1994. Phytochrome-mediated closure of Albizzia lophantha leaflets as affected by sorbitol. mannitol and fusicoccin. -Physiol. Plant. 91: 307-311.The effect of sorbitol and mannitol and their interaction with the effect of fusiccocin has been investigated in phytochrome-mediated nyctinastic closure of Albizzia. lophantha leaflets. Treatments were commenced 2 h into the photoperiod. Pairs of leaflets were excised, floated on test solutions, and transferred to darkness immediately after red or far red in'adiation. Leaflet angles were measured in darkness for 3 h. Fusicoccin (I to 100 JLM) inhibited nyctinastic closure and enhanced reopening in the presence of Pft (far-red-absorbing form of phytochrome). Fusicoccin ef'fects on far red treated leaflets were not constant and whichever fusiccoccin concentration was applied, the effects were small. These results confirm the role of the plasma membrane proton pump in extensor cells during opening. Sorbitol and mannitol (25-100 mM) increased nyctinastic closure for about 2 h and then enhanced reopening in the presence of Pf,. When sugar alcohols were applied together with fusicoccin, sorbitol and matmitol enhanced the fusicoccin inhibition of closure and a marked synergistic effect was observed. These results indicate that both fusiccocin and the reduction of external osmotic potential caused by sorbitol or matinitol supply may stimulate the activity of the extensor H+ pump promoting the reopening.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.