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Insects can survive subzero temperatures by two main strategies: freeze tolerance and freeze avoidance. An array of techniques have been used to investigate the physiological limits of insects to low temperatures, such as differential scanning calorimetry, temperature-controlled cooling apparatus, thermocouples, and computer-controlled chart recording equipment. However, these techniques require animals to be stationary, precluding behavioral data. We used infrared video thermography to investigate cold adaptation in an alpine insect, expanding such investigations to include behavioral response as an indicator of physiological stress. This technique is noninvasive and provides a large amount of physiological information, such as supercooling points, lower lethal temperatures, and hemolymph melting points. Insect supercooling points in response to a constant cooling rate were variable; however, temperatures at the initiation of behavioral stress response were less variable. Assessments of supercooling points and lower lethal temperatures obtained in this way are more biologically meaningful because allowing unhindered movement of insects more closely resembles natural environments.

Equations for non-destructive determination of chlorophyll b:aratios in grasses were developed from reflectance spectra of intact leaves of barley (Hordeum vulgareL.) and two barley mutants: clorina f2, which lacks chlorophyll band clorina f104, which has a low chlorophyll bcontent. These plants enabled separation of effects of chlorophyll composition on reflectance spectra due to differential light absorption by chlorophylls aand band to measure the effects of chlorophyll bon the contribution of fluorescence emitted by chlorophyll ato the reflectance spectra. Indices developed from these data were then tested on growth chamber-grown leaves from six C3and 17C4grass species (7 NAD-ME and 10 NADP-ME subtypes). We used the chlorophyll b:aratio because the data were less skewed than the chlorophyll a:bratio. The best index for determination of the chlorophyll b:aratio utilised wavelengths affected by chlorophyll absorbance: [R626– 0.5 (R603+R647)]/[R552– R626]. The chlorophyll b:aratio was significantly lower in the C4than C3grasses, but was not sufficient in itself to separate these two functional groups. However, because of differences in fluorescence characteristics, C3and C4species could be distinguished by an index based on wavelengths affected by chlorophyll fluorescence: [R696 to 709/R545 to 567]. [ABSTRACT FROM AUTHOR]