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Does leaf shedding increase the whole‐plant carbon gain despite some nitrogen being lost with shedding?
Author(s) -
Oikawa Shimpei,
Hikosaka Kouki,
Hirose Tadaki
Publication year - 2008
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.2008.02415.x
Subject(s) - photosynthesis , xanthium , nitrogen , irradiance , biology , botany , photosynthetic capacity , carbon fibers , horticulture , agronomy , chemistry , mathematics , physics , organic chemistry , algorithm , quantum mechanics , composite number
Summary• When old leaves are shed, part of the nitrogen in the leaf is retranslocated to new leaves. This retranslocation will increase the whole‐plant carbon gain when daily C gain : leaf N ratio (daily photosynthetic N‐use efficiency, NUE) in the old leaf, expressed as a fraction of NUE in the new leaf, becomes lower than the fraction of leaf N that is resorbed before shedding ( R N ). • We examined whether plants shed their leaves to increase the whole‐plant C gain in accord with this criterion in a dense stand of an annual herb, Xanthium canadense , grown under high (HN) and low (LN) nitrogen availability. • The NUE of a leaf at shedding expressed as a fraction of NUE in a new leaf was nearly equal to the R N in the LN stand, but significantly lower than the R N in the HN stand. Thus shedding of old leaves occurred as expected in the LN stand, whereas in the HN stand, shedding occurred later than expected. • Sensitivity analyses showed that the decline in NUE of a leaf resulted primarily from a reduction in irradiance in the HN stand. On the other hand, it resulted from a reduction in irradiance and also in light‐saturated photosynthesis : leaf N content ratio (potential photosynthetic NUE) in the LN stand.