Plant Cell & Environment · 1998 · 99 citations · 34 references
Life SciencesBotanyPlant SciencesPhotosynthesisPlant EcophysiologyPlant PhysiologyDroughtDrought Stress PhysiologyDrought ToleranceEnvironmental Responses Of PhotosynthesisPhotosynthetic AcclimationWater RelationsDrought Effects On PhotosynthesisPhotosynthetic AdaptationsPhotosynthetic Performance Under DroughtPhotosynthetic RatePhotosynthetic Response To DroughtPhotosynthetic Response To EnvironmentPhotosynthetic Responses To DroughtWater Stress Effects On Photosynthesis
The photosynthetic response of Larrea tridentata Cav., an evergreen Mojave Desert shrub, to elevated atmospheric CO 2 and drought was examined to assist in the understanding of how plants from water‐limited ecosystems will respond to rising CO 2 . We hypothesized that photosynthetic down‐regulation would disappear during periods of water limitation, and would, therefore, likely be a seasonally transient event. To test this we measured photosynthetic, water relations and fluorescence responses during periods of increased and decreased water availability in two different treatment implementations: (1) from seedlings exposed to 360, 550, and 700 μ mol mol –1 CO 2 in a glasshouse; and (2) from intact adults exposed to 360 and 550 μ mol mol –1 CO 2 at the Nevada Desert FACE (Free Air CO 2 Enrichment) Facility. FACE and glasshouse well‐watered Larrea significantly down‐regulated photosynthesis at elevated CO 2 , reducing maximum photosynthetic rate ( A max ), carboxylation efficiency (CE), and Rubisco catalytic sites, whereas droughted Larrea showed a differing response depending on treatment technique. A max and CE were lower in droughted Larrea compared with well‐watered plants, and CO 2 had no effect on these reduced photosynthetic parameters. However, Rubisco catalytic sites decreased in droughted Larrea at elevated CO 2 . Operating C i increased at elevated CO 2 in droughted plants, resulting in greater photosynthetic rates at elevated CO 2 as compared with ambient CO 2 . In well‐watered plants, the changes in operating C i , CE and A max resulted in similar photosynthetic rates across CO 2 treatments. Our results suggest that drought can diminish photosynthetic down‐regulation to elevated CO 2 in Larrea , resulting in seasonally transient patterns of enhanced carbon gain. These results suggest that water status may ultimately control the photosynthetic response of desert systems to rising CO 2 .
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