A NOVEL EFFECT OF UV‐B IN A HIGHER PLANT (SORGHUM VULGARE)

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Abstract
Abstract— Two non‐photosynthetic photoreceptors (phytochrome and the usual blue/UV light photoreceptor) were previously found to be involved in light‐mediated anthocyanin synthesis in the mesocotyl of Sorghum seedlings (Drumm and Mohr, 1978). The decisive point is that phytochrome can act only after a blue/UV light effect has occurred. On the other hand, the expression of the blue/UV light effect is controlled by phytochrome (‘obligatory sequential action’). A strong positive interaction between the blue/UV‐A and the UV‐B part of the spectrum was found, in addition to the above sequential action: an inductive effect of blue or UV‐A light can only express itself fully if short wavelength UV (approximately 300–320nm. UV‐B range) is also given, either after the blue/UV‐A light or simultaneously. Since even small amounts of the UV‐B are strongly effective it is probable that this effect plays a role under natural conditions and may not be considered as a mere laboratory artifact.