Q: Stomatal movement is not affected by

Light, temperature and concentration of CO2 affect opening and closing of stomata while they are not affected by O2 concentration.

Question 1

Stomatal movement is not affected by

Accepted Answer

Light, temperature and concentration of CO2​ affect opening and closing of stomata while they are not affected by O2​ concentration.

Question 2

Which of the following facilitates opening of stomatal aperture?

Accepted Answer

. The tiny pores found on the surface of young green stems and leaves are stomata. Each stoma is covered by two unique epidermal cells known as guard cells. The shape of guard cells is kidney-shaped, which plays an essential role in the opening and closing of stomata. The guard cells' cell walls' microfibrils work together to control the opening of the stomata. The orientation of cellulose microfibrils takes place radially rather than Iongitudinally, which makes it easier for the stomata to open.. The movement of water takes place inwards when the osmotic concentration of the guard cell enhances. This makes the stomata to get open and thus water moves inside. Due to the contraction of the outer walls of the guard cells, the closing of stomata takes place.. The changes in the guard cell’s turgidity are accountable for the instantaneous opening and closing of stomata. With the increase in turgidity within the two guard cells, the opening of each stomatal pore takes place.. The opening of the stomata is mediated because of the coordination of the microfibrils, however, these microfibrils are not oriented longitudinally.

Question 3

What causes the opening and closing of guard cells of stomata during transpiration?

Accepted Answer

The tiny pores present on the surfaces of leaves, called stomata, help in the exchange of gases. Each stoma consists of bean-shaped or dumbbell-shaped guard cells. The epidermal cells surrounding the guard cells are modified to form subsidiary cells. The opening and closing of the guard cells are caused by a change in their turgidity. The inner walls of the guard cells are thick and elastic, while the outer walls are thin. The numerous microfibrils present in the guard cells facilitate the opening and closing of the guard cells.At the time of the opening of the stomata, the turgidity of the guard cells increases. As a result, the outer walls bulge and the inner walls become crescent-shaped. The stomatal opening is facilitated by the radial arrangement of the microfibrils.At the time of the closing of the stomata, the guard cells lose their turgidity, the outer and inner walls retain their original shapes, and the microfibrils get arranged longitudinally.

Question 4

Transpiration and root pressure cause water to rise in plants by :

Accepted Answer

The transpiration process, pulls water upwards with the help of cohesion and adhesion properties of water molecules. According to transpiration pull theory,due to transpiration, the water column inside the plant comes under tension. This is called ‘transpiration pull’.On account of this tension, the water column is pulled up passively from below to top of the plant (almost like a rope). Root pressure is the pressure that forces water,absorbed from the soil, to move through the roots and up (i.e., pushes it up) the stem of a plant. It may be due to both the osmosis of water from the soil into the root cells, and the active pumping of salts into xylem tissue which maintains a concentration gradient along which the water moves.

Question 5

रन्ध्रों की गतिशीलता किससे प्रभावित नहीं होती?

Accepted Answer

प्रकाश, तापमान तथा कार्बन डाइऑक्साइड का सांद्रण पर्णरंध्रों के खुलने तथा बंद होने की क्रिया को प्रभावित करते हैं। ये ऑक्सीजन के सांद्रण से प्रभावित नहीं होते हैं।

Question 6

पादप पत्ती से जल वाष्प रन्ध्रों के द्वारा बाहर आता है। प्रकाश संश्लेषण के दौरान उसी रन्ध्र से कार्बन डाइऑक्साइड पादप में विसरित होती है। उपर्युक्त कथनों में (कारणों पर विचार कर) एक विकल्प चुनिए।

Accepted Answer

तीव्रता के साथ वृद्धि करने वाले पादपों में पत्तियों के सतह से वायुमंडल में जल का वाष्पन पर्ण रन्ध्रों के द्वारा होता रहता है, इसे वाष्पोत्सर्जन कहा जाता है। प्रकाश संश्लेषण के दौरान इन रन्ध्रों के द्वारा कार्बन डाईआक्साइड का विसरण होता है। सरल विसरण के दोनों प्रक्रियाओं के दौरान विसरण दाब गुणांक या विसरण सहगुणांक घटित होता है।

Question 7

द्वार कोशिकाओं को घेरने वाली विशिष्टीकृत बाह्यत्वचीय कोशिकाओं को क्या कहा जाता है?

Accepted Answer

रक्षक कोशिकाओं के आस-पास वाली विशेषकृत एपिडर्मल कोशिकाएं सहायक कोशिका कहलाती है।

Question 8

The shape of guard cells in the stomata of sugarcane plant is

Accepted Answer

In the majority of the plants, the shape of guard cells in stomatal apparatus are kidney-shaped in outline, which are joined at their ends. In the members of Cyperaceae and Poacease, the shape of guard cells is dump-bell shaped in outline. Their middle portion are thick walled, while expanded ends are thin walled.

Question 9

Transpiration is measured by

Accepted Answer

The rate of transpiration can be measured by Farmer’s protometer or Ganong’s photometer. These are based on the assumption that the rate of transpiration is nearly equal to the rate of absorption of water. The opening and closing of stomata are measured by porometer.

Question 10

Guard cells control

Accepted Answer

Stomata are minute pore complexes found mainly in the epidermis of leaves. Each stoma is surrounded by two small but specialized green epidermal cells called guard cells. Their walls are differentially thickend and elastic. They control opening and closing of stomata.

Question 11

A red blood cell (RBC) was kept in a certain solution for a few minutes and it got burst. The said solution was

Accepted Answer

When an RBC is kept in a hypotonic solution then, water enters the RBC by the process of osmosis (endosmosis). The RBC will increase in size and ultimately burst. Osmosis is the movement of solvent particles from hypotonic to hypertonic medium through semi-permeable membrane.

Question 12

Mechanism of opening and closing of stomata is controlled by

Accepted Answer

Opening and closing of stomata is controlled and regulated by guard cells of stomata. Each stoma is surrounded by two small specialised green epidermal cells. These two cells are called as guard cells. Their walls are differentially thickened and elastic. The shape of guard cells are kidney shaped and dump-bell shaped in dicot and monocot, respectively.

Question 13

Which of the following lacks stomata?

Accepted Answer

Transpiration is the loss of water from the aerial parts of a living plant. Transpiration may be stomatal (90%), cuticular (3-9%) and lenticular (0.1%). Transpiration is absent in submerged hydrophytes due to the absence of stomata in the leaves of submerged plants.

Question 14

The factor, most important in regulating transpiration, is

Accepted Answer

Temperature is the most important factor that regulates transpiration. Transpiration takes place through stomata.
At 38−40∘C stomata can open in complete darkness while at 0∘C they remain closed even in continuous light.
Normally high temperature above 30∘C reduce stomatal opening in many species.

Question 15

In which of the following plants, there will be no transpiration?

Accepted Answer

The loss of water from aerial parts of living plants is known as transpiration. Transpiration may be stomatal (80-90%), cuticular (3-9%) and lenticular (0.1%). Transpiration is absent in submerged hydrophytic plants because stomata are completely absent in the leaves of submerged plants, e.g., Anacharis and Potamogeton.

Question 16

This amongst the following facilitates the opening of stomatal aperture?

Accepted Answer

The radial orientation of cellulose microfibrils aids in the opening of stomata. Stomata open as the turgidity of guard cells increases.

Question 17

Potometer works on the principle of

Accepted Answer

Measurement of transpiration can be done with the help of potometer. It works on the principle that amount of water absorbed equals the amount of water transpired.

Question 18

This hormone affects opening and closing of stomata.

Accepted Answer

ABA (abscisic acid) causes stomata to close by inhibition of an ATP dependent pump in the plasma membrane of guard cells. The application of exogenous ABA on leaves of normal plants causes closing of stomata within a few minutes. ABA acts in the presence of CO2​, which decreases the pH of guard cells. ABA includes the loss of K+ ions, which decreases the osmotic concentration of guard cells as compared to adjacent epidermal cells. This causes exosmosis and turgidity of guard cell decreases.

Question 19

Stomatal opening is regulated by

Accepted Answer

The most significant physiological feature of stomata is their response to light. Generally stomata open in the day time, i.e., light and close at night or in darkness. These are called as photoactive stomata. However, in succulent plants like Kalanchoe of family- Crassulaceae, the stomata open at night and close in the day time. Such stomata are called scotoactive stomata.

Question 20

The stomata in CAM plants open during

Accepted Answer

Stomata of CAM plants are closed during most of the day time and open during night (i.e., scotoactive) because these plants survive in dry and hot environmental conditions. These plants have the capacity to store 
CO2​ during night and this CO2​ is used in photosynthesis during day time when stomata are closed.

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Solution for Class 11, Biology, Transport in plants

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