Abstract:
The objectives of this investigation were to measure the seasonal and diurnal variations of starch as well as to relate these variations to growth of the trees. This study also microscopically examined the
needles to determine if starch exists in granular form in Douglas-fir. The objectives were designed to gain some insight into the patterns of energy storage in young growth Douglas-fir, and ts role in seasonal
growth. Diurnal starch variation followed a cycle of synthesis and depletion with three peaks in concentration; one around noon, another in early evening, and the third one during the early morning hours. Seasonal
starch concentrations peak in the spring before bud burst. Following bud burst, starch concentration decreased. Higher levels of starch were observed in the upper crown than the lower crown level. Starch was
shown to exist in the form of granules in the chloroplasts of cells in the needles of Douglas-fir. In the early evening lipid droplets were observed within the chloroplasts, however by early morning no visible sign of these droplets was to be seen.
