Loading...
2 results
Search Results
Now showing 1 - 2 of 2
- 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.
- 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.