump hypothesis was first proposed by Levitt, 1974. According to this theory, there is a decrease of carbon dioxide in guard cells. During light exposure there is hydrolysis of starch to form phospho enol pyruvate (PEP). PEP combines with carbon dioxide to form organic acids, like oxalic acid. The organic acids get ionised and the proton passes out of guard cells and potassium ion is actively absorbed and accumulated. 

Potassium ions combine with malate and passes into small vacuoles. Chloride ions are also absorbed from outside to maintain electroneutrality. As a result of accumulation of ions there is a reduction in water potential of guard cells. The reduction in water potential causes absorption of water from adjacent cells, guard cells become turgid and stomata open.