Carbon assimilation, water use efficiency and photochemical activity in xerophytes from semiarid ecosystems of Venezuela

Abstract:

This work compares, with values already published and others taken for this purpose, the ecophysiological characteristics (water potential, ψ, photosynthetic rate, A; stomatal conductance, g<inf>s</inf>; water use efficiency, WUE; integrated daily carbon gain, A<inf>D</inf>; and PSII relative quantum efficiency, Φ<inf>PSII</inf>) in xerophytes of different life forms and photosynthetic metabolisms in four northern coastal locations of Venezuela in the rainy and dry seasons. Water potential of all species varied between -0.3 and -4.8 MPa. The highest A (22 μmol m^-2 s^-1) and g<inf>s</inf> (0.4 mol m^-2 s^-1) were found during the rainy season in Calotropis procera while the lowest (1 μmol m^-2 s^-1, A and 0.03 mol m^-2 s^-1, g<inf>s</inf>) corresponded to Cissus trifoliata during the dry season. In all life forms A was highly correlated to g<inf>s</inf>. Daily carbon gain in most of the studied species may be estimated from maximum photosynthetic rate (A<inf>max</inf>). In deciduous life forms, WUE was reduced with drought, whereas it did not change in evergreen trees and shrubs and decreased in herbs. Drought reduced Φ<inf>PSII</inf> while non-photochemical quenching (NPQ) increased, suggesting down-regulation of the photochemical system.

Año de publicación:

2010

Keywords:

• carbon balance
• Fluorescence
• Carbon isotopic composition
• water potential
• Xerophytes

Fuente:

scopus