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

Among these groups, one element is involved in opening and closing of stomata, the other helps to maintain ribosome structure. Choose the correct option.

  1. K and Ca

  2. P and S

  3. K and Mg

  4. Fe and Mg
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Potassium (K) and Magnesium (Mg) are essential macronutrients for plants.

K is absorbed as $K^+$. In plants, it is required in more abundant quantities in the meristematic tissues, buds, leaves and root tips. It helps to maintain an anion-cation balance in cells. It is involved in opening and closing of stomata.
Mg is absorbed by plants in the form of divalent magnesium ion ($Mg^{2+}$). It is required in the growing area of roots and stem, seeds, leaves, etc. It occurs as magnesium pectate in middle lamella. It is responsible for maintenance of ribosome structure because it is required for the binding of ribosome subunits during protein synthesis

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

Which process is responsible for controlling the movement of guard cells? 

  1. Transpiration

  2. Photosynthesis

  3. Osmosis

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

Osmosis is the process which regulates the opening and closing of stomata by guard cells. When potassium ions accumulate in the cells, the water potential drops and endosmosis occurs making the cell turgid. This causes the cells to take a shape so that the stomatal pore is opened up. When water moves out of the cells, the cells become flaccid and the pore closes.

So, the correct answer is 'Osmosis'.

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

According to modern theory of stomatal opening, proposed by Levitt, $pH$ of guard cell can rise due to 

  1. $CO _2$ assimilation by guard cells only
  2. Active eflux of $H^+$ ion by guard cell

  3. Conversion of starch into PEP
  4. Active uptake of $K^+$ in guard cell
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Modern theory of stomatal movement is proposed by Levitt. According to it, entry of K+ ions leads to the opening of stomata during day time and exist of k+ results the closure of stomata during night time. Simultaneously, carbon dioxide assimilation occur during day time in the guard cells.

So, the correct option is ‘CO2 assimilation by guard cells only’.

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'.