Abscisic acid signaling pathway | ABA mediated stomatal opening and closure

Summary

The video script delves into the role of abscisic acid in regulating stomatal movement in plants. Stomata, crucial for gas exchange, open during the day for carbon dioxide intake and close at night to conserve water, influenced by abscisic acid. Guard cells control this process, swelling with water during the day to open stomata and losing water at night due to abscisic acid, leading to closure. The script explains the cellular mechanisms involving ion channels, the proton pump, and the impact of sunlight on these processes, highlighting the dynamic balance between environmental cues and plant physiology.

Takeaways

• 🌿 Stomata are crucial structures in plant leaves that regulate gas and water exchange with the environment.
• 🌞 Abscisic acid (ABA) plays a significant role in controlling stomatal opening and closing, which is essential for plant water conservation.
• 💧 During the day, stomata open to allow carbon dioxide and water intake, and ABA is not present, facilitating this process.
• 🌑 At night or in hot conditions, ABA is secreted, leading to stomatal closure to prevent water loss through evaporation.
• 🔬 Guard cells, with their unique structure, are responsible for the movement of ions and water that control stomatal aperture.
• 💧 The opening of stomata involves the influx of water into guard cells, causing them to swell and the stomata to dilate.
• 🌡️ ABA binds to its receptor on guard cells, initiating a signaling cascade that leads to water loss from the guard cells and stomatal closure.
• 🔄 Ion channels, including potassium and chloride channels, are integral to the movement of ions that regulate guard cell turgor and, consequently, stomatal movement.
• 🌱 The proton pump in guard cells contributes to creating an osmotic imbalance that drives water movement into or out of the guard cells.
• 🌅 Blue light during the day activates the proton pump, leading to the production of ATP and the influx of potassium and sugars into guard cells, promoting stomatal opening.

Q & A

What is the primary function of stomata in plant leaves?

Stomata in plant leaves are crucial for regulating the intake of carbon dioxide, oxygen, and water from the environment by the plants.

How does abscisic acid influence stomatal opening and closing?

Abscisic acid plays a significant role in stomatal regulation. It triggers closure during conditions like high temperatures to prevent water evaporation, while stomata open in the presence of sunlight without the influence of abscisic acid.

What are guard cells, and how are they related to stomata?

Guard cells are specialized cells surrounding the stomatal pore. They regulate the opening and closing of stomata by swelling or shrinking, which is influenced by the presence of abscisic acid.

What happens to the guard cells when abscisic acid is secreted?

When abscisic acid is secreted, it binds to the abscisic acid receptor, leading to cell signaling processes that cause the guard cells to lose water, become flaccid, and ultimately close the stomata.

What are the roles of vacuoles and endoplasmic reticulum in stomatal regulation?

Vacuoles, particularly the storage vacuoles in guard cells, and the endoplasmic reticulum are important for ion storage and regulation, which are crucial for the movement of ions and water that control stomatal opening and closing.

How do ion channels contribute to the stomatal movement?

Ion channels, including potassium and calcium channels in the guard cell membrane and vacuole membrane, as well as chloride ion channels, facilitate the movement of ions in and out of the guard cells, which affects the turgor pressure and thus the opening and closing of stomata.

What is the role of the proton pump in guard cells?

The proton pump in guard cells helps maintain the osmotic balance by pumping protons (H+) out of the cell. It also contributes to ATP synthesis, which is important for the energy required during stomatal movement.

How does the presence of sunlight affect stomatal opening?

Sunlight, particularly the blue wavelength, activates the proton pump, leading to an osmotic imbalance that causes potassium and sugars to flow into the guard cells. This influx of solutes draws water into the guard cells, causing them to swell and open the stomata.

What is the significance of the calcium influx in guard cells?

Calcium influx in guard cells, triggered by the binding of abscisic acid to its receptor, leads to the deactivation of potassium influx carriers and the activation of chloride export channels, resulting in the loss of water and closure of stomata.

Can you explain the role of reactive oxygen species (ROS) in stomatal regulation?

Reactive oxygen species, such as H2O2, are activated by the abscisic acid receptor and contribute to the calcium influx, which further drives the stomatal closure process by affecting ion channels and pumps.

How does the absence of abscisic acid during the daytime lead to stomatal opening?

In the absence of abscisic acid during the daytime, the proton pump is activated by sunlight, leading to the influx of potassium and sugars into the guard cells. This creates an osmotic imbalance that draws water into the guard cells, causing them to swell and open the stomata.

Outlines

00:00

🌿 Regulation of Stomatal Movement by Abscisic Acid

This paragraph explains the crucial role of abscisic acid in regulating stomatal opening and closure in plant leaves. Stomata are essential for plants to intake carbon dioxide, oxygen, and water. During daytime, stomata open to allow gas exchange, but they must close during hot temperatures to prevent water loss. Guard cells, which consist of two cells surrounding a pore, control stomatal movement. Abscisic acid, secreted in the absence of sunlight, binds to its receptor and triggers a signaling cascade that leads to the loss of water from guard cells, causing them to shrink and stomata to close. The paragraph also discusses the involvement of vacuoles, endoplasmic reticulum, ion channels, and the proton pump in this process.

05:01

🌞 Stomatal Response to Abscisic Acid and Sunlight

This paragraph delves into how abscisic acid and sunlight influence stomatal movement. In the presence of abscisic acid, stomata close due to the loss of water from guard cells, leading to a reduction in cell turgor and stomatal constriction. Conversely, during sunlight, blue light activates the proton pump, promoting the influx of potassium and sugars into guard cells, which increases cell turgor and opens the stomata. The paragraph highlights the osmotic imbalances created by ion movements and the subsequent water transport that drives stomatal opening and closure. The summary underscores the dual role of abscisic acid in stomatal regulation, closing stomata at night and allowing them to open during the day in the absence of the hormone.

Keywords

💡Abscisic Acid

Abscisic acid is a plant hormone that plays a crucial role in regulating stomatal opening and closure. It is particularly important in response to environmental stressors such as drought, high temperatures, and salinity. In the context of the video, abscisic acid is secreted when there is no sunlight, leading to stomatal closure to prevent water loss through evaporation. The script mentions that 'abscisic acid binds to the abscisic acid receptor and due to some cell signaling processes, ultimately this guard cell loses water, and as a result, the stomata will close up.'

💡Stomata

Stomata are small pores found on the surface of plant leaves, which are essential for gas exchange. They regulate the intake of carbon dioxide for photosynthesis and the release of oxygen and water vapor. The video script describes how stomata open during the day to allow carbon dioxide intake and close at night or during stress to conserve water, as indicated by 'stomata is a very important structure in the plant leaves, that regulates, the intake of carbon dioxide oxygen and water from the environment by the plants.'

💡Guard Cells

Guard cells are specialized plant cells that surround the stomata and control their opening and closing. They are unique because they have the ability to change shape, allowing them to regulate the size of the stomatal pore. The script explains that 'the stomatal opening and closure are regulated by known as the guard cells, two guard cells and one simple pore in the center.'

💡Water Transport

Water transport in plants is essential for maintaining turgor pressure, which in turn affects the opening and closing of stomata. During the day, water flows into the guard cells, causing them to swell and the stomata to open. Conversely, at night or in the presence of abscisic acid, water is lost from the guard cells, leading to stomatal closure. The video script illustrates this with 'during daytime, water start to flow inside of this guard cell make this guard cell, really really target as a result of which the stomata gets opened.'

💡Ion Channels

Ion channels are proteins embedded in the cell membrane that allow the passage of ions across the membrane. In the context of the video, potassium and calcium ion channels are mentioned as playing a role in the movement of ions in and out of the guard cells, which influences the opening and closing of stomata. The script states, 'there are different ion channels like positive ion channels of potassium channel and calcium channel, both are present in the membrane of the guard cell as well as in the vacuole membrane.'

💡Calcium Influx

Calcium influx refers to the movement of calcium ions into the cell. In the video, it is described as a key process in the signaling pathway that leads to stomatal closure. The script explains that 'this IP3 can easily go and interact with the calcium channels in the vacuole and allow the calcium to be transported from black hole into the guard cell cytosol as a result what we see is a calcium influx.'

💡Reactive Oxygen Species (ROS)

Reactive oxygen species are molecules containing oxygen that are highly reactive due to the presence of unpaired electrons. In plants, ROS such as H2O2 can act as signaling molecules. The video script mentions that 'this reactive oxygen species also causes the calcium influx channels to drive more calcium ions inside this guard cell,' indicating a secondary calcium influx triggered by ROS.

💡Proton Pump

A proton pump is a type of membrane protein that uses energy to move protons (H+ ions) across a membrane, typically from a region of lower to higher concentration. In the video, the proton pump is activated by blue light during the day, contributing to the opening of stomata. The script describes this process: 'the sun provides the blue light, particularly the blue wavelength of the light interacts to the for proton pump, and activates the proton pump so start to attach with atp synthase activity.'

💡Osmotic Imbalance

Osmotic imbalance occurs when there is a difference in solute concentration across a membrane, leading to the movement of water to balance the concentration. In the context of the video, osmotic imbalance is created when ions move out of the guard cells, causing water to move out as well, leading to stomatal closure. The script states, 'as a result of this outside movement of positively and negatively charged ions there is an osmotic imbalance created and to tackle this osmotic imbalance the only way is the movement of water.'

💡ATP Synthase

ATP synthase is an enzyme that catalyzes the synthesis of ATP from ADP and inorganic phosphate (Pi), using energy stored in a proton gradient. In the video, ATP synthase activity is linked to the proton pump's function during the day, contributing to the osmotic imbalance that leads to stomatal opening. The script mentions, 'because the proton pump has a ATP synthesis activity, ATP gets hydrolyzed into ADP and Pi as a result the proton pump start to transfer protons from the guard cell outside.'

Highlights

Stomata are crucial structures in plant leaves that regulate gas and water exchange.

Abscisic acid plays a key role in controlling the opening and closing of stomata.

During daytime, stomata need to open for CO2 and water intake, but must close during hot temperatures to prevent water loss.

In the presence of sunlight, stomata open without the influence of abscisic acid.

Guard cells regulate stomatal movement, swelling when water flows in and shrinking when it flows out.

Abscisic acid binds to its receptor, initiating a series of cell signaling processes.

The release of abscisic acid leads to guard cell water loss and stomatal closure.

Vacuoles and endoplasmic reticulum within guard cells are important for calcium storage.

Ion channels, including potassium and calcium channels, are involved in the regulation of stomatal movement.

The proton pump in the guard cell membrane helps maintain osmotic balance.

Abscisic acid receptor activation leads to the production of inositol trisphosphate (IP3), which triggers calcium release from vacuoles.

Reactive oxygen species (ROS), such as H2O2, contribute to calcium influx in guard cells.

High calcium concentration deactivates potassium influx carriers and activates chloride export channels.

The proton pump is inhibited by calcium, leading to an acidic internal environment in guard cells.

Osmotic imbalance due to ion movement causes water to move out of guard cells, leading to stomatal closure.

In the absence of abscisic acid and presence of sunlight, blue light activates the proton pump, promoting stomatal opening.

ATP hydrolysis and potassium influx are activated by the proton pump during daytime, contributing to stomatal opening.

Sugars produced during photosynthesis also contribute to the osmotic pressure that opens stomata.

Stomata close at night due to abscisic acid and open during the day in its absence, balancing water loss and gas exchange.

Transcripts

okay now let's look into the matter of

how abscisic acid regulates the stomatal

opening and clogging stomata is a very

important structure in the plant leaves

that regulates

the intake of carbon dioxide oxygen and

water from the environment by the plants

and abscisic acid play a very important

role in terms of opening and closing the

stomata plants need to open the stomata

during day time in order to get the

carbon dioxide and water and also plant

need to prevent the stomatal opening

during very very hot temperatures to

prevent the water evaporation

so here we will see that in the presence

of

sunlight the stomata must open and in

presence of sunlight there is no role of

abscisic acid no presence of abscisic

acid as a result the stomata

will be opened the stomatal opening and

closure are regulated by known as the

guard cells two guard cells and one

simple pore in the center as you can see

in this picture

and this guard cell will get a rush of

water during the daytime during daytime

water start to flow inside of this guard

cell make this guard cell

really really target as a result of

which the stomata gets opened but when

there is no sunlight

then there is secretion of abscisic acid

and as a result of release of abscisic

acid the abscisic acid binds to the

abscisic acid receptor and due to some

cell signaling processes

ultimately this guard cell loses water

and as a result the guard cells will

become flashy and the stomata will close

up so let's see how exactly this

abscisic acid regulates the stomatal

opening and closure

and this stomatal opening closure there

are different components important one

of such component is the vacuole and

endoplasmic reticulum that are present

inside the cells particularly here the

specific

calcium stored storage vacuoles of the

guard cells are important

apart from them there are different ion

channels like positive ion channels of

potassium channel and calcium channel

both are present

in the membrane of the guard cell as

well as in the vacuole membrane

and then chloride ion channels that are

present again in the back pole as well

as in the guard cell membrane

apart from that there is a proton pump

present in the guard cell membrane that

usually pumps proton h plus from the

guard cell outside of the cell

and this potassium transporters are of

two types in flux as well as efflux

influx takes potassium inside if flux

takes potassium outside but the chloride

channels that we find in the surface of

the guard cell membrane are export

channels only

and the most important thing is the

abscisic acid receptor that is found on

the surface of this guard cell and the

signaling begins when there is a ligand

in this case the abscisic acid act as a

ligand will bind to the abscisic acid

receptor or abar and due to this

interaction there is a cell membrane

associated component known as

phospholipid c and produces inositol

tris phosphate ip3 this ip3 can easily

go and interact with the calcium

channels in the vacuole and allow the

calcium to be transported from black

hole into the guard cell cytosol as a

result what we see is a calcium influx

this is the primary calcium influx

this abscisic acid receptor once

activated also activate reactive

reactive oxygen species or ros this

reactive oxygen species example is h2o2

simply this reactive oxygen species also

causes the calcium influx channels to

drive more calcium ions inside this

guard cell

so what happen is a secondary calcium

influx so both this calcium influx

causes high calcium concentration inside

the guard cell this high calcium

concentration have two different

consequences these calciums will go and

interact to the potassium influx

carriers and what it does is

deactivating the potassium influx

carrier as a result potassium ions

cannot be transported inside of the

guard cell

this calcium ions also move and interact

with the chloride export channels and

they allow chlorides cl minus to be in

exported out of the guard cell

outside

this calcium also interacts with the

proton pump and inhibits the function of

the proton pump as a result the proton

cannot be pumped out so there is a high

concentration of h plus building up in

the guard cell making the guard cell

inside ambience acidic and outside

alkaline

and as a result of this high

concentration of chloride

potassium efflux channels or exporters

are activated which will start taking up

potassium outside to compensate this

balance of potassium outflow potassium

and chlorides start to transport via

calcium and chloride both start to

transport from vapor into the guard cell

cytoplasm

see

they start moving outside into the guard

cell cytoplasm

now the more calcium influx is done the

more chloride is transported to the

cytoplasm of guard cell the more they

are transported out the more they are

transported out via potassium channel

via chloride channel so ultimately what

we see is a movement of potassium and

chlorides rapidly from the guard cell

outside and as a result of this outside

movement of positively and negatively

charged ions there is an osmotic

imbalance created and to tackle this

osmotic imbalance the only way is the

movement of water from

the low solute concentration to the high

solute concentration and in this case

the high solute concentration is

surrounding of the guard cell so water

will move from the guard cell outside

via specific water transporter channels

in the gut cell which are not shown in

this picture

this is what happens when there is

presence of abscisic acid and as a

result of this net water movement

outside

the

guard cells become really flashy and as

a result of which the guard cells

overall opening becomes constricted and

stomata gets closed

now let's look at another situation when

there is sunlight

when there is sunlight

the sun provides the blue light

particularly the blue wavelength of the

light interacts to the for proton pump

and activates the proton pump so start

to attach with atp synthase activity

because the proton pump has a atp

synthesis activity

atp gets hydrolyzed into adp and pi as a

result the proton pump start

to

transfer protons from the guard cell

outside and as a result of this proton

movement outside there is a osmotic

imbalance start to be created and soon

this potassium

influx carriers also activated potassium

start to flow inside so potassium start

flowing inside as the potassium start to

rush flowing inside and we know during

day time the plants start producing

their food so food means glucose and

sucrose and other sugars are produced

the sugars will also start their journey

to move inside this guard cell via the

sugar transporter the sugar can migrate

on its own by the sugar transporters or

the sugar can migrate along with a

proton inside of the guard cell with a

co-transport model in both the way there

is a high flow of proton sugar as well

as potassium inside the guard cell in

presence of blue light that means in the

daytime as a result of which

again there is an osmotic imbalance more

electrolytes sugar inside the guard cell

than outside so as a result water which

is present surrounding the guard cell

start to rush in via water channels

inside the guard cell and as a result of

which what will happen as water rushes

in this guard cell will become

hugely turgid as a result of this high

turgidity of the guard cell they open up

the stomata and this is how the stomatal

opening is done in the absence of

abscisic acid in the daytime so for

summary in the abscisic acid when it's

present the stomata will be closed when

there is no abscisic acid the stomata

will be open the abscisic acid closes

the stomata during night time and

without abscessing acid during daytime

stomata opens up