New research gives insight into how “Living Stones” adapt to extreme conditions

Research by scientists at the University of Sheffield has given new insight on how some plants adapt to extreme conditions which could help in the future development of efficient crops.

The study was carried out on plants native to southern Africa known as "Living Stones", or Lithops. These little succulents survive in the blazing deserts and rocky ground of southern Africa by blending in with surrounding pebbles to avoid being eaten and by burying themselves underground.

Now researchers have discovered how the partially subterranean "Living Stones" still manage to harvest enough sunlight while avoiding drying out in the parched landscape, according to a study published in the journal PLOS ONE.

The Sheffield-based team used a combination of cutting-edge techniques to show that individual leaves of Lithops species are adapted for both high-light and shade-tolerance, revealing for the first time the novel combination of physiological mechanisms used to optimize simultaneous above-ground and underground photosynthesis while minimising water loss.

The research shows Lithops combines a top surface with "windows" of translucent tissue that allows light through to photosynthetic tissues deep in the underground portion of the leaf, with a biochemical sunscreen to block out harmful UV light.

To offset damage to the plant associated with too much sunlight, the plants also use a protective mechanism known as non-photochemical quenching in the above-ground parts of the leaves. The below-ground parts of the leaves are adapted more towards a shaded way of life, with highly specialised cell shapes, tissue chemistry and crystalline deposits to help maximise limited light levels.

The study, carried out by Dr Katie Field and Miss Rachel George from the University of Sheffield’s Department of Animal and Plant Sciences and Dr Matthew Davey at the University of Cambridge, observes for the first time extreme physiological flexibility in Lithops and offers new insight into how plants respond to extreme conditions.

Dr Katie Field, said: "This work highlights the incredible adaptations that have evolved in "Living Stones" in response to the blazing sunshine they experience in their desert habitat.

"Unlike most members of the plant kingdom, these amazing little plants photosynthesise underground. We’ve discovered that by using a sunscreen and moving their photosynthetic machinery beneath the soil, "living stones" manage to avoid the effects of too much sun yet simultaneously maximise photosynthesis through previously unrecorded mechanisms. This suits them for life both in full sun and in full shade, at the same time.

"This research helps us to understand how plants cope with extreme environments on Earth and may play a part in future development of efficient crop plants."