| Method |
Fluorescence measurements. These were made at 77 K with an apparatus similar to that described by Powles and Bjorkman (1982). The new apparatus was designed for field use and differs from the previous one in the following respects: it is capable of simultaneous measurements of fluorescence at 692 nm and 734nm the design is much more compact and lighter the power consumption is much lower (20-30 W in total) the new electronic circuitry permits operation in the field from a conventional 12-V lead-acid battery, and less than one-half of the amount of liquid N 2 is consumed per run (approx. 150 ml). |