Collaborating scientists from Russia and Israel have been studying the aloe plant, known for its widespread use in cosmetic products and alleged medicinal properties.

Under sustained intense light, both alone and in drought conditions, many plants respond by building up levels of red pigments. In most cases these are anthocyanins, but the aloe plant uses rhodoxanthin.

Mark Merzlyak at Moscow State University, and his colleagues have found that Aloe arborescens plants, grown in the Negev Desert, Israel, accumulate the chemical inside chloroplasts, in the place of chlorophyll: hence the colour change from green to red.

Merzlyak suggests the red pigment absorbs some of the excessive light, which might otherwise cause damage to molecules. He explains that rhodoxanthin and anthocyanins have similar optical properties, but different biosyntheses and photochemistries, as well as different subcellular properties.

Aloe is a commercially important crop and understanding it in more depth could lead to improved cultivation.

Robin Forder