Plant water loss can be used as a screening criterion for enhanced stomatal responsiveness only at moderate RH conditions

Cultivar differences in plant transpiration rate at high relative air humidity are not related to genotypic variation in stomatal responsiveness

Giday H. , Kjaer K. H., Ottosen C.-O., Fanourakis D., (2013)

Acta Horticulturae 1064(1064):99–106 – DOI 10.17660/ActaHortic.2015.1064.12 –

https://www.actahort.org/books/1064/1064_12.htm

Abstract

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 (T_leaf). 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, T_leaf 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 T_leaf differences.

Genotypic variation in stomatal responsiveness

Photo credit: NCBI

Transpiration rate as a function of relative water content (RWC) during leaflet desiccation of four pot rose cultivars grown at moderate (60 %, open symbols) or high (90 %, closed symbols) relative air humidity. Leaflets were left to desiccate for 4 h. Values are means of nine leaflets ± SEM.

Foliar abscisic acid content underlies genotypic variation in stomatal responsiveness after growth at high relative air humidity

by Giday H., Fanourakis D., Kjaer K. H., Fomsgaard I. S., Ottosen C.-O. (2013a)

in Ann. Bot. 112(9): 1857-1867

(CrossRef, Medline).

Abstract

BACKGROUND AND AIMS:

Stomata formed at high relative air humidity (RH) respond less to abscisic acid (ABA), an effect that varies widely between cultivars. This study tested the hypotheses that this genotypic variation in stomatal responsiveness originates from differential impairment in intermediates of the ABA signalling pathway during closure and differences in leaf ABA concentration during growth.

METHODS:

Stomatal anatomical features and stomatal responsiveness to desiccation, feeding with ABA, three transduction elements of its signalling pathway (H2O2, NO, Ca(2+)) and elicitors of these elements were determined in four rose cultivars grown at moderate (60 %) and high (90 %) RH. Leaf ABA concentration was assessed throughout the photoperiod and following mild desiccation (10 % leaf weight loss).

KEY RESULTS:

Stomatal responsiveness to desiccation and ABA feeding was little affected by high RH in two cultivars, whereas it was considerably attenuated in two other cultivars (thus termed sensitive). Leaf ABA concentration was lower in plants grown at high RH, an effect that was more pronounced in the sensitive cultivars. Mild desiccation triggered an increase in leaf ABA concentration and equalized differences between leaves grown at moderate and high RH. High RH impaired stomatal responses to all transduction elements, but cultivar differences were not observed.

CONCLUSIONS:

High RH resulted in decreased leaf ABA concentration during growth as a result of lack of water deficit, since desiccation induced ABA accumulation. Sensitive cultivars underwent a larger decrease in leaf ABA concentration rather than having a higher ABA concentration threshold for inducing stomatal functioning. However, cultivar differences in stomatal closure following ABA feeding were not apparent in response to H2O2 and downstream elements, indicating that signalling events prior to H2O2 generation are involved in the observed genotypic variation.

ABA and genotypic variation in stomatal responsiveness

 

Foliar abscisic acid content underlies genotypic variation in stomatal responsiveness after growth at high relative air humidity

by Giday H., Fanourakis D., Kjaer K. H., Fomsgaard I. S., Ottosen C.-O. (2013a)

in Ann. Bot. 112(9): 1857-1867

(CrossRef, Medline).

Abstract

Background and Aims Stomata formed at high relative air humidity (RH) respond less to abscisic acid (ABA), an effect that varies widely between cultivars. This study tested the hypotheses that this genotypic variation in stomatal responsiveness originates from differential impairment in intermediates of the ABA signalling pathway during closure and differences in leaf ABA concentration during growth.

Methods Stomatal anatomical features and stomatal responsiveness to desiccation, feeding with ABA, three transduction elements of its signalling pathway (H₂O₂, NO, Ca²⁺) and elicitors of these elements were determined in four rose cultivars grown at moderate (60 %) and high (90 %) RH. Leaf ABA concentration was assessed throughout the photoperiod and following mild desiccation (10 % leaf weight loss).

Key Results Stomatal responsiveness to desiccation and ABA feeding was little affected by high RH in two cultivars, whereas it was considerably attenuated in two other cultivars (thus termed sensitive). Leaf ABA concentration was lower in plants grown at high RH, an effect that was more pronounced in the sensitive cultivars. Mild desiccation triggered an increase in leaf ABA concentration and equalized differences between leaves grown at moderate and high RH. High RH impaired stomatal responses to all transduction elements, but cultivar differences were not observed.

Conclusions High RH resulted in decreased leaf ABA concentration during growth as a result of lack of water deficit, since desiccation induced ABA accumulation. Sensitive cultivars underwent a larger decrease in leaf ABA concentration rather than having a higher ABA concentration threshold for inducing stomatal functioning. However, cultivar differences in stomatal closure following ABA feeding were not apparent in response to H₂O₂ and downstream elements, indicating that signalling events prior to H₂O₂generation are involved in the observed genotypic variation.

See the text: Ann. of Bot.

A growth [ABA]-related threshold for stomatal sensitivity to desiccation

Photo credit: JXB

Fig. 4.

Leaflet relative water content (RWC) following overnight (12h) rehydration, as a function of RWC before rehydration of pot rose ‘Mandarina’ grown at moderate (60%, A) or high (90%, B) relative air humidity (RH) under different soil water deficit treatments. Control plants at each RH were maintained well-watered based on evapotranspiration (continuous line). The soil water deficit treatment was obtained by adjusting the irrigation to 1/4 of evapotranspiration throughout growth (fine dashed line; see soil water potential in Fig. 1). The rehydration method used was independent of the stomatal component. Values are means of 15 leaflets ±SEM.

Threshold response of stomatal closing ability to leaf abscisic acid concentration during growth

by Giday H., Fanourakis D., Kjaer K. H., Fomsgaard I. S., Ottosen C.-O. (2014)

in J. Exp. Bot. 65(15): 4361-4370

(CrossRef, Medline).

Abstract

Leaf abscisic acid concentration ([ABA]) during growth influences morpho-physiological traits associated with the plant’s ability to cope with stress. A dose–response curve between [ABA] during growth and the leaf’s ability to regulate water loss during desiccation or rehydrate upon re-watering was obtained.

Rosa hybrida plants were grown at two relative air humidities (RHs, 60% or 90%) under different soil water potentials (–0.01, –0.06, or –0.08MPa) or upon grafting onto the rootstock of a cultivar sustaining [ABA] at elevated RH. Measurements included [ABA], stomatal anatomical features, stomatal responsiveness to desiccation, and the ability of leaves, desiccated to varying degrees, to recover their weight (rehydrate) following re-watering.

Transpiration efficiency (plant mass per transpired water) was also determined. Soil water deficit resulted in a lower transpiration rate and higher transpiration efficiency at both RHs. The lowest [ABA] was observed in well-watered plants grown at high RH. [ABA] was increased by soil water deficit or grafting, at both RHs.

The growth environment-induced changes in stomatal size were mediated by [ABA]. When [ABA] was increased from the level of (well-watered) high RH-grown plants to the value of (well-watered) plants grown at moderate RH, stomatal responsiveness was proportionally improved. A further increase in [ABA] did not affect stomatal responsiveness to desiccation. [ABA] was positively related to the ability of dehydrated leaves to rehydrate.

The data indicate a growth [ABA]-related threshold for stomatal sensitivity to desiccation, which was not apparent either for stomatal size or for recovery (rehydration) upon re-watering.

Read the full text: JXB

Smaller stomata and drought

 

Smaller stomata require less severe leaf drying to close: A case study in Rosa hydrida

Habtamu Giday – http://i1.rgstatic.net/i/profile/9c9605239adbf382d5_l_201a9.jpg

Katrine Kjaer – http://i1.rgstatic.net/i/profile/4895455793fce6ee9e_l_de5b2.jpg

Dimitrios Fanourakis –
http://i1.rgstatic.net/ii/profile.image/AS%3A272724337623073@1442033957602_m

by Giday H. , Kjaer K. H., Fanourakis D., Ottosen C.-O. (2013b)

in Journal of Plant Physiology, vol. 170, no. 15, pp. 1309 – 1316, 2013. –

CrossRef, Medline

Abstract

Stomata formed at high relative air humidity (RH) close less as leaf dries; an effect that varies depending on the genotype.

We here quantified the contribution of each stomatal response characteristic to the higher water loss of high RH-grown plants, and assessed the relationship between response characteristics and intraspecific variation in stomatal size.

Stomatal size (length multiplied by width), density and responsiveness to desiccation, as well as pore dimensions were analyzed in ten rose cultivars grown at moderate (60%) or high (85%) RH. Leaf morphological components and transpiration at growth conditions were also assessed. High growth RH resulted in thinner (11%) leaves with larger area.

A strong positive genetic correlation of daytime and nighttime transpiration at either RH was observed. Stomatal size determined pore area (r = 0.7) and varied by a factor of two, as a result of proportional changes in length and width.

Size and density of stomata were not related. Following desiccation, high RH resulted in a significantly lower (6–19%) decline of transpiration in three cultivars, whereas the relative water content (RWC) of high RH-expanded leaflets was lower (29–297%) in seven cultivars. The lower RWC of these leaflets was caused by (a) higher (33–72%) stable transpiration and/or (b) lower (12–143%) RWC at which this stable transpiration occurred, depending on the cultivar.

Stomatal size was significantly correlated with both characteristics (r = 0.5 and -0.7, respectively).

These results indicate that stomatal size explains much of the intraspecific variation in the regulation of transpiration upon water deprivation on rose.

See the text: Science Direct

Read the full article: Researchgate