Abstract
Plants developed under constant high (>85%) relative air humidity (RH) have larger stomata that are unable to close completely in response to closing stimuli. Roses (Rosa x hybrida) developed in high RH have previously been shown to have high water loss during leaf dehydration and reduced dark-induced closure resulting in a shorter postharvest life. In this study, the effect of B-light on stomatal function under high RH conditions was investigated. The ability of rose leaves developed under continuous high (90%) or moderate (60%) RH to close their stomata in response to darkness and leaf dehydration assay was studied. Moreover, the level and regulation of ABA in light and darkness in relation to B-light was measured. Our results show that increased B-light proportion improved stomatal function and dark-induced stomatal closure under high RH conditions and that was associated with increased [ABA] in general and a dynamic ABA peak during darkness. Furthermore, increased B-light during the day was associated with the presence of high β-glucosidase activity during night. This indicates that B-light is important as a signal to activate the β-glucosidase enzyme and release ABA during night. Altogether, the improved stomatal function and reduced transpiration in combination with increased [ABA] indicate that preharvest B-light plays an important role in governing stomatal functionality and ABA homeostasis under high RH and can be a useful method to improve postharvest water balance of roses.
Highlights
In greenhouse production systems, the relative air humidity (RH) can exceed 85% in certain periods of the year when heating costs are high and ventilation of humid air is avoided to save energy
In this study we showed that a high portion of B-light (≥20%) can improve the stomatal function, a better dark-induced stomatal closure of roses grown under high RH conditions, and in turn improve postharvest water relations and product longevity
Continuous measurements of stomata conductance during day and night and a leaf dehydration assay further confirmed that roses grown under high RH under light-emitting diodes (LEDs) had lower transpiration rate and improved dehydration tolerance (Figure 2; Table 1) as compared to plants grown with high pressure sodium (HPS) lamps
Summary
The relative air humidity (RH) can exceed 85% in certain periods of the year (e.g. during winter) when heating costs are high and ventilation of humid air is avoided to save energy. Stomatal morphology, density, and function are reported to be modified in response to elevated RH (Torre et al, 2003; Arve et al, 2013). Sometimes more stomata (higher density/frequency) that are less responsive to environmental closing signals. Blue Light Stomata Roses slower and do not close fully in response to darkness and/or drought resulting in plants with reduced dehydration tolerance and higher nocturnal transpiration (Torre and Fjeld, 2001; Arve, 2013; Fanourakis et al, 2013a). Insight into the influence of preharvest greenhouse environment on stomatal functionality is important for enabling growth of robust, drought tolerant plants of high quality
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