Field measurements of the diurnal rates of photosynthesis of Picea mariana, the dominant tree species at the subarctic tree line, were made during the summers of 1972 and 1973 at Schefferville, Quebec (latitude 55° N). All relevant plant physiological and environmental parameters were also monitored. Photosynthesis was measured with an open gas analysis system with temperature-controlled cuvettes. Maximum daily rates were 2.0–3.5 mg CO2 g−1 dry weight h−1. Daily totals were between 15 and 30 mg CO2 g−1 dry weight. Temperature was unimportant in affecting daily photosynthesis totals during the summer months. The photosynthesis vs. needle temperature curve had an optimum of 15C. Dark respiration rates were 0.2–0.4 mg CO2 g−1 dry weight h−1 at 15C. The photosynthesis vs. light intensity curve was saturated at 0.8 ly min−1 (1.0 μE cm−2 s−1 PhAR.). As a result, heavy cloud cover considerably reduced daily photosynthesis. No seasonal variations in photosynthesis over June, July, and August were observed. No differences in maximum rates occurred between the three experimental sites. Needle temperatures within the cuvettes were 2–4C above air temperature under full sunlight (1.2 ly min−1). Needle temperatures under natural conditions were up to 7C above Stevenson screen temperatures and fluctuated rapidly with changes in turbulence.

A solid medium was developed for callus cultures originating from explants of root, hypocotyl, and cotyledon of seedlings of bush bean, and a liquid medium was developed for the growth of cell suspension cultures derived from the callus cultures. Some unsatisfactory media are recorded. Concentrations of mineral salts for cell suspension cultures are lower than for callus cultures. Both coconut milk and other organic substances are required for maximum growth. With cell suspensions the effect of deproteinized coconut milk is the same as that of raw coconut milk but, with callus cultures, deproteinized coconut milk gives greater yield. There are no obvious differences in yield of callus derived from root, hypocotyl, or cotyledon. Few differences in yield were obtained between cell suspension cultures from root, hypocotyl, and cotyledon but those from root gave the highest yield in dry weight. However, in the same medium, cells from the three origins are very similar in form and appearance. Some effects of different media on cell form and clumping are described. The yield in suspension culture is very high. Increase in cell number, fresh weight, and dry weight is about 100-fold in 12 days involving about six to seven divisions per cell.

No abstract

Changes in cell number, cell size, fresh weight, and dry weight were recorded for the growth cycle of a serially subcultured cell suspension culture derived from hypocotyl of bush bean (var. Contender). The various cell types and growth patterns from single cells were also recorded. The culture showed unique features including a relatively sharp separation of a phase of exponential cell division from a phase of cell expansion. Complete separation of cell clumps gave a free cell culture, of viable cells, by day 16. The growth cycle, cell types, and growth patterns are compared with those in other plant cell suspension cultures. The potential value of the culture for study of growth regulation is discussed.

Work was designed to study the decarboxylation of serine and biosynthesis of ethanolamine as part of an investigation into the replacement of vitamin B6by ethanolamine in the nutrition of excised tomato roots in sterile culture. A working hypothesis to explain the replacement involves repression, by ethanolamine, of a postulated vitamin B6dependent serine decarboxylase yielding ethanolamine.Evidence is presented, from studies using uniformly labelled serine-14C, serine-1-14C, serine-3-14C, and ethanolamine-1,2-14C (i) for the incorporation of serine and ethanolamine into the corresponding phosphatides, (ii) for the occurrence of a pathway whereby phosphatidyl serine is decarboxylated to phosphatidyl ethanolamine, which is further methylated to phosphatidyl choline, and (iii) for the existence of more than one molecular species of phosphatidyl ethanolamine.Experiments are reported in which uniformly labelled serine-14C was supplied in the presence and absence of the inhibitors ethionine, p-chloromercuribenzoate, or diethylethanolamine. The results suggest that in the excised tomato root a pathway of choline biosynthesis other than the phosphatide pathway may exist.Some evidence is given that the replacement of vitamin B6by ethanolamine decreases the decarboxylation of phosphatidyl serine.