How the tallest parts of redwoods get a drink

Redwoods are giants of the tree world. Living individuals of the tallest species, Sequoia sempervirens, can be more than 100m high.

Life at those levels presents challenges. One of the big constraints that can limit height in plants is the need to transport water from ground to the top of the plant. For the redwoods that is a pretty tall order, but a new study of S sempervirens suggests it has a few tricks up its sleeve.

It’s thought the redwood can absorb moisture from the air – particularly from foggy air – through its leaf surfaces, so that higher parts of the tree do not depend solely on water coming up from the roots.

A study published this week suggests that at least some of the water collected by the lofty leaves of S sempervirens may be stored internally, and this could help the tree to reduce its water stress.

Researchers from Humboldt State University and Kobe University analysed leaves from various levels of redwoods growing in California and found that the ability of the leaves to store water increased with height and light availability. As you move up the tree, the internal anatomy seems to be more allocated to water storage and less to channelling water up from the roots.

The findings could help to explain how "the world's tallest species solves the dilemma that water stress is greatest where light availability for photosynthesis is highest", write the researchers in the journal Functional Ecology.