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Publication Type J
Authors Maricle, B. R., R. W. Lee, C. E. Hellquist, O. Kiirats and G. E. Edwards
Title Effects of salinity on chlorophyll fluorescence and CO2 fixation in C-4 estuarine grasses
Source Photosynthetica
Author Keywords Distichlis spicata; gas exchange; net photosynthetic rate; salt stress; Spartina species; species differences; stomatal conductance carbon-isotope discrimination; photosynthetic electron-transport; miscanthus x giganteus; photosystem-ii; salt-marsh; low-temperature; quantum yields; stomatal conductance; spartina-densiflora; o-2 evolution
Abstract The effects of salinity (sea water at 0 %(0) versus 30 %(0)) on gross rates of 02 evolution (J(O2)) and net rates of CO2 uptake (P-N) were measured in the halotolerant estuarine C-4 grasses Spartina patens, S. alterniflora, S. densiflora, and Distichlis spicata in controlled growth environments. Under high irradiance, salinity had no significant effect on the intercellular to ambient CO2 concentration ratio (C-i/C-a). However, during photosynthesis under limiting irradiance, the maximum quantum efficiency of CO2 fixation decreased under salinity across species, suggesting there is increased leakage of the CO2 delivered to the bundle sheath cells by the C4 pump. Growth under salinity did not affect the maximum intrinsic efficiency of photosystem 2, PS2 (F-v/F-m) in these species, suggesting salinity had no effect on photosynthesis by inactivation of PS2 reaction centers. Under saline conditions and high irradiance, P-N was reduced by 75 % in Spartina patens and S. alterniflora, whereas salinity had no effect on PN in S. densiflora or D. spicata. This inhibition of P-N in S. patens and S. alterniflora was not due to an effect on stomatal conductance since the ratio of C-i/C-a did not decrease under saline conditions. In growth with and without salt, P-N was saturated at similar to 500 mu mol(quantum) m(-2) s(-1) while J(O2) continued to increase up to full sunlight, indicating that carbon assimilation was not tightly coupled to photochemistry in these halophytic species. This increase in alternative electron flow under high irradiance might be an inherent function in these halophytes for dissipating excess energy.
Author Address Washington State Univ, Sch Biol Sci, Pullman, WA 99164 USA. Maricle, BR, Ft Hays State Univ, Dept Biol Sci, 600 Pk St, Hays, KS 67601 USA. brmiracle@fhsu.edu
29-Character Source Abbreviation Photosynthetica
Year Published 2007
Volume 45
Issue 3
Beginning Page 433-440
Unique Article Identifier ISI:000248975800015
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