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When 8-day seedlings were exposed to 14CO2 in light, approximately 2 hours were required for 14C to reach the apices of the roots. One method used to detect the progress of 14C down the root was to scan the root with a radiochromatogram strip scanner. At this stage most in aqueous ethanol extracts of roots was present as sucrose, equally labelled in glucose and fructose. This was converted only slowly to other components of the soluble fraction so that after 12 hours almost 50% of 14C was still retained in sucrose. 14C exuded from intact roots into surrounding solutions was present in both volatile and non-volatile compounds. In the non-volatile fraction glutamine, glutamic and aspartic acids were the main 14C-amino acids. Exudation of 14C was not affected by changing the inorganic composition of the collecting solution. A change in pH of collecting solution from 6.4 to 5.9 increased exudation. Exudation also increased markedly when 2,4-dinitrophenol or potassium cyanide was present in the collecting solution. [ABSTRACT FROM AUTHOR]

Young plants of the wilty tomato mutant, flacea, in which the stomata resist closure, were sprayed with abscisic acid eight times over a period of 24 hours in light and darkness. The hormone induced closure of stomata similarly in leaves treated either in light or in darkness. Abscisic add does not appear to induce stomatal closure in darkness by increasing the internal CO2 concentration in the leaf, since this concentration should already be very high in darkness. A considerable and rapid decrease of CO2 assimilation and increase of CO2 evolution were demonstrated in mutant as well as in normal plants transferred from light to darkness. [ABSTRACT FROM AUTHOR]

The state of knowledge of the transition of sapwood into heartwood in trees is reviewed, and attention is drawn to the composition of the gas mixture available to such cells as remain alive in wood. The probable effect of such a mixture is postulated and experiments indicate that the high concentrations of carbon dioxide known to exist inside wood are conducive to formation of compounds known to be typical of the heartwood of Acacia mearnsii. [ABSTRACT FROM AUTHOR]

Four mosses, Bryum argenteum, Grimmia pulvinata, Hypnum cupressiforme and Tortula muralis were exposed to sulphite, and their uptake of radioactive bicarbonate measured. About 50% reduction in 14C uptake was caused by 0.01-0.1 mM suiphite. The effect of pH indicated that SO2 (or H2SO3') was the active molecular species. Fluoride had little effect on 14C uptake. [ABSTRACT FROM AUTHOR]

Uninfected plantlets of Goodyera repens and plantlets infected with the endophyte Rhizoctonia goodyerae-repentis were fed with 14CO2. Quantities of 14C fixed varied greatly between individuals, but there was a consistent pattern of distribution of label which remained unaltered over four weeks. Very little 14C moved to the rhizomes. The endophytic fungus readily grew from infected plantlets on to Pfeffer agar and small amounts of radioactivity were found in the mycelium growing from previously fed plantlets. 14C leakage from uninfected plantlets was negligible, although low levels of radiactivity occurred in serial washings from them. When the tops alone of infected plants were fed with 14CO2, no radioactivity could be detected in the emerging fungal mycelium. Where rhizomes alone were exposed, small quantities of 14C were detected in the growing mycelium. The fungus readily translocated 14C from the remains of dead protocorms. It appears that R. goodyerae-repentis does not freely utilize recent photosynthate from its host under the conditions of these experiments. [ABSTRACT FROM AUTHOR]

The limitations of present methods for describing the relative importance of different processes in controlling rates of photosynthesis are discussed, and a new method proposed. It is suggested that 'photosynthetic limitations', instead of resistances, should be used to describe the relative importance of different component processes at normal ambient carbon dioxide concentrations. The limitation approach is particularly relevant if the photosynthetic rate is not limited entirely by the supply of carbon dioxide. [ABSTRACT FROM AUTHOR]

The incorporation of radioactivity into polyols and carbon dioxide was measured for cultures of Dendryphiella salina incubated in media containing [1-14C]- or [6-14C]-glucose, with nitrate, ammonium or glutamate as nitrogen sources. The labelling patterns show that mannitol is synthesized partly via a direct route from substrate glucose and partly from hexose-phosphate derived from the pentose-phosphate pathway. Rapid turnover of the mannitol pool and the redistribution of radioactivity caused by the symmetry of the mannitol molecule lead to the synthesis of labelled arabitol from both forms of radioactive glucose. After a 6-hour incubation period, the proportion of mannitol synthesized via the pentose-phosphate pathway ranges from 36% in nitrate media to 19% in glutamate media. C1/C6 ratios for yields of 14CO2 also indicate that the activity of the pentose-phosphate pathway is greatest in the nitrate media and least in the presence of glutamate. Furthermore, there is an increase in the C1/C6 ratio when nitrate or methylene blue is added to cultures in ammonium media. The results are discussed in relation to previous studies of the pentose-phosphate pathway in fungi containing mannitol. [ABSTRACT FROM AUTHOR]

Freshly-cut slices of mature tubers liberated little 14CO2 from [2-3 14C] succinate even when sprouting after 9 months storage at 5 °C. Output from 24-hour washed slices was considerable; it increased in amount with increasing length of storage period and was enhanced when light was excluded during washing and incubation in succinate. A comparison was made between non-tuberizing stolon tips and young tubers taken within a day or so of tuber initiation. The fresh stolon tips released an appreciable quantity of CO2 from succinate, much less after washing. Fresh young tubers liberated much less 14CO2, slightly more after washing. Although tiffs indicated that the tricarboxylic acid- (TCA-) cycle block might arise soon alter initiation, the qualitative distribution of the label in tissue extracts showed stolon tips and young tubers to be similar to each other and distinct from mature tuber tissue. [ABSTRACT FROM AUTHOR]