Eine Quantitative Analyse von Wachstumsvorgängen im Zusammenhang Mit der Photomorphogenese von Senfkeimlingen (Sinapis alba L.)

1. Under the influence of continuous far-red light, i.e. under the influence of optimal contents of active phytochrome 730 (Hartmann 1965), the rate of translocation of dry matter within the mustard seedling is drastically changed compared with the dark grown seedling. - The main results are (Fig. 4): Under the influence of light (i.e. continuous far-red) relatively more material remains in the cotyledons or is translocated to the radicle and much less material is incorporated into the hypocotyl. - If dark-grown seedlings are irradiated with continuous far-red the rate of translocation of dry matter from the cotyledons to the hypocotyl is reduced very rapidly. A lower rate is reached at least within 3 hours (Fig. 5). 2. The absolute contents of water can be regarded as a reliable gauge of growth of the different organs (radicle, hypocotyl, cotyledons; Fig. 6a, b, c). - The data of the radicle (Fig. 6c) indicate that control of growth by light is at least twofold: light determines the final extent of growth of a particular organ, and light determines the rate of growth. 3. The relative water contents of the organs are the following: cotyledons < hypocotyl < radicle. - Light decreases the relative water contents of radicle and hypocotyl but increases the relative water contents of the cotyledons. -Therefore changes in the relative water contents can be regarded as indicative of changes in the growth activity of a particular organ. 4. In order to compare seedlings which have been differently treated with respect to light (e.g. dark and continuous far-red) it seems to be necessary -following Backman (1943) - to introduce the "biological time" s=log_x (t+z) (t=physical time; z=const.). 5. The differential equation {Mathematical expression} then describes a number of growth phenomena of the mustard seedling. This has been demonstrated in extenso for the growth of length of the hypocotyl in darkness and under continuous far-red light (Fig. 7). - The equation accounts for the observation that light controls the final extent of growth as well as the rate of growth of a particular organ, and it also takes into account the fact that differently treated seedlings do have different physiological ages after the same period of physical time and are therefore not immediately comparable. 6. The mathematical analysis just mentioned shows that statements (e.g. Thomson 1954, Thomson and Miller 1963, Vince 1964) like "the effect of light is to accelerate a normal growth pattern that is taking place at a slower rate in the dark" cannot be generalized and are probably inadequate. 7. In the statistical part of this paper characteristic shifts with time of the distribution of growth parameters are mentioned. These shifts are also controlled by light.