Hylocereus undatus possess certain adaptations that allow the plant to survive in relatively arid conditions. For one, H. undatus undergoes CAM (Crassulacean Acid Metabolism) photosynthesis. Unlike in the other types of photosynthesis, in CAM photosynthesis, plants open their stomata during the night instead of during the day in order to reduce water loss via evaporation. The carbon dioxide entering the stomata at night is stored as an acid until the enzyme RUBISCO breaks down the acid and releases the carbon dioxide when light is present. When environmental conditions are severe, CAM plants have the ability to CAM idle for a short period of time. In these cases the plant is able to keep its stomata closed both during the day and the night to prevent water loss. Carbon dioxide needed for photosynthesis comes from the carbon dioxide given off in respiration while the oxygen given off during photosynthesis is used for respiration.

Another adaptation H. undatus possesses to help it survive dry conditions has to do with how water is transferred in the tissues of the plant. During a period of drought it has been shown that the water-storage parenchyma cells release water to the chlorenchyma cells (chlorenchyma cells are parenchyma cells which contain chloroplasts) (Nobel, 2006). This allows for the chlorenchyma cells to maintain a positive net uptake of carbon dioxide, which is necessary for photosynthesis. Processes like these help H. undatus to survive in arid conditions as well as in short periods of drought (up to six weeks). It has also been seen that during periods of drought, H. undatus continues to maintain stem growth and is able to do so through phloem transport mechanisms (Nerd, 2004). Often in plants receiving inadequate water, stem growth is stunted, but researchers believe H. undatus may continue its stem growth under these conditions since it is a hemi-epiphytic plant often found in tropical forests where growth upwards is necessary to compete for sunlight (Nerd, 2004).

Learn more about the nutrition of Hylocereus undatus.

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