Are winter adaptive changes in glutathione and chlorophyll contents in spruce needles triggered by low temperatures or short days?

Concentrations of glutathione and chlorophyll a and b in spruce needles und ergo seasonal variations in the field. Most prominent changes including inc reases in glutathione contents take place in autumn when winter adaptation begins. Since in the field studies the factors low temperature and light pe riod length cannot be separated, the present experiment was conducted in cl imate chambers. In August young trees of Picea abies (L.) Karst. were trans ferred to climate chambers conditions: One experimental variant with contro l temperature and short days and the second with control day length and low temperature. The conditions of the control chambers were outdoor condition s in August. Low temperature caused an increase in glutathione and decrease s in chlorophyll a and b. On the contrary, short days induced a decrease in glutathione and increases in chlorophylls. The results indicate that the f actor temperature might be more import for winter adaptations than the fact or day length.