Loading...
10 results
Search Results
Now showing 1 - 10 of 10
- 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.
- Pre-harvest relative humidity level influences water uptake and transpiration during post-harvest phase of cut rosesPublication . Fanourakis, D.; Matkaris, N.; Heuvelink, E.; Carvalho, S. M. P.
- Genotypic variation of cut chrysanthemum response to high CO2 concentration: growth, time to flowering and visual qualityPublication . Fanourakis, D.; Heuvelink, E.; Maaswinke, R.; Carvalho, S. M. P.In this study sixteen cut chrysanthemum cultivars were used to evaluate the effects of high CO2 concentration (1500 μmol mol-1) on growth, time to flowering and visual quality as compared to the concentration used in commercial greenhouses (600 μmol mol-1). CO2 enrichment increased light use efficiency (11-41%) and total plant dry mass (TDM) (5-40%) in a cultivar dependent manner. This TDM increase was a result of: (i) higher relative growth rate during the long day period (i.e., 0 to 2 weeks; LD); and (ii) higher absolute growth rate both during the period between 2 to 6 weeks (SD1), and 6 weeks to final harvest (SD2). Cultivar differences in TDM at flowering between the two CO2 concentrations could be explained by differences in growth rate during the LD and SD2 periods. Furthermore, growing at high CO2 regime enhanced the number of flowers and flower buds per plant (NoF, 4-48%). Interestingly, the cultivars that showed the highest percentage of TDM increase, with CO2 enrichment, were not the ones that had the highest increase in the percentage of NoF. In contrast, high CO2 concentration had only a minor or no effect on the number of internodes on the main stem and on the reaction time in all the cultivars examined. From this research it is concluded that there is a large variation in the response of cut chrysanthemum cultivars to CO2 enrichment, in terms of TDM and NoF, which gives possibilities for breeding.
- Qualidade pós-colheita de rosas: efeitos da humidade relativa e da variação genotípicaPublication . Carvalho, Susana M.P.; Fanourakis, D.; Tapia, A.; Almeida, Domingos P. F.; Malcata, F. Xavier; Heuvelink, E.
- Cultivar differences in the stomatal characteristics of cut roses grown at high relative humidityPublication . Fanourakis, D.; Tapia, A.; Heuvelink, E.; Carvalho, S. M. P.High relative air humidity (RH>85%) during cultivation is known to reduce the vase life of cut roses, but the magnitude of such effect is cultivar dependent. The reasons behind this genotypic variation are not yet known. In this study, the stomatal density and stomatal responses to two closing stimuli (i.e. desiccation and abscisic acid (ABA) application) were evaluated using detached fully expanded leaves of two contrasting rose cultivars in their sensitivity to high RH (‘Frisco’ and ‘Prophyta’) which were grown at moderate (60%) and high (90%) RH. High RH significantly increased the stomatal density in both cultivars, but the effect was stronger in the tolerant cultivar (14% increase for ‘Frisco’, 8% increase for ‘Prophyta’). ‘Frisco’ also showed a higher stomatal density at moderate RH (53 stomata/mm2) as compared to the sensitive cultivar (43 stomata/mm2). Moreover, high RH decreased the speed and the degree to which stomata responded to different closing stimuli in both cultivars, resulting in higher transpiration rates. This effect was more pronounced in the sensitive cultivar. It was concluded that the tolerance to high RH during cultivation is related to more responsive stomata, while the stomatal density is apparently an irrelevant character. Furthermore, this study showed that the rose guard cell dimensions are not representative for the pore dimensions.
- Qualidade pós-colheita de rosas: efeitos da humidade relativa e da variação genotípicaPublication . Carvalho, Susana M. P.; Fanourakis, D.; Tapia, A.; Almeida, Domingos P. F.; Malcata, F. Xavier; Heuvelink, E.Elevada humidade relativa (i.e. HR > 85%) durante a produção de rosas de corte reduz a sua longevidade em jarra, mas a magnitude desse efeito depende em larga medida da cultivar em causa. Na tentativa de compreender melhor os mecanismos ligados à sensibilidade a valores de HR elevada, foram analisadas folhas completamente desenvolvidas de quatro cultivares de rosas de corte: as tolerantes ‘Frisco’ e ‘Dream’, e as sensíveis ‘Vendela’ e ‘Prophyta’; tais plantas foram produzidas em ambiente de HR moderada (60%) e elevada (90%). As plantas produzidas em ambiente de HR elevada apresentaram, em média, uma maior densidade estomática (14% mais estomas por mm2), estomas de maior dimensão (8% mais compridos) e com maior abertura (15% de aumento) comparativamente a plantas produzidas sob HR moderada. Esta tendência foi observada em todas as cultivares, embora a intensidade do efeito dependesse da cultivar. Paralelamente, o grau e a rapidez do fecho dos estomas, quando submetidos a estímulos apropriados, diminuíram significativamente em plantas produzidas sob HR de 90%, resultando num acentuado aumento da taxa de transpiração. Contudo, tal efeito foi mais pronunciado nas cultivares sensíveis. Conclui-se, assim, que a sensibilidade à HR elevada durante a produção está relacionada com uma menor capacidade de resposta dos estomas (i.e. dependente da fisiologia estomática), enquanto que a morfologia dos mesmos é aparentemente pouco relevante.
- Breeding cut roses for better keeping quality: first stepsPublication . Fanourakis, D.; Carvalho, D.R.A; Gitonga, V.; Heusden, A.W. van; Almeida, Domingos P. F.; Heuvelink, E.; Carvalho, Susana M.P.
- Effect of relative air humidity on the stomatal functionality in fully developed leavesPublication . Fanourakis, D.; Matkaris, N.; Heuvelink, E.; Carvalho, S.M.P.Several studies have shown that stomata developed under long-term high relative air humidity (RH ≥85%) are malfunctional, resulting in a poor control of water loss. Yet, little is known about the dynamics of stomatal adaptation to moderate RH, and the possibilities to improve or reverse the destabilized stomatal responsiveness. In this study, a reciprocal transfer experiment was conducted in climate chambers using Rosa hybrida ‘Prophyta’, grown at moderate RH (60%) or at high RH (90%). The adaptation of fully developed leaves to the new RH environment was assessed at day 0, 4, 8 and 12 after plant transfer by measuring the transpiration rate in detached leaves. Stomata fully developed at high RH had a lower closing capacity in response to a decrease in leaf Relative Water Content (RWC) (i.e. water loss was considerably high at RWC below 20%, whereas in moderate RH stomata the water loss almost ceased at 57% RWC). Furthermore, stomata developed at high RH did not become functional after 12 days of cultivation at moderate RH. Similarly, stomata developed at moderate RH and transferred to high RH for a 12 day period did not loose their ability to close in response to desiccation. This indicates that stomatal functionality is determined during leaf development, while after this period stomata have a limited capacity to adapt to new RH environment. It is concluded that stomata from fully developed rose leaves conserve their behaviour independently of the post-development humidity level.
- 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.