The reason for the growth of plants towards light is that one side prompts auxin to be transported f

Let's start with growing towards the light. Auxin is transported to the backlight side under light, and the backlight side grows fast and the light side slowly, so it grows towards the light.

Second, unilateral light promotes auxin lateral transport. Transported from the light-facing side to the backlighted side.

Hope it helps.

Under the action of unilateral light, auxin is transported from the tip of the stem to the backlit side laterally along the parenchyma tissue, and the auxin concentration on the backlit side is higher than that on the phototropic side, and the cell growth on the backlit side is greater than that on the phototropic side, which causes phototropic bending. Reference.

At the tip of the plant, auxin will be transferred from the light side to the backlight measurement, because the concentration of auxin on the backlight side is higher than that on the light side, so the growth rate of the backlight side is faster than that of the light side, so the phenomenon of auspicious light bending growth occurs. At this time, the auxin concentration increases for the stem, which promotes growth. If, in the question, the concentration of auxin in the roots increases, the growth of the roots is inhibited.

Because roots are more sensitive to auxin concentrations than stems. In your question, this is only for lateral transport. It does not belong to polar transportation, nor does it belong to non-polar transportation.

Promote the lateral transport of auxin, high auxin concentration will inhibit plant growth, so the low auxin concentration on the light-facing side of the plant promotes growth, and the high concentration on the backlight side is inhibited, so the plant grows to light.

Under the irradiation of light, auxin moves to the backlit side, and the backlit side has a high concentration of auxin and grows fast, so that the plant grows towards the light.

There are two hypotheses for phototropic growth.

1. It is caused by the uneven division of auxin, but there are also some unexplained phenomena.

2. It is the division problem of growth inhibitors.

Auxin is transported from the light-oriented side to the backlight side, and the plant grows towards the light due to the low promotion and high inhibition (the effect of auxin on the stem).

Auxin backlight transverse transport, from the light-side to the light-sided.

Polar transport, morphologically upper to morphologically lower.

Polar transport up to bottom transverse transport to the light side to the backlight side.

Transport at the tip to the backlit side, from top to bottom at the lower part of the tip, without transporting left and right.

Auxin is sensitive to light, so it is transported laterally.

Lateral transport, moving to the light side to the backlight side.

This is very cute and that is related.

The reason should be the cause of gravity. This is the most fundamental reason.

Other subordinate causes.

a. Under unilateral light irradiation, auxin.

Transverse transport from the coleoplasty to the light side to the backlight side, a error;

b. Back gravity growth of plant stems: under the action of gravity, the distribution of auxin on the ground side of plant stems is more than that on the far side, and the growth on the ground side is fast and the growth on the far side is slow; Photo-oriented growth of plant stems: under unilateral light, auxin is transversely transported from the phototropin side to the backlight side, the auxin concentration on the backlit side is high and grows fast, and the concentration on the photo-side is low and the growth is slow, both of which are weak in low concentration and strong in high concentration in promoting growth, both of which do not reflect the duality of auxin action, b is correct;

c. In the experiment of rooting cuttings, the base (lower end) of the cuttings is generally soaked in auxin solution, and C is wrong;

d. In the weightless state, the auxin in the plant placed horizontally will not undergo lateral transport, but polar transport will occur, d. error

Therefore, b

Polar transport refers to the mode of transport in which auxin can only be transported from the upper end of the morphology (the part that grows after the plant body) to the lower end of the morphology (the part that grows first from the plant body). It is an active transport.

The transport of auxin in the plant body is mainly transported from the upper end of the plant morphology to the lower end, and cannot be reversed for transportation. The reason for this is the distribution of the vectors.

Plant auxin is a polar transport, that is, active transport, which requires a carrier, and the distribution of the carrier determines the direction of its movement.

Auxin is mostly concentrated in the parts of vigorous growth: germ sheath, meristem at the tip of the shoot and root, cambium, ovary after fertilization, young seeds, etc., but rarely in the tissues and organs that go to senescence.

There are two modes of auxin transport: 1. Like other assimilants, the transport speed through the phloem is about, and the direction of transport determines the concentration difference between the concentration of organic matter at both ends; The other is a short-distance unidirectional polar transport (which can only be transported downward from the morphological upper end of the plant body) confined to the parenchyma of the germ sheath and young roots. Not as wide as you say it is from the top of the tree to the roots, too rough.

Here's an example: a small branch (young) is transported from the top down, but if you turn it upside down (top down), it is not transported from the top down.

The formation of phototropism in <> plants is due to the lateral transport of auxin at the tip by the unilateral balance, so that the auxin concentration on the backlit side is higher than that on the phototropin side, and the backlit side of the plant grows faster than the light-definitive side, and the plant shows sun-han lightward curved growth (as shown in the figure).

Therefore, c

Meristems at the tips of shoots and roots, auxin is transported from the top downwards. 4 cm, the transport speed through the phloem is about 1-2, and the direction of transport determines the concentration difference with the concentration of organic matter at both ends: a short distance of polar transport between a small branch (young and tender), cambium, and parenchyma of young roots (can only be transported downward from the morphological upper end of the plant body).

For example, it is too extensive, and most of the ovary auxin after fertilization is concentrated in the vigorous growth parts, young seeds, etc., like other assimilants, but you turn it upside down (top down), and very little in the tissues and organs that go to aging; h。Not as wide as you say, from the top of the tree to the roots.

There are two modes of auxin transportation; The other is confined to the germ sheath: the germ sheath.

Does the lack of oxygen affect the polar transport of auxin in the plant.

1. The transportation direction of auxin is polar transportation, the transportation mode is active transportation, and the conditions require carriers and energy

2. When there is a lack of oxygen or aerobic respiration is inhibited, the energy released by cellular respiration is reduced, and the rate of active transport slows down

It may be the result of "high concentration inhibition of auxin and promotion of low concentration".

In the process of transportation, due to various factors (such as light, and some complex reactions in the plant), the auxin concentration continues to decrease--- so we now conclude that "the upper end of the morphology of auxin concentration is the highest, and then it gradually decreases downward".

Now let's assume that there is a region of the plant where the auxin concentration is high enough to suppress it, and then we apply a single dose to that area, and then the photoreceptor auxin concentration will decrease due to decomposition.

To what extent?

1: The inhibition effect on the photographic side is less than that on the backlit side 2: The inhibition effect on the photo-side is low enough to play a promoting role, while the backlit side is still in the inhibition effect.

Your question is wrong, it should be growing towards the light, because the light side is slower than the backlight side, so it bends to the light side.

Is it because the auxin concentration on the light side becomes lower because of the transfer of the cis-concentration difference, and then the rapid growth to the light side? Has the theory changed...

The transport of auxin is polar and not lateral.

Unilateral light causes uneven distribution of auxin, with more on the backlit side and less on the lightward side.

For stems, the higher the auxin concentration, the more obvious the promoting effect, so the backlit side grows faster and bends towards the light.

Roots are sensitive to auxin, and the concentration that promotes stem growth is already in a state of high concentration inhibiting growth for roots. Therefore, the backlight side grows slowly, showing backlight growth.