Leaf gas exchange and growth of flood-tolerant and flood-sensitive tree species under low soil redox conditions

Abstract

Seedlings of Taxodium distichum L., Quercus lyrata Walt. and Q. falcata var. pagodaefolia Ell. were grown for 22 days in a rhizotron system providing two soil redox potential regimes, +170 mV (low Eh) and +560 mV (high Eh). Leaf chlorophyll concentration and gas exchange, root alcohol dehydrogenase (ADH) activity, root and leaf ethylene production, and growth and biomass partitioning were measured. In response to the low Eh soil treatment, stomatal conductance was reduced in Q. falcata and Q. lyrata but not in T. distichum, whereas net photosynthesis was reduced significantly in all species; however, net photosynthesis in T. distichum began to recover within 2 weeks of treatment initiation. Within each treatment, mean stomatal conductance and net photosynthesis were significantly greater in T. distichum than in the oak species. Leaf chlorophyll concentration was not affected by the soil treatments. All species showed significant reductions in root and leaf dry weights in response to the low Eh soil condition. The low Eh soil treatment resulted in increased root ADH activity and ethylene production in T. distichum, but had no effect on root ADH activity and ethylene production in the oak species.

Crescimento inicial de Piptadenia gonoacantha (Leguminosae, Mimosoideae) sob inundação em diferentes níveis de luminosidade

“…Esta foi mais drasticamente reduzida em plantas inundadas a pleno sol quando comparada às plantas inundadas sombreadas. É possível especular que esta resposta reflita um efeito sinergístico do estado de água e da luminosidade sobre eventos como abertura estomática e absorção de água (Björkman & Powles 1984, Pezeshki et al 1996.…”

“…A redução no crescimento da parte aérea das plântulas inundadas deve ter ocorrido principalmente devido à supressão da formação e expansão de folhas e internós, pois sintomas como necrose, senescência e abscisão foliares não foram expressivos. Considerando que a anoxie é a principal causa dos efeitos adversos da inundação (Kozlowski 1997), o crescimento reduzido das plântulas inundadas de P. gonoacantha, poderia ser explicado pelas seguintes hipóteses: a) baixa produção de ATP (Joly 1986, Vartapetian 1991; b) redução na produção e translocação de fotoassimilados para a respiração (Kozlowski 1997); c) decréscimo na taxa de assimilação de CO 2 em razão do fechamento estomático (Tang & Kozlowski 1982a, b;Pezeshki et al 1996); d) redução na síntese e translocação de substâncias reguladoras do crescimento, como giberelinas e citocininas, do sistema radicial para a parte aérea (Reid & Bradford 1984).…”

Physiology of citrus fruiting

“…In the shoot, flooding reduces stomatal conductance and net CO 2 assimilation, leading to photosynthesis inhibition, altered production and transport of carbohydrates (Phung and Knipling, 1976) and oxidative damages (Gómez-Cadenas, unpublished results). Reduced transpiration impairs hydraulic root conductivity, and hence water uptake (Syvertsen et al, 1983;Vu and Yelenosky, 1991;Pezeshki et al, 1996). In addition, waterlogged soils are very propitious to the proliferation of soil-borne fungi such as Phytophtora.…”

Seasonal changes of leaf Nitrogen content in trees of Amazonian floodplains

“…Only adapted species can tolerate these conditions, e.g. by reducing the metabolic activity as in the temperate species Alnus rubra, Fraxinus latifolia, Nyssa aquática, Taxodium distichum or Quercus lyrata (Ewing, 1996;Pezeshki, 1987;Pezeshki et al, 1996). Some species, for example the tropical trees Hymenaea courbaril and Chorisia speciosa, can maintain or even in crease growth and photosynthetic ac tivity despite flooding (Joly & Crawford, 1982).…”