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- Avoiding high relative air humidity during critical stages of leaf ontogeny is decisive for stomatal functioningPublication . Fanourakis, Dimitrios; Carvalho, Susana M. P.; Almeida, Domingos M. P.; Domingos, P.F.; Heuvelink, EpPlants of several species, if grown at high relative air humidity (RH >= 85%), develop stomata that fail to close fully in case of low leaf water potential. We studied the effect of a reciprocal change in RH, at different stages of leaf expansion of Rosa hybrida grown at moderate (60%) or high (95%) RH, on the stomatal closing ability. This was assessed by measuring the leaf transpiration rate in response to desiccation once the leaves had fully expanded. For leaves that started expanding at high RH but completed their expansion after transfer to moderate RH, the earlier this switch took place the better the stomatal functioning. Leaves initially expanding at moderate RH and transferred to high RH exhibited poor stomatal functioning, even when this transfer occurred very late during leaf expansion. Applying a daily abscisic acid (ABA) solution to the leaves of plants grown at continuous high RH was effective in inducing stomatal closure at low water potential, if done before full leaf expansion (FLE). After FLE, stomatal functioning was no longer affected either by the RH or ABA level. The results indicate that the degree of stomatal adaptation depends on both the timing and duration of exposure to high RH. It is concluded that stomatal functionality is strongly dependent on the humidity at which the leaf completed its expansion. The data also show that the effect of ambient RH and the alleviating role of ABA are restricted to the period of leaf expansion.
- Physiological and phytochemical quality of ready-to-eat rocket leaves as affected by processing, modified atmosphere and storage temperaturePublication . Amaro, Ana Luísa; Pereira, Maria João; Carvalho, Susana; Vasconcelos, Marta; Pintado, Maria ManuelaRocket leaves are widely consumed as a ready-to-eat (RTE) leafy vegetable, valued by its wide range of health promoting phytonutrients, including vitamin C and phenolic compounds. Processing and storage conditions are known to affect quality of RTE rocket leaves, with package atmosphere and low temperature as key factors in quality maintenance throughout processing to consumption. However, information on rocket leaves nutritional quality as affected by modified atmosphere and storage temperature is scarce. In order to generate recommendations to optimize phytochemical preservation of rocket leaves during processing, a nutritional audit of the processing line of a fresh-cut vegetables enterprise was performed. Samples were collected at each step of the production flowchart of RTE rocket-leaves: at rocket leaves reception, after washing and decontamination, after centrifugation and after packaging. All samples were analyzed for nutritional characterization. Furthermore, the effect of modified atmosphere and temperature conditions during storage on physiological and phytochemical quality of RTE rocket leaves was evaluated and the relative changes determined. To study modified atmosphere effects on quality, freshly harvested rocket leaves were processed, packaged in low oxygen permeability film bags, flushed with different oxygen concentrations (2.5; 5; 10 and 20% O2), thermo sealed with a vacuum packing machine and to analyze the effect of temperature on quality, freshly harvested rocket leaves were processed, packaged and stored at different temperatures (0, 5 and 10 °C) for 14 days. All rocket leaves samples were assessed for respiration rate, chlorophyll content and phytochemical composition during storage. Processing, modified atmosphere and storage temperature significantly affected respiration rate, chlorophyll content and phytochemical composition of RTE rocket leaves. The integration of these results contributes to the understanding of the effects of processing and storage conditions on overall quality of RTE vegetables and provide useful information for developing processes aimed at the modulation of nutritional quality and shelf-life extension.
- Phenotypic evaluation of the IDC profile of soybean plants after inoculation with plant growth-promoting bacteriaPublication . Castro, Paula M. L.; Carvalho, Susana M. P.; Vasconcelos, Marta W.; Roriz, Mariana
- QTL analysis for stomatal functioning in tetraploid Rosa × hybrida grown at high relative air humidity and its implications on postharvest longevityPublication . Carvalho, Dália R. A.; Koning-Boucoiran, Carole F. S.; Fanourakis, Dimitrios; Vasconcelos, Marta W.; Carvalho, Susana M. P.; Heuvelink, Ep; Krens, Frans A.; Maliepaard, ChrisHigh relative air humidity (RH >= 85 %) during leaf development disturbs stomatal functioning leading to excessive water loss in conditions of high evaporative demand, resulting in severe reduction in postharvest longevity. In roses, this effect depends on the genotype, opening the possibility for breeding cultivars with more responsive stomata. In this study, we aim at identifying genomic regions associated with the control of water loss following growth at high RH. The F1 generation (108 offspring) and the two parents (P540 and P867) of a tetraploid cut rose population grown at high (85 %) RH were phenotyped for stomatal control to water loss by assessing the relative water content after 4 h of leaflet desiccation (RWC_4 h). The RWC_4 h varied between 7 and 62 % across the 110 studied individuals, with parents P540 and P867 showing 51 and 20 % RWC_4 h, respectively. Based on these data, a quantitative trait locus (QTL) analysis was performed. The impact of the identified QTLs on postharvest longevity of ten selected offspring was further evaluated. Three QTLs were identified: two major [positioned on linkage group 5 of the integrated consensus map (ICM 5) of both parents and on ICM 2 of the parent P867] and one putative minor (mapped to ICM 6 of both parents), explaining 32 % of the variability in the RWC_4 h. Low RWC_4 h was found to be a good proxy for eliminating the offspring with short vase life. This study constitutes a first step toward identifying the most likely regions for genes of interest controlling stomatal functioning in high RH-grown plants.
- A virtual plant that responds to the environment like a real one: the case for chrysanthemumPublication . Kang, MengZhen; Heuvelink, Ep; Carvalho, Susana M. P.; Reffye, Philippe dePlants respond to environmental change through alterations in organ size, number and biomass. However, different phenotypes are rarely integrated in a single model, and the prediction of plant responses to environmental conditions is challenging. The aim of this study was to simulate and predict plant phenotypic plasticity in development and growth using an organ-level functional–structural plant model, GreenLab. Chrysanthemum plants were grown in climate chambers in 16 different environmental regimes: four different temperatures (15, 18, 21 and 24 C) combined with four different light intensities (40%, 51%, 65% and 100%, where 100% is 340 lmol m)2 s)1). Measurements included plant height, flower number and major organ dry mass (main and side-shoot stems, main and side-shoot leaves and flowers). To describe the basipetal flowering sequence, a position-dependent growth delay function was introduced into the model. The model was calibrated on eight treatments. It was capable of simulating multiple plant phenotypes (flower number, organ biomass, plant height) with visual output. Furthermore, it predicted well the phenotypes of the other eight treatments (validation) through parameter interpolation. This model could potentially serve to bridge models of different scales, and to link energy input to crop output in glasshouses.
- Elevated air movement enhances stomatal sensitivity to abscisic acid in leaves developed at high relative air humidityPublication . Carvalho, Dália R. A.; Torre, Sissel; Kraniotis, Dimitrios; Almeida, Domingos P. F.; Heuvelink, Ep; Carvalho, Susana M. P.High relative air humidity (RH ≥ 85%) during growth leads to stomata malfunctioning, resulting in water stress when plants are transferred to conditions of high evaporative demand. In this study, we hypothesized that an elevated air movement (MOV) 24 h per day, during the whole period of leaf development would increase abscisic acid concentration ([ABA]) enhancing stomatal functioning. Pot rose 'Toril' was grown at moderate (61%) or high (92%) RH combined with a continuous low (0.08 m s-1) or high (0.92 m s-1) MOV. High MOV reduced stomatal pore length and aperture in plants developed at high RH. Moreover, stomatal function improved when high MOV-treated plants were subjected to leaflet desiccation and ABA feeding. Endogenous concentration of ABA and its metabolites in the leaves was reduced by 35% in high RH, but contrary to our hypothesis this concentration was not significantly affected by high MOV. Interestingly, in detached leaflets grown at high RH, high MOV increased stomatal sensitivity to ABA since the amount of exogenous ABA required to decrease the transpiration rate was significantly reduced. This is the first study to show that high MOV increases stomatal functionality in leaves developed at high RH by reducing the stomatal pore length and aperture and enhancing stomatal sensitivity to ABA rather than increasing leaf [ABA].
- Melhoramento para elevada qualidade pós-colheita: validação do método de selecção de genótipos promissoresPublication . Carvalho, D.R.A.; Carvalho, S. M. P.; Fanourakis, D.; Heuvelink, E.; Almeida, Domingos P. F.
- Melhoramento para elevada qualidade pós-colheita: validação do método de selecção de genótipos promissoresPublication . Carvalho, D.R.A.; Carvalho, S. M. P.; Fanourakis, D.; Heuvelink, E.; Almeida, Domingos P. F.
- The potencial role of soil application of a tris (3-hydroxy-4-pyridinonate) iron (III) complex in iron deficiency chlorosis treatmentPublication . Rodrigues, Elsa; Ferreira, Sofia; Leite, Andreia; Moniz, Tânia; Rangel, Maria; Vasconcelos, Marta W.; Carvalho, Susana M. P.; Santos, Carla S.
- Estimativa da área foliar em diferentes estados fenológicos baseada em descritores alométricos de rosas de corte cv 'Red Naomi'Publication . Costa, P. M.; Poças, I.; Alves, S.; Pereira, M.; Carvalho, S. M. P.; Cunha, M.A área foliar (AF) é uma variável fundamental para a fotossíntese, transpiração, e produtividade. Métodos expeditos e não destrutivos para a estimativa da AF ao longo do ciclo de produção são necessários para o desenvolvimento de modelos ecofisiológicos e apoiar práticas culturais, tais como a aplicação de fitofármacos e gestão da água. Existem diversos modelos para a estimativa da AF, mas por terem sido desenvolvidos para uma fase do ciclo de produção (geralmente a colheita) têm uma aplicabilidade limitada. Neste trabalho, estudamos como a área de folhas compostas da rosa de corte cv 'Red Naomi ' poderia ser estimada, em diferentes fases fenológicas, a partir de medições expeditas e não-destrutivas. A experiência realizou-se numa estufa localizada na região costeira do norte de Portugal, para a produção de roseiras em sistema sem solo, com uma densidade de 8 plantas/m2, em saco plástico com substrato de fibra de coco e turfa. Para estimativa da AF das roseiras, foi desenvolvido um modelo estatístico baseado em descritores alométricos tais como: comprimento da folha (CF), largura da folha (LF), posição da folha na haste (PF), número de folíolos (NF), assim como relações entre estas medições tais como: forma de folha (relação LL vs PV), e a posição relativa da folha na haste - (RF). A estimação do modelo, baseada na técnica de regressão “stepwise”, foi avaliado por diversos testes de qualidade de ajuste e de verificação da colinearidade entre variáveis. Para a estimativa do modelo foram utilizadas 176 folhas de 20 hastes colhidas em diferentes estados fenológicos. A AF, obtida por um método não-destrutivo, variou entre 7,5-111,8 cm2, a CF de 4,7- 18,9 cm, LF de 3,8-12,2 cm, o NF de 3 a 8 e a PF de 1 a 15. O modelo selecionado, baseado nas medidas de CF, LF, PF e NF, explicou 93% (R2 = 0,93; N = 176, p <0,000) da variabilidade da AF ao longo do ciclo de produção e a diferença média relativa entre a AF medida e modelada foi inferior a 9 %. A validação do modelo, realizada com dados independentes provenientes de 24 folhas, permitiu obter testes de ajustamento semelhantes aos obtidos para o modelo da serie de estimação. A precisão e operacionalidade do modelo desenvolvido para a obtenção da AF, justifica o seu uso em estudos de eco-fisiológicos, modelos de simulação do desenvolvimento, bem como para apoiar práticas culturais em rosas de corte.