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Effect of the Reproductive Sink on 14 C‐Assimilate Partitioning between Starch and Water‐Soluble Compounds in Soybean Leaves 1
Author(s) -
Carlson Dale R.,
Brun William A.
Publication year - 1985
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/cropsci1985.0011183x002500020018x
Subject(s) - biology , starch , dry weight , point of delivery , petiole (insect anatomy) , sink (geography) , horticulture , botany , zoology , food science , hymenoptera , cartography , geography
The objective of this study was to determine if changes in reproductive sink demand influence the partitioning of carbon within the source leaf. Temporary (Late R2‐R4) and continuous (Late R2‐R8) light and CO 2 enrichment treatments were used increase the pod number and weight on field.grown soybeans ( Glycine max L. Merr. ‘Hodgson 78’). During the last week of the temporary treatment, and at 1, 2, and 4 weeks thereafter, plants were pulse‐labeled with 14 4CO 2 at the tenth trifoliolate leaf. Leaf discs were removed at 0.5, 2, 4, 8 and 24 h after labeling and subsequently extracted for determination of 14 C in the starch, water‐soluble compounds (WSC), and residual fractions. Temporary and continuous CO 2 and light enrichment increased the reproductive sink load of field.grown soybeans at all sampling dates. On the average, total number of pods was increased 35% by light enrichment, and 38% by CO 2 enrichment. During this same period, light enrichment res~resulted in at least a 38% increase in total pod wall and seed dry weight while CO 2 enrichment resulted in a 28% increase. Light and CO 2 enrichment increased plant size during the sampling period. Leaf dry weight was increased 30% by light enrichment, and 39% by CO 2 enrichment. Stem plus petiole dry weight was increased 26% by light enrichment and 51% by CO 2 enrichment. Hence, light enrichment had a greater effect on reproductive than on vegetative growth, while CO 2 enrichment had a greater effect on vegetative than on reproductive growth. On the first sampling date, 11 August, significantly less label was incorporated and retained as starch in the light‐enriched plants. No differences were observed in the levels of 14 C‐labeled WSC or starch for the light‐enriched plants on 18 and 25 August, and during the entire experiment for the CO 2 ‐enriched plants. On 7 September, 4 weeks after removal of the temporary treatment, significantly less label was retained as WSC, starch, and residual material in the light‐enriched plants. The hypothesis that increased sink demand may influence assimilate partitioning is supported by these data.