the Hormonal control of speed and a growth direction. Auksin

you are: the Hormonal control of speed and a growth direction

Auksin is developed growing apikalnymi by zones of stalks, including young leaves. From apeksa auksin migrates in a stretching zone where it specifically influences growth by a stretching.

At removal of a top of quickly growing stalk growth in a zone located below a cut, very quickly is slowed down and within several hours or days (depending on plant type) absolutely stops. If a remote top at once again to place on a former place stalk growth will proceed almost normally. It testifies that any stimulus proceeding from a top, passes through a wound to growing cages. If the block gelatin or an agar on which within several hours there was a stalk top to transfer on penek dekapitirovannogo a stalk it will partially replace a top in stimulation of growth of underlaying sites. From this experience we conclude that any substance (auksin) moves from a top to the block, and from the block, downwards to the basis. It has been established that natural auksin represents simple connection - indolil-3-acetic acid (IUK) (fig. 9.2), synthesised in a plant by fermentativnogo amino acid transformations triptofana (fig. 9.3).

Auksin accelerates growth of plants, promoting a stretching of cages by means of influence on components of a cellular wall.

It is possible to show Activity IUK also on slices of the fabric separated from a plant. If to separate growing parts of a stalk, for example peas, and to place them on cups of Petri with a solution of sucrose and any mineral salt growth will be very slow. However after addition of small amounts IUK growth is considerably accelerated, and the effect appears directly proportional (in certain limits) to the logarithm of concentration added auksina. Usually after excess of optimum concentration growth again is a little slowed down. The further addition IUK can lead finally to full inhibition of growth (fig. 9.4).

Processing auksinom intaktnyh stalks, as a rule, does not cause their additional gain. From here it is possible to conclude that the stalk in norm is sated auksinom, made by its own top. Processing auksinom roots, on the contrary, usually ingibiruet their growth. In some cases root growth amplifies at removal of its tip. Hence, we can draw a conclusion that the root usually functions in conditions when auksina is available more, than there is enough. In comparison with a stalk stimulation and inhibition of growth of a root are caused by lower concentration auksina. In any case roots are more sensitive to auksinu, than stalks.

Sections