PHYTOCHROME LEVELS DETECTABLE BY IN VIVO SPECTROPHOTOMETRY IN PLANT PARTS GROWN OR STORED IN THE LIGHT

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Abstract
Tissues of fruits and vegetables from local markets were tested for reversible optical density changes at 660 and 730 m μ as a phytochrome assay. Over one‐third showed activity, which bore no obvious relationship to any morphological or taxonomic category. Reports of high activity in Brassica oleracea botrytis (cauliflower) were confirmed, but the highest activities were in tissues from roots of Pastinaca (parsnip), receptacles of Cynara (globe artichoke) and vegetative buds of Brassica oleracea gemmifera (Brussels sprouts). Activity in Pastinaca and Cynara appears light‐stable, with the far‐red‐absorbing form reverting to the red‐absorbing form more or less quantitatively in darkness. Activity in B. o. gemmifera, by contrast, is light‐labile, decaying without any apparent reversion; the high level of phytochrome initially present is due to light exclusion by the surrounding green tissues. Several of the materials described should prove valuable for further investigations on the nature and role of phytochrome.

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