Your cactus may be growing a long stem because it is not getting enough sunlight. Cacti need plenty of sunlight to grow compact and healthy. If they don't get enough light, they may stretch out to try to reach for more. Try moving your cactus to a sunnier spot to help it grow more compactly.
Water, dissolved nutrients, and byproductsof photosynthesis are stored in the cactus stem. The water and the dissolved nutrients are sent up into the stem from the cactus plant's roots. They're held in the stem until they can be used in the photosynthetic interaction with sunlight. From that interaction are made the energizing carbohydrates, starches and sugars that the cactus needs for such activities as flowering, fruiting, growing, reproducing, and responding to stresses and stressors.
cactus have a hollow stem. it is where they store water and food for survival
The cactus has the ability to store water in its fleshy stem so it can survive long periods of drought.
The stem will expand to store any sporadic rain water to help the plant survive the long periods of drought.
A cactus that stores water in its stem is called a stem succulent. The stem has tissues that are capable storing large quantities of water. The stem also has a thick waterproof epidermis covered by a waxy cuticle that prevents loss of water due by evaporation. Examples of stem succulents - Cardon Cactus, Organ Pipe Cactus, Saguaro Cactus
In cactus leaves are absent. Chlorophyll are found in trunk mainly.
The 'spines' of a cactus attach directly to the stem of the plant.
Water is stored in tissue in the stem of the cactus.
A cactus stores water in its stem.
You possibly have a grafted cactus which don't last long.
To prevent your cactus from growing long and skinny, make sure it receives enough sunlight, rotate it regularly to promote even growth, and avoid overwatering which can cause it to stretch out. Additionally, consider pruning or trimming the cactus to encourage a more compact and healthy growth pattern.
A cactus stores most of its water in its stem or body