Seasonal changes in photosynthesis of trees in the flooded forest of the Mapire River

Abstract

We studied the flood tolerance of five tree species growing in the flooded forest adjacent to the Mapire river, in SW Venezuela. Mean photosynthetic rate and leaf conductance were 11 &mgr;mol m(-2) s(-1) and 700 mmol m(-2) s(-1), respectively. Xylem water potential ranged from -0.08 to -1.15 MPa. Based on leaf gas exchange as a criterion of tolerance to flooding, two response patterns were identified: (1) decreasing photosynthetic rate with increasing flooding and leaf conductance (Psidium ovatifolium Berg. ex Desc., Campsiandra laurifolia Benth., Symmeria paniculata Benth. and Acosmium nitens (Vog.) Benth); and (2) independence of photosynthesis and leaf conductance from flooding (Eschweilera tenuifolia (Berg.) Miers.). In the first response pattern, declining photosynthetic rate with flooding may be interpreted as a sign of reduced flood tolerance, whereas the second response pattern may indicate increased flood tolerance. An increase in xylem water potential with depth of water column was found for all species (with the possible exception of P. ovatifolium), indicating that flooding does not cause water stress in these trees. Submerged leaves that had been under water for between four days and four months generally had photosynthetic rates and leaf conductances similar to those of aerial leaves, indicating maintenance of photosynthetic capacity under water. Daily positive oscillations in glucan content in submerged leaves of P. ovatifolium and C. laurifolia suggest that submerged leaves do not represent a sink for photosynthates produced by aerial leaves.

Leaf anatomy changes related to physiological adaptations to flooding in Amazonian tree species

“…This is in contrast to previous reports that in C. laurifolia, P. ovatifolium and S. paniculata SD differed on average 26 % between submerged leaves formed prior to flooding and emerged leaves that developed during flooding. However, the direction of change was not the same in each species (Fernández et al 1999). The inconsistency between these data and ours could be due to the fact that our samples had been preserved in isopropanol, whereas their varnish impressions were done on fresh leaves.…”

“…The flood cycle is very regular, rising-waters occurring in May, full flood in July-August, falling-waters in September, and drainage in November-April, with a dry season that may impose some degree of water deficit in trees far removed from the river bed (Fernández et al, 1999;Herrera et al, 2008a).…”

Tree Species Composition, Structure, and Aboveground Wood Biomass of a Riparian Forest of the Lower Miranda River, Southern Pantanal, Brazil

“…Trees subjected to periodic flooding often compensate anaerobic soil conditions by developing morpho-anatomical adaptations and by reducing metabolism during the waterlogged period, resulting in decreased photosynthetic rates, leaf shedding, and reduced wood growth and/or cambial dormancy (Fernandez et al 1999;Parolin et al 2004;Worbes 1997). Inundation is thus a powerful factor selecting the occurrence and distribution of tree species (Jackson and Colmer 2005), which in turn influences structure and biomass of seasonally flooded tree species communities.…”

Efeito da inundação de longa duração sob o crescimento de Pouteria glomerata (Sapotaceae), uma arbórea da várzea da Amazônia Central

“…Diante das respostas apresentadas para o período experimental avaliado, a ausência da inundação representou a melhor condição ambiental para P. glomerata. Os resultados são corroborados pelos obtidos por Worbes et al (1992), Schluter et al (1993) Fernandez et al, (1999 e Parolin et al, (2001) em ambiente natural, que verificaram maior produtividade na fase terrestre que durante a fase aquática, bem como os maiores valores de assimilação fotossintética das plântulas controle em outros estudos com inundação artificial (Pimenta et al, 1998;Waldhoff et al, 1998;Parolin, 2001;Lopez e Kursar, 2003;Armbrüster et al, 2004) As plântulas que permaneceram sob inundação parcial apresentaram desenvolvimento ligeiramente menor que às plântulas controle. Sob este tratamento a espécie não produziu novas folhas, mas as manteve desde o início do experimento em bom estado fisiológico.…”

“…Sob condições naturais e controladas, estudos relatam uma diminuição da assimilação fotossintética líquida em plantas alagadas (Waldhoff et al, 1998(Waldhoff et al, , 2002Piedade et al, 2000;Parolin et al, 2001;Armbrüster et al, 2004;Fernandez et al, 1999). Os ajustes fisiológicos resultam em considerável impacto sobre a alocação de biomassa para órgãos vegetais como folhas, caules e raízes.…”