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Whole‐plant gas exchange responses of S partina alterniflora (Poaceae) to a range of constant and transient salinities
Author(s) -
Hwang YuanHsun,
Morris James T.
Publication year - 1994
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1994.tb15500.x
Subject(s) - salinity , photosynthesis , spartina alterniflora , stomatal conductance , respiration , biology , ecophysiology , botany , phragmites , transpiration , zoology , horticulture , ecology , wetland , marsh
A two‐chamber‐system was used to study whole‐plant gas exchange responses of Spartina alterniflora to long‐term and transient salinity treatments over the range of 5 to 40 ppt NaCl. Lower photosynthetic rates, leaf water vapor conductances, belowground respiration rates, and higher aboveground respiration rates in plants adapted to 40 ppt NaCl were observed. Area‐specific leaf weight increased with salinity, although the salt content of leaf tissues did not. A reduced rate of gross photosynthesis and higher aboveground respiration rate in 40‐ppt NaCl plants significantly lowered the net whole‐plant CO 2 gain below that of 5‐ppt NaCl plants, while the net CO 2 gain of 25‐ppt NaCl plants was intermediate. Within 6 hr of increasing the salinity of 5‐ and 25‐ppt NaCl plants by 20 and 15 ppt NaCl, S. alterniflora responded by reducing leaf water vapor conductance, which in turn reduced the photosynthetic rate. This response was reversed by returning the plants to their original salinity, which indicates that S. alterniflora adjusts water loss and gas exchange in response to transient salinity stress by regulating stomatal aperture. On the other hand, decreasing salinity of the growth media of plants cultured at 25 and 40 ppt NaCl had little or no effect on gas exchange characteristics. This suggests that S. alterniflora adapts to constant salinity through fixed, salinity‐dependent structural modifications, such as stomatal density.