Although most foods do not want to be eaten, there are exceptions to the rule in the form of fruits and nuts. These contain the seeds of the plant and they rely on animals eating them to disperse the seed. The wild version of a fruit such as an apricot consists of a juicy, sweetish layer on the outside, with which the plant tempts birds and other animals. Inside is the seed, which is protected by a hard kernel or ‘stone’. The idea is that the animal eats the fruit, but that the seed passes through its gut to the outside and is voided with the animal’s droppings, some distance away from the parent plant.
The seed itself is highly nutritious – it contains all the food the young seedling will need to become established – so the plant must guard its seeds well.
Animals who might be tempted to break the apricot stone open and eat the seed as well are deterred by toxins, principally cyanides (the chemicals that give almonds and apricot kernels their characteristic smell and flavour). As a final safeguard, die parent plant adds a chemical to the outer skin of the fruit that affects the animal’s gut. It speeds up the movements of the gut, making it void the stone more rapidly, so that the damage done by the digestive juices is minimised. This is why so many fruits have a laxative effect.
Nuts are rather more generous to their animal partners. They rely on animals such as squirrels that hoard food for the winter months, and they operate a ‘planned loss’ strategy, whereby a great many of the seeds are actually eaten. The pay-off is that the squirrels not only disperse the seed, but also plant them in a suitable spot when creating their winter stores. Since they inevitably forget where some are planted, a proportion of the nuts survive and grow into trees.
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