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14 C‐Labelled Assimilate Utilization by Soybeans Grown with Three Nitrogen Sources 1
Author(s) -
Pearen J. R.,
Hume D. J.
Publication year - 1981
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1981.0011183x002100060032x
Subject(s) - biology , nitrogen , respiration , maturity (psychological) , photosynthesis , ammonium , labelling , botany , ontogeny , horticulture , chemistry , psychology , developmental psychology , biochemistry , organic chemistry , genetics
The use of a non‐destructive method of determining 14 C content of soybean plants after labelling allowed the fate of this 14 C, including proportions distributed to various plant parts or lost in respiration, to be studied. Plants grown in buckets in the field with Low‐N, nitrate (NO − 3 ), or ammonium (NH + 4 ) N sources were allowed to assimilate 14 CO 2 in photosynthesis at five stages in ontogeny. Plants were harvested after 1 week or at maturity and 14 C in plant parts was determined. In the first week after each labeling, NO − 3 ‐N plants lost an average of 14% of their 14 C, compared to 23% in NH + 4 ‐N plants and 34% in Low‐N plants fixing N 2 . Between labellings and maturity, average 14 C losses were 40% in NH + 4 ‐N plants, 45% in NO − 3 ‐N plants, and 52% in Low‐N plants. The largest proportion of the assimilated 14 C was either lost in respiration or contained in plant parts that were growing rapidly at labelling. Nodules of Low‐N plants contained more than those grown on NO − 3 ‐N or NH + 4 ‐N 1 week after labelling at stages R1 and R2.5. The percentages of assimilated at stages V4, R1, R2.5, R4 and R5.5 which were recovered in beans at maturity were 2.2, 3.7, 5.5, 13.8 and 36.5% respectively. Losses of 14 C from vegetative parts between 1 week after early labelllngs and maturity were mainly a result of respiration rather than retranslocation to beans.