Acclimation of photosynthetic phenotype to environmental heterogeneity
- Univ. of Michigan, Ann Arbor, MI (United States)
- Univ. of Alabama, Tuscaloosa, AL (United States)
Inducible C[sub 4]-like photosynthetic metabolism in Hydrilla verticillate leaf tissue elicits variability in photosynthetic phenotype, expressed as CO[sub 2] compensation point ([Gamma]). A field and laboratory study investigated the ecological and adaptive significance. Spatial horizontal environmental heterogeneity was observed within clonal populations of H. verticillata in Florida. Measured at midday, the edge habitat at the expanding periphery of the clone exhibited a dissolved inorganic carbon (DIC) concentration of 0.7 mmol/L, pH 7.1, a dissolved oxygen (DO) level of 0.13 mmol/L, and biomass of 0.2 kg/m[sup 2]. The mat habitat, located 200 cm towards the interior of the surface mat, exhibited DIC 0.1 mmol/L, pH 10.2, DO 0.48 mmol/L, and biomass 0.8 kg/m[sup 2]. DIC depletion and DO supersaturation characterized the mat habitat for most of the day and much of the growing season. Net photosynthesis, daily carbon gain, and relative growth rate (RGR) of H. verticillata were reduced 80% by mat conditions compared to edge conditions. [Gamma]s of H. verticillata were positively 80% by mat conditions compared to edge conditions. [Gamma]s of H. verticillata were positively correlated with CO[sub 2] and vicarbonate concentration, and negatively correlated with pH, DO, and biomass. Low and high [Gamma] photosynthetic phenotypes were associated with the mat and edge habitats, respectively. Photosynthetic phenotype of H. verticillata appears to acclimate to environmental heterogeneity within a clone in the field. Net photosynthesis and daily carbon gain of low [Gamma] phenotype H. verticillata was 128% and 40% greater than the high [Gamma] phenotype when measured in the mat habitat, but was 21% lower than the high [Gamma] photosynthetic phenotype when measured in the edge habitat under low quantum flux. Laboratory experiments showed a negative curvilinear relationship between the [Gamma] of H. verticillata and plant density. 42 refs., 6 figs., 5 tabs.
- DOE Contract Number:
- FG02-87ER60515
- OSTI ID:
- 7034407
- Journal Information:
- Ecology; (United States), Journal Name: Ecology; (United States) Vol. 75:2; ISSN 0012-9658; ISSN ECOLAR
- Country of Publication:
- United States
- Language:
- English
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