Final answer:
Desert cacti grow slowly as a survival mechanism in harsh environments. They perform photosynthesis at night to minimize water loss, transforming CO₂ into glucose and then ATP. This energy-efficient process of slow growth allows them to conserve energy and essential resources.
Step-by-step explanation:
A cactus in the desert grows slowly as part of its adaptation to survive in a dry and harsh environment where water is scarce. This evolved tactic involves a complex interplay between photosynthesis, cellular respiration, transpiration, and the properties of stomata, glucose, cellulose, water, ATP, and carbon dioxide.
Cacti, being xerophytes, have a unique mechanism of photosynthesis whereby stomata mostly open during the night to minimize water loss through transpiration. This is because, during active photosynthesis, water evaporates out of the leaf when stomata open for uptake of CO₂. During the night, CO₂ is captured and stored as a preliminary reaction, which is then used for photosynthesis during the day when temperatures are higher. This prevents stomata from opening, thus conserving water. The use of CO₂ and water in photosynthesis produces glucose, which is a source of energy for plants. The glucose undergoes cellular respiration, producing ATP (adenosine triphosphate) - a molecule that provides energy for plant cells.
Further, the slow growth of desert plants like cacti helps them conserve energy and vital resources. The amount of water, ATP, and CO2 that would be used in growth is instead utilized in surviving in the harsh conditions. Unlike plants in less harsh conditions, this slow growth and efficient use of resources enable cacti to survive and thrive in deserts.
Learn more about Cactus Adaptation