Dynamics of extractable carbohydrates in Pisum sativum. I. Carbohydrate and nitrogen content in pea plants and cuttings grown at two different irradiances

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Abstract
When pea plants (Pisum sativum L. cv. Alaska) were grown in controlled environment rooms, a stock plant irradiance of 38 W m‐2 decreased the rooting ability of the cuttings compared to 16 W m‐2. Also the origin of the seeds was of importance. The experiments were done in 1976 (1975 seed lot) and 1979/80 (1978 seed lot). At 38 W m‐2 the 1975 seed lot produced 7.2 roots, whereas the 1978 seeds produced 20.7 roots per cutting. The content of fructose, glucose, inositol and sucrose was determined from an ethanol extract, and extractable starch from a perchloric acid extract. The irradiance treatment regulated the carbohydrate content of the plants at the time they were made into cuttings. Cuttings from 16 or 38 W m‐2 contained initially 6.8 and 8.5% carbohydrate, on a dry weight basis respectively. If the plants were not excised to cuttings, a stable level of carbohydrates was maintained throughout the growing period, whereas in the cuttings, the carbohydrate content increased five fold during the rooting period. The content of extractable carbohydrates did not show any correlation to the root initiation process, but might be of importance for the further growth of the new roots. The C/N‐ratio of the plants at the time they were made into cuttings reflected the pre‐growth condition and was not related to the rooting ability of the cuttings.