INTERORGAN CORRELATION IN A PHYTOCHROME-MEDIATED RESPONSE IN THE MUSTARD SEEDLING

Abstract —Phytochrome ( P_fr )-mediated threshold control of apparent lipoxygenase (LOG) synthesis in the cotyledons of the mustard seedling depends on the presence of the hypocotylar hook. With isolated cotyledons, no suppression by light of apparent LOG synthesis can be detected. As soon as the cotyledons are separated from the hook, the control of apparent LOG synthesis by P_fr is completely lost. The data are consistent with the hypothesis advanced in a previous paper [Oelze-Karow, H. and H. Mohr (1973) Photochem. Photobiol. 18, 319–330] that apparent LOG synthesis in the cotyledons is controlled by phytochrome located in the hypocotylar hook. The data support the concept [De Greef, J. A. and R. Caubergs (1972) Arch. Int. Physiol. Biochim. 80, 959–960] that a very precise and highly ordered biophysical recognition and transmission system of light signals exists in plants.