The distribution of 14C labelled assimilates in young apple trees as influenced by doses of supplementary nitrogen. i. total 14C radioactivity in extracts | Distribution of 14C [carbon isotopes] labelled assimilates in young apple trees as influenced by doses of supplementary nitrogen. i. total 14C radioactivity in extracts
1976
Priestley, C.A. | Catlin, P.B. | Olsson, E.A.
Rooted shoots of apple rootstock MM.104 were grown in soil and supplied with doses of ammonium nitrate at different stages of shoot extension growth. 14CO2 was supplied in association with the supplementary nitrogen via the largest healthy leaf near the base of the current season's shoot. Samples from the various regions of the plants were extracted, giving methanolic solutions (containing principally sugars and soluble resources) and T.C.A. extracts (containing principally hydrolysis products of available polysaccharides). These were counted for total 14C activity using liquid scintillation spectrometry. Around 90 per cent of the activity was present in the methanolic extracts. Virtually no 14C activity was transferred to the root region before shoot extension was under way whereas up to 45 per cent of the translocated activity occurred in the roots during and after the main period of shoot extension. Nitrogen uptake had been confined to these later stages but no influence of nitrogen supply on the gross distribution of 14C outside the source leaf was detected.
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