Changes in photosynthesis and fluorescence in response to flooding in emerged and submerged leaves of Pouteria orinocoensis

Abstract

In the seasonally flooded forest of the Mapire River, a tributary of the Orinoco, seedlings remain totally covered by flood water for over six months. In order to characterize the physiological response to flooding and submergence, seedlings of the tree Pouteria orinocoensis, an important component of the forest vegetation, were subjected experimentally to flooding. Flooding was imposed gradually, the maximum level of flood including submerged and emerged leaves. After 45 d a severe reduction of net photosynthetic rate (P N ) and stomatal conductance (g s ) was observed in emerged leaves, whereas leaf water potential remained constant. The decrease in P N of emerged leaves was associated to an increase in both relative stomatal and non-stomatal limitations, and the maintenance of the internal/air CO 2 concentration (C i /C a ) for at least 20 d of flooding. After this time, both P N and g s became almost zero. The decrease in photosynthetic capacity of emerged leaves with flooding was also evidenced by a decrease in carboxylation efficiency; photon-saturated photosynthetic rate, and apparent quantum yield of CO 2 fixation. Oxygen evolution rate of submerged leaves measured after three days of treatment was 7 % of the photosynthetic rate of emerged leaves. Submersion determined a chronic photoinhibition of leaves, viewed as a reduction in maximum quantum yield in darkadapted leaves, whereas the chlorophyll fluorescence analysis of emerged leaves pointed out at the occurrence of dynamic, rather than chronic, photoinhibition. This was evidenced by the absence of photochemical damage, i.e. the maintenance of maximum quantum yield in dark-adapted leaves. Nevertheless, the observed lack of complementarity between photochemical and non-photochemical quenching after 12 d of flooding implies that the capacity for photochemical quenching decreased in a non-co-ordinate manner with the increase in non-photochemical quenching.

Leaf gas exchange characteristics and chlorophyll fluorescence of three wetland plants in response to long-term soil flooding

“…According to Demmig-Adams and Adams (1992), it is often related to light induced formation of the carotenoid zeaxanthin in the xanthophyll cycle (Maxwell and Johnson 2000). In our study, significant increase was found in H. altissima similarly to Eschweilera tenuifolia (Rengifo et al 2005) and Pouteria orinocoensis (Fernández 2006). This photo-protection mechanism is enhanced under any stress due to an excess of reducing power (NADPH+H + ) brought by the decrease of CO 2 available at carboxylation sites or a sink limitation (Schreiber et al 1986, Björkman andDemmig-Adams 1995).…”

Evidence of ecotypic differentiation between populations of the tree species Parapiptadenia rigida due to flooding

“…Flooding and subsequent submergence of vegetation in tropical rivers is a common phenomenon (Fernández, 2006). Flooding constitutes a limiting factor to plant growth and survival.…”

Tolerância à inundação de Cecropia pachystachya Trec. (Cecropiaceae): aspectos ecofisiológicos e morfoanatômicos

“…A hipoxia provoca variações na respiração aeróbia (Joly 1994;Rogge et al 1998;Matsui & Tsuchiya 2006) no nível nutricional (Drew 1991;Medri et al 2002;Alaoui-Sossé et al 2005) e na fotossíntese (Liao & Lin 1996;Olivella et al 2000;Pryor et al 2006;Fernandez 2006) o que podem afetar o crescimento e desenvolvimento das diferentes partes da planta em um ambiente alagado Medri et al 2002;Davanso et al 2002;Pryor et al 2006). Além disso, as plantas apresentam modificações morfológicas e anatômicas quando submetidas ao alagamento (Armstrong et al 1994;Evans 2004).…”