Young plants are bent in a direction toward the sun, due to the effect caused by auxin.
Sunflower also known as sun flower, sunflower seeds, turn Nichiren. Its flowers flower heads, commonly referred to as disk. Every morning, the sun comes out, it will own round faceplate to the sun. As the sun slowly rises, it slowly rise. Whether the sun go, where it is related to, until the sun goes down, and it just looked down.
Sunflowers follow the sun mainly because it contains a stem faceplate below auxin. An encounter light irradiation, which will be transferred to auxin backlight side to go, and the backlight side to stimulate cell division and proliferation, thus, sunflower toward the side of the sun relatively small number of growth hormone, it looks a little bit slower . And that side away from the sun, because the growth hormone more, grow faster. Thus, it makes sunflower produced phototropism bent toward the sun disk has been tilted side. As the sun moves in the air in auxin in the stem are constantly carrying the sun moved. So we say, sunflower always follow the sun.
In fact, many plants have a sunflower always towards the sun. For example, placed on the windowsill flower, their leaves are always out the window sunny place tilt. This property is called "phototropism." However, some of the leaves always turn back to the sun. So, sunflower this nature has been called "the positive phototropism", while those carrying the sun rotates called "negative phototropism."
This phenomenon is found in British biologist Charles Darwin. After that time, he observed that rice, wheat seedlings exposed to sunlight, will bend to the direction of the sun. If the top of these seedlings cut or covered with something, then not again seedling sun bent. So he made such a hypothesis: the tip of the seedling containing a substance under the action of light, this material will go to the side of the backlight seedlings, causing the growth curve. Later, people from the tip Seedling extracted several substances that stimulate plant growth effect, allowing the seedlings back side of the solar cell division and growth acceleration, so the seedlings bent toward the side of the sun, and it is referred to as auxin.
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