How do the guard cells regulate opening and closing of stomatal pores?
Stomata are the specialized structures that are responsible for the exchange of gases between the plant and the environment. Stomata consist of small pores which are surrounded by a pair of kidney shaped guard cells which helps in the regulation of stomatal apertures. The opening and closing of the stomata is caused by the changes in the turgidity of the guard cells. Process of opening and closing of stomata:-
Stomata opening occurs due to the osmotic entry of water into the guard cells. When the water level or turgidity increases within two guard cells the thin outer walls bulge out and they elongate themselves because of the microfibrils in the cell wall of the guard cells. This expansion pulls off the guard cells and the increased turgidity of the cell wall causes the stomata to open.
Closing of stomata involves the reverse process in which when the guard cells lose turgidity due to the water loss from the elastic inner walls helps to regain their original shape. Then the guard cell becomes flaccid and closes the stomata.
Diagram:
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How is the amount of urine produced regulated?
What criteria do we use to decide whether something is alive?
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The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a) cytoplasm. (c) chloroplast.
(b) mitochondria. (d) nucleus.
What are the differences between autotrophic nutrition and heterotrophic nutrition?
What are outside raw materials used for by an organism?
What are the components of the transport system in highly organised plants?
What would be the consequences of a deficiency of haemoglobin in our bodies?
What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
What is a good source of energy?
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What is the difference between a reflex action and walking?
What is the importance of DNA copying in reproduction?
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Why should a magnesium ribbon be cleared before burning in air?
Define the principal focus of a concave mirror.
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
Draw magnetic field lines around a bar magnet.
A battery of 9 V is connected in series with resistors of 0.2 Ω, 0.3 Ω, 0.4 Ω , 0.5 Ω and 12 Ω, respectively. How much current would flow through the 12 Ω resistor?
Write word equations and then balanced equations for the reaction taking place when –
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(b) dilute hydrochloric acid reacts with magnesium ribbon.
(c) dilute sulphuric acid reacts with aluminium powder.
(d) dilute hydrochloric acid reacts with iron filings.
State whether the following statements are true or false.
(a) An electric motor converts mechanical energy into electrical energy.
(b) An electric generator works on the principle of electromagnetic induction.
(c) The field at the centre of a long circular coil carrying current will be parallel straight lines.
(d) A wire with a green insulation is usually the live wire of an electric supply.
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(a) pupil. (b) retina.
(c) ciliary muscles. (d) iris.
Name some sources of direct current.
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(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat