Abstract:

Phosphatidyl glycerol (PG) was isolated from leaves of different cold resistant varie ties of poplar and their hybrids, and phase-transition temperatures were determined by electronic spin resonance spectroscopy (ESR) method using Tempo [2, 2, 6, 6-tetram-ethylpiperidine-I-oxy1 (structure)] as the spin label. The fatty acid composition of their PG was analyzed by gas-chromato-graphy method. The results showed that PG from the cold-sensitive plant Cottonwood (Populus deltoides cv. ' Lux' I-69/55, female parent) underwent a thermotropic phase-separation at about 4 ℃. In contract, PG from the cold-resistant poplar Populus euramericana cv. I-45 /51 (male parent) went into the phase-separation state at about -12 ℃. PG from the six hybrids entered the phase-separation state at the temperature ranging from -2 ℃ to 11 ℃. The analyzation of fatty acids compositions in phosphatide suggest that saturated fatty acids level (the sum of palmiate plus hexadeca-trans-3-enoate plus stearate) as a proportion of total phosphatidyl glycerol fatty acids was closely related to the thermotropic phase-transition behavior of phosphatidyI glycerol from different cold-resistance varieties. The saturated fatty acid level of PG from cold-resistance plant was lower than that from cold-sensitive plant so that the phase-transition temperature of PG from the former was lower than that of the latter and displayed the cold resistance.

Key words: Poplar, Phosphatidyl glylcerol, Electronic spin resonance, Phase-transition temperature, Cold resistance