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We studied the effects of apical maturation on the vascular cambium of juvenile and mature scions of Larix laricina (Du Roi) K. Koch that had been grafted on seedling rootstocks. Comparisons between the juvenile and mature cambium in nuclear genome size, nuclear shape, DNA concentration, number and
Polar regions were covered with extensive forests during the Cretaceous and early Tertiary, and supported trees comparable in size and productivity to those of present-day temperate forests. With a winter of total or near darkness and a summer of continuous, low-angle illumination, these temperate,
Biochemical models of photosynthesis suggest that rising temperatures will increase rates of net carbon dioxide assimilation and enhance plant responses to increasing atmospheric concentrations of CO(2). We tested this hypothesis by evaluating acclimation and ontogenetic drift in net photosynthesis