Effects of applied cadmium on its accumulation, dry matter production and net photosynthesis in okra and amelioration of cadmium toxicity through lime application

Aim: Vegetables grown in cadmium contaminated soils accumulate cadmium in their tissues and are risky for consumption. The aim of the study was to get an insight into the effect of different levels of cadmium in soil, on accumulation in different plant parts of okra and its effect on overall growth, biomass production and photosynthesis rate so that suitable management option is explored to produce safe vegetable in cadmium contaminated soils. Methodology: The study was conducted in replicated pots with three soil pH (5.46, 6.54 and 7.45) attained through addition of CaCO3 as main treatment and four Cd levels viz., 0, 3, 6 and 9 mg kg-1 of soil as sub-treatment. Okra (Abelmoschus esculentus) was taken as the test crop. The experiment was conducted in a net house. Results: The Cd concentrations were minimum in fruits (0.54, 0.31 and 0.14 mg kg-1) and higher in leaves at acidic pH (5.5), while in soil limed to slightly acidic (6.5) and alkaline pH (7.5) roots retained maximum Cd among plant parts. Net photosynthesis and biomass production decreased significantly with higher Cd doses at acidic pH (5.5). The rate of decline in net photosynthesis was lesser at higher soil pH. The transfer factors decreased with increase in soil pH. The DTPA extractable soil Cd decreased from 8.5 to 2% when soil pH increased rendering the Cd less available for plant uptake. Interpretation: Liming can be an effective ameliorative measure to mitigate Cd toxicity in acidic soils and can ensure safe consumption. Lowest accumulation of cadmium in fruit part suggests okra to be a potential vegetable crop for Cd polluted soils.

Potential increase in photosynthetic response of taro (Colocasia esculenta L.) to photon flux density and elevated CO2

Aim: The present study was undertaken to study the net photosynthetic rate (Pn), stomatal conductance (gs) and intercellular CO2 (Ci) in five eddoe and four dasheen type taro genotypes under ambient and elevated CO2 , and subjected to different photon flux densities. Methodology: The critical evaluation of Pn was assessed at different photosynthetic photon flux densities (PPFDs) viz., 200, 400, 600, 800, 1000, 1200 and 1500 µmol m-2 hr-1 under ambient CO2 (400 ppm) and at saturation PPFD (1500 µmol m-2 hr-1) at short-term (ten min) exposure of leaves to elevated CO2 (eCO2; 600, 800 and 1000 ppm) at 30oC using portable photosynthesis system LI-6400, LICOR, USA in a controlled-climate cuvette system. Results: The Pn in the leaves of nine taro genotypes persistently augmented upon short-term (10 min) exposure to eCO2 concentrations which ranged between 400 ppm and 1000 ppm. Taro genotypes exhibited 61.80 – 113.3% hike in Pn at eCO2 (1000 ppm) as compared to ambient CO2 (400 ppm). However, the per cent increase in Pn at eCO2 for every 200 ppm between 400 to1000 ppm significantly declined (4.4-18.4%) at 1000 ppm CO2. The differences in gs were statistically significant across taro genotypes (P>0.001) and CO2 concentrations (P>0.001). Further, the Ci was also found to increase constantly at eCO2 concentrations (400 ppm to 1000 ppm). However, there was significant reduction (16.2 - 31.3%) in Ci for every 200 ppm between 400-1000 ppm. Interpretation: Results of the study revealed that the genotypes Muktakeshi, Sree Pallavi and Telia are promising in the context of climate change as they significantly responded to eCO2 concentrations. Response mechanism to eCO2 need to be elucidated.

Elevated CO2 concentration improves functional traits and early growth of the widespread species Enterolobium contortisiliquum (Vell. ) Morong / Elevada concentração de CO2 melhora as características funcionais e o crescimento inicial da espécie generalista Enterolobium contortisiliquum (Vell. ) Morong

Enterolobium contortisiliquum is a neotropical widespread species that occurs in native AtlanticForest, Cerrado and Caatinga vegetation in Brazil. Outside Brazil, it occurs in Argentina, Bolivia, Paraguay, and Uruguay. The objective of this study was to investigate the influence of high carbon dioxide concentration [CO2] on leaf gas exchange, chlorophyll content, chlorophyll a fluorescence, growth, and biomass allocation among roots, stems, and leaves in young plants of E. contortisiliquum. After germination, twenty days old individuals of E. contortisiliquum were grown in open-top chambers (OTC) at two different [CO2] (400 ppm and 700 ppm). Physiological measurements were made when the plants had been grown in OTC for 170, 200, 230, and 260 days. The higher [CO2] favored the early growth of E. contortisiliquum by increasing maximum net photosynthesis (PN) and water use efficiency. Under high [CO2], root dry mass increased in E. contortisiliquum, which might be a trait that will benefit this species by enhancing water uptake, particularly in seasonally dry environments.

Enterolobium contortisiliquum é uma espécie neotropical generalista, encontrada na vegetação nativa da Mata Atlântica do Brasil, no Cerrado e na Caatinga. Fora do país, também pode ser encontrada empaíses como Argentina, Bolívia, Paraguai e Uruguai. O objetivo deste estudo foi investigar a influência da alta concentração de dióxido de carbono [CO2] nas trocas gasosas foliares, no teor de clorofila, na fluorescência da clorofila a, no crescimento e alocação de biomassa entre raízes, caules e folhas em plantas jovens de E. contortisiliquum. Após a germinação, indivíduos de E. contortisiliquum de 20 dias de idade foram cultivados em câmaras de topo aberto (CTA), em duas diferentes [CO2] (400 ppm e 700 ppm). Asmedições fisiológicas foram realizadas no momento do cultivo das plantas em CTA por 170, 200, 230 e 260 dias. A alta [CO2] favoreceu o crescimento inicial de E. contortisiliquum aumentando a fotossíntese líquida máxima (PN) e a eficiência do uso da água. Sob alta [CO2], a massa seca da raiz aumentou em E. contortisiliquum, o que pode ser uma característica que beneficiará esta espécie, aumentando a absorção de água, particularmente em ambientes sazonalmente secos.

Shading effects on leaf life span and functional traits in the widespread species Enterolobium contortisiliquum (Vell) Morong / Efeitos do sombreamento sobre o tempo de vida foliar e características funcionais na espécie com ampla distribuição Enterolobium contortisiliquum (Vell) Morong

Enterolobium contortisiliquum occurs in native forests formations from southeast to northeast Brazil, and too in Argentina, Bolivia and Paraguay. The objective of this study was to evaluate shading effects in the early growth of E. contortisiliquum plants. We measured leaf gas exchange, chlorophyll content index, biomass allocation and leaf development in plants in sunny and shaded areas. The experiment was performed in Universidade Federal de Viçosa, campus Florestal, Minas Gerais, Brazil. To determine the effects of different light regimes (full sunlight and shade) on the growth of E. contortisiliquum plants, we divided plants into two groups: plants grown in a greenhouse under full sunlight, and plants grown under 70% shade tissue. E. contortisiliquum plants grown in full sunlight showed an increase in maximum net photosynthesis, root, stem, and leaf dry mass, root length, root/stem ratio, and length of the stem. However, E. contortisiliquum under shade showed larger specific leaf area, leaf area ratio, chlorophyll content, long leaf life span, and slow growth. These ecophysiological adjustments in sunny and shaded areas may explain the wide geographical distribution of E. contortisiliquum in many vegetation types.

Enterolobium contortisiliquum ocorre em formações florestais nativas do sudeste ao nordeste do Brasil e também na Argentina, Bolívia e Paraguai. O objetivo deste estudo foi avaliar os efeitos do sombreamento no crescimento inicial de E. contortisiliquum. As trocas gasosas foliares, o índice de conteúdo de clorofila, a alocação de biomassa e o desenvolvimento foliar foram avaliados em plantas sob sol pleno e sombra. O experimento foi realizado na Universidade Federal de Viçosa, campus Florestal, Minas Gerais, Brasil. Para determinar os efeitos de diferentes regimes de luz sobre o crescimento das plantas de E. contortisiliquum, dividimos as plantas em dois grupos: plantas que cresceram em estufa a pleno sol e plantas que cresceram sob sombrite 70%. As plantas de E. contortisiliquum que cresceram em pleno sol apresentaram aumento na fotossíntese líquida máxima, massa seca de raiz, de caule e folhas, comprimento de raiz, razão massa de raiz/caule e comprimento do caule. Entretanto, plantas de E. contortisiliquum sob sombra apresentaram maior área foliar específica, razão de área foliar, conteúdo de clorofila, tempo de vida foliar e crescimento lento. Esses ajustes ecofisiológicos em áreas sob sol e sombra podem explicar a ampla distribuição geográfica de E. contortisiliquum em muitos tipos vegetacionais.

Diurnal and seasonal carbon balance of four tropical tree species differing in successional status / Balanço de carbono diurno e sazonal de quatro espécies tropicais arbóreas de diferentes grupos sucessionais

This study addressed some questions about how a suitable leaf carbon balance can be attained for different functional groups of tropical tree species under contrasting forest light environments. The study was carried out in a fragment of semi-deciduous seasonal forest in Narandiba county, São Paulo Estate, Brazil. 10-month-old seedlings of four tropical tree species, Bauhinia forficata Link (Caesalpinioideae) and Guazuma ulmifolia Lam. (Sterculiaceae) as light-demanding pioneer species, and Hymenaea courbaril L. (Caesalpinioideae) and Esenbeckia leiocarpa Engl. (Rutaceae) as late successional species, were grown under gap and understorey conditions. Diurnal courses of net photosynthesis (Pn) and transpiration were recorded with an open system portable infrared gas analyzer in two different seasons. Dark respiration and photorespiration were also evaluated in the same leaves used for Pn measurements after dark adaptation. Our results showed that diurnal-integrated dark respiration (Rdi) of late successional species were similar to pioneer species. On the other hand, photorespiration rates were often higher in pioneer than in late successional species in the gap. However, the relative contribution of these parameters to leaf carbon balance was similar in all species in both environmental conditions. Considering diurnal-integrated values, gross photosynthesis (Pgi) was dramatically higher in gap than in understorey, regardless of species. In both evaluated months, there were no differences among species of different functional groups under shade conditions. The same was observed in May (dry season) under gap conditions. In such light environment, pioneers were distinguished from late successional species in November (wet season), showing that ecophysiological performance can have a straightforward relation to seasonality.

Este estudo considerou algumas questões sobre como um adequado balanço de carbono foliar pode ser obtido por diferentes grupos funcionais de espécies tropicais arbóreas sob contrastantes ambientes luminosos em uma floresta. O estudo foi realizado em um fragmento de floresta estacional semidecidual localizada no município de Narandiba, Estado de São Paulo. Plântulas com dez meses de idade de quatro espécies, Bauhinia forficata Link (Caesalpinioideae) e Guazuma ulmifolia Lam. (Sterculiaceae) como espécies pioneiras, e Hymenaea courbaril L. (Caesalpinioideae) e Esenbeckia leiocarpa Engl. (Rutaceae) como espécies secundárias, cresceram em um ambiente de clareira e um de sub-bosque durante nove meses. Cursos diários da fotossíntese líquida (Pn) e transpiração foram medidos com um medidor portátil de trocas gasosas por infravermelho nas estações seca e chuvosa. A respiração no escuro (Rd) e a fotorrespiração (Pr) foram também avaliadas nas mesmas folhas utilizadas para as medidas de Pn após um período de adaptação ao escuro. Nossos resultados mostraram que a respiração integrada ao longo do dia foi similar entre as espécies dos dois grupos sucessionais. Por outro lado, a fotorrespiração das espécies pioneiras foi freqüentemente maior do que nas espécies secundárias em condições de clareira. Todavia, a contribuição relativa de Pr no balanço de carbono nas folhas foi similar em todas as espécies em ambos os ambientes. Independentemente da espécie, a fotossíntese bruta, considerando os valores integrados ao longo do dia, foi significativamente maior na clareira que no sub-bosque. Nas duas épocas avaliadas, não foram observadas diferenças significativas em nenhum dos parâmetros avaliados entre as espécies crescidas no ambiente de sub-bosque. O mesmo foi observado no mês de maio sob condições de clareira. No mês de novembro, as espécies pioneiras apresentaram uma performance ecofisiológica significativamente distinta das espécies secundárias no ...