Stomata

Transpiration is the loss of water through stomata.

The rate of transpiration

• decreases on very hot days

• is less on very hot days

• changes only on very hot days

• increases on very hot days

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What happens to the guard cells when water is not available within a plant?

• The guard cells close.

• The guard cells open.

• The guard cells become double.

• The guard cells increase.

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Which process opens and closes guard cells when regulating water in the plant?

• Diffusion

• Osmosis

• Active Transport

• Passive Transport

What is the relationship between stomata and photosynthesis in plants?

• The stomata is dependent on photosynthesis.

• The stomata are reactants of photosynthesis.

• Photosynthesis is dependent on stomata.

• Photosynthesis is independent of stomata.

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The Control of Transpiration

Plants normally lose water from openings (stomates) in their leaves.

The water loss typically occurs during daylight hours when plants are exposed to the Sun. This water loss, known as transpiration, is both beneficial and harmful to plants.

Scientists believe wind and high temperatures increase the rate of transpiration, but the size of each stomate opening can be regulated.Reducing the size of the openings during drought conditions may help reduce the dehydration and wilting that would otherwise occur.

A leaf may lose more than its own weight in water each day.Transpiration also lowers the internal temperature of the leaf as water evaporates. On hot days, temperatures in the leaves may be from 3°C to 15°C cooler than the outside air. With stomates open, vital gases maybe exchanged between the leaf tissues and the outside environment.

Researchers have also found many plants that use another response when leaf temperatures rise. Special molecules known as heat shock proteins are produced by plant cells and help to hold enzymes in their functional shapes.

State one way transpiration is beneficial to plants.

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NGSS.HS-LS2-6

Guard cells are specialized cells in the surface of the leaf of a green plant.

The main function of these cells is to

• change the size of the stomate to regulate water loss

• close the stomate to keep dust and dirt out of the leaf

• close the stomate to keep dust and dirt out of the leaf

• close the stomate to keep dust and dirt out of the leaf

Which sequence represents structures organized

from most complex to least complex?

• chloroplast - guard cell -leaf - oak tree

• guard cell - chloroplast -leaf - oak tree

• oak tree -guard cell - leaf -chloroplast

• oak tree - leaf- guard cell -chloroplast

A student designed an experiment to determine if air temperature had an effect on the rate of photosynthesis in corn plants.

Which tool is correctly paired with a procedure that could be used during this experiment?

• an electronic balance to measure the volume of soil in which each corn plant is grown

• a graduated cylinder to measure 30 mL of water for each plant daily

• a metric ruler to determine the mass of each plant each week

• a Celsius thermometer to determine the pH of the soil

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Leaves of green plants contain openings known as stomates, which are opened and closed by specialized cells allowing for gas exchange between the leaf and the outside environment. Which phrase best represents the net flow of gases involved in photosynthesis into and out of the leaf through these openings on a sunny day?

• carbon dioxide moves in; oxygen moves out

• carbon dioxide and oxygen move in; ozone moves out

• oxygen moves in; nitrogen moves out

• water and ozone move in; carbon dioxide moves out

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NGSS.MS-LS1-6

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Which situation is not an example of the maintenance of a dynamic equilibrium in an organism?

• A runner perspires while running a race on a hot summer day.

• The release of insulin lowers the blood sugar level in a human after eating a big meal.

• Water passes into an animal cell causing it to swell.

• Guard cells contribute to the regulation of water content in a geranium plant.

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