Which part of a plant takes in water?

The roots, though the real work is done by root hairs - single cells drawn out into fine projections that multiply the absorbing surface enormously. A single rye plant was once measured as having over 600 kilometres of roots and something like 10,000 kilometres of root hairs, all within a small pot of soil.

Most plants do not do it alone. Their roots are wrapped in fungal threads far finer than any root hair, which reach into pores no root could enter and trade water and phosphorus for sugar the plant has made. Something like ninety per cent of land plants have this partnership, and it appears in the fossil record at the same time as the first land plants - the arrangement may be what made leaving the water possible.

The fungal networks also connect neighbouring plants to each other, and there is evidence of sugar and chemical signals moving between trees through them. The popular version of this, the wood wide web with mother trees feeding their seedlings, has recently drawn sharp criticism from within the field for running well ahead of what the data support.