Journal Article

Growth, water relations, and survival of drought-exposed seedlings from six maternal families of honey mesquite (<i>Prosopis glandulosa</i>): responses to CO<sub>2</sub> enrichment

H. Wayne Polley, Charles R. Tischler, Hyrum B. Johnson and Rodney E. Pennington

in Tree Physiology

Volume 19, issue 6, pages 359-366
Published in print May 1999 | ISSN: 0829-318X
Published online May 1999 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/19.6.359
Growth, water relations, and survival of drought-exposed seedlings from six maternal families of honey mesquite (Prosopis glandulosa): responses to CO2 enrichment

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Low water availability is a leading contributor to mortality of woody seedlings on grasslands, including those of the invasive shrub Prosopis. Increasing atmospheric CO2 concentration could favor some genotypes of this species over others if there exists intraspecific variation in the responsiveness of survivorship to CO2. To investigate such variation, we studied effects of CO2 enrichment on seedling survival in response to uniform rates of soil water depletion in six maternal families of honey mesquite (P. glandulosa Torr. var. glandulosa). Three families each from the arid and mesic extremes of the species' distribution in the southwestern United States were studied in environmentally controlled glasshouses. Relative water content at turgor loss and osmotic potential were not affected by CO2 treatment. Increased atmospheric CO2 concentration, however, increased growth, leaf production and area, and midday xylem pressure potential, and apparently reduced transpiration per unit leaf area of seedlings as soil dried. Consequently, CO2 enrichment about doubled the fraction of seedlings that survived soil water depletion. Maternal families of honey mesquite differed in percentage survival of drought and in several other characteristics, but differences were of similar or of smaller magnitude compared with differences between CO2 treatments. There was no evidence for genetic variation in the responsiveness of survivorship to CO2. By increasing seedling survival of drought, increasing atmospheric CO2 concentration could increase the abundance of honey mesquite where establishment is limited by water availability. Genetic types with superior ability to survive drought today, however, apparently will maintain that advantage in the future.

Keywords: heritable variation; osmotic potential; water deficit; xylem pressure potential

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Subjects: Plant Sciences and Forestry

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