Why do sunflowers always face the sun?

The reason why sunflowers rotate with the sun: Sunflowers are named because the tips of young plants in the early stage of growth and the young discs in the middle stage will obviously rotate with the sun. From the biological science, this paper analyzes the reasons why sunflowers are sunny: the sunflower disk is sunny from germination to flowering, and its leaves and disk follow the sun from east to west during the day, but not immediately. Botanists have measured that its disk direction is about 12 degrees behind the sun, which is 48 minutes. After the sun goes down, the sunflower tray slowly swings back, facing east at about 3 am, waiting for the sun to rise.

As we all know, plants will synchronize with the surrounding light. This is called circadian rhythm. They are produced by plants themselves and are self-sufficient. Plants have different ways to realize them and how to express them. Sunflowers have their own way, and this way is to use some kind of hormone. Sunflowers contain a hormone called auxin. These hormones are sensitive to sunlight and do everything they can.

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Zhang (surname)

sunflower

Looking for shadows. Therefore, they migrate from the plant parts bathed in the sun to the shaded areas in the stems. Once there, auxin (basically growth hormone) stimulates the growth of cells. This causes the stem to become heavy in the shaded area, so the flowers bend in the opposite direction and face the sun. When the sun moves in the sky, auxin will continue to migrate to the covered stem part, which will make the shadow part more bulky by stimulating cell growth. This is how the sunflower continues to face the sun-constantly bending from the larger part of the stem. Mainly young flower heads, with this delay. This is because young flowers have green "bracts", which basically look like bristles, and the leaves of plants face the sun. The obvious reason why flowers follow the sun at this stage is to maximize photosynthesis.

The auxin in sunflower receptacle is distributed in the backlight, so the stem on the backlight side grows faster and bends towards the light source. Under the irradiation of sunlight, the auxin content on the back of sunflower increases, which stimulates the cells on the back to elongate and rotate towards the sun. After the sun goes down, auxin is redistributed, which makes sunflower turn to the east again. After the disc is in full bloom, it no longer turns to the sun, but is fixed in the east. Sunflower pollen is afraid of high temperature. If the temperature is higher than 30℃, it will be burned. So you can avoid direct sunlight at noon and reduce radiation. When the disk is exposed to sunlight in the morning, it helps to dry the dew condensed at night and reduce the possibility of being attacked by mold; In addition, the temperature is low in the morning, and the sunlight makes the sunflower tray a warm nest, which can attract insects to help pollinate.