The tip of the coleoplasty of a seedling, the distribution of auxin

A side more. Because the germ sheath is photosensitized.

Auxin transports ...... to the backlit side

The transport of auxin in the germ sheath is characterized by (polar transport), i.e., auxin can only be transported from the upper end of the morphology to the lower end of the morphological end of the morphological bucket, and not the other way around. Polar transport is an active transport that requires a bond rock carrier and consumes energy, and is only affected by genetic material and not by gravity.

The transport of auxin in the tip of the coleoplasty is characterized by (lateral transport), that is, auxin is transported laterally from the photogenic side to the photosensitive side of the dorsal pin, so that the concentration of auxin on the backlit side is higher than that on the phototropic side, and finally the germ sheath bends and grows towards the light.

Apical meristem cells can produce auxin.

Because the apical meristem is a thriving tissue site, auxin is transported from the upper morphological end to the lower morphological end.

The book says that the apex young leaf embryo should be given a few examples, and the meristem also belongs to the book, and the book can't be completely listed.

So to give a few examples.

Definition: The content of free indoleacetic acid in plants is very low, about 1 100 micrograms per kilogram of fresh weight, depending on the location and tissue type, and the content of vigorous tissues or organs such as growth points and pollen is more.

I hope it will help you, if you don't understand, please ask.

...Of course, you can, the biology book doesn't make it clear.

B: It only proves that auxin has a promoting effect at this concentration, so it is wrong.

C: D point is auxin inhibition, the left side growth is inhibited, and it is impossible to bend to the left.

First of all, option B, there is no control group, so there is no way to know if it will bend like this when there is no agar block.

c option, the coleoplasty will not bend. The left side is growth inhibition, that is, it does not grow (because it cannot go back), while the right side does not have auxin and also does not grow.

Auxin is mainly produced in leaf primordium, young leaves, and developing seeds.

Auxin is a class of endogenous hormones containing an unsaturated aromatic ring and an acetic acid side chain, abbreviated as IAA in English, and its chemical essence is Yuchai Naindole acetic acid. In addition, 4-chloro-IAA, 5-hydroxy-IAA, naphthalene acetic acid (NAA), indolebutyric acid, etc. are auxinoids.

Auxin was the first plant hormone to be discovered. The most important chemical in auxin is 3-indoleacetic acid. Auxin has the functions of regulating the growth rate of stems, inhibiting lateral buds, and promoting rooting, and is used in agriculture to promote the rooting of cuttings, and the effect is remarkable.

Only the tip can be transported laterally. Lateral transport is an active transport. Because auxin is a small molecule organic matter, it is actively transported into the cell.

Due to the effect of gravity, the concentration of auxin in the near-ground side of the plant is higher than that on the back-to-ground side, which is called lateral transport and also belongs to active transport, because it occurs at the tip and belongs to lateral transport.

Auxin cannot be transported laterally at the lower end of the coleoplasty: because the transport of plants is done by a transport system, that is, the xylem and phloem, which are all ducts one by one, from top to bottom.

At the tip of the coleoplast, auxin is synthesized to produce regoli.

Due to the irradiation of unilateral light, lateral transport occurs at the same time as the downward polar transport, so the main transport direction of auxin is B a

Therefore, the omission of Butan: b