Do Guard Cells Have Chloroplasts:7 Facts You Should Know

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Chloroplasts essential for photosynthesis are present in guard cells. The guard cells aid in gas exchange. In this article, we will find out “Do guard cells have chloroplasts”

Guard cells localized in the stems and epidermis of leaves play a crucial role in photosynthesis and transpiration. Let us learn some interesting facts about guard cells and the role played by chloroplasts in guard cells.

7 different facts on guard cells:

  1. The only epidermal cells having chloroplasts are guard cells.
  2. Ploidy of the species is directly proportional to the number of chloroplasts in the guard cells.
  3. The number of guard cells varies with the different species.
  4. The guard cells are morphologically different from other epidermal cells.
  5. The adjustable pores formed by guard cells are known as stomata.
  6. Stomata aid in the cooling of leaves through transpiration.
  7. Carbon dioxide and water pass through stomatal pores.

Why do guard cells have chloroplasts?

Chloroplasts present in guard cells act as photoreceptors. Chlorophyll present in chloroplasts helps in trapping sunlight.

Guard cell chloroplasts also contribute to ATP supply, starch storage, and blue-light signaling. The opening of the stomatal pore created by guard cells is dependent on light availability.

Guard cell chloroplasts have different morphological features as compared to the general ones. Less number of granal stackings are identified in guard cell chloroplasts. Also, several guard cell chloroplasts accumulate starch in the dark, unlike mesophyll chloroplasts.

do guard cells have chloroplasts
Leaf structure from Wikimedia

Guard cell chloroplasts play four specific functions: ATP production via electron transport in guard cells; chloroplasts respond to blue-light signaling; in guard cells, chloroplasts store starch that synthesizes malate; chloroplasts are responsible for assimilating carbon.

Do guard cells do photosynthesis?

Yes, guard cells do photosynthesis.

The light reaction stage and dark reaction stage are the two stages of photosynthesis. The site of light reaction is the chloroplast grana while for the dark reaction it is the chloroplast stroma. Chlorophyll helps in the conversion of light energy to chemical energy. The two products of the light reaction are ATP and NADPH. Both these products are used for the production of sugar in the dark reaction stage.

Photosystem I and photosystem II are the two protein complexes of the thylakoid membrane used for the conversion of light energy to chemical energy.

Two types of light-dependent reactions are identified: cyclin and non-cyclic. The electron transport chain of non-cyclic reactions is popularly known as Z-scheme. During photosynthesis, ATP is generated with the help of the ATP synthase enzyme and the terminal redox reaction produces NADPH.

There are several controversial reports regarding the presence of the dark reaction stage or Calvin cycle in guard cell chloroplasts. In this reaction, sugar is produced by using carbon dioxide, ATP, and NADPH. The product of the dark reaction stage i.e; the sugar can be used for cellulose production or stored as starch.

Apart from the production of ATP and NADPH, photolysis of water also takes place.

RuBisCO enzyme is the key player in the dark stage reaction. It traps atmospheric carbon dioxide with the help of NADPH in order to produce three-carbon sugar. RuBisCO fixes carbon.

Do Monocot guard cells have chloroplasts?

No, monocot guard cells do not have chloroplasts.

Do guard cells have more chloroplasts than spongy mesophyll?

Guard cells have more chloroplasts than spongy mesophyll.

On the leaf surface, the epidermis is the outermost layer. The two types of cells of mesophyll tissue; spongy and palisade are also known to have chloroplasts.

Do guard cells have more chloroplasts than palisade mesophyll?

No, guard cells do not have more chloroplasts than palisade mesophyll.

Number of chloroplasts in guard cells

Guard cells of most of the species are reported to have 10 – 15 chloroplasts.

In Selaginella, 3-6 chloroplasts were reported per guard cell. In Polypodium vulgare, the number of chloroplasts goes up to 100 in the guard cell.

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