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Carbon and Nitrogen Supply during Seed Filling and Leaf Senescence in Soybean
Author(s) -
Hayati R.,
Egli D. B.,
CraftsBrandner S. J.
Publication year - 1995
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/cropsci1995.0011183x003500040024x
Subject(s) - photosynthesis , biology , senescence , dry matter , chlorophyll , horticulture , agronomy , botany , microbiology and biotechnology
Leaf senescence and N redistribution during seed filling may limit soybean [ Glycine max (L.) Merr.] yield by restricting the seed filling period. Experiments were conducted in the field and greenhouse to evaluate the relationship between seed N demand and leaf senescence. Plants (cv. McCall) were grown under shade cloth (which reduced insolation by 63%) from R1 to R5 (beginning seed fill), then the shade was removed from some plants with the objective of increasing photosynthesis, seed dry matter, and N accumulation. Experiments included plants grown in soil with no nodules (NO − 3 as primary source), plants grown in soil with many nodules (N from NO − 3 and N 2 fixation), and in a hydroponics system (NO − 3 as primary N source) where N was removed from the media at R5. Increasing photosynthesis at R5 increased seed dry matter accumulation and the response was larger when N was available. Seed N accumulation also increased if N was available. Increasing photosynthesis had no effect on seed N accumulation when N was not available to the plant. Temporal changes in chlorophyll and N of an upper leaf were measured to characterize leaf senescence. Increasing photosynthesis did not accelerate leaf senescence in any of the treatments. If N was available, N uptake increased when photosynthesis increased. If N was not available, seed N concentration decreased. The data suggest that leaf senescence does not occur because of seed N demand, but may be regulated by processes in the leaf.