What is the role of guard cells in stomata?

Answer 1

To protect the stomas.

Related Information:

However, most plants do not have the aforementioned facility and must therefore open and close their stomata during the daytime in response to changing conditions, such as light intensity, humidity, and carbon dioxide concentration. It is not entirely certain how these responses work. However, the basic mechanism involves regulation of osmotic pressure.

When conditions are conducive to stomatal opening (eg. high light intensity and high humidity), a proton pump drives protons (H+) from the guard cells. This means that the cells' electrical potential becomes increasingly negative. The negative potential opens potassium voltage - gated channels, and so an uptake of potassium ions (K+) occurs.

To maintain this internal negative voltage, so that entry of potassium ions does not stop, negative ions balance the influx of potassium. In some cases chloride ions enter, while in other plants the organic ion malate is produced in guard cells. This in turn increases the osmotic pressure inside the cell, drawing in water through osmosis. This increases the cell's volume and osmotic pressure.

Then, because of rings of cellulose microfibrils that prevent the width of the guard cells from swelling, and thus only allow the extra turgor pressure to elongate the guard cells, whose ends are held firmly in place by surrounding epidermal cells, the two guard cells lengthen by bowing apart from one another, creating an open pore through which gas can move.

When the roots begin to sense a water shortage in the soil, abscisic acid (ABA) is released. ABA binds to receptor proteins in the guard cells' plasma membrane and cytosol, which first raises the pH of the cytosol of the cells and causes the concentration of free calcium ions (Ca2+) to increase in the cytosol, due to the influx from outside the cell and the release of Ca2+ from internal stores such as the endoplasmic reticulum and vacuoles.

This causes the chloride (Cl-) and other inorganic ions to exit the cells. Secondly, this stops the uptake of any further K+ into the cells and subsequently the loss of K+. The loss of these solutes causes a reduction in osmotic pressure, making the cell flaccid, and so it closes the stomatal pores.

Interestingly, guard cells have more chloroplasts than the other epidermal cells from which guard cells are derived. Explanations of the function of these chloroplasts' are controversial.

See related links for explanation of terms.

Answer 2

Stomata are surrounded by a pair of guard cells. The guard cells open and close it, when the stomata close the plant stops photosynthesis due to carbon dioxide (CO2) not being able to enter the plant. Stomata are found on the underside of the leaf -lower epidermis-! Stomata often close when the weather is very hot and dry to stop too much water loss and prevent excess transpiration!

(sunlight & chlorophyll)

photosynthesis - Water + carbon dioxide =========== C6H12O6 + 6O2

You guys are so lucky I know all this, I wish someone knew when I needed the answer -.- and your welcome =D <3

Answer 3

There are two theories for this mechanism:-

1. Starch concentration theory-guard cells become turgid when they are saturated with starch.
2. K+ ion concentration theory- guard cells become turgid when there are more of potassium ions in the surrounding cells

But, always, guard cells work only due to alternate flaccidity and turgidity.

Answer 4

The stomata opens and closes to let out or get in water particles which are required for every carbon dioxide particle, for photosynthesis. In Theory the stomata would close in dry settings, so photosynthesis would not take place if the plant was in a dry place, so moisture is key to photosynthesis.

Answer 5

they control the opening and closing of the stomata

Answer 6

I cannot answer it sorry