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Patterns of carbon allocation in northern red oak (Quercus rubra L.), characterized by episodic growth through recurrent single-season flushing, vary by growth stage. To examine post-transplant timing and carbohydrate sources for new root growth, dormant, bare-root, half-sibling northern red oak seedlings were transplanted to pots and placed in a favorable growth chamber environment. Unlabeled seedlings were harvested at transplant and at the bud swell stage. After leaf emergence, seedlings were exposed to (14)CO(2) at the linear shoot, linear leaf or lag growth stages. Seedlings were then placed in a growth room for 48 h to allow for translocation of (14)C-labeled current photosynthate and its stabilization in sink component plant parts. Seedlings were subsequently harvested and tissue (14)C:(12)C ratio analyzed. New root growth began during the linear shoot growth stage. However, no increase in (14)C:(12)C ratio was found in new roots until the linear leaf and lag growth stages, indicating a downward shift in translocation of current photosynthate to fuel new root growth. In old roots, (14)C:(12)C ratio increased at the lag stage. Our results indicate that both stored carbohydrates and current photosynthate contribute to new root growth of transplanted northern red oak seedlings; stored carbohydrates promote initial new root proliferation, whereas current photosynthate assumes a greater role as new leaves mature and the flush terminates. Optimizing nursery practices to increase carbohydrate reserves may reduce the time required to establish root-soil contact and facilitate early post-planting survival.

A series of growth room experiments was carried out aiming to establish the role of abscisic acid on dormancy of Salix viminalis L. The inhibitor content and abscisic acid levels of extracts from roots, sap, leaves, and apical tissues of willow were measured using biological assay and gas-liquid chromatography. No evidence was obtained that photoperiodically mediated dormancy is associated with changes in abscisic acid levels or β-inhibitor activity.

The growth in area of the first eight leaves of broad bean plants was investigated in growth room experiments. Plants were grown at either 20 or 14 °C or transferred from 20 to 14 °C. Rates of leaf appearance and unfolding increased with temperature. The duration of growth of a leaf increased with leaf number for the first five leaves and then remained constant. The mean growth rate declined or remained constant with increasing leaf number. Durations of growth were shorter and growth rates larger at 20 °C than at 14 °C. Plants responded immediately to the change in temperature. Final areas of leaves which expanded after transfer from 20 to 14 °C were larger than those grown at 20 °C.

The effects of daylength and temperature on the induction of dormancy in shoots of Calluna vulgaris were investigated using controlled environment growth rooms. Short days did not induce dormancy in Calluna but flowering was inhibited and shoots having a characteristic end-of-season morphology were formed. Short days combined with low temperatures arrested growth but the depth of dormancy was not as great as that of plants in the field in late autumn. Long days combined with low temperature did not induce dormancy or the end-of-season morphology. Results from the growth room experiments may be interpreted in relation to the annual cycle of development of Calluna under field conditions.