Methods were developed to study delayed light emission (luminiscence) and fluorescence changes in intact leaves of plants. Delayed light emission, detected from plants in darkness, was used to produce images of the plant leaves. The procedure was termed "phytoluminography". The use of the method is suggested for dia- nostic purposes at early stages of disturbances of the leaf tissues, not detectable with the naked eye. The delayed light emission is associated with the photochemistry of photosystem II and the light induced conversion and storage of energy in the thylakoid membrane system of chloroplasts. Fluorescence yield changes were induced by lowering temperature between 20 C and -20 C. The temperature induced fluorescence changes in leaves parallel the temperature induced changes in isolated chloroplasts in reaction preparations mediating photosynthetic electron transport from endogenous water splitting to added NADP. At above freezing temperatures, lowering the temperature at a constant rate of 1 C per minute caused supressed electron transport and increased fluorescence yield which were linearely dependent on the temperature change in frost resistent plants. Repeated freeze-thaw cycles between 20 °C and -20 °C induced variable fluorescence yield changes which were gradually depleated to F0 or Fm when the electron transport was injuried on the oxidizing or on the reduzing side of photosystem II, respectively. The temperature induced fluorescence changes were used to characterize plants with different ability to withstand freezing temperatures. The method also discriminates between plants of different frost resistance, and the method was used in screening for frost tolerance. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1981, härtill 5 uppsatser.</p> / digitalisering@umu