Chloroplast thylakoid membrane fluidity and its sensitivity to temperature

✍ Scribed by J. Barber; R. C. Ford; R. A. C. Mitchell; P. A. Millner

• Publisher: Springer-Verlag
• Year: 1984
• Tongue: English
• Weight: 640 KB
• Volume: 161
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00398729

✦ Synopsis

In order to investigate membrane fluidity, the hydrophobic probe, 1,6-diphenyl-l,3,5hexatriene (DPH), has been incorporated into intact isolated thylakoids and separated granal and stromal lamellae obtained from the chloroplasts of Pisum sativum. The steady-state polarization of DPH fluorescence was measured as a function of temperature and indicated that at physiological values the thylakoid membrane is a relatively fluid system with the stromal lamellae being less viscous than the lamellae of the grana. According to the DPH technique, neither region of the membrane, however, showed a sharp phase transition of its bulk lipids from the liquid-crystalline to the gel state for the temperature range -20 ~ to 50 ~ C. Comparison of intact thylakoids isolated from plants grown at cold (4~176 and warm (14~ ~ C) temperatures indicate that there is an adaptation mechanism operating which seems to maintain an optimal membrane viscosity necessary for growth. Using a modified Perrin equation the optimal average viscosity for the thylakoid membrane of the chill-resistant variety used in the study (Feltham First) is estimated to be about 1.8 poise.