Surviving drought

We’ve all felt it: a quickening of the heart and a slight shortness of breath as you walk into an exam room. Most of us recognise that the hormone adrenaline is responsible for this reaction, but we’re not unique in responding to stress with a release of hormones.

Plants do this too – but unlike you and I, they don’t have the option to flee; rooted to the spot, they can only stay and fight it out. To do this, plants release the hormone abscisic acid (ABA), which coordinates their response to stresses such as drought, extreme temperature and high salt levels.

ABA acts as a chemical courier, relaying messages from one cell to another. Cells respond to the hormone if they possess a receptor, which, once bound to the hormone, signals to the cell to go on the offensive. For plants, this means closing the tiny holes in their leaves to avoid water loss, diverting resources to their roots to increase water uptake and switching on the production of proteins that protect cells from dehydration.

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Waxing cutaneous

When we’re in the bath, our skin prevents both water from moving into our bodies and essential nutrients from leaching into the tub. But because most of us don’t spend our entire lives submerged underwater, our skin’s chief role is to control how much water evaporates from our bodies. In fact, the skin’s role as a semi-impermeable barrier to fluid loss is so important that people suffering from serious burns often die, not as a direct consequence of their injuries, but from de hydration.

Each of us is covered by about 2 square meters of skin – about the area of a queen-size bed. For this waterproof suit to do its job, stem cells at the base of the skin replenish the layers above by producing a continuous stream of new cells initially like themselves and then a variety of specialised cell types. As a result of this continuous production, the specialised cells – which are destined to become the different layers of skin – move outwards until they are finally shed.

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