Seasonal leaf gas exchange and water potential in a woody cerrado species community

Abstract

Predawn leaf water potential (psipd) and morning values of leaf gas exchange, as net photosynthesis (A), stomatal conductance (gs), transpiration (E), and morning leaf water potential (psimn) were determined seasonally in 22 woody cerrado species growing under natural conditions. Despite the lower mean values of psipd in the dry season (-0.35 ± 0.23 MPa) compared to the wet season (-0.08 ± 0.03 MPa), the lowest psipd in the dry season (-0.90 ± 0.00 MPa) still showed a good nocturnal leaf water status recovery for all species studied through out the year. Mean gs values dropped 78 % in the dry season, when the vapor pressure of the air was 80% greater than in the wet season. This reduction in gs led to an average reduction of 33% in both A and E, enabling the maintainance of water use efficiency (WUE) during the dry season. Network connectance analysis detected a change in the relationship between leaf gas exchange and psimn in the dry season, mainly between gs-E and E-WUE. A slight global connectance value increase (7.25 %) suggested there was no severe water stress during the dry season. Multivariate analysis showed no link between seasonal response and species deciduousness, suggesting similar behavior in remaining leaves for most of the studied species concerning leaf gas exchange and psimn under natural drought.

Seasonal variation in the maximum rate of leaf gas exchange of canopy and understory tree species in an Amazonian semi-deciduous forest

“…These data are consistent with other studies in tropical savanna (Franco 1998;Prado et al 2004), semi-deciduous forest (Hogan et al 1995;Miranda et al 2005), and rainforest (de A. Sa et al 1996;Bonal et al 2000), and suggest that periodic drought represents a key control on tropical tree productivity. Given the anticipated 3-4ºC increase in average annual temperature for the Brazilian tropics (Giorgi et al 2001), the potential magnitude and/or duration of seasonal drought is likely to increase.…”

Transpiração de espécies típicas do cerrado medida por transpirômetro de equilíbrio e porômetro

“…Este efeito é também observado nas plantas, quando as temperaturas são baixas no inverno, e quando ocorrem os veranicos, durante a estação chuvosa (FRANCO, 2005;PRADO, 1998;MORAES, 1983;PRADO et al, 2004).…”

The role of root buds in the regeneration of Casearia sylvestris Swartz (Salicaceae) in the cerrado, São Carlos, São Paulo state, Brazil

“…Such adaptations include functionally herbaceous or woody geoxylic suffrutices with enlarged underground xylopodia or lignotubers, thick corky bark, pachycaul rosette-forming shrubs and trees with sparse branching, thick shoots and leaves concentrated at shoot tips, perennial herbs, and specialized flowering and fruiting phenologies (Simon et al 2009). Plants subjected to water stress decrease their transpiration and thus their net photosynthesis (Prado et al 2004). …”