|Authors: ||H. Giday, K.H. Kjaer, C.-O. Ottosen, D. Fanourakis|
|Keywords: ||daytime transpiration, leaf temperature, nighttime transpiration, relative water content, selection criteria|
Plants grown at high relative air humidity (RH) often show disturbed water relations due to less responsive stomata.
The attenuation of stomatal responsiveness as a result of high RH during leaf expansion depends on the cultivar.
We hypothesized that tolerant cultivars to high RH experience a lower decline in plant transpiration by high RH, and that the variation in plant transpiration rate can be reflected by differences in leaf temperature (Tleaf). Plant leaf area, stomatal responsiveness to desiccation, together with plant transpiration and leaf temperature at growth conditions were analyzed in ten rose cultivars grown at moderate (60%) or high (85%) RH. Plants grown at high RH had a larger (9%) leaf area, and transpired less (45-50%) during the light period.
At nighttime, plant transpiration decreased (28-49%) by high RH in three or four cultivars, depending on the light conditions.
Within a given cultivar, Tleaf was generally higher, (1.5-3.7°C) at high as compared to moderate RH. Following desiccation, leaf weight loss was differentially enhanced (8-66%) in high RH-grown plants, indicating a wide variation in high RH tolerance.
High RH mainly decreased plant water loss during the light period, though tolerant cultivars experienced the same decrease in plant transpiration with sensitive ones.
Cultivars with more responsive stomata transpired less at moderate RH, whereas stomatal responsiveness was not related to plant transpiration at high RH. Therefore, plant water loss can be used as a screening criterion for enhanced stomatal responsiveness only at moderate RH conditions, while genotypic variation in plant water loss is not detectable by Tleaf differences.
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