CAM plants have adapted to arid environments by closing their stomata during the day. However, photosynthesis still occurs. This is because .

Please see below.

Explanation:

CAM or crassulacean acid metabolism plants are those that fix carbon dioxide as malate during the night so that they do not have to open their stomata during the day in order to conserve water.

At nights, the stomata of CAM plants open and carbon dioxide diffuses into the mesophyll cells of their leaves. CO2 then combines with phosphoenol pyruvate in the presence of an enzyme to form oxaloacetate.

The later then receive an electron and become oxidized to malate which is then stored in the vacuole until photosynthesis starts.When photosynthesis commences,  malate can then enter the Calvin cycle.

the tricuspid valve is present between right atrium and right ventricle