ISSN:
1432-2048
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary Lengthening of the hypocotyl ofSinapis alba L. is mainly controlled by the longer wave lengths of visible radiation, whereas a phototropic curvature of the hypocotyl can only be induced by the shorter wave lengths of visible radiation. In all regions of the visible spectrum inhibition of hypocotyl lengthening is due exclusively to an inhibition of cell lengthening. The main question is why no bending occurs with unilateral visible radiation at longer wave lengths in spite of the fact that the reaction is not saturated, and that a strong gradient of radiation exists between the light side and the shaded side of the hypocotyl. A hypothesis has been presented to explain these facts. It has been assumed that long wave length visible light reduces the level of endogenus gibberellins. It is known from the literature that in stems of many plants gibberellic acid is translocated laterally so rapidly after an unilateral application that the compound induces the entire stem to elongate more or less uniformly without pronounced curvature. In this way it is understandable that unilateral visible radiation at longer wave lengths reduces the level of endogenous gibberellic acid without inducing a curvature. On the other hand the effect of unilateral blue light remains localized and is not translocated. A curvature is the result.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01884806
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