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The influence of water content and leaf anatomy on carbon isotope discrimination and photosynthesis in Sphagnum
Author(s) -
RICE S. K.,
GILES L.
Publication year - 1996
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.1996.tb00233.x
Subject(s) - sphagnum , photosynthesis , respiration , botany , isotopes of carbon , water content , biology , horticulture , chemistry , zoology , ecology , peat , total organic carbon , geotechnical engineering , engineering
The relative effect of diffusional resistance due to water films ( r wf ) and leaf anatomy ( r p ) on rates of net photosynthesis and on‐line measures of carbon isotope discrimination (Δ=Δδ 13 C) was investigated in Sphagnum. Sphagnum species differ in the exposure of photosynthetic cells at the leaf surface. In S. affine , photosynthetic cells are widely exposed at the surface, whereas in S. magellanicum , photo‐synthetic cells are enclosed within water‐filled hyaline cells. This difference is expected to lead to variation in diffusive resistance within leaves ( r p ). Net photosynthesis and on‐line Δ were measured at two water contents: greenhouse water content (wet) and blotted dry (dry). Without correcting for respiration, on‐line Δ values differed significantly between wet (23.7% o ) and dry (30.9% o ) plants. However, there was no significant difference between species means and no species × water content interaction. Corrections for respiration lowered Δ values by approximately 8.1% o and reduced the mean difference to 3.1% o , but did not alter the rank order of treatments. Net photosynthesis also decreased by 16% in wet plants, but there was no significant difference between the two species. In addition, five populations of S. affine and S. magellanicum grown in a common garden were analysed for their organic matter carbon isotope composition (δ 13 C). These values varied more within each species (0.9–1.2% o ) than between the two species (0.6% o ). Therefore, we conclude that variation in surface water films leads to a greater difference in resistance to CO 2 uptake and carbon isotope discrimination than that due to variation in leaf anatomical properties in Sphagnum .