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About This Video ........................
In This Video Lecture You Will Learn Basic Concept Of Mechanisms of opening and closing of stomata
The guard cells function as multisensory hydraulic valves. Environmental factors, such as
light intensity and quality, temperature, relative humidity, and intracellular CO2
sensed by guard cells and these signals are integrated into well-deined stomatal responses.
guard cells (during night) water leaves the guard cells by exosmosis and guard cells become laccid
There are two hypotheses which may explain the opening and closing of stomata.
from guard cells followed
too dark for photosynthesis.
potential decreases - and the guard cells become turgid due to entry of water and they separate
upon plant species.
followed by water uptake resulting in increased turgidity of guard cells. So in general stoma are
i) Starch Sugar Hypothesis : The German botanist H. Van Mohl proposed that the guard cells
into and out of guard cells?
from one another, and stoma or pore opnes. During night there is no photosynthesis the sugars
Stomata open due to active transport of potassium ions (K+
Level of carbon dioxide in the spaces inside the leaf and light, control this movement. A low level
ions : Potassium concentration in guard cells increases several fold, depending
and increased rate of photosynthesis.
are either converted into insoluble starch or are used in respiration, this decreases free sugars
) into the guard cells from the surrounding
epidermis. The accumulation of K+
decreases the osmotic potential of guard cells. Water enters
of carbon dioxide favours opening of the stomata, thus allowing an increased carbon dioxide level
Exposure to blue light, which is also efective in photosynthesis has been shown to acidify the
to account for the rapid rise in turgor, of guard cells.
the guard cells by osmosis, which become more turgid and stretched and stomata are opened.
by water moving out by osmosis. What controls the movement of K+
open during day and closed at night. This prevents needless loss of water by the plant when it is
day time when light is available. When sugar level rises i.e. solute concentration increases or water
ii) Inlux of K+
The stoma closes by reverse process; involving passive difusion of K+
by osmosis. Guard cells become turgid and stoma or pore opens. When Potassium leaves the
The plants open their stomata by actively pumping Potassium in guard cells causing water to follow
become laccid and stoma or pore between them closes. But these processes are not fast enough
are the only photosynthesising cells of epidermis of leaf and sugars are produced in them during
environment of the guard cells (i.e. pumps out protons) which enable the guard cells to take up K+
in cell. So the osmotic pressure of guard cells is lowered, and water leaves the guard cells, which
and stoma or pore between guard cells closes.
About This Channel.....................
I make these videos cause I love to draw and connect the complexity of science and medicine into art. I'm not saying. I'm 100% correct in all my videos, but I do try to obtain the information from credible sources.
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Visit My Other Channel Playlist .....................
NMDCAT PART 1: • New 1st Year Biology
NMDCAT PART 2: • New 2nd Year Biology
Class 11th Lectures: • New 1st Year Biology
Class 12th Lectures: • New 2nd Year Biology
Class 10th Lectures:
• Matric Biology
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