Fernanda Reinert

Influence of nitrogen supply on the photoprotective response of Neoregelia cruenta under high and low light intensity

This paper originates from a presentation at the IIIrd International Congress on Crassulacean Acid Metabolism, Cape Tribulation, Queensland, Australia, August 2001. We investigated preference for nitrogen source and the influence of ammonium nitrate on leaf pigment content, crassulacean acid metabolism (CAM) activity, and the efficiency of PSII in Neoregelia cruenta (R.Graham) L.B. Smith, a CAM bromeliad of major ecological importance to restinga (coastal sand ridge plains) environments. Plants showed a preference for ammonium over nitrate in a 24-h experiment where plants were exposed to 15NH4NO3 or NH415NO3. Mature individuals of N. cruenta were exposed to 95 and 20% full sunlight, and treated with 5 mm NH4NO3 or tap water only. After 4 months under the different treatments we found that nitrogen uptake and carotenoid content were independent of light exposure. Total chlorophyll decreased under nitrogen limitation and high light. Net titratable acid accumulation was not influenced by light or nitrogen regimes. Plants under low light showed consistently high photochemical efficiency of PSII (Fv/Fm) throughout the day. In contrast, plants under high light and nitrogen limitation showed a significant decline in Fv/Fm around midday, which recovered by the end of the light period. This decline in Fv/Fm was attributed to increased non-photochemical quenching. Our findings that plants under high light and with high nitrogen behave similarly to shade plants were unexpected. They suggest that the high light, high nitrogen leaves used a greater portion of the light absorbed in PSII antennae for photochemistry than the high light, low nitrogen plants. High nitrogen content in the leaves of N. cruenta appears to protect this CAM bromeliad against photoinhibition.

Photosynthetic properties of three Brazilian seaweeds

Photosynthetic performance of distinct marine macroalgae, Ulva fasciata Delile (green alga), Lobophora variegata (J. V. Lamouroux) Womersley ex E. C. Oliveira (brown alga), and Plocamium brasiliensis (Greville) M. A. Howe & W. R. Taylor (red alga), were compared using a pulse amplitude-modulated fluorometer. The maximum quantum yield (Fv/Fm) ranged from 0.80 to 0.51, and the lowest value was found in P. brasiliensis. Under 400 µmol photons m-2 s-1 irradiance, the highest value of photochemical quenching (qP = 0.92 ± 0.13) was observed for U. fasciata. The red alga P. brasiliensis dissipated high amounts of excitation energy (qN = 0.56 ± 0.09), resulting in relatively low values for the effective quantum yield of PS-II (0.23 ± 0.04), as well as for the relative electron transport rate (3.3 ± 0.7). The high photosynthetic potential found for U. fasciata partially explains the species ability for rapid growth and high productivity.

EPIPHYTES: PHOTOSYNTHESIS, WATER BALANCE AND NUTRIENTS

Epiphytes are plants adapted to living in the canopy and can be classified as facultative, hemiepiphytes or obligatory depending n the period spent in the canopy and if the species also occur as soil-rooted plants. Epiphytes are subjected to same environmental pressures as soil-rooted plants, such as demand water, light and nutrients, although environmental fluctuation tend to be more frequent. Epiphytes do not show any exclusive photosynthesis pathway, even though CAM is relatively common within this group, specially among orchids. In general, epiphytes are slow growing plants with high water use efficiency. This trait can be less competitive in environments with more favorable conditions where competition is more pronounced. Yet, among other epiphytes the vegetative growth phase coincides with the rain season. These plants can spend as much as 1.000g water per gram of organic matter produced, whereas among plants with high water use efficiency typical rates are 100:1. This variety of strategies demonstrates that, as in soil-rooted plants, a more parsimonious use of water does not necessarily represent the best mechanism to compromise water economy and growth.

Influence of blue light on the leaf morphoanatomy of in vitro Kalanchoe pinnata (Lamarck) Persoon (Crassulaceae).

Kalanchoe pinnata (Lamarck) Persoon (Crassulaceae) (air plant, miracle leaf) is popularly used to treat gastrointestinal disorders and wounds. Recently, the species was tested to treat cutaneous leishmaniasis with successful results. This medicinal activity was associated with the phenolic fraction of the plant. Blue light induces biosynthesis of phenolic compounds and many changes in anatomical characteristics. We studied the effects of supplementary blue light on the leaf morphology of in vitro K. pinnata. Plants cultured under white light (W plants) only and white light plus blue light (WB plants) show petioles with plain-convex section, amphistomatic leaf blades with simple epidermis, homogeneous mesophyll with densely packed cells, and a single collateral vascular bundle in the midrib. W plants have longer branches, a larger number of nodes per branch, and smaller leaves, whereas WB plant leaves have a thicker upper epidermis and mesophyll. Leaf fresh weight and leaf dry weight were similar in both treatments. Phenolic idioblasts were observed in the plants supplemented with blue light, suggesting that blue light plays an important role in the biosynthesis of phenolic compounds in K. pinnata.

Variation in nitrogen use strategies and photosynthetic pathways among vascular epiphytes in the Brazilian Central Amazon

A variacao nas estrategias de uso do nitrogenio e das vias fotossinteticas de familias de epifitas vasculares foi investigada em uma vegetacao de areia branca na Amazonia Central. Foram medidas as concentracoes e composicoes isotopicas de nitrogenio e carbono (δ15N e δ13C, respectivamente) de folhas de epifitas (Araceae, Bromeliaceae e Orchidaceae), assim como de suas arvores hospedeiras. As folhas da arvore hospedeira Aldine heterophylla tiveram a maior concentracao de nitrogenio foliar e menor razao C:N (2,1 ± 0,06% e 23,6 ± 0,8) que de suas hospedes. O valor de δ15N foliar da arvore somente diferiu do valor das orquideas. Ao comparar as familias de epifitas, a maior concentracao de nitrogenio foliar e menor razao C:N foi observada nas araceas (1,4 ± 0,1% e 34,9 ± 4,2, respectivamente). As orquideas tiveram valores mais negativos de δ15N foliar (-3,5 ± 0,2‰) que araceas (-1,9 ± 0,7‰) e bromelias (-1,1 ± 0,6‰). Ao comparar os taxons de cada familia, observou-se que tanto os taxons de araceas como os de orquideas diferiram em relacao ao nitrogenio foliar e razao C:N, enquanto que nao foi detectada variacao entre os taxons de bromelias. As diferencas nos valores de δ15N foliar aqui observadas podem ser relacionadas a variacao na dependencia das fontes de nitrogenio disponiveis para as epifitas, assim como na variacao da qualidade do microhabitat no dossel. Em relacao aos valores de δ13C foliar das epifitas analisadas, verificou-se que a maioria usa a via fotossintetica CAM (valores em torno de -17‰), comumente associada com plantas que vivem em condicoes de suprimento de agua limitado ou intermitente. Apenas as araceas e um taxon de orquidea mostraram usar a via C3 (valores em torno de -30‰).

Are sun- and shade-type anatomy required for the acclimation of Neoregelia cruenta?

Sun and shade plants are often discriminated by a number of sun- and shade-type anatomies. Nonetheless, we propose that among tank-bromeliads, changes in rosette architecture satisfy the requirements for coping with contrasting light levels. The tank-bromeliad Neoregelia cruenta naturally colonises sub-habitats ranging from full exposure to direct sunlight, to shaded environments in sand ridge plains. We quantified anatomical and morphological traits of leaves and rosettes of N. cruenta grown under sun and shade conditions. Cells with undulated lateral walls within the water parenchyma are for the first time described for the family. Under high light, leaf blades were wider, shorter, and yellowish. The rosette diameter of sun plants was less than half that of shade plants. Sun leaves overlapped with neighbouring leaves for most of their length, forming a cylindrical rosette where water accumulates. Shade leaves only overlapped in the centre of the rosette. Most anatomical traits were similar under both growth conditions. Stomata were absent from the base of sun leaves, which is probably explained by limited gas exchange at the base of the tight sun-type rosette. Data suggest that the ability of N. cruenta to acclimate to sun and shade is better explained by changes in rosette architecture than by leaf anatomy.

Characterization of the photosynthetic conditions and pigment profiles of the colour strains of Hypnea musciformis from field-collected and in vitro cultured samples

Hypnea musciformis (Wulfen) JV Lamour. is a species of great economic interest as it produces Κ-carrageenan and has shown biological activities against HIV and HSV viruses. This species displays different colour strains in its natural habitat, which may have implications for the biotechnological potential of the species. The aim of this study was to characterize the photosynthetic apparatus and pigment profile of three colour strains of H. musciformis (green, brown and red) in their natural habitat and in culture. Chlorophyll a fluorescence of photosystem II was measured with a pulse-amplitude modulated fluorometer and pigments were quantified by spectrofluorimetry (chlorophyll a) and spectrophotometry (phycobiliproteins). In the natural habitat, we detected significant differences between the colour strains for the following photochemical parameters: the green strain had a higher effective quantum yield (ΦPSII) than the red strain and a higher maximum relative electron transport rate (rETRmax) than the brown and red strains. Saturation irradiances were 1000 µE.m-2.s-1 (green) and 500 µE.m-2.s-1 (brown and red). Concerning in vitro culture, the green strain presented the lowest ΦPSII, rETRmax, and α rETR, while the brown strain presented the highest values for these same parameters. The chlorophyll a content of the cultured green strain was the lowest. The phycoerythrin contents of the three colour strains were unchanged by either natural of in vitro conditions: lower in green, intermediate in brown and higher in the red strain, ensuring the chromatic identity of the strains. Our results suggest that the green strain has a better performance when exposed to high irradiance, but a lower efficiency under low irradiance compared to the brown and red strains.

Habitat utilization and CAM occurrence among epiphytic bromeliads in a dry forest from southeastern Brazil

Investigamos a comunidade e a ocupacao de epifitas da floresta seca de Jacarepia, Rio de Janeiro para entender: i) como epifitas em geral ocupam troncos das arvores; ii) como bromelias epifitas ocupam arvores suporte; iii) distribuicao espacial de bromelias CAM. A coleta de dados sobre epifitas, forofitos e arvores foi baseada no metodo ponto quadrante central. A via fotossintetica das bromelias epifitas foi determinada por espectrometria de massa. A presenca de Gesneriaceae, Araceae e Cactaceae indicam umidade suficiente para permitir a presenca de epifitas supostamente menos especializadas. Nao houve correlacao entre abundância de epifitas e diâmetro dos forofitos, e forofitos possuiram maior tamanho que arvores sem epifitas. Houve correlacao entre diâmetro das arvores e abundância de bromelias e falta de correlacao entre diâmetro e riqueza de bromelias. Somente uma especie foi tipica da submata e outra do dossel. Estes resultados diferem do padrao de ocupacao de micrositios por epifitas, sugerindo que as copas das arvores sao locais super-expostos para bromelias. A unica especie C3 (Vriesea procera (Mart. ex Schult. f.) Wittm.) estava significativamente mais exposta que as demais especies no dossel. Se a ocorrencia de CAM e relacionada a economia de agua, o fato desta especie estar sujeita a condicoes de maior exposicao e notavel. Comentarios adicionais sao apresentados sobre a proporcao entre especies de bromelia CAM e abundância. Em relacao as formas de vida, holoepifitas ocorreram em todos os diâmetros dos forofitos ao contrario das hemiepifitas, sugerindo que holoepiftas possuem um estabelecimento melhor sucedido que hemiepifitas.

Diagnosing the level of stress on a mangrove species (Laguncularia racemosa) contaminated with oil: A necessary step for monitoring mangrove ecosystems.

Monitoring the effects of pollution on mangrove vegetation is a challenge. A specific study using an oil spill simulation on mangrove species was conducted to address this challenge. We tested the effectiveness of the chlorophyll a fluorescence kinetics as a fast and robust method to diagnose the vitality of Laguncularia racemosa. We used L. racemosa plants contaminated with marine fuel oil in mangrove microcosm models. Several parameters of the JIP-test were capable of detecting the impairment of the photosynthetic function prior to the visual manifestation of symptoms in response to oil contamination. The results support the use of the chlorophyll fluorescence transient as a reliable, fast and easy to apply diagnostic method for evaluating oil-impacted mangroves. To the best of our knowledge, it is the first time that consistent data showing photosynthetic impairment in response to oil contamination is shown for a mangrove tree species.

Anatomy and ultrastructure of embryonic leaves of the C4 species Setaria viridis

Background and Aims Setaria viridis is being promoted as a model C4 photosynthetic plant because it has a small genome (~515 Mb), a short life cycle (~60 d) and it can be transformed. Unlike other C4 grasses such as maize, however, there is very little information about how C4 leaf anatomy (Kranz anatomy) develops in S. viridis. As a foundation for future developmental genetic studies, we provide an anatomical and ultrastructural framework of early shoot development in S. viridis, focusing on the initiation of Kranz anatomy in seed leaves. Methods Setaria viridis seeds were germinated and divided into five stages covering development from the dry seed (stage S0) to 36 h after germination (stage S4). Material at each of these stages was examined using conventional light, scanning and transmission electron microscopy. Key Results Dry seeds contained three embryonic leaf primordia at different developmental stages (plastochron 1-3 primordia). The oldest (P3) leaf primordium possessed several procambial centres whereas P2 displayed only ground meristem. At the tip of P3 primordia at stage S4, C4 leaf anatomy typical of the malate dehydrogenase-dependent nicotinamide dinucleotide phosphate (NADP-ME) subtype was evident in that vascular bundles lacked a mestome layer and were surrounded by a single layer of bundle sheath cells that contained large, centrifugally located chloroplasts. Two to three mesophyll cells separated adjacent vascular bundles and one mesophyll cell layer on each of the abaxial and adaxial sides delimited vascular bundles from the epidermis. Conclusions The morphological trajectory reported here provides a foundation for studies of gene regulation during early leaf development in S. viridis and a framework for comparative analyses with other C4 grasses.