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Most parts of the cell are replaceable if damaged, but DNA is a crucial exception. At higher radiation doses, DNA becomes garbled and cells die quickly. Lower doses can cause subtler damage in the form of mutationsaltering the way that the cell functions – for example, causing it to become cancerous, multiply uncontrollably, and spread to other parts of the body.In animals this is often fatal, because their cells and systems are highly specialised and inflexible. Think of animal biology as an intricate machine in which each cell and organ has a place and purpose, and all parts must work and cooperate for the individual to survive. A human cannot manage without a brain, heart or lungs.Plants, however, develop in a much more flexible and organic way. Because they can’t move, they have no choice but to adapt to the circumstances in which they find themselves. Rather than having a defined structure as an animal does, plants make it up as they go along. Whether they grow deeper roots or a taller stem depends on the balance of chemical signals from other parts of the plant and the “wood wide web”, as well as light, temperature, water and nutrient conditions.Critically, unlike animal cells, almost all plant cells are able to create new cells of whatever type the plant needs. This is why a gardener can grow new plants from cuttings, with roots sprouting from what was once a stem or leaf.All of this means that plants can replace dead cells or tissues much more easily than animals, whether the damage is due to being attacked by an animal or to radiation.And while radiation and other types of DNA damage can cause tumours in plants, mutated cells are generally not able to spread from one part of the plant to another as cancers do, thanks to the rigid, interconnecting walls surrounding plant cells. Nor are such tumours fatal in the vast majority of cases, because the plant can find ways to work around the malfunctioning tissue.
