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- Avaliação do contributo da expressão genética na tolerância à desidratação em Rosa × hybrida cultivada em humidade relativa elevadaPublication . Carvalho, D. R. A.; Vasconcelos, Marta; Koning-Boucoiran, C. F. S.; Krens, F. A.; Heuvelink, E; Carvalho, S. M. P.Cultivation of cut flowers with high postharvest longevity is of extreme importance for consumer’s satisfaction. A negative water balance is indicated as the most important factor reducing longevity. This problem is more severe in plants grown at high relative air humidity (i.e. RH > 85%) mainly due to a poor stomatal functioning associated to lower abscisic acid (ABA) concentrations, leading to higher water loss. In this paper it is analysed whether a sensitive cut rose cultivar to high RH show different gene expression related to ABA metabolism when grown at moderate (60%) or high (90%) RH. RNA was isolated from fully developed leaves, harvested 180 min after the beginning of the dark period (stomatal closing stimulus) and the relative gene expression was evaluated in genes involved in: biosynthesis (AAO3 and NCED1), oxidation (CYP707A1 and CYP707A3) and conjugation (UGT75B2) of ABA. The stomatal conductivity in the dark period was 5.6-fold higher in intact plants developed at high RH compared to moderate RH-grown plants, showing the reduced closure capacity of the stomata during darkness. After 4 h of leaflet desiccation, leaflets grown at high RH showed a relative water content (RWC) 69% lower than the moderate RH-grown leaflets, validating the sensitivity of K023 to high RH during growth. At last, from the five studied genes only the expression of CYP707A3 was significantly reduced by high RH, without significant differences found in the other genes. In conclusion, the sensitivity of the genotype K023 to high RH cannot be explained by the expression of the genes evaluated in this study, using leaves harvested 180 min after the beginning of the dark period (closing stimulus). We expect that after transferring the plants to the postharvest conditions, inducing water stress, a more contrasting gene expression among RH levels will appear.
- Avaliação do contributo da expressão genética na tolerância à desidratação em Rosa × hybrida cultivada em humidade relativa elevadaPublication . Carvalho, D. R. A.; Vasconcelos, Marta; Koning-Boucoiran, C. F. S.; Krens, F. A.; Heuvelink, E; Carvalho, S. M. P.
- Estudos anatómicos e histológicos em folhas de roseira desenvolvidas em diferentes condições de humidade relativaPublication . Monteiro, A.; Carvalho, D. R. A; Vasconcelos, Marta; Correia, C.; Moutinho-Pereira, J. M.; Gonçalves, B.; Bacelar, E.; Carvalho, S. M. P.High relative air humidity (RH > 85%) during growth has a negative impact on postharvest longevity of cut roses, being described a different susceptibility among cultivars. Poor stomatal functioning has been pointed out as the principal cause of excessive water loss during postharvest in plants grown at high RH. However, to the best of our knowledge up to date no comprehensive studies on the effect of RH on leaf anatomical, histological and biochemical characteristics have been carried out. In this study, we evaluated six genotypes from a cut rose segregating tetraploid population (four sensitive and two with intermediate response to desiccation) grown at moderate (60%) and high (90%) RH. It was found that RH played a very important role on the modification of leaf structure. Leaves developed at high RH showed larger specific leaf area (increasing 12.8% and 26.8% on the sensitive and intermediate genotypes, respectively) and lower succulence (reducing 9.5% on the sensitive and 10.7% on the intermediate genotypes). Moreover, these leaves also showed a reduced thickness of the total lamina, of the cuticle and of the upper and lower epidermis. Stomatal density was also reduced but stomatal dimensions were significantly larger at high RH. At cell level, the sensitive genotypes grown at 90% RH showed higher ion leakage, reflecting the loss of the membrane integrity with negative consequences on the longevity and postharvest quality. Additionally, the lower concentration of photosynthetic pigments and total soluble sugars observed on high RH grown leaves can also contribute to the reduction of the quality and longevity of the flower stalks during postharvest.
- Estudos anatómicos e histológicos em folhas de roseira desenvolvidas em diferentes condições de humidade relativaPublication . Monteiro, A.; Carvalho, D. R. A; Vasconcelos, Marta; Correia, C.; Moutinho-Pereira, J. M.; Gonçalves, B.; Bacelar, E.; Carvalho, S. M. P.High relative air humidity (RH > 85%) during growth has a negative impact on postharvest longevity of cut roses, being described a different susceptibility among cultivars. In this study, we evaluated the effect of RH on leaf anatomical and histological characteristics in six genotypes from a cut rose segregating tetraploid population (four sensitive and two with intermediate response to desiccation) grown at moderate (60%) or high (90%) RH. Leaves developed at high RH showed larger specific leaf area (increasing 12.8% and 26.8% on the sensitive and intermediate genotypes, respectively) and lower succulence (reducing 9.5% on the sensitive and 10.7% on the intermediate genotypes). Moreover, these leaves also showed a reduced thickness of the total lamina, cuticle and the upper and lower epidermis. Stomatal density was also reduced but stomatal dimensions were significantly larger at high RH. It is concluded that RH plays a very important role on the modification of leaf structure.
- 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.Breeding for better keeping quality: validation of the selection method of promising genotypes. Water stress is one of the most important postharvest quality problems, resulting in shorter vase life and reduced consumer‟s satisfaction. This problem is enhanced in plants grown at high RH (RH > 85%) due to stomatal malfunctioning leading to shorter postharvest longevity. Previously, a subset of a segregating tetraploid population (60 genotypes) cultivated in a greenhouse under noncontroled RH was characterized for stomatal responsiveness to water stress (i.e. desiccation). The population screening revealed extreme differences of relative water content (RWC) after 4 h leaf desiccation. This study aims at the validation of a selection method for promising genotypes with good stomatal responsiveness to desiccation (i.e. high RWC after 4 h desiccation) when grown under contrasting HR conditions. Therefore, five genotypes with expected good stomatal response to desiccation were selected for this study. These genotypes were grown under moderate RH (60%) and high RH (90%). The RWC was significantly different within the five studied genotypes. K099 was the most tolerant genotype to desiccation, with a RWC after 4 h desiccation 19% higher than the least tolerant genotype. Genotypes cultivated at high RH had on average only 10% lower RWC, as compared to genotypes grown at moderate RH, confirming a good stomatal response. The postharvest longevity varied between 12 (K119) and 25 (K099) days and it was not significantly affected by the two different RH during growth. It is concluded that the analysis of the stomatal responsiveness in leaves of cut roses is an efficient method that allows, in the early stages of the selection process, to identify tolerant genotypes to high RH.