Multipurpose cryogenic surface apparatus: A liquid nitrogen-chilled sampletray

The use of cryogenic techniques allows collection and storage of large numb ers of samples for later processing for biochemical assays. In large field studies it is very difficult to obtain an accurate measure of leaf area as the samples are collected while preserving biological activity. Measurement of leaf area at the time of processing is also difficult because thawing o f leaf tissue can cause degradation of leaf biochemical components and proc esses. The objective of this study was to design a liquid N-2-chilled tray that allows cryogenically preserved samples to be sorted and measured witho ut the risk of sample thawing. A stainless steel lid (working surface) was brazed to a stainless steel pan, creating a reservoir that could be filled with liquid N-2. The working surface could then be maintained at approximat ely the temperature of liquid N2. Enzyme activities and polyacrylamide gel separations of ribulose-1,5-bisphosphate carboxylase (Rubisco) and phosphoe nol pyruvate carboxylas (PEPCase) of sorghum [Sorghum bicolor (L.) Moench] were used to assess the performance of the tray. Enzyme activity assays and gel separations of Rubisco and PEPCase confirm that biological activity is maintained through use of the multipurpose cryogenic surface (MCS) tray.