Growth process of sunflower

Because the auxin in sunflower receptacle is distributed in the backlight, the stem on the backlight side grows faster and bends towards the light source.

Sunflower, named after the tip of its young plant in the early growth stage and the young disc in the middle growth stage, will obviously rotate with the sun. It is generally believed that the sunrise of sunflower is only related to light, but it is also closely related to gravity. ?

Plants will produce a wonderful auxin, mostly concentrated in the vigorous growth parts, and less in the aging tissues and organs. This auxin has three characteristics: first, it can promote (inhibit) the growth of cells and accelerate (slow down) the division and reproduction of cells; Second, the backlight, when irradiated by light energy, runs to the backlight side; Third, to the ground, under the action of gravity, plants are transported from the top to the bottom, and from the back to the ground, not the other way around. ?

As the sun rises, the east side of the green sunflower is exposed to the sun, resulting in a large distribution of auxin on the west side of its backlight. The cells on this side are elongated and grow rapidly in the longitudinal direction. As a result, the young stems bend to the slow-growing east side, that is, the top (disk) of the sunflower bends eastward in the morning. As the sun moves in the air and changes the direction of illumination, the top (disc) of sunflower also changes direction constantly, standing upright at noon and bending to the west in the afternoon, all of which show the phototropism of bending the stem top. ?

After sunset, the earth was dark, and the uneven distribution of auxin in plants caused by light disappeared. The uneven distribution of auxin in plants caused by gravity has risen from a secondary position to a dominant position. More auxin is distributed on the lower side (towards the ground) of the young stem of sunflower bent to the west, which makes the cells on this side divide and elongate, grow rapidly to the ground, and bend the stem to the upper side of the slow-growing back ground. As a result, the plants bent during the day are straight. Sunflower plants stand tall and straight at night, which is the natural response of sunflowers to gravity like other plants-the stems grow behind their backs and are upright.

With the increase of sunflower disk, sunflower bends eastward in the morning, stands upright at noon, bends westward in the afternoon, and the repeated rotation of standing upright at night gradually stops. The direction of sunflower disk has not changed except for the increasingly obvious blue head. The factors that inhibit steering are: first, the increase of disk gravity; 2. As maturity approaches, the growth process of meristem and elongation zone basically ends. It is no longer that the tissues of young stems tend to be aging, and the auxin content is less. When the steering is inhibited, the cork layer begins to form, and when the stem tip is upright at night, the oriental sunshine is first received in the morning. Therefore, most of the disk faces east, and because there is also a process of restraint, it is relatively slow, so it can be fixed in the southeast for a long time at an angle of about 30-40 degrees south.