Tag: blackman's principle of limiting factors

Questions Related to blackman's principle of limiting factors

Opening and closing of stomata is controlled by

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

  1. $K^{+}$

  2. $Mg^{2+}$

  3. $Ca^{2+}$

  4. None of the above

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Correct Option: A
Explanation:

Potassium ions are involved in turgor movement of guard cells. Formation of organic acids like malic acid in guard cells promotes intake of potassium into the guard cells, which causes a decrease in water potential leading to intake of water by guard cells.

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

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

  1. K and Ca

  2. P and S

  3. K and Mg

  4. Fe and Mg

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Correct Option: C
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

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

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

  1. Transpiration

  2. Photosynthesis

  3. Osmosis

  4. Diffusion

Show answer
Correct Option: C
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'.

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

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

  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

Show answer
Correct Option: A
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’.

Stomatal mechanism operates in response to

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

  1. Temperature

  2. Light

  3. Soil moisture

  4. All of the above

Show answer
Correct Option: D
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.  

Opening and closing of stomata is due to the : -

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

  1. Hormonal change in guard cells

  2. Change in Turgor pressure of guard cells

  3. Gaseous exchange

  4. Respiration

Show answer
Correct Option: B
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'.

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

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

  1. P

  2. K

  3. Mg

  4. Ca

Show answer
Correct Option: B
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.

The most abundant intracellular cation is

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

  1. $Ca^{++}$

  2. $H^+$

  3. $K^+$

  4. $Na^+$

Show answer
Correct Option: C
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 '$K^+$'

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

  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)

Show answer
Correct Option: A

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.

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

  1. Only statement B is correct.

  2. Only statement B is incorrect.

  3. Both statement are incorrect.

  4. Both statement are correct.

Show answer
Correct Option: B