Endogenous gibberellin-like substances in relation to short day induced flowering in the strawberry variety "Cambridge Favourite"

Abstract

Flowering and the factors controlling flowering have intrigued scientists and laymen alike for centuries. Over the years, developments in scientific research have revealed that flowering is controlled or at least affected by a wide range of environmental and physiological factors. This should have suggested that flower induction and evocation results from a complicated interaction of physiological processes. However many plant physiologists hoped to find a substance common to all plants which caused flowering. Some were less ambitious and thought that each species or genus may have a specific floral hormone. Such ideas have never been supported by more than a few grafting experiments and many photoperiod studies using the presence or absence of flowers as the criterion of success. These methods gave no information of the biochemical processes operating in intact plants. As techniques were refined the search for specific flowering hormones became intensified only to reveal more and more information which did not support the specific hormone theory.

However this intense research has yielded very little information on biochemical and physiological processes. “Quite often as compensation.........there is intensive speculation involving a host of unproved assumptions. Speculation and hypothesis are, of course, an essential part of experimental work. But this does not mean that each hypothesis needs to be published” (Lang, 1970). A decade before writing this Lang (1959) discussed the state of knowledge about flowering physiology and today. Little of significance can be added.

When reporting their studies of strawberry plant responses to varying environmental conditions Porlingis and Boynton (1961b) emphasised the need for sequential analyses of endogenous GA-like substances in plants under different photoperiod regimes. The following year, Moore and Hough (1962) applied this concept to endogenous auxin actively in strawberries. But since that time there have been few studies which have attempted to relate the activity of endogenous hormones to growth processes. The present study is an attempt to partially fill this gap. The GA-like activity in strawberry plant tissues is determined and related to the process of floral induction in response to SD conditions. As the study progresses the techniques being used were found to be inadequately accurate and sensitive for a study of this nature. This suggested a reason for the slow advance in the state of knowledge about flowering physiology. A review of the literature revealed a lack of standardisation of techniques making it virtually impossible to realistically compare results from different research laboratories.

New techniques now coming into use and the standardisation of the old methods should help to provide the important biochemical and physiological facts now so scarce in the field of flowering physiology.