Browsing by Author "Barrote, Isabel"
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- Alterações sazonais da fotossíntese e do ciclo das xantófilas em alfarrobeira (Ceratonia siliqua L.)Publication . Barrote, Isabel; Correia, Maria João; David, Maria ManuelaThis study aimed to follow the seasonal changes in the photosynthetic performance of two Ceratonia siliqua cultivars – Mulata and Mulata do Espargal – growing in a non-irrigated orchard in Algarve (South Portugal). Measurements and sampling (leaf water potential, leaf gas exchange, pigments and dark-adapted chlorophyll fluorescence) were taken in days with similar photon flux density, during the dry season in June and July, and in November after the first autumnal rainfalls (»91 mm) when minimum temperatures droped below 10°C. Photosynthetic rates remained low for both cvs, and did not recover in November despite the observed increase in stomatal conductance and y. Fv/Fm slowly decreased from June to November, specially at midday. This changes in Fv/Fm were attributed mainly to increasing F0 which might reflect structural changes or damages at the chloroplast membranes level. Dry season conditions seemed to have triggered some thermal photoprotective mechanisms, as indicated through the increased ratio A+Z/VAZ. In November, however, the ratio A+Z/VAZ decreased. We suggest that the lack of recovery of A associated with higher F0 measured in both cvs, either at pre-dawn or midday, could be attributed to structural changes within the membranes mediated either by rehydration and/or by chilling temperatures.
- Citrus Pruning in the Mediterranean climate: a reviewPublication . Matias, Pedro; Barrote, Isabel; Azinheira, Gonçalo; Continella, Alberto; Duarte, AmilcarPruning is a common practice in citrus for various reasons. These include controlling and shaping the canopy; improving phytosanitary health, productivity, and fruit quality; and facilitating operations such as harvesting and phytosanitary treatments. Because pruning is an expensive operation, its need is sometimes questioned. However, it has been proven to be particularly important in Mediterranean citriculture, which is oriented towards producing fruits for a high-quality demanding fresh market. Herein, we summarize and explain the pruning techniques used in Mediterranean citriculture and refer to the main purposes of each pruning type, considering citrus morphology and physiology.
- Compared photophysiology of native seagrasses with an invasive macroalga in Sydney Harbour, AustraliaPublication . Silva, João; Runcie, J. W.; Barrote, Isabel; Costa, Monya; Santos, RuiThe comparative photophysiology of the seagrasses Zostera capricorni and Halophila ovalis and the invasive macroalgae Caulerpa taxifolia was investigated in a shallow mixed meadow at Chowder Bay (Sydney, Australia), where the three species coexist. This study was developed under the auspices of the COST Action “Seagrasses: from genes to ecosystems”, targeting one of its objectives, the development of innovative devices for the continuous measurement of seagrass photosynthesis. Automated multi-channel chlorophyll fluorometers were deployed for 24-hour periods to examine and compare the changes in the photosynthetic efficiency and energy quenching mechanisms of the 3 species. Tissue samples were collected at predawn and noon, frozen and analysed by HPLC for detailed pigment analysis. The invasive C. taxifolia showed generally higher photosynthetic efficiency than both Z. capricorni and H. ovalis. Both seagrass species showed down-regulation of photosynthesis at noon, evidenced by the low quantum yield and the significant reduction of the antennae pigments between pre-dawn and noon. In contrast, C. taxifolia showed no reduction in antennae pigments or total photosynthetic pigments along the day. While both seagrasses showed 3- to 7-fold increases in the epoxidation state of xanthophyll cycle pigments between pre-dawn and noon, in C. taxifolia there was no significant change. Our results show that C. taxifolia is better adapted to high light conditions than Z. capricorni and H. ovalis, which means that, from the photophysiological point of view, this invasive macroalgae constitutes a serious competitor for seagrasses in shallow areas with high irradiance.
- Daily regulation of key metabolic pathways in two seagrasses under natural light conditionsPublication . Ruocco, Miriam; Barrote, Isabel; Hofman, Jan Dirk; Pes, Katia; Costa, Monya; Procaccini, Gabriele; Silva, João; Dattolo, EmanuelaThe circadian clock is an endogenous time-keeping mechanism that enables organisms to adapt to external environmental cycles. It produces rhythms of plant metabolism and physiology, and interacts with signaling pathways controlling daily and seasonal environmental responses through gene expression regulation. Downstream metabolic outputs, such as photosynthesis and sugar metabolism, besides being affected by the clock, can also contribute to the circadian timing itself. In marine plants, studies of circadian rhythms are still way behind in respect to terrestrial species, which strongly limits the understanding of how they coordinate their physiology and energetic metabolism with environmental signals at sea. Here, we provided a first description of daily timing of key core clock components and clock output pathways in two seagrass species, Cymodocea nodosa and Zostera marina (order Alismatales), cooccurring at the same geographic location, thus exposed to identical natural variations in photoperiod. Large differences were observed between species in the daily timing of accumulation of transcripts related to key metabolic pathways, such as photosynthesis and sucrose synthesis/transport, highlighting the importance of intrinsic biological, and likely ecological attributes of the species in determining the periodicity of functions. The two species exhibited a differential sensitivity to light-to-dark and dark-to-light transition times and could adopt different growth timing based on a differential strategy of resource allocation and mobilization throughout the day, possibly coordinated by the circadian clock. This behavior could potentially derive from divergent evolutionary adaptations of the species to their bio-geographical range of distributions.
- Depth-specific fluctuations of gene expression and protein abundance modulate the photophysiology in the seagrass Posidonia oceanicaPublication . Procaccini, Gabriele; Ruocco, Miriam; Marin-Guirao, Lazaro; Dattolo, Emanuela; Brunet, Christophe; D'Esposito, Daniela; Lauritano, Chiara; Mazzuca, Silvia; Serra, Ilia Anna; Bernardo, Letizia; Piro, Amalia; Beer, Sven; Bjork, Mats; Gullström, Martin; Buapet, Pimchanok; Rasmusson, Lina M.; Felisberto, Paulo; Gobert, Sylvie; Runcie, John W.; Silva, João; Olive, Irene; Costa, Monya M.; Barrote, Isabel; Santos, RuiHere we present the results of a multiple organizational level analysis conceived to identify acclimative/adaptive strategies exhibited by the seagrass Posidonia oceanica to the daily fluctuations in the light environment, at contrasting depths. We assessed changes in photophysiological parameters, leaf respiration, pigments, and protein and mRNA expression levels. The results show that the diel oscillations of P. oceanica photophysiological and respiratory responses were related to transcripts and proteins expression of the genes involved in those processes and that there was a response asynchrony between shallow and deep plants probably caused by the strong differences in the light environment. The photochemical pathway of energy use was more effective in shallow plants due to higher light availability, but these plants needed more investment in photoprotection and photorepair, requiring higher translation and protein synthesis than deep plants. The genetic differentiation between deep and shallow stands suggests the existence of locally adapted genotypes to contrasting light environments. The depth-specific diel rhythms of photosynthetic and respiratory processes, from molecular to physiological levels, must be considered in the management and conservation of these key coastal ecosystems.
- Efeitos a posteriori dos défices hídricos sobre a actividade fotossintética: mecanismos de fotoprotecção e sistema enzimático antioxidantePublication . Barrote, IsabelA resposta dos mecanismos fotossintéticos à duração e intensidade do défice hídrico e posterior rehidratação foi investigada em plantas envasadas de Helianthus annuus L. e Lupinus albus L. A rega foi manipulada de modo a induzir diferentes intensidades de défice hídrico e posterior rehidratação. Nas plantas de H. annuus foram analisadas comparativamente folhas jovens e folhas maduras, tendo-se também avaliado nas folhas jovens o efeito da diminuição temporária da intensidade luminosa nas plantas em défice hídrico e rehidratação. Foram também avaliados comparativamente os efeitos dos défices hídricos e da rehidratação na actividade fotossintética e no sistema antioxidante em folhas de H. annuus e L. albus, espécies com estratégias diferentes perante o défice hídrico (H. annuus é tolerante ao défice hídrico e L. albus evita o défice hídrico). Os resultados obtidos indicam que, apesar de as taxas de fotossíntese terem diminuído em resposta ao défice hídrico, não ocorreu fotoinibição crónica nem foi induzida senescência foliar nas folhas de H. annuus amostradas. Nestas plantas, em situação de défice hídrico, ocorreram limitações metabólicas à actividade fotossintética, que nas folhas maduras podem ter incluído a activação da reacção de Mehler e da fotorrespiração. As folhas jovens revelaram possuir a capacidade de reforçar a sua protecção antioxidante em resposta ao défice hídrico, através do aumento do teor foliar em carotenóides. No entanto, as diferenças registadas entre as folhas jovens e as folhas maduras nas plantas em défice hídrico não se repercutiram na sua capacidade de recuperação da actividade fotossintética após rehidratação, que foi semelhante. Os dados obtidos mostraram que o aumento do ‘quenching’ não fotoquímico nem sempre está directamente relacionado com o aumento do índice de desepoxidação do ciclo das xantofilas e confirmaram a relação de dependência entre ambos os parâmetros e a densidade de fluxo quântico. Nas plantas em défice hídrico transferidas para intensidade luminosa baixa, a ausência de stresse oxidativo pode ter implicado falhas na sinalização interna das plantas, enquanto o estímulo aparente da exportação de fotoassimilados durante a rehidratação pode ter conduzido à inibição do crescimento, pelo que não se observaram vantagens na imposição do défice hídrico e da rehidratação a baixas densidades de fluxo quântico. A manutenção de altos teores foliares de sacarose nas plantas rehidratadas sob irradiância alta não evitou que estas não recuperassem completamente a actividade fotossintética. O défice hídrico induziu senescência foliar em L. albus. Esta pode ter resultado do stresse oxidativo induzido nas plantas em défice hídrico, aparentemente devido ao desequilíbrio entre as actividades da dismutase do superóxido e da peroxidase do ascorbato. Os resultados mostram que o défice hídrico pode, por si só, induzir respostas normalmente associadas à ocorrência conjunta de défice hídrico e intensidade luminosa alta, tais como o stresse oxidativo e o aumento no teor foliar em pigmentos antioxidantes.
- Effectiveness and consistency of a suite of descriptors to assess the ecological status of seagrass meadows (Posidonia oceanica L. Delile)Publication . Rotini, Alice; Belmonte, A.; Barrote, Isabel; Micheli, C.; Peirano, A.; Santos, Rui; Silva, JoãoThe increasing rate of human-induced environmental changes on coastal marine ecosystems has created a demand for effective descriptors, in particular for those suitable for monitoring the status of seagrass meadows. Growing evidence has supported the useful application of biochemical and genetic descriptors such as secondary metabolite synthesis, photosynthetic activity and genetic diversity. In the present study, we have investigated the effectiveness of different descriptors (traditional, biochemical and genetic) in monitoring seagrass meadow conservation status. The Posidonia oceanica meadow of Monterosso al Mare (Ligurian sea, NW Mediterranean) was subjected to the measurement of bed density, leaf biometry, total phenols, soluble protein and photosynthetic pigment content as well as to RAPD marker analysis. This suite of descriptors provided evidence of their effectiveness and convenient application as markers of the conservation status of P. oceanica and/or other seagrasses. Biochemical/genetic descriptors and those obtained by traditional methods depicted a well conserved meadow with seasonal variability and, particularly in summer, indicated a healthier condition in a portion of the bed (station C), which was in agreement with the physical and sedimentological features of the station. Our results support the usefulness of introducing biochemical and genetic approaches to seagrass monitoring programs since they are effective indicators of plant physiological stress and environmental disturbance.
- Effects of a severe recovery pruning in the productivity and fruit quality of two late orange cultivarsPublication . Matias, Pedro; Duarte, Beatriz; Mendonça, Angélica; Oliveira, Silvino; Barrote, Isabel; Guerrero, Carlos; Duarte, AmilcarCurrently, citrus production plays a major role in worldwide agriculture, especially in the Mediterranean. However, the typical irregular branch development and the formation of large canopies and dense exterior foliage can be significant limitations to light entry and air circulation through the canopy. Consequently, dead branches appear in the inner canopy, which becomes unproductive; flowering and vegetative growth occur only on the outer canopy, and the fruits formed usually are of lower quality. Furthermore, dead branches can be an inoculum for some pathogenic microorganisms, chemical treatments become less efficient since reaching the inner canopy branches becomes more difficult, and fruit harvest becomes harder and more expensive. Pruning is a cultural practice that allows canopy management and the control of the problems mentioned above. However, many citrus growers avoid or postpone pruning, or prune insufficiently due to pruning’s high costs and, sometimes, direct production losses. To assess the effects of pruning, two experiments were performed on large canopy trees: one in ‘Valencia Late’ and the other in ‘Dom João’. In both experiments, some trees were left unpruned (control) and others were severely pruned in November 2019 (recovery pruning). The pruning was made by removing at least 30% of the canopy, with the complete removal of a few large branches. Pruning allowed a significant increase in light availability inside the canopy. In the 2020 harvest, there were no differences in fruit size between treatments. The production decreased in the pruned trees in the ‘Dom João’ experiment, as expected, and was similar in the ‘Valencia Late’ experiment. In the 2021 harvest, in both experiments, the pruned trees had a smaller canopy, and the production was similar in both treatments. However, the fruits from pruned trees were bigger in the ‘Dom João’ experiment and several quality parameters were better in the ‘Valencia Late’ experiment.
- Effects of in situ shading on the photophysiology of Zostera marina and Cymodocea nodosaPublication . Silva, João; Barrote, Isabel; Albano, Sílvia; Costa, Monya; Neves, Pedro; Graça, Gonçalo Nuno Santos Neto da; Sharon, Yoni; Beer, S.; Santos, RuiThe effects of light reduction were investigated in natural stands of the seagrasses Zostera marina and Cymodocea nodosa in Ria Formosa coastal lagoon, southern Portugal. Four shading plots and a control were set in each of two neighbouring meadows (2-3 m depth), each dominated by one species. The experiment lasted for 3 weeks, at the end of which the response of plant photosynthesis to light was determined via oxygen electrode measurements. Tissue samples were also analysed for photosynthetic pigment, soluble protein, soluble sugar and malondialdehyde contents. All plants presented a shade-adapted profile, mostly revealed by their biochemical composition. In both species the chlorophyll a/chlorophyll b ratio decreased sharply whereas the total chlorophyll/total carotenoids and the total chlorophyll/soluble protein ratios increased. Soluble protein content was reduced more noticeably in Z. marina. Soluble sugars dropped almost 40% in Z. marina leaves and roots, a more pronounced effect than the one observed in C. nodosa. Overall, Z. marina revealed to be more sensitive than C. nodosa to reductions in incident irradiance, suggesting that it will be more sensitive to human-induced disturbances that result in an increase of water turbidity.
- Effects of water deficit on the activity of nitrate reductase and content of sugars, nitrate and free amino acids in the leaves and roots of sunflower and white lupin plants growing under two nutrient supply regimesPublication . Correia, Maria João; Fonseca, Filomena; Azedo-Silva, João; Dias, Celeste; David, Maria Manuela; Barrote, Isabel; Osório, Maria Leonor; Osório, JúlioThe effects of a two weeks soil drying period on the activity of nitrate reductase (NR; EC 1.6.6.6) were studied on Helianthus annuus L. and non-nodulated Lupinus albus L. plants, growing under two nutrient supply regimes. NR activity was assessed in leaf and root extracts, by measuring the activity of the unphosphorylated active form (NRact), the maximal extractable activity (NRmax) and the activation state. To get insight into potential signalling compounds, nitrate, amino acids and soluble sugars concentrations were also quantified. On both species, foliar NRact and NRmax were negatively affected by soil drying and reduced supply of nutrients, the observed changes in NR activity being linearly-correlated with the depletion of nitrate. Similar results were obtained in the roots of sunflower. Conversely, in white lupin roots NRmax was found to be independent of tissue nitrate concentration. Regardless of the species and organ, the activation state of the enzyme was unaffected by the nutrient supply regime. In well-watered sunflower roots only about 50% of the existing NR was unphosphorylated, but the activation state increased significantly in response to drought. In contrast, lupin roots always exhibited NR activation state values close to 80% or even higher. At the leaf level, NR activation state was hardly changed in response to soil drying. The contribution of changes in the concentrations of soluble 5 sugars and amino acids to explain the observed variations in NR activity are discussed.