All cacti have leaves

Although most of the cacti appear to have no leaves on the surface, a new study confirms that all these thorny plants actually have microscopic leaves.

Discovering not only adds interesting insights into this unusual group of plants, but also broadens the known functions of the leaves.

"If people look closely at the cactus to find leaves, they need to be wary of prickling eyes," warns James Mauseth.

He collected samples of 141 different cacti species, most of them wild, then analyzed their plants and tissues under great magnification. Mauseth said that the newly discovered cactus leaves (best seen under a microscope) are at the base of the thorns.

With a size of 30 to 2,310 micrometers (one micrometre is one millionth of a meter), cactus leaves can be considered the smallest leaves in the world. Normally, leaves are responsible for absorbing sunlight, producing sugar and supporting the absorption of water and respiration. However, with the microscopic leaves of the cactus, Mauseth thinks it may have another mission.

He hypothesized that cacti needed these tiny leaves to make room for bouncing buds (shoots often grow in leaf axils), avoiding "getting lost, or unable to grow".

A giant cactus in Arizona, USA, with tiny leaves that can only be seen with a microscope.(Photo: Discovery)

T. An