Fábio Pinto Gomes

Leaf gas exchange, chlorophyll fluorescence and growth responses of Genipa americana seedlings to soil flooding

Abstract Effects of soil flooding on photosynthesis and growth of Genipa americana L. seedlings, a neotropical fruit-tree species used in gallery forest restoration programs, were studied under glasshouse conditions. Despite the high survival rate and wide distribution in flood-prone habitats of the neotropics, previous studies demonstrated that growth of G. americana is reduced under soil flooding. Using leaf gas exchange and chlorophyll fluorescence measurements, we tested the hypothesis that stomatal limitation of photosynthesis is the main factor that reduces carbon uptake and growth rates of G. americana seedlings. Throughout a 63-day flooding period, the survival rates were 100%. The maximum values of the net photosynthetic rate ( A ) and stomatal conductance to water vapor ( g s ) of control seedlings were 9.86 μmol CO 2 m −2 s −1 and 0.525 mol H 2 O m −2 s −1 , respectively. The earliest effects of flooding were significant decreases in g s and A , development of hypertrophied lenticels and decrease in the dry weight of roots. A strong effect of the leaf-to-air vapor pressure deficit (LAVPD) on g s and A were observed that was enhanced under flooded conditions. Between 14 and 63 days after flooding, significant reductions in g s (31.7% of control) and A (52.9% of control) were observed followed by significant increments in non-photochemical quenching ( q N ) (187.5% of control). During the same period, there were no differences among treatments for the ratio between variable to initial fluorescence ( F v / F 0 ), the maximum quantum efficiency of the photosystem II ( F v / F m ) and photochemical quenching ( q P ), indicating that there was no damage to the photosynthetic apparatus. Based on the results, we conclude that decreases in stomatal opening and stomatal limitation of photosynthesis, followed by decrease in individual leaf area are the main causes of reductions in carbon uptake and whole plant biomass of flooded seedlings.

Tolerance and prospection of phytoremediator woody species of Cd, Pb, Cu and Cr

High concentrations of Cd, Pb, Cu and Cr can cause harmful effects to the environment. These highly toxic pollutants constitute a risk for aquatic and terrestrial life. They are associated with diverse bioavailable geochemical fractions, like the water-soluble fraction and the exchangeable fraction, and non-available fractions like those associated with the crystalline net of clays and silica minerals. Depending upon their chemical and physical properties we can distinguish different mechanisms of metal toxicity in plants, such as production of reactive oxygen species from auto-oxidation, blocking and/or displacement of essential functional groups or metallic ions of biomolecules, changes in the permeability of cellular membranes, reactions of sulphydryl groups with cations, affinity for reactions with phosphate groups and active groups of ADP or ATP, substitution of essential ions, induction of chromosomal anomalies and decrease of the cellular division rate. However, some plant species have developed tolerance or resistance to these metals naturally. Such evolution of ecotypes is a classic example of local adaptation and microevolution, restricted to species with appropriate genetic variability. Phytoremediator woody species, with (i) high biomass production, (ii) a deep root system, (iii) high growth rate, (iv) high capacity to grow in impoverished soils, and (v) high capacity to allocate metals in the trunk, can be an alternative for the recovery of degraded soils due to excess of metallic elements. Phytoremediation using woody species presents advantageous characteristics as an economic and ecologically viable system, making it an appropriate, practical and successful technology.

Sodium–potassium synergism in Theobroma cacao: stimulation of photosynthesis, water‐use efficiency and mineral nutrition

In ecological setting, sodium (Na(+)) can be beneficial or toxic, depending on plant species and the Na(+) level in the soil. While its effects are more frequently studied at high saline levels, Na(+) has also been shown to be of potential benefit to some species at lower levels of supply, especially in C4 species. Here, clonal plants of the major tropical C3 crop Theobroma cacao (cacao) were grown in soil where potassium (K(+)) was partially replaced (at six levels, up to 50% replacement) by Na(+), at two concentrations (2.5 and 4.0 mmol(c) dm(-3)). At both concentrations, net photosynthesis per unit leaf area (A) increased more than twofold with increasing substitution of K(+) by Na(+). Concomitantly, instantaneous (A/E) and intrinsic (A/g(s)) water-use efficiency (WUE) more than doubled. Stomatal conductance (g(s)) and transpiration rate (E) exhibited a decline at 2.5 mmol dm(-3), but remained unchanged at 4 mmol dm(-3). Leaf nitrogen content was not impacted by Na(+) supplementation, whereas sulfur (S), calcium (Ca(2+)), magnesium (Mg(2+)) and zinc (Zn(2+)) contents were maximized at 2.5 mmol dm(-3) and intermediate (30-40%) replacement levels. Leaf K(+) did not decline significantly. In contrast, leaf Na(+) content increased steadily. The resultant elevated Na(+)/K(+) ratios in tissue correlated with increased, not decreased, plant performance. The results show that Na(+) can partially replace K(+) in the nutrition of clonal cacao, with significant beneficial effects on photosynthesis, WUE and mineral nutrition in this major perennial C3 crop.

Some photosynthetic and growth responses of Annona glabra L. seedlings to soil flooding

Um experimento foi conduzido com o objetivo de analisar os efeitos do alagamento e da posicao das folhas na produtividade primaria liquida e no balanco de carbono em plântulas de Annona glabra L. (Annonaceae), uma especie altamente tolerante ao alagamento e nativa na America tropical. Todas as plântulas sobreviveram ao periodo de alagamento de 56 dias sem apresentarem sintomas de estresse. O alagamento induziu incrementos significativos (P <0,01) na biomassa de raizes, caules e planta inteira, e na razao raizes/parte aerea. Medicoes das trocas gasosas foliares foram conduzidas aos quatro, 11, 18 e 56 dias apos o alagamento, na primeira (L1), quarta (L4) e setima (L7) folha completamente expandida a partir do apice em cada plântula. Os valores medios da condutância estomatica ao vapor de agua (gs) e da taxa fotossintetica liquida (A) nas plântulas controle foram 0,26 mol m-2s-1 e 8,8 µmol m-2s-1, respectivamente. Reducoes significativas (P <0,05) em A foram observadas entre L1 e L7 nas plântulas controle em todos os tres dias de medicoes. As reducoes em A com o aumento da idade foliar tambem ocorreram nas plantas alagadas, apenas nos dias 4 e 18. O alagamento induziu alteracoes significativas em gs (P <0,05), alcancando 65% em relacao ao controle no dia 4 e 152% em relacao ao controle no dia 56. Com base nos resultados obtidos foi possivel concluir que as elevadas taxas de sobrevivencia e de crescimento de plântulas de A. glabra estao diretamente relacionadas com a capacidade de manter elevados valores de condutância estomatica e de taxa fotossintetica liquida em condicoes de alagamento do solo.

ALUMINUM EFFECTS ON GROWTH, PHOTOSYNTHESIS, AND MINERAL NUTRITION OF CACAO GENOTYPES

A solution culture experiment was conducted in a greenhouse with two cacao genotypes (Catongo and Theobahia). Plants were subjected to seven aluminum (Al) concentrations and Al effects on growth, photosynthesis, and mineral content were assessed. Inter-genotypic differences for Fo, Fm and Fv fluorescences, as well as for Fv/Fm, were observed with increasing Al concentrations. There was a decreasing of Fo, Fm, Fv and Fv/Fm for the Catongo. Increasing Al concentration decreased photosynthetic rate, stomatal conductance and leaf transpiration rate, however, inter-genotypic differences in these parameters were not observed. The Al-treatments decreased content of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) in different plant parts, with the exception of K content in stems of Theobahia and in leaves of both genotypes. Theobahia showed higher tolerance to Al phytotoxicity, manifested mainly in the higher levels of Al in the growth medium. Inter-genotypic differences were observed in the growth and mineral nutrition.

Molecular, physiological and morphological analysis of waterlogging tolerance in clonal genotypes of Theobroma cacao L.

In soil, anoxia conditions generated by waterlogging induce changes in genetic, morphological and physiological processes, altering the growth and development of plants. Mass propagation of cacao (Theobroma cacao L.) plantlets (clones) is affected by waterlogging caused by heavy rains and irrigation methods used to induce rooting. An experiment was undertaken to assess the effects of a 45-day flooding (anoxia) on physiological and morphological traits of 35 elite cacao genotypes, aiming at potentially identifying those with greater tolerance to flooding of the growth substrate. Eighteen fluorochrome-labeled microsatellite (SSR) primer pairs were used to assess genetic variability among clones, with 248 alleles being amplified and used to calculate similarity coefficients. The resulting dendrogram indicated the presence of four major groups, in which two represented 60% and 31% of the genotypes tested. A general trend toward high levels of heterozygosity was also found for physiological and morphological traits. The survival index (IS) for flood tolerance observed varied from 30 to 96%. Clones TSA-654, TSA-656, TSA-792, CA-1.4, CEPEC-2009 and PH-17 showed an IS value above 94%, whereas CEPEC-2010, CEPEC-2002, CA-7.1 and VB-903 clones were those mostly affected by waterlogging, with IS value below 56%. All genotypes displayed lenticel and adventitious root formation in response to waterlogging, although with different intensities. To determine whether patterns of physiological response could be associated with tolerance to anoxia, a similarity-grouping analysis was performed using the ratio between waterlogged and control values obtained for a series of physiological variables assessed. No specific pattern of physiological and morphological responses to waterlogging was strictly associated with survival of plantlets. However, results revealed by the dendrogram suggest that absence of leaf chlorosis may be a proper trait to indicate cacao clones with higher survival rates under flooding conditions. Consequences of these findings are discussed in the context of developing improved strategies for mass production of clones from elite cacao genotypes.

Photosynthetic traits of five neotropical rainforest tree species: interactions between light response curves and leaf-to-air vapour pressure deficit

Medicoes das trocas gasosas foliares em diferentes niveis do densidade de fluxo de fotons fotossinteticamente ativos (PPFD) foram realizadas com o objetivo de comparar as caracteristicas fotossinteticas de cinco especies arboreas de florestas umidas neotropicais, com especial enfase em modelos matematicos empiricos para estimativa de parâmetros derivados das curvas de resposta a radiacao luminosa e dos efeitos da diferenca de pressao de vapor entre a folha e o ar (D) na taxa fotossintetica em saturacao luminosa (Amax). Os modelos analisados proporcionaram boas estimativas para os parâmetros derivados das curvas de resposta a radiacao luminosa. Comparacoes entre as caracteristicas fotossinteticas de diferentes especies devem sempre considerar os modelos utilizados, seguidas de indicacoes pormenorizadas das condicoes microambientais no momento em que os dados foram coletados. Quando a diferenca de pressao de vapor nao for controlada artificialmente durante as medicoes, a incorporacao de uma funcao linear ou exponencial, explicando os efeitos de D nos parâmetros de trocas gasosas, e um excelente metodo para incrementar a performance dos modelos.

PHOTOSYNTHETIC CHARACTERISTICS AND FIBRE PRODUCTION FOLLOWING DEFOLIATION IN ATTALEA FUNIFERA MART., ARECACEAE, GROWING UNDER FULL SUN AND FOREST UNDERSTOREY

SUMMARY The effects of leaves cut during fibre harvesting of Attalea funifera under contrasting irradiance availability were evaluated, studying defoliation-induced changes in photosynthetic and growth characteristics and fibre production in adult individuals of A. funifera growing under full sun and forest understorey. Fibre harvesting was performed with or without (control plants) leaf removal twice in a 12-month interval. Maximum measured values of net photosynthesis (A), stomatal conductance and transpiration were higher in full sun defoliated palms than in non-defoliated palms in the same environment or in understorey palms of the two treatments. Non-defoliated palms from the two environments emitted more leaves than defoliated palms in the same evaluation period. The increment in the leaf-level rate of carbon assimilation following defoliation did not lead to high production of fibre, suggesting that the photosynthetic compensation for leaf removal was not effective, at least during the period of evaluation. The results indicate that leaf removal during harvesting did not represent an advantage for fibre production and may even lead to decreases in leaf and fibre production.

Low light availability affects leaf gas exchange, growth and survival of Euterpe edulis seedlings transplanted into the understory of an anthropic tropical rainforest

Euterpe edulis Mart. (Arecaceae) is a threatened palm tree of the Brazilian Atlantic Rainforest understory with fundamental importance for the restoration of degraded forest environments. We assessed the leaf gas exchange, growth and survival of E. edulis seedlings transplanted at three different forest sites (S1, S2 and S3) in the same area in which cocoa trees had been cultivated in a rustic agroforestry system. Measurement was carried out during the first year after seedling transplantation. The sites were characterised according to canopy openness (CO) and total daily photosynthetic photon flux density (PPFD). Average CO and PPFD values were 13.3%, 8.0% and 6.7%, and 3.34, 2.79 and 0.62 mol m−2 d−1 for S1, S2 and S3, respectively. A progressive decline in seedling survival was observed in all sites throughout the experiment. At 387 d after planting, survival at S1, S2 and S3 was 57%, 44% and 37%, respectively. The gross light-saturated photosynthetic rate (Amax), leaf area and plant biomass were significantly higher (P < 0.05) in S1 and S2 when compared with S3. The values of dark respiration rate (R d) and photosynthetic compensation irradiance (I c) were sufficiently low for a positive carbon balance. Notwithstanding, the interpretation of results of microclimate variables together with leaf gas exchange and growth variables indicated that seedlings at all sites were in a suboptimal condition to achieve Amax, which is probably the main cause of the dramatic decline in the seedlings’ survival throughout the first year after transplantation. From a practical point of view, if the values of CO and PFD are lower than 10% and 3 mol m−2 d−1, respectively, it is suggested that the transplanting of E. edulis seedlings to the understory of abandoned agroforestry systems be accompanied by cultural practices, such as the thinning and pruning of tree tops.

Effects of substrate flooding on growth and chemical composition of Theobroma cacao L. clonal genotypes

O alagamento do solo pode promover alteracoes no metabolismo celular e causar desvios nas condicoes otimas de crescimento das plantas, gerando uma condicao de estresse. Objetivou-se no presente trabalho avaliar os efeitos do alagamento no crescimento e na nutricao mineral de seis clones de T. cacao (CP-49, CCN-10, CP-06, CEPEC-2007, CEPEC-2008 e PS-1319), para elucidar possiveis mecanismos de tolerância ao alagamento. Mudas clonais de T. cacao, com 6 meses de idade, foram submetidas ao alagamento, juntamente com o tratamento-controle (nao alagado), por 30 dias. Observou-se, no final desse periodo, que o alagamento promoveu diminuicao nas taxas de crescimento relativo radicular (exceto para CP-06) e de area foliar, acumulo de materia seca e incremento nas taxas de crescimento relativo caulinar (exceto para os clones CP-06 e CEPEC-2008) e assimilatoria liquida (exceto para o clone alagado PS-1319) e de massa foliar especifica para os clones CP-49, CCN-10 e CP-06. Os clones que sobreviveram aos 30 dias de alagamento apresentaram baixos valores de razao de area foliar. De modo geral, o alagamento do substrato acarretou deficiencia na absorcao de macro e micronutrientes minerais, exceto de Fe. Dentre os clones avaliados, o CP-49 foi tolerante e o CEPEC-2008 nao tolerante ao alagamento. Os demais clones ficaram numa posicao intermediaria. Logo, o clone CP-49 tem grande potencial para ser cultivado em condicoes de alagamento.