Cactus is a type of plant that can store large amounts of water and survive in extremely hot and dry habitats. There are around 2000 different species of cactus that differ in size, shape, color and type of habitat. Almost all cacti are native to deserts and dry regions of South and North America. Due to their attractive morphology, cacti can be found throughout the world today. Not all succulents are cacti; only one quarter of the 10,000 species of succulents belong to the cactus family. Most cacti store moisture in their stems rather than in thick, fleshy leaves like other succulents. Since cacti rarely have leaves, an unusual characteristic of a cactus plant is its ability to photosynthesize with its stem. Unlike other plants, cactus have adapted to taking in carbon dioxide at night, when temperatures are cooler and less evaporation occurs. The carbon dioxide is stored and used during the day, bonding with water to make sugar and oxygen. All cacti have flowers. Generally, cactus flowers are short-lived and provide the primary characteristics that separate cacti from other succulents. Cacti flowers have at least 10 petals, with the sepals combined with the petals, and have numerous stamens surrounding a multi-lobed stigma. If a succulent doesn't produce a flower, it is not a cactus. Cacti photosynthesize at night. During the day, they use ____ to generate sugar and oxygen.

Question

Cactus is a type of plant that can store large amounts of water and survive in extremely hot and dry habitats. There are around 2000 different species of cactus that differ in size, shape, color and type of habitat. Almost all cacti are native to deserts and dry regions of South and North America. Due to their attractive morphology, cacti can be found throughout the world today.

Not all succulents are cacti; only one quarter of the 10,000 species of succulents belong to the cactus family. Most cacti store moisture in their stems rather than in thick, fleshy leaves like other succulents.

Since cacti rarely have leaves, an unusual characteristic of a cactus plant is its ability to photosynthesize with its stem. Unlike other plants, cactus have adapted to taking in carbon dioxide at night, when temperatures are cooler and less evaporation occurs. The carbon dioxide is stored and used during the day, bonding with water to make sugar and oxygen.

All cacti have flowers. Generally, cactus flowers are short-lived and provide the primary characteristics that separate cacti from other succulents. Cacti flowers have at least 10 petals, with the sepals combined with the petals, and have numerous stamens surrounding a multi-lobed stigma. If a succulent doesn't produce a flower, it is not a cactus.

Cacti photosynthesize at night. During the day, they use ____ to generate sugar and oxygen.