​hansatech-instruments.​com) was strong enough to extract admirable oscillations in both parameters from spongy mesophyll cells, in conformity with then current concepts of photosynthetic regulation.” The team assembled in Sheffield at the time endorsed the event (Fig. 6), then proceeded for a celebratory excursion to an adjacent watering hole. The “subsequent ramifications” were explored during

David’s next visit downunder (Walker and Osmond 1986). It is difficult to overstate the creative stimulus that gushed from such encounters or the camaraderie and support David lavished on his colleagues wherever and whenever they met. Fig. 6 “At last, photosynthetic oscillations in spinach leaves”. Endorsement and celebration of the observance of oscillations in photosynthesis in 1982. Signatures: NSC 683864 order Peter Selleck Fludarabine Horton, Ulrich Heber, Geoffrey Hind, Richard Leegood and David Walker Selleck PRIMA-1MET David’s last crusade on biofuels, like all others was imbued with careful assessment and presented

in compelling prose. “Retro-agriculture (the use of biomass for transport fuels) may, despite its intrinsic drawbacks …. still be judged to have a role in energy security and conservation. As such, its purpose will not, however, be well served by exaggeration of the yields…or failure to recognize the constraints imposed by the laws of physics.” (Walker 2009). We have lost a giant and will long rest on the shoulders of David Alan Walker.” David is survived by his wife Shirley, at their homes in Sheffield, Yorkshire, and Biddlestone, Northumberland, and by his daughter Marney, son Richard, and granddaughter, Billie. Acknowledgments We thank Govindjee for editing Rutecarpine this Tribute. He marveled at David and told us that David was his hero, as he himself was the recipient of ISPR’s 2nd Communication Award in 2007, the 1st having been awarded to David Walker. We also thank Zoran Cerovic (France), Bob Furbank

(Australia), Geoffrey Hind (USA), John Humby (UK), Agu Laisk (Estonia), Peter Lea (UK), Ross Lilley (Australia), Barry Osmond (Australia), Simon Robinson (Australia) and Charles Stirling (UK) for their valuable contributions to this Tribute. We appreciate the help of Dr. Elena Voznesenskaya in organizing the figures for publication. References Allen JF (2002) Photosynthesis for ramblers and browsers. Trends Plant Sci 7:484–486 Björkman O, Demmig B (1987) Photon yield of O2 evolution and chlorophyll fluorescence characteristics at 77 K among vascular plants of diverse origin. Planta 170:489–504CrossRef Delieu T, Walker DA (1972) An improved cathode for the measurement of photosynthetic oxygen evolution by isolated chloroplasts. New Phytol 71:201–225CrossRef Delieu T, Walker DA (1981) Polarographic measurement of photosynthetic O2 evolution by leaf discs. New Phytol 89:165–175CrossRef Delieu TJ, Walker DA (1983) Simultaneous measurement of oxygen evolution and chlorophyll fluorescence from leaf pieces.