Reservoir is the answer to your question.
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Guard cells are located in the leaf epidermis and pairs of guard cells surround and form stomatal pores, which regulate CO2 influx from the atmosphere into the leaves for photosynthetic carbon fixation.
Stomatal guard cells also regulate water loss of plants via transpiration to the atmosphere.
They are all part of the Carbon cycle
The amswer on which us population is currently exp. a mental disorder id D. 35 %
