Plant sleep is called sleep exercise in plant physiology, which is not only an interesting natural phenomenon, but also a scientific mystery. Every sunny night, as long as we observe carefully, we will find that some plants have undergone wonderful changes. For example, the leaves of a common acacia tree are made up of many small feathers, which stretch and are flat during the day. When night falls, the countless small feathers are folded in pairs, like mimosa touched by hands.
Sometimes, we can see a red clover with small purple flowers and three leaflets in the wild. When there is sunshine during the day, the leaves on each petiole stretch in the air, but in the evening, the three leaflets close and hang their heads to get ready for sleep. Peanut is also a kind of plant that loves to sleep. Its leaves start to close up in the evening, indicating that it is going to sleep. The above examples are just some common examples. In fact, there are many plants that can sleep, such as Sedum, Chelidonium majus and Crotalaria.
mimosa
Not only the leaves of plants need sleep, but also the delicate and gorgeous flowers need sleep. Sleeping lotus growing on the water, when the sun rises, its beautiful petals slowly spread out, as if just waking up from a dream, and when the sun sets, it closes its petals and goes back to sleep. Because of its obvious regularity of "waking up in the day and sleeping at night", it got the name of "water lily".
all kinds of flowers have different sleeping postures. When dandelion falls asleep, all the petals stand up and close, looking like a yellow feather broom. The flowers of carrots hang down, like a little old man dozing off.
what benefits does sleep exercise bring to plants? In recent decades, scientists have carried out extensive research around this problem.
The first person who discovered the sleeping movement of plants was Darwin, a famous British biologist. More than 1 years ago, in the process of studying the growth behavior of plants, he observed the nocturnal activities of 69 kinds of plants for a long time, and found that some leaves covered with dew were inconvenient to move because of bearing the weight of water droplets, and were often injured more easily than other leaves that could move freely. Later, he artificially fixed the blades and got similar results. Although Darwin could not directly measure the temperature of leaves, he concluded that the sleeping movement of leaves was very beneficial to plant growth, perhaps mainly to protect leaves from the cold at night.
Darwin's statement seems to have some truth, but it lacks sufficient evidence, so it has not attracted people's attention. In 196s, with the rapid development of plant physiology, scientists began to deeply study the sleep movement of plants and put forward many explanation theories.
At first, the most extensive theory to explain the sleep movement of plants was "moonlight theory". Scientists who put forward this argument believe that the sleeping movement of leaves can make plants suffer from moonlight as little as possible. Because too much moonlight exposure may interfere with the normal photoperiod sensory mechanism of plants and damage the adaptation of plants to diurnal changes. However, what puzzles people is why many tropical plants without photoperiod also have sleep movements, which cannot be explained by "moonlight theory"
oxalis oxalis
Later, scientists found that the sleeping movement of some plants is not controlled by temperature and light intensity, but is caused by the swelling pressure changes of some cells in the base of petiole. Such as acacia trees, sorrel, red clover, etc., can reduce the loss of heat and evaporation of water by closing the leaves at night, especially acacia trees, whose leaves not only close their sleep at night, but also gradually close when encountering strong winds and heavy rains to prevent the tender leaves from being destroyed by storms. This protective response is an adaptation to the environment.
Scientists put forward one viewpoint after another, but they failed to have a satisfactory explanation basis. Just when scientists were puzzled, American scientist Enright put forward a new explanation after a series of interesting experiments. He used a sensitive temperature probe to measure the temperature of leaves of many plants at night, and found that the temperature of leaves in the horizontal direction (without sleeping exercise) was always about L lower than that in the vertical direction (with sleeping exercise). Enright believes that it is this tiny temperature difference of only 1 that has become an important factor to prevent or slow down the growth of leaves. Therefore, in the same environment, plants that can sleep exercise grow faster, and they have stronger survival competitiveness than other plants that can't sleep exercise.
With the deepening of research, scientists have also found interesting things about plant sleep. Jujube plants have the habit of taking a nap just like people.
It turns out that the nap of plants refers to the phenomenon that the stomata of leaves are closed and photosynthesis is obviously reduced from about 11 noon to 2 pm. Scientists believe that plant siesta is mainly caused by the dryness and fierceness of the atmospheric environment. Siesta is an instinct of plants to resist drought in the long-term evolution process, in order to reduce water loss and survive in adverse environment.