Prickly Pear Cactus (Opuntia chlorotica)
Nutrition
The prickly pear is an autotroph which means that it is "self feeding", or it does not get energy from other living beings. Instead it produces its energy from organic molecules created through the process of photosynthesis. To do this they require water, nutrients from the soil, carbon from carbon dioxide in the air, and light energy from the sun.
There are two types of reactions that occur in photosynthesis. These are the light reactions and the Calvin cycle. In the light reactions, energy from the sun splits water into oxygen gas and hydrogen ions. This creates a source of electrons and protons. A pair of electrons plus a hydrogen ion (H+) are transferred to NADP+. NADP+ then becomes NADPH. Here they are carried to the second part of photosynthesis know as the Calvin cycle.
In the Calvin cycle carbon dioxide (CO2)
from the air is combined into organic molecules. This is called carbon
fixation. By reducing the fixed carbon with the electrons, it is
transformed into sugar.
The equation for the chemical reaction of photosynthesis is: 6 CO2 + 12 H2O → C6H12O6 + 6 O2 + 6 H2O
The prickly pair cactus performs this reaction, but different than most other plants. Instead gathering the CO2 during the day, it gathers the CO2 during the night. This allows the stomas (openings in the leaves used for gas exchange) to remain closed and conserve water. The CO2 gathered at night is converted into an organic acid and stored in the plant until the sun can provided the needed energy and NADPH for the reaction to occur.