The natural environment is always changing, sometimes predictably, but more often not. Unlike animals, plants cannot move away or seek shelter from unfavorable conditions, so it is crucial that they are able to adapt quickly to such changes. Unpredictable changes include daily temperature, rainfall, and amount of light, and plants have developed a range of responses to deal with these changes. However, some aspects of the environment change regularly, such as the seasons; the monthly waxing and waning of the moon; the cycle of the tides coming in and out; and, of course, the daily changing of light and dark. It is therefore not surprising that, like most other living organisms, plants have evolved so that their behavior or development changes in synchrony with these predictable changes in the environment.

A boojum tree in Mexico during the dry season. The plant adapts...