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Photomorphogenetic responses have been studied in a cucumber (Cucumis sativus L.) mutant (lh), which has long hypocotyls in white light (WL). While Photomorphogenesis in higher plants is a complex process regulated by a number of different photoreceptors, including phytochrome, cryptochrome, and UV-B photoreceptor (13,14). In addition, there is evidence for multiple types of a particular photoreceptor (e.g. the light-stable and light-labile types of phytochrome [20, 21], sometimes referred to as green-plant and etiolated-plant phytochrome, respectively). There is interaction between these photoreceptor systems in time and space during differentiation (13,14). The interpretation of physiological experiments is therefore often difficult, if not impossible, particularly in experiments utilizing light which is absorbed by more than one photoreceptor, as is the case for phytochrome and cryptochrome in the BL1 region of the spectrum (8, 13). To understand the roles played by the different photoreceptor systems we have taken a genetic approach in an attempt to resolve the inevitable confusion that has arisen (1,(10)(11)(12) MATERIALS AND METHODS Plant Material. The long-hypocotyl (1h) mutant and isogenic wild type of Cucumis sativus L. used here have been described elsewhere (1).Light Sources. White light was obtained from Philips TL40/33 fluorescent tubes. The broadband light sources for BL, RL, and FR used in long-term growth experiments were qualitatively the same as those described previously (11), and the fluence rates utilized are given in the figure legends. In short-term growth experiments, narrow-band BL (459 nm) and RL (658 nm

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