||This is one of the greatest mysteries in biology. Nobody knows why plants contain alkaloids. There are many theories though. One is that alkaloids are defense mechanisms. They make plants taste bad or have poisonous effects, which may keep animals from eating them. They may help kill bacteria. Other possibilities are that alkaloids may actually encourage animals to eat certain parts of the plant, to help spread seeds - for example the opium poppy produces its alkaloids primarily in the seed pods. |
Nobody has found any internal use of alkaloids by plants, but this doesn't mean that they don't serve a purpose in the plant's metabolism or other life processes - it just means we don't know of any such purposes. In all likelihood, whatever caused their initial evolution, alkaloids probably now serve different purposes in different plants. For now, however, nobody really knows what alkaloids do or why they exist. Let's just be glad that they do!