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The contribution of drought‐related decreases in foliar nitrogen concentration to decreases in photosynthetic capacity during and after drought in prairie grasses
Author(s) -
Heckathorn Scott A.,
DeLucia Evan H.,
Zielinski Raymond E.
Publication year - 1997
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1997.tb01834.x
Subject(s) - photosynthesis , rubisco , phosphoenolpyruvate carboxylase , thylakoid , perennial plant , photosystem ii , photosynthetic capacity , biology , poaceae , botany , chemistry , horticulture , chloroplast , biochemistry , gene
While stomatal closure usually limits photosynthesis during drought, our previous results suggest that drought‐related decreases in foliar nitrogen concentration (N L ) limit photosynthesis during recovery from drought in prairie grasses. Here we estimate the importance of decreases in N L to decreased photosynthetic capacity (PS cap ) during drought and a subsequent recovery period in three perennial C 4 prairie grasses. PS cap (O 2 evolution at light and CO 2 saturation) decreased 69 to 78% during drought in these grasses, and full recovery of PS cap required 8 to 12 days, until younger leaves were expanded or older leaves were repaired, depending on species. Decreases in N L explained 38 to 51% of the loss of PS cap during drought and accounted for 51 to 69% of the total loss of PS cap integrated over the post‐drought recovery period. N‐related loss of PS cap appeared to result more from decreases in ribulose‐1,5‐bisphosphate carboxylase/oxygenase (EC 4.1.1.39), phosphoenolpyruvate carboxylase (4.1.1.31), and other soluble photosynthetic enzymes, than from decreases in thylakoid N‐containing compounds. Decreases in quantum yield of O 2 evolution and F v /F m (variable‐to‐maximum fluorescence of dark‐adapted leaves) during drought were small, so we assumed that little damage to photsystem II (PSII) and thylakoid membrane function occurred. Further, F 0 (minimum F) decreased or remained unchanged, dark F 0 was greater than light F 0 , and decreases in photochemical quenching (the fraction of oxidized PSII) were reversed within 1–3 days after drought. Therefore, prolonged increases in non‐photochemical quenching (q n ; thermal dissipation of excess light energy) during and after drought were indicative of protective downregulation and were likely associated with disproportionate loss of soluble photosynthetic proteins during drought. In support of this, post‐drought recovery of q n paralleled recovery of N L and PS cap . Thus, in C 4 prairie grasses, loss of PS cap during drought is largely the result of decreases in shoot N L and of associated protective downregulation, decreasing carbon assimilation for 1–2 weeks after drought.