Tag: botany

Questions Related to botany

Venation is a term used to describe the pattern of arrangement of

botany leaf - external morphology venation arrangement of leaves morphology of leaf

  1. Floral organs

  2. Flower in inflorescence

  3. Veins and veinlets in a lamina

  4. All of the above

Show answer
Correct Option: C
Explanation:

The arrangement of veins and veinlets on the lamina of the leaf is called as venation.
Correct option C.

Which one of the following is correct?

botany leaf - external morphology venation arrangement of leaves morphology of leaf

  1. In dorsiventral leaf, stomata are on lower (abaxial) surface.

  2. Protoxylem disintegrates to produce lacuna (lysigenous) in monocot stem.

  3. Reticulate venation in dicot leaf, parallel venation in monocot leaf.

  4. All of the above

Show answer
Correct Option: D
Explanation:
a) Dorsiventral leaf has stomata only on the lower surface because it is more often in the shade and so it is cooler, which means evaporation won't take place as much. 
b) Protoxylem lacuna is a space surrounded by parenchyma cells in the protoxylem of a vascular bundle. Appears in some plants after the protoxylem has ceased to function, after these elements have been stretched and torn, thus forming the cavity (lacuna) in monocot stem. 
c) Leaf veins are arranged either in parallel through the length of the leaf or in a reticulate arrangement throughout the leaf. In most species, monocot leaves have parallel arrangement while dicots have reticulate venation of leaves.
So, the correct answer is 'All the above'.

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

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

  1. Increases

  2. Decreases

  3. Both A and B

  4. None of the above

Show answer
Correct Option: B
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.

Transpiration is regulated by the movements of

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

  1. Epidermal cells of the leaf

  2. Subsidiary cells of the leaf

  3. Guard cells of the stomata

  4. Mesophyll tissue of the leaf

Show answer
Correct Option: C
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.

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

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

  1. Decreases

  2. Increases

  3. Both A and B

  4. None of the above

Show answer
Correct Option: A
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.

Stomata in angiosperms does not open during

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

  1. Noon

  2. Twilight

  3. 11 O'clock

  4. Midnight

Show answer
Correct Option: D
Explanation:

Usually in angiosperms stomata open during daytime and are closed during night.

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

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

  1. Levitt

  2. Milborrow

  3. Ziegler

  4. None of the above

Show answer
Correct Option: A
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.

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

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

  1. Completely open

  2. Partially open

  3. No effects

  4. Closed

Show answer
Correct Option: A

Which ones regulate stomatal movements 
(a) IAA
(b) $GA _3$
(c) Zeatin 
(d) ABA.

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

  1. a,c

  2. b,c

  3. c,d

  4. b,d

Show answer
Correct Option: A

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

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

  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.

Show answer
Correct Option: B
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.