Microautoradiographic localisation of [3H]sucrose and [3H]mannitol in Robinia pseudoacacia pulvinar tissues during phytochrome-mediated nyctinastic closure.
We have analysed the incorporation of [(3)H]sucrose and [(3)H]mannitol in pulvinar motor cells of Robinia pseudoacacia L. during phytochrome-mediated nyctinastic closure. Pairs of leaflets, excised 2 h after the beginning of the photoperiod, were fed with 50 mM [(3)H]sucrose or [(3)H]mannitol, irradiated with red (15 min) or far-red (5 min) light and placed in the dark for 2-3 h. Label uptake was measured in whole pulvini by liquid scintillation counting. The distribution of labelling in pulvinar sections was assessed by both light and electron microautoradiography. [(3)H]Sucrose uptake was twice that of [(3)H]mannitol incorporation in both red- and far-red-irradiated pulvini. In the autoradiographs, [(3)H]sucrose and [(3)H]mannitol labelling was localised in the area from the vascular bundle to the epidermis, mainly in vacuoles, cytoplasm, and cell walls. Extensor and flexor protoplasts displayed a different distribution of [(3)H]sucrose after red and far-red irradiation. Far-red light drastically reduced the [(3)H]sucrose incorporation in extensor protoplasts and caused a slight increase in internal flexor protoplasts. After red light treatment, no differences in [(3)H]sucrose labelling were found between extensor and flexor protoplasts. Our results indicate a phytochrome control of sucrose distribution in cortical motor cells and seem to rule out the possibility of sucrose acting as an osmoticum.
Moysset
L
L
Department of Plant Physiology, Faculty of Biology, University of Barcelona, Barcelona, Spain.
Llambrich
E
E
López-Iglesias
C
C
Simón
E
E
D001345:Autoradiography / Q000379:methods; D001692:Biological Transport / Q000528:radiation effects; D020285:Cryoelectron Microscopy / Q000379:methods; D003624:Darkness; D008353:Mannitol / Q000378:metabolism* / Q000493:pharmacokinetics; D010834:Phytochrome / Q000378:metabolism*; D018516:Pulvinus / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D031301:Robinia / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D013395:Sucrose / Q000378:metabolism* / Q000493:pharmacokinetics; D014316:Tritium
D014316:Tritium; D010834:Phytochrome; D008353:Mannitol; D013395:Sucrose