The picture above is not the creation of a computer genius with a flair for the artistic. It is a head of romanesco, an edible relative of broccoli. Romanesco’s mesmerizing beauty is attributable to the fact that each of its smaller buds resembles in miniature the entire vegetable. Mathematicians refer to such repetitive patterns as fractals. If romanesco looks as if it were generated by a computer, it’s because its growth pattern follows a repetitive sequence of instructions. As in most plants, the growing shoot tips lay down a pattern of stem… leaf… bud, over and over again. These repetitive developmental patterns are genetically determined and subject to natural selection. For example, a mutation that shortens the stem segments between leaves will generate a bushier plant. If this altered architecture enhances the plant’s ability to access resources such as light and, by doing so, to produce more offspring, then this trait will occur more frequently in later generations— the population will have evolved. Romanesco is unusual in adhering so rigidly to its basic body organization. Most plants show much greater diversity in their individual forms because the growth of most plants, much more than in animals, is affected by local environmental conditions. All adult lions, for example, have four legs and are of roughly the same size, but oak trees vary in the number and arrangement of their branches. This is because plants respond to challenges and opportunities in their local environment by altering their growth. (In contrast, animals typically respond by movement.) Illumination of a plant from the side, for example, creates asymmetries in its basic body plan. Branches grow more quickly from the illuminated side of a shoot than from the shaded side, an architectural change of obvious benefit for photosynthesis. Changes in growth and development facilitate a plant’s ability to acquire resources from its local environment.
Urry, Lisa A.. Campbell Biology (p. 756). Pearson Education. Kindle Edition.