Carbon dioxide assimilation by Apple leaves as affected by lime-sulphur sprays. II. Field experiments

Hoffman, M.B.

Proceedings of the American Society for Horticultural Science 30: 169-175


ISSN/ISBN: 0099-4065
Accession: 013327282

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Orchard experiments to ascertain the effect of lime-sulphur spraying on the carbon dioxide utilization of apple leaves, ordinary summer strength lime-sulphur (2 1/2 in 100 galls.) being applied by means of a small atomizer to both surfaces of the leaves, in general confirmed the results obtained in previous tests in the greenhouse . One leaf sprayed on a sunny afternoon when the temperature was 29 degrees C. next day showed a reduction of 41 per cent. in its assimilation of carbon dioxide, as compared with a loss of only 5 per cent. efficiency in an untreated leaf on an adjoining twig of the same tree. Although the maximum reduction in assimilation attributable to spraying occurs on the day after treatment, the reduction shown by the sprayed leaf continued in an appreciable and consistent amount for seven days, after which the observations were discontinued. Practically the same results were obtained with two other sprayed and unsprayed leaves. When three leaves on two comparable trees were sprayed at 1.40 p.m. (temperature 21.5 degrees) and three others on the same trees at 6.45 p.m. (temperature 16 degrees) on the same day, all six showed reduced carbon dioxide assimilation during the next three days, but the reduction was greater in the leaves sprayed at the higher temperature. New Jersey dry-mix caused less reduction in efficiency of assimilation than lime-sulphur spray, the data obtained suggesting a difference in the effects of the mixtures on photosynthesis.