Tag: homeostasis in plants

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Multiple choice botany transport in plant homeostasis in plants regulation of stomatal opening stomata

Loss of $k^{+}ions$ causes ......... of turgidity of guard cell.

  1. Increases

  2. Decreases

  3. Both A and B

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

Loss of $k^{+} ions$ decreases the osmotic concentration of guard cells as compared to adjacent epidermal cells. This causes exosmosis and hence turgidity of guard cells decreases.

Multiple choice botany transport in plant homeostasis in plants regulation of stomatal opening stomata

Transpiration is regulated by the movements of

  1. Epidermal cells of the leaf

  2. Subsidiary cells of the leaf

  3. Guard cells of the stomata

  4. Mesophyll tissue of the leaf
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In higher plants transpiration occurs through stomata. The stomatal pore is regulated by the turgidity of guard cells. When the guard cells are turgid the stomatal pores open. When guard cells are flaccid, stomatal pore closes.

Multiple choice botany transport in plant homeostasis in plants regulation of stomatal opening stomata

Loss of $k^{+}$ ion ..... osmotic concentration of guard cells on compared to adjacent epidermal cell

  1. Decreases

  2. Increases

  3. Both A and B

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

Loss of $k^{+}$ ions decreases the osmotic concentration of guard cells as compared to adjacent epidermal cells. This causes exosmosis and hence turgidity of guard cell decreases.

Multiple choice botany transport in plant homeostasis in plants regulation of stomatal opening stomata

For photoactive opening of stomata, the proton transport concept was given by

  1. Levitt

  2. Milborrow

  3. Ziegler

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

Proton transport concept in stomata was given by Levitt and is most widely accepted theory.
According to this theory, protons formed due to malic acid dissociation in guard cells are transported to subsidiary cells and in exchange potassium ions move into guard cells. This ion exchange requires ATP. The potassium ions are osmotically active. Their influx into the guard cells increases osmotic pressure of guard cells and results in endosmosis, which opens the stomata.

Multiple choice botany transport in plant homeostasis in plants regulation of stomatal opening stomata

What will be the effects on stomata, if relative humidity is $100\%$ in atmosphere?

  1. Completely open

  2. Partially open

  3. No effects

  4. Closed
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

At 100% relative humidity, transpiration is inhibited, which often leads to stomatal closure to prevent water loss or maintain turgor, but in some contexts, it is stated they remain open.

Multiple choice botany transport in plant homeostasis in plants regulation of stomatal opening stomata

Stomata opening in most of the plants is during the day instead of night because

  1. Enzymes convert starch into sugar at night.

  2. Formation of sugar increases osmotic concentration of the cell sap, which results in more absorption of water, which provides turgidity to the guard cells.

  3. The starch converts into sugar by enzymatic activity during the night and the whole process of the day becomes reversible, thus resulting in the closure of stomata.

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

Most widely accepted theory for opening and closing of guard cells is the malate or potassium ion pump theory, first proposed by Levitt, 1974. According to this theory, during day time, 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. 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.

Multiple choice botany transport in plant homeostasis in plants regulation of stomatal opening stomata

Which one keeps its stomata open during night and closed during day?

  1. Cactus

  2. Water lily

  3. Ivy

  4. Hibiscus
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Scotoactive stomata are the stomata which open in dark and close during the day time. Scotoactive stomata occur in succulent like Cactus, Bryophyllum, Opuntia. The succulents perform crassulacean acid metabolism or CAM type of photosynthesis and their stomata are accordingly modified.

Multiple choice botany transport in plant homeostasis in plants regulation of stomatal opening stomata

Which of the following is a plant showing scotoactive opening of stomata?

  1. Opuntia

  2. Nerium

  3. Arachis

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

Scotoactive stomata are the stomata, which open in dark and close during the day time. 

Scotoactive stomata occur in succulent, like cactus, Bryophyllum, Opuntia. The succulents perform crassulacean acid metabolism or CAM type of photosynthesis and their stomata are accordingly modified.