How do green Ephedra stems carry out photosynthesis?

In the genus Ephedra, which belongs to the division Gnetophyta, the green stems serve as the primary site for photosynthesis.12

This adaptation is a response to the plant's desert environment. Because these shrubs inhabit arid regions, they have evolved to reduce their leaf surface area to small, scale-like structures. By minimizing leaf size, the plant effectively reduces water loss through transpiration, which is essential for survival in dry climates. Consequently, the green, jointed stems take over the metabolic role of energy production that is typically performed by leaves in other plants.12