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:
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
How is the amount of urine produced regulated?
What criteria do we use to decide whether something is alive?
What are the different ways in which glucose is oxidised to provide energy in various organisms?
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 would be the consequences of a deficiency of haemoglobin in our bodies?
What are the components of the transport system in highly organised plants?
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?
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
What changes can you make in your habits to become more environment-friendly?
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?
Translate the following statements into chemical equations and then balance them.
(a) Hydrogen gas combines with nitrogen to form ammonia.
(b) Hydrogen sulphide gas burns in air to give water and sulpur dioxide.
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
What is a good source of energy?
Compare the power used in the 2 Ω resistor in each of the following circuits:
(i) a 6 V battery in series with 1 Ω and 2 Ω resistors, and (ii) a 4 V battery in parallel with 12 Ω and 2 Ω resistors.
Outline a project which aims to find the dominant coat colour in dogs.
State two ways to prevent the rusting of iron.
Why do we apply paint on iron articles?
How is the equal genetic contribution of male and female parents ensured in the progeny?
What are the disadvantages of fossil fuels?
Only variations that confer an advantage to an individual organism will survive in a population. Do you agree with this statement? Why or why not?
What do you mean by a precipitation reaction? Explain by giving examples.