(a) How does carbon dioxide from the air enter the leaves of a plant to be used in photosynthesis ?
(b) How does water from the soil reach the leaves of a plant to be used in photosynthesis ?
The Carbon Dioxide CO2 from the air enters the plant through the stomatal openings located on the leaf lamina densely populating the ventral side and sparsely populating the dorsal side.
Sun light in the form of pockets of energy called photons gets trapped by the leaf pigment called chlorophyll located in the thylakoids in the cell organelle called chloroplasts . This energy is used to split the water molecule into H1+ ions and O2−. H1+ ions proceeds to form the glucose molecule C6 H12 O6 along withCO2 . Oxygen is released through the stomatal opening or it is simply used up in respiration.
The figure below shows a stomatal opening .Here when guard cells are turgid, stomata remain open . When Guard Cells are flaccid, stomatal opening remain closed.
Water is transported upwards from the roots by a process called osmosis. This occurs in a layer of tissue called xylem consisting of elongated cells joined end to end. Xylem extends from the root all the way to the veins of a leaf.Xylem transports water in an unidirectional way by the combined help of four specialised cells called Sieve tubes, tracheids, xylem fibres and xylem parenchyma.The rise of water from the stem to the leaves is further accelerated by the transpirational pull.