what are the environment condition influence the opening and close of stomata?

Answer 1

There are many factors which lead to stomata opening and closing.

i) There is an endogenous rhythm (a biological clock). Stomata open during the day and close during the night. (Though certain succulents which are native to hot, dry conditions have a reversed rhythm to enable them to economise on water loss.) However, stomata continue to open and close on an approximately 24 hour clock (circadian = about a day) even when switched to continuous light. The phase of this opening and closure can be shifted (made to occur at other times of the day) by contol of the end of the dark period.

ii) The water balance of a plant affects stomatal apperture. Wilting plants close their stomata. The plant growth regulator abscisic acid (ABA) seems to act as a mediator under these conditions. Water stress in the roots can transmit (in xylem?) its influence to stomata in leaves by the signal of ABA.

iii) Low concentrations of CO2 cause stomata to open. If CO2-free air is blown across stomata in darkness, their stomates open. High CO2 causes stomates to close.

iv) Light causes stomates to open. The minimum light level for opening of stomates in most plants is 1/1000 to 1/30 of full sunlight, just enough to cause some net photosynthesis. Blue light (430-460nm) is nearly 10 times as effective as red light (630-680nm). The wavelengths that are effective in the red part of the spectrum are the same as those that are effective in photosynthesis ie is absorbed by chlorophyll. However, the blue light effect is quite independent of photosynthesis. Photosynthesis will change intercellular CO2 concentrations and may have its effect through number iii) above.

So, how are these movements brought about?

Blue-light wavelengths of daylight, detected by zeaxanthin (a carotenoid) activate proton pumps in the guard cell membranes, which proceed to extrude protons from the cytoplasm of the cell; this creates a "proton motive force" (an electrochemical gradient across the membrane) which opens voltage operated channels in the membrane, allowing positive K ions to flow passively into the cell, from the surrounding tissues. Chloride ions also enter the cell, with their movement coupled to the re-entry of some of the extruded protons (Cl/H symport) to act as a counter-ions to the potassium. Water passively follows these ions into the guard cells, and as their tugidity increases so the stomatal pore opens, in the morning. As the day progresses the osmotic role of potassium is supplanted by that of sucrose, which can be generated by several means, including starch hydrolysis and photosynthesis. At the end of the day (by which time the potassium accumulation has dissipated) it seems it is the fall in he concentration of sucrose that initiates the loss of water and reduced turgor pressure, which causes closure of the stomatal pore.

ABA also seems to trigger a loss of K ions from guard cells. Some workers suggest that in some species, ABA alters turgor pressure without changing solute potential or water potential.

There is evidence of a role for increased cytoplasmic calcium (Ca2+) in closure, possibly by effects on opening/closing of ion channels at the plasma membrane.

Starch break down to phosphoenol pyruvate (PEP) is stimulated by blue light. This PEP then combines with CO2 to fom oxaloacetic acid, which is converted to malic acid. It is H ions from the malic acid which leave the cell in the mechanism outlined above. Thus the intake of K ions is matched by formation of anions from malic acid in the guard cells. This causes an increase in osmotically active substances in exchange for the breakdown of starch in guard cells.

References:-

Hart, J.W. in Light & Plant Growth (1988), 2nd Impression 1990. (pp 135-6).

Taiz and Zeiger in Plant physiology - 2nd ed.(1998) published by Sinauer, ISBN 0-87893-831-1 (pp 522-530)

Salisbury and Ross in Plant Physiology 4th ed (1992) published by Wadsworth, California, ISBN 0-534-15162-0

A good recent source of information is J.exp.Bot., volume 49, March, 1998, which is a special issue on Stomatal Biology.

John Hewitson, Roger Delpech and Richard Price (SAPS)

Answer 2

Basically, the moisture content and hydrology of the plant's surroundings. The dampness correlates with the water content of the atmosphere. If the air is extremely damp, then it is humid. This can affect the transpirational pull of plants as the air around it has a different water content. The water within plants exits via transpiration and with the aid of adhesion-cohesion mechanism and water potential. So, if water cannot exit easily due to the external factor of humidity [or moisture], water is more likely to be contained within the cells and renderring them more dilute, i.e. higher water potential, less sucrose concentration. The converse is also true, leading to high solute potential because of less water but more sucrose. The variation of solute and water potential will then affect the movement of water molecules by the osmotic pressure. Hence, when the cells of stomata are high in solute, water enters easily because the stomata is now hypertonic to the neighbouring cells, and vice versa. The water content of the cells will then cause the cells [guard cells of stomata] to expand or shrink, thus controlling the opening of the stomata.

Other factors such as the sunlight, will alter the osmotic pressure of the guard cells of stomata. If there is sunlight, sucrose is produced through photosynthesis, thus increasing the solute potential of the guard cells. Then the same thing occurs as the case mentioned above on water content.

Answer 3

Usually in C4 plants, the stomata closes due to the hot climate and the need to store their water supply. (hope it helps?)

Answer 4

the dryness of the air surrounding the stomata causes them to open and close. osmosis of water into the cells surrounding the stomata opens and closes them. when its drier they close up and keep water in, when tis moist out they open up.

i beleive that's how it works

Answer 5

A stoma opens as the guar cells take in water, lengthen, and bow apart. A stoma closes as the guard cells lose water, shorten, and come together