cactus

[dolphin99]

how does a cactus adapted to conserve water.

[wildwood]

It has spikes instead of leafs so it keeps evaporation to a minimum. Many of the larger cacti can expand their trunk manyfold to store an amazing amount of water from one rain shower to the next.

[Rabelais]

Cacti are adapted in many ways to conserve water. As has been said their leaves have become needles to reduce water loss. As they have no leaves the stem of the cactus has become the seat of photosynthesis. This allows them to grow into a barrel shape giving them a low volume to surface area ratio, reducing evaporation and allowing them to store a reservoir of water. In addiction they also shut their stomata during the day which reduces the water loss by transpiration. They then open them at night to replenish their carbon dioxide reserves at night when water loss is minimal. The stomata are also surrounded by hairs and spines still further reducing water loss. They are covered with a thick waxy cuticle prevent water from escaping the plant. They used specialist sugars called trehalose which prevents cell damage should they experience water loss. And finally they have extremely deep extensive root systems maximising the water they can extract from the ground.