Light or high (30°C) temperature effects on l-[U-14C]leucine incorporation and protein patterns in embryos and endosperm during the early phase of germination of the negatively photoblastic and thermosensitive seeds of Phacelia tanacetifolia

Abstract

The activities of l- [U- 14 C]leucine uptake and incorporation into proteins of embryos and endosperm of seeds of Phacelia tanacetifolia Benth. cv Bleu-Clair were analysed during the first 24 h of incubation under conditions optimal for germination (16°C in darkness) and in two inhibitory conditions: 16°C in the light and 30°C in darkness. Blocking germination induced by light or 30°C was accompanied by the inhibition of l- [U- 14 C]leucine uptake and incorporation in embryos. In the endosperm, the activation of l- [U- 14 C]leucine uptake was of the same magnitude for the non-inhibited and the light-inhibited seeds and much higher for the 30°C-inhibited seeds; the activation of l- [U- 14 C]leucine incorporation was quantitatively similar in all three conditions, with the patterns of newly synthesised proteins qualitatively different in the endosperm from light- or 30°C-inhibited seeds. The results showed that germination of P. tanacetifolia seeds is controlled by light or super-optimal temperature through the inhibition of the activation of transport and protein synthetic activities in embryo without effect on the endosperm. We suggest, on the basis of the translational activity, the possibility that in the inhibitory conditions the blockade of the embryo to operate as a sink affects the transition of the endosperm to operation as a source.