Variations in life-form composition and foliar carbon isotope discrimination among eight plant communities under different soil moisture conditions in the Xilin River Basin, Inner Mongolia, China

A comparative study has been made of the photosynthetic physiological ecology and carbon isotope discrimination characteristics for modern-day bryophytes and closely related algal groups. Firstly, the extent of bryophyte distribution and diversification as compared with more advanced land plant groups is considered. Secondly, measurements of instantaneous carbon isotope discrimination ( Δ ), photosynthetic CO 2 assimilation and electron transport rates were compared during the drying cycles. The extent of surface diffusion limitation (when wetted), internal conductance and water use efficiency (WUE) at optimal tissue water content (TWC) were derived for liverworts and a hornwort from contrasting habitats and with differing degrees of thallus ventilation (as intra-thalline cavities and internal airspaces). We also explore how the operation of a biophysical carbon-concentrating mechanism (CCM) tempers isotope discrimination characteristics in two other hornworts, as well as the green algae Coleochaete orbicularis and Chlamydomonas reinhardtii . The magnitude of Δ was compared for each life form over a drying curve and used to derive the surface liquid-phase conductance (when wetted) and internal conductance (at optimal TWC). The magnitude of external and internal conductances, and WUE, was higher for ventilated, compared with non-ventilated, liverworts and hornworts, but the values were similar within each group, suggesting that both factors have been optimized for each life form. For the hornworts, leakiness of the CCM was highest for Megaceros vincentianus and C. orbicularis (approx. 30%) and, at 5%, lowest in C. reinhardtii grown under ambient CO 2 concentrations. Finally, evidence for the operation of a CCM in algae and hornworts is considered in terms of the probable role of the chloroplast pyrenoid, as the origins, structure and function of this enigmatic organelle are explored during the evolution of land plants.

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Correlations Between Carbon Isotope Discrimination and Climate of Native Habitats for Diverse Eucalypt Taxa Growing in a Common Garden

Functional Plant Biology ◽

10.1071/pp9960311 ◽

1996 ◽

Vol 23 (3) ◽

pp. 311 ◽

Cited By ~ 50

Author(s):

JE Anderson ◽

J Williams ◽

PE Kriedemann ◽

MP Austin ◽

GD Farquhar

Keyword(s):

Soil Moisture ◽

Leaf Area ◽

Carbon Isotope ◽

Carbon Isotope Discrimination ◽

Common Garden ◽

Potential Evaporation ◽

Unit Leaf Area ◽

Isotope Discrimination ◽

Unit Leaf ◽

Native Habitats

Distributions of common species of Eucalyptus in south-eastem Australia are related to gradients in temperature and rainfall. To determine whether intrinsic water-use efficiency (as indexed by carbon isotope discrimination, Δ) or other leaf attributes were related to climate of native habitats, we sampled 17 populations representing 14 species of Eucalyptus growing in a common garden in south- central New South Wales. Phreatophytes were clearly distinguished from populations that are totally dependent upon soil moisture derived from rainfall by having higher Δ at a particular level of rainfall. Among 12 non-phreatophytic populations (11 species), Δ was positively correlated with mean annual precipitation (r = 0.75, P = 0.005), December-March precipitation (r = 0.79, P = 0.002), an index of annual soil moisture (r = 0.81, P = 0.001) and seasonality of precipitation (r = 0.85, P < 0.001). There were similarly strong but negative correlations between Δ and potential evaporation during the summer months, but Δ was not correlated with annual potential evaporation of the source sites. Leaf mass per unit area (ρe) was negatively correlated with indices of water availability, positively correlated with nitrogen per unit leaf area (r = 0.90, P < 0.001), and negatively correlated with Δ (r = -0.73, P = 0.007). A was negatively correlated with area-based leaf nitrogen (r = -0.79, P = 0.002). These complementary correlations among Δ, ρe, and nitrogen per unit leaf area indicate that variation in Δ may stem largely from variation in photosynthetic capacity. The results provide strong evidence that variation in Δ and ρe reflect genetic adaptations to native habitats.

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