Why do plants bend towards light?

Plant backlit side growth hormone.

It has more distribution, fast growth, less distribution to the light side, slow growth, and bends growth from the fast growing side to the slow growing one.

The cause of phototropism in plants is that unilateral light induces ulcanic auxin.

The distribution is not uniform, so that the auxin distribution on the backlit side is more quietly than on the lightward side, and the backlit side grows faster, so the plant grows bent towards the light source

Therefore, c

It cannot be said that "plants are phototropic in dust", but it should be said that "green plants are phototropic" (bacteria, yeast, etc. are also plants. ）

The phototropism of plants is caused by the uneven distribution of auxin in the body, that is, the concentration of auxin on the sunny side is lower, and the concentration of auxin on the dorsal side is higher, so the cell volume of the dorsal side grows faster, which leads to the sunshine of the plant's organs. This is true for sunflowers and plants placed on windowsills.

1) Indoleacetic acid, that is, auxin, can make the cell lengthening longitudinally and cause plant growth, it is a trace amount of organic matter, the sensitivity of each plant tube to auxin is different, such as roots are more sensitive than shoots and stems, auxin can be transported from the production site to the action site, long-distance transportation

2) Flowering is an important symbol of perennial plants from vegetative growth to reproductive growth, which is jointly regulated by factors such as sunshine length, low temperature induction, and plant age According to the title, gibberellin can promote the degradation of DEL protein in some plants, DEL prevents SPL protein from playing a role, SPL directly activates the transcription of SoC-encoding genes, and the presence of SOC protein is a prerequisite for plant flowering, so DEL protein can inhibit flowering. Gibberellin, SPL protein and SOC protein can promote flowering

3) According to the title, gibberellin will increase SoC, which is beneficial to flowering, and gibberellin degrades DEL to increase the effect of SPL, and after the increase of DEL, flowering is not easy to form Only when the content of MIR156 is lower than the flowering value, there is the potential to bloom and laugh, according to the figure, there are 4 times

4) Because the flowering will be accelerated when MIR156 is reduced, the vegetative growth period can be shortened by reducing the expression of MIR156

So the answer is: (1) AD

2)C3)4 Because only when the content of mirl56 in the plant was lower than the flowering threshold, it was hidden that C. bendula had the flowering potential, so it was judged that C. bendula began to bloom at the turn of the fourth winter and spring. And because the inhibition effect on flowering can only be lifted when the content of FLC reaches the lowest value, the frequency of flowering is once a year.

4) Reduce the expression of miR156.

The phenomenon of growth bending caused by unidirectional light irradiation of plant growth organs is called phototropism. For higher plants, phototropism mainly refers to the positive phototropism of the stems and leaves of the aboveground parts of plants. In the past, roots were thought to have no phototropic reaction, but in recent years, Arabidopsis thaliana has been used as a research material, and roots have been found to be negatively phototropic.

Positive photogenicity. The upper part of the plant is affected by light, causing the growth to tend to the light side.

Negative phototropism. Wang Zhong (1999) hydroponics of freshly germinated rice in transparent containers (such as glass jars) and irradiated the roots with one-sided light, also observed that the roots had negative phototropism, that is, the seed roots grew obliquely to the backlit side (about 60° angle to the horizontal plane).

Experiments and studies show that the root has negative optotropy, and the control mechanism of negative phototropism and gravity exist independently of each other. (Ishiguro and Okada, 1994).

Transverse photogenicity. The perpendicular property of plant organs to the light coming from them.

Auxin is more abundant in the backlight than in the light, and the bending of the light occurs.

a. There are more inhibitors on the light-facing side than on the backlight side under unilateral light, which inhibits the growth of the light-facing side, and a is wrong;

b. Under unilateral light, the tip auxin is transported laterally, from the light-facing place to the backlight, so that the auxin on the backlight side is more than that on the light-facing side, and B is correct;

c. It has nothing to do with the need for light on the leaves, and c is wrong;

d, related to the horizontal transportation of the long cord of the raw stove, d wrong spike.

Therefore, b