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Photosynthetic down‐regulation in Larrea tridentata exposed to elevated atmospheric CO 2 : interaction with drought under glasshouse and field (FACE) exposure
Author(s) -
Huxman T. E.,
Hamerlynck E. P.,
Moore B. D.,
Smith S. D.,
Jordan D. N.,
Zitzer S. F.,
Nowak R. S.,
Coleman J. S.,
Seemann J. R.
Publication year - 1998
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 - 10.1046/j.1365-3040.1998.00379.x
Subject(s) - larrea , photosynthesis , evergreen , transpiration , stomatal conductance , horticulture , botany , zygophyllaceae , shrub , rubisco , water use efficiency , chemistry , soil water , agronomy , biology , ecology
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 .