Tag: biology

Questions Related to biology

The starch - sugar interconversion theory was given by

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

  1. Steward

  2. Scarth

  3. Levitt

  4. Raschke

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Correct Option: A

Element involved in stomatal regulation, its opening and closing is 

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

  1. Zinc

  2. Magnesium

  3. Potassium

  4. Iron

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Correct Option: C
Explanation:

Stomata open and closes due to water and ion movement. When the light falls on the parts of the plant, chloroplast carries out photosynthesis. ATP from photosynthesis powers sodium and potassium pump. Then the K$^+$ ions are pumped (influx of K$^+$) into the guard cells, by creating a concentration gradient and also water enter into the guard cell through osmosis. As a result of this, guard cells swells and stomata open. The reverse process occurs in the closing of stomata, i.e, loss of K$^+$ ions (efflux of K$^+$) by guard cells and water also leave the guard cells by the process osmosis. As a result, guard cells become flaccid and stomata close. 

So, the correct answer is option C.

Who proposed that opening and closing of stomata is connected with the change in pH of guard cells?

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

  1. Lloyd

  2. Von Mohl

  3. Sayre

  4. Levitt

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Correct Option: C
Explanation:

Botanist Sayre observed that stomatal opening is connected to change in ph of guard cells due to carbon dioxide. 

Stomata open in neutral and alkaline pH which is present in the daytime when carbon dioxide is constantly used.
In acidic condition, stomata remain closed which is present in night time when no photosynthesis occurs due to which accumulation of carbon dioxide occurs that results in the formation of carbonic acid. Thus guard cells movement is regulated by pH due to interconversion of starch and sugar.
So the correct answer is 'Sayre'.

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

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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

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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

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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

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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

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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

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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'.