A study in connection with the problem of hormonization of seeds
Acta botanica neerlandica , Volume 3 - Issue 1 p. 1- 82
In the treatment of seeds for the purpose of stimulating growth and development, the application of synthetic plant growth substances in practice has not yet produced the desired result. This will be easily understood, considering the strongly divergent ways in which experiments have been made on a large number of different objects: the results, often contradictory, did not admit of any valuable conclusions. A more profound knowledge of the process of germination and of the mechanism of growth substance action during the initial stages of development is deemed necessary if advance is to be made in this domain. An investigation aiming at this purpose was carried out on the pea. Standardized, sterile conditions were maintained during the in vitro study of normal correlation-phenomena of the developing embryo and the influence exerted on it by various factors. The effect of a growth substance (indole-3-acetic acid, naphthalene-1-acetic acid, 2,4-dichlorophenoxyacetic acid) can be clearly distinguished from that of other influences. It is presumed that the obtaining of contradictory results in seedtreatment may be due chiefly to: a) variability of the starting material; b) selecting action of the seedcoat, and c) the manner in which the growth substance is passed on to the young plant by the cotyledons or by the endosperm (filled with different reserve substances in different types of seed). By means of various experiments it was ascertained that the growth substance administered acts upon the embryo not only directly, but also in an indirect way, like a thrust via the reserve substance mass. So, the role of the cotyledons would not be comparable to that of a reservoir gradually giving off the growth substance absorbed. With the aid of a new, sensitive technique the initial water uptake was studied in five kinds of seed. The results could be recorded in characteristic swelling-curves. Although in this process and also in the exuding of certain substances the seed-coat plays an important part, no influence of indole-3-acetic acid on these processes in the pea could be ascertained.
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