Leaf optical properties of two liana species Canavalia parviflora Benth. and Gouania virgata Reissk in different light conditions

Abstract

-(Leaf optical properties of two liana species Canavalia parviflora Benth. and Gouania virgata Reissk in different light conditions). Lianas are plants that depend on support to reach some appreciable height, and they represent an important structural component of tropical forests. Although they predominate in clearings and gaps, some species survive in the understory. Changes in irradiance between these environments can affect leaf morphology and absorption of photosynthetic active radiation (PAR). We had examined the effects of different light regimes on leaf optical properties, chlorophyll content, specific leaf area, and leaf surface morphology in young seedlings of Canavalia parviflora Benth. (Fabaceae) and Gouania virgata Reissk (Rhamnaceae). The seedlings were distributed on workbenches covered by different layers of neutral shade netting, thus creating three levels of light intensity corresponding to about 40%, 10% and 1.5% of solar irradiance. Plants growing in full sun were used as a control. Both species exhibited an increase in reflectance in full sun and alterations in leaf morphology. Reduction in irradiance induced an increase in absorptance (decrease in reflectance and transmittance) in C. parviflora leaves in the green due to higher chlorophyll content. In G. virgata the spectral leaf changes were less observable. However, the efficiency of absorption was more pronounced in G. virgata than in C. parviflora leaves under 40%, 10% and 1.5% photon flux density (PFD). The greater efficiency of absorption in G. virgata was due to a larger specific leaf area (SLA) under these conditions. The adjustments in leaf optical properties can aid these species in overall carbon gain under limited light conditions. Key words -leaf absorptance, lianas, light conditions, reflectance, specific leaf area RESUMO -(Propriedades ópticas foliares de duas espécies de lianas Canavalia parviflora Benth. e Gouania virgata Reissk, em diferentes condições de luz). Lianas são plantas que dependem de um suporte para atingir uma altura apreciável, formando um importante componente das florestas tropicais. Embora sejam dominantes em clareiras, algumas espécies sobrevivem no sub-bosque. Mudanças da irradiância entre estes ambientes podem afetar a morfologia foliar e a absorção da radiação fotossinteticamente ativa. Neste estudo foram avaliadas as propriedades ópticas foliares, o conteúdo de clorofila, a área foliar específica e a morfologia da superfície foliar de duas espécies de lianas jovens Canavalia parviflora Benth. (Fabaceae) e Gouania virgata Reissk (Rhamnaceae), sob diferentes regimes de luz. Plantas jovens foram cultivadas em bancadas cobertas com sombrites possibilitando intensidades luminosas correspondentes a 40%, 10% e 1,5% da densidade de fluxo de fótons (DFF). Plantas em radiação plena foram usadas como controle. Ambas as espécies exibiram aumentos da reflectância sob radiação plena e alterações na morfologia foliar. Reduções na irradiância induziram um aumento na absorção (decréscimo na reflectância e tra...

Photosynthetic response of two tropical liana species grown under different irradiances

“…This species showed larger specific leaf area and a significant increase of absorption efficiency (ratio between absorptance at 400−700 nm per unit of biomass in photosynthetic tissues) under equal irradiance (Sanches and Válio 2006). Such attributes could contribute to the higher P N observed enhancing their possibilities for growth and survival in lowirradiance environments.…”

“…From optical property measurements, it was possible to work with a specific radiation absorbance for Canavalia and Gouania leaves. The A values varied from 0.72 to 0.91 for leaves under different irradiances (Sanches and Válio 2006).…”

Optimization of Photosynthetic Photon Flux Density and Light Quality for Increasing Radiation-Use Efficiency in Dwarf Tomato under LED Light at the Vegetative Growth Stage

“…In contrast, leaves under high PPFD conditions have thicker cuticles and lower SLA and chlorophyll concentrations than those grown under low PPFD conditions [53,54]. These characteristics increase the reflectance of leaves [54,55], which may explain the higher reflectance and lower transmittance (lower absorptance) of leaves under high PPFD than those under low PPFD (Table 4 and Figure 1). In addition, lower leaves shared more light because of the significantly low reflectance and absorptance of the top-layer leaves at low PPFD, and might have a more uniform vertical PPFD distribution, which could contribute to the canopy RUE [56].…”

“…In natural conditions, light is one of the limiting resources, and plants grown under low PPFD must adapt to capture light efficiently [52]. In contrast, leaves under high PPFD conditions have thicker cuticles and lower SLA and chlorophyll concentrations than those grown under low PPFD conditions [53,54]. These characteristics increase the reflectance of leaves [54,55], which may explain the higher reflectance and lower transmittance (lower absorptance) of leaves under high PPFD than those under low PPFD (Table 4 and Figure 1).…”

Chlorophyll fluorescence and initial growth of two liana species, Cuspidaria sceptrum (Cham.) L.G. Lohmann and Fridericia florida (DC) L.G. Lohmann, under changes of natural light conditions

“…Furthermore, the higher values of SLA, i.e., the production of thinner leaves, as found in C. sceptrum under shade, probably had an influence on the marked reduction of Fv/Fm on the first days of transfer. Higher SLA values can lead to higher absorption efficiency under shade (Sanches and Válio 2006), but when these thinner leaves are suddenly exposed to full sunlight, photoinhibition could be exacerbated. Similar findings were found by Tobita et al (2010), where the leaves of Sasa senanensis with higher LMA (the opposite of SLA) were less susceptible to photoinhibition after increases in irradiance than that of Quercus mongolica and Acer mono.…”