Starch Content in Douglas-Fir: Diurnal and Seasonal Dynamics

Bethesda

1993

S. 359-367

18 Lit. Ang.

Bandaufführung

64691

Diurnal and seasonal starch dynamics in the crowns of young-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), and seasonal starch dynamics in various tissues of field-grown Douglas-fir seedlings, were determined in coastal mountains and valley sites in Oregon. The accumulation of photoassimilated carbon in the starch pools of seedlings also was investigated with steady-state 14C labeling. The pattern of starch buildup in twigs and attached needles of the young-growth Douglas-fir in spring and subsequent decline to nondetectable levels in fall was found to be correlated with budburst-later budburst at higher elevation signaled later increases in starch content. Starch content in the needles, stems, and roots of the Douglas-fir seedlings also was highest just after budburst and lowest in fall and winter. The daily starch pattern, which fluctuated considerably over 24 hr, was similar at all crown locations, and for needles and twigs. These data, and those from the 14C labeling, indicate that starch buildup in spring is from current photosynthesis. However, total starch content is too small to directly affect growth rates during the growing season-indeed, starch may be a buffer between rapidly fluctuating photosynthesis rates and ensuing translocation or growth processes.