Plants need sleep, and the sleep of some plants is easy to observe. For example, acacia trees put small sickle-shaped leaves together in pairs every night and enter a "dream". At this point, all the leaves of the peanut are folded up and the shoots droop feebly. Obviously, it has fallen asleep. The same is true of water lilies. Flowers that bloom during the day are all closed at this time. The next morning, when the sun came up, the leaves of Albizia Albizia and peanuts, which had slept all night, spread out again, and the water lilies slowly opened their petals.

In addition to acacia and peanuts, there are red clover, sorrel, chelidonium majus, croton and so on. Their leaves are closed at night and open during the day. Besides water lilies, there are tulips, crocuses, dandelions and so on.

Some plants sleep not at night, but during the day. Tuberose is like this. She is energetic at night, but listless during the day. Tobacco flowers also close during the day and open at night.

With the change of seasons and the coming of severe winter, the leaves of plants began to wither and fall off, and the whole plant went into a dormant state, and all parts stopped growing and spent the winter in a deep sleep. Some plants are only partially dormant, such as axillary buds.

Botanists call this phenomenon sleep exercise, which has long been concerned by scientists.

As early as 1880, the dormancy movement of plants attracted the attention of the famous scientist Darwin. After observing and recording the activities of 69 kinds of plants at night, he found that if some leaves can't move freely because of dew accumulation on the leaves, or artificially maintain their appearance during the day, they are more susceptible to cold dew or frost than those leaves that can move freely. He believes that the activity of plant leaves at night can effectively resist the cold at night, thus contributing to the growth of plants. Darwin's view has not been proved by facts, so it has not attracted the attention that scientists deserve.

It was not until the 1960s that some scientists in Europe, America and Japan began to study the sleep movement of plants and put forward various hypotheses. Some people think that the sleeping movement of leaves can protect plants from the damage of moonlight, because too much moonlight exposure may interfere with the photoperiod sensing mechanism of plants and damage the adaptation of plants to the length of day and night. This is a very popular "moonlight theory". However, this theory is difficult to explain many phenomena, such as: some tropical plants do not have photoperiod phenomenon, but they also have sleep movement.

Not long ago, Enlet, a behavioral physiologist at the Ripas Institute of Oceanography in California, USA, put forward a new explanation for the sleep phenomenon of plants based on his own experiments. He thought that this posture of plant leaves at night could keep their own temperature, thus promoting the growth of leaves. His results were measured on the leaves of broad beans and legumes with a sensitive "thermal probe". He found that the average temperature of the blades with daytime posture was always 65438 0℃ lower than that of the blades with vertical blades. Although the temperature difference is so small, it has an important influence on the growth of plants. In the same environment, plants with sleeping activities grow faster, and the growth amount is greater than that of plants without sleeping, and the growth rate can be increased by 20%.

The mystery of plant sleep has been revealed step by step, and people's understanding of this phenomenon of plants is becoming more and more clear. However, there are still some phenomena that cannot be satisfactorily explained by the above theory: do plants that have been exercised by sleep really grow faster than other plants that have not been exercised by sleep? Do some plants sleep during the day to keep warm? Don't plants that don't sleep clearly sleep? These are still mysteries.