Resilience of a semi-deciduous shrub, Cistus salvifolius, to severe summer drought and heat stress

2015 ◽  
Vol 42 (2) ◽  
pp. 219 ◽  
Author(s):  
Olga M. Grant ◽  
Łukasz Tronina ◽  
José I. García-Plazaola ◽  
Raquel Esteban ◽  
João Santos Pereira ◽  
...  
Keyword(s):  
Stomatal Closure ◽  
Tocopherol Content ◽  
Severe Drought ◽  
Summer Drought ◽  
Light Harvesting Complex ◽  
Oak Woodlands ◽  
Parallel Increase ◽  
Soil Moisture Availability ◽  
Cistus Salvifolius ◽  
Drought And Heat Stress

Shrubs often form the understorey in Mediterranean oak woodlands. These shrubs are exposed to recurrent water deficits, but how they will respond to predicted future exacerbation of drought is not yet understood. The ecophysiology of the shrub Cistus salvifolius L. was studied over the summer of 2005, which was during a heat-wave superimposed on the most severe drought in the Iberian Peninsula in the last 140 years. Branch water potential fell drastically during the summer, accompanied by stomatal closure and downregulation of PSII, with a concomitant loss of chlorophyll in the leaves. A parallel increase in the ratio of light-dissipating to light-capturing pigments and the proportion of xanthophyll cycle pigments in the de-epoxidated state, along with alterations in the structure of the light harvesting complex, may have reduced the potential for damage to leaves. Substantial increases in leaf tocopherol content during high radiation may have reduced damage from free radicals. Following autumn rains, leaves of the same shrubs showed physiological recovery, indicating the resilience of this Mediterranean species, for which an extremely dry hydrological year with 45% less rainfall than average, did not prevent healthy leaf functioning in response to renewed soil moisture availability.

scholarly journals The impact of drought on total ozone flux in a mountain Norway spruce forest

2020 ◽  
Vol 66 (No. 7) ◽  
pp. 280-278 ◽  
Author(s):  
Thomas Agyei ◽  
Stanislav Juráň ◽  
Kojo Kwakye Ofori-Amanfo ◽  
Ladislav Šigut ◽  
Otmar Urban ◽  
...  
Keyword(s):  
Norway Spruce ◽  
Stomatal Closure ◽  
Severe Drought ◽  
Summer Drought ◽  
Spruce Forest ◽  
Soil Humidity ◽  
Drought Period ◽  
The Impact ◽  
Mild Drought ◽  
Norway Spruce Forest

In order to understand the impact of summer drought on dry deposition of tropospheric ozone (O<sub>3</sub>), we compared severe and mild drought periods of summer 2018 in a mountain Norway spruce forest at Bílý Kříž, Beskydy Mts. An eddy covariance technique was applied to measure diurnal courses of the ecosystem O<sub>3</sub> and CO<sub>2</sub> fluxes. Low O<sub>3</sub> deposition was recorded in the morning and evening, while the highest CO<sub>2</sub> and O<sub><sup>3</sup></sub> fluxes were recorded during the central hours of the day. Total O<sub>3</sub> deposition during severe drought (soil humidity 13%) was significantly higher than the deposition during the mild drought period (soil humidity 19%). Our data indicate that high vapour pressure deficit and low soil humidity during severe drought led to the stomatal closure, while non-stomatal O<sub>3</sub> deposition, associated with chemical reactions of O<sub>3</sub> with NO and volatile organic compounds, are responsible for higher total O<sub>3</sub> deposition during the severe drought period. Therefore, we assume that under severe drought stomatal O<sub>3</sub> uptake decreases but non-stomatal depositions to forest ecosystems substantially increase.

scholarly journals Cavitation Limits the Recovery of Gas Exchange after Severe Drought Stress in Holm Oak (Quercus ilex L.)

Forests ◽  
2018 ◽  
Vol 9 (8) ◽  
pp. 443 ◽  
Author(s):  
José Peguero-Pina ◽  
Óscar Mendoza-Herrer ◽  
Eustaquio Gil-Pelegrín ◽  
Domingo Sancho-Knapik
Keyword(s):  
Drought Stress ◽  
Quercus Ilex ◽  
Stomatal Closure ◽  
Maximum Velocity ◽  
Holm Oak ◽  
Severe Drought ◽  
Summer Drought ◽  
Co2 Uptake ◽  
Partial Recovery ◽  
Xylem Embolism

Holm oak (Quercus ilex L.) is a Mediterranean species that can withstand intense summer drought through a high resistance to cavitation far beyond the stomatal closure. Besides stomatal limitations, both mesophyll and biochemical limitations to CO2 uptake could increase in holm oak under drought. However, no studies have addressed how hydraulic and non-hydraulic factors may limit the recovery of photosynthesis when re-watering after inducing 50% loss of hydraulic conductivity. We measured photosynthetic traits, xylem embolism, and abscisic acid (ABA) in holm oak with increasing levels of drought stress and seven days after plant re-watering. Drought stress caused a sharp decrease in net CO2 assimilation (AN), stomatal and mesophyll conductance (gs and gm), and maximum velocity of carboxylation (Vcmax). The stomatal closure could be mediated by the rapid increase found in ABA. The high level of xylem embolism explained the strong down-regulation of gs even after re-watering. Therefore, only a partial recovery of AN was observed, in spite of non-hydraulic factors not limiting the recovery of AN, because i/ABA strongly decreased after re-watering, and ii/gm and Vcmax recovered their original values. Therefore, the hydraulic-stomatal limitation model would be involved in the partial recovery of AN, in order to prevent extensive xylem embolism under subsequent drought events that could compromise holm oak survival.

scholarly journals Solvent Retention Capacity and Gluten Protein Composition of Durum Wheat Flour as Influenced by Drought and Heat Stress

Plants ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 1000
Author(s):  
Maryke Labuschagne ◽  
Carlos Guzmán ◽  
Keneuoe Phakela ◽  
Barend Wentzel ◽  
Angeline van Biljon
Keyword(s):  
Lactic Acid ◽  
Heat Stress ◽  
Durum Wheat ◽  
Stress Conditions ◽  
Severe Drought ◽  
Gluten Protein ◽  
Retention Capacity ◽  
Solvent Retention ◽  
Drought And Heat Stress ◽  
Solvent Retention Capacity

Drought and temperature stress can cause considerable gluten protein accumulation changes during grain-filling, resulting in variations in wheat quality. The contribution of functional polymeric components of flour to its overall functionality and quality can be measured using solvent retention capacity (SRC). The aim of this study was to determine the effect of moderate and severe drought and heat stress on SRC and swelling index of glutenin (SIG) in six durum wheat cultivars with the same glutenin subunit composition and its relation with gluten protein fractions from size exclusion high performance liquid chromatography. Distilled water, sodium carbonate and sucrose SRC reacted similarly to stress conditions, with moderate heat causing the lowest values. Lactic acid SRC and SIG reacted similarly, where severe heat stress highly significantly increased the values. SIG was significantly correlated with sodium dodecyl sulphate sedimentation (SDSS) and flour protein content (FPC) under all conditions. Lactic acid SRC was highly correlated with FPC under optimal and moderate heat stress and with SDSS under moderate drought and severe heat. SIG was negatively correlated with low molecular weight glutenins under optimal and drought conditions, and combined for all treatments. The relationship between SRC and gluten proteins was inconsistent under different stress conditions.

scholarly journals Caucasian clover performance in a year of severe drought

1998 ◽  
pp. 119-125
Author(s):  
R.N. Watson ◽  
F.J. Neville ◽  
N.L. Bell
Keyword(s):  
White Clover ◽  
Growth Rates ◽  
Volcanic Ash ◽  
Severe Drought ◽  
Summer Drought ◽  
Volcanic Ash Soil ◽  
Summer Growth

In a year of spring-summer drought on a sandy volcanic ash soil, ryegrass/caucasian clover (RG/ CC) and RG/white clover (RG/WC) pastures had similar rapid increases in pasture growth rates during September. Growth rates peaked around 25 October (65-70 kg DM/ha/day) for RG/CC and around 14 October (50-60 kg DM/ha/day) for RG/ WC. As drought intensified the declines in pasture growth rates were similar, but delayed by up to 3 weeks for RG/CC. Both pastures reached minimum summer growth rates of

scholarly journals HEAT AND DROUGHT STRESS EFFECT IN WHEAT GENOTYPES: A REVIEW

2021 ◽  
Vol 1 (2) ◽  
pp. 77-79
Author(s):  
Sandesh Paudel ◽  
Netra Prasad Pokharel ◽  
Susmita Adhikari ◽  
Sarah Poudel
Keyword(s):  
Heat Stress ◽  
Drought Stress ◽  
Harmful Effect ◽  
Winter Season ◽  
Triticum Aestivum L ◽  
High Yield ◽  
Severe Drought ◽  
Stress Effect ◽  
Cereal Crop ◽  
Drought And Heat Stress

Bread wheat (Triticum aestivum L.) belonging to family Poaceae is the most important cereal crop as it contributes major portion to the world food for the world’s population. Similarly, it is the third most cultivated cereal crop in Nepal in terms of production and area. Wheat is a winter season crop which is usually grown within a temperature range of 15-250C in cold and dry weather. However frequent irrigations are crucial for proper growth of the plant, high yield and high quality of the grain. The annual productivity of wheat has been reported to be 2.49 tons per hectare. Water is found to be one of the most important factors in wheat production and by far not a single water stress tolerant variety has been introduced thus water management is necessary. In Nepal around 35% of the total wheat is cultivated under rainfed condition annually and in Terai this is around 19%. This cultivated area faces a severe drought stress during growing stage and heat stress during anthesis stage. Various studies have suggested that the combined impacts of drought and heat stress had a significant harmful effect on wheat than individual stresses (Stress and Review, 2017). Under drought stress days to anthesis and days to maturity were reduced by 10% and 14% while under heat stress these were reduced by 16% and 20% respectively. Combined effect of drought and heat stress caused reduction in DTA by 25% DTH by and 31%.

Differential drought resistance strategies of co-existing woodland species enduring the long rainless Eastern Mediterranean summer

2019 ◽  
Vol 40 (3) ◽  
pp. 305-320 ◽  
Author(s):  
Päivi J Väänänen ◽  
Yagil Osem ◽  
Shabtai Cohen ◽  
José M Grünzweig
Keyword(s):  
Drought Resistance ◽  
Tree Mortality ◽  
Eastern Mediterranean ◽  
Stomatal Closure ◽  
Woody Species ◽  
The Other ◽  
Severe Drought ◽  
Resistance Strategies ◽  
Safety Margins ◽  
Species Specific

Abstract In anticipation of a drier climate and to project future changes in forest dynamics, it is imperative to understand species-specific differences in drought resistance. The objectives of this study were to form a comprehensive understanding of the drought resistance strategies adopted by Eastern Mediterranean woodland species, and to elaborate specific ecophysiological traits that can explain the observed variation in survival among these species. We examined leaf water potential (𝛹), gas exchange and stem hydraulics during 2–3 years in mature individuals of the key woody species Phillyrea latifolia L., Pistacia lentiscus L. and Quercus calliprinos Webb that co-exist in a dry woodland experiencing ~ 6 rainless summer months. As compared with the other two similarly functioning species, Phillyrea displayed considerably lower 𝛹 (minimum 𝛹 of −8.7 MPa in Phillyrea vs −4.2 MPa in Pistacia and Quercus), lower 𝛹 at stomatal closure and lower leaf turgor loss point (𝛹TLP ), but reduced hydraulic vulnerability and wider safety margins. Notably, Phillyrea allowed 𝛹 to drop below 𝛹TLP under severe drought, whereas the other two species maintained positive turgor. These results indicate that Phillyrea adopted a more anisohydric drought resistance strategy, while Pistacia and Quercus exhibited a more isohydric strategy and probably relied on deeper water reserves. Unlike the two relatively isohydric species, Phillyrea reached complete stomatal closure at the end of the dry summer. Despite assessing a large number of physiological traits, none of them could be directly related to tree mortality. Higher mortality was observed for Quercus than for the other two species, which may result from higher water consumption due to its 2.5–10 times larger crown volume. The observed patterns suggest that similar levels of drought resistance in terms of survival can be achieved via different drought resistance strategies. Conversely, similar resistance strategies in terms of isohydricity can lead to different levels of vulnerability to extreme drought.

scholarly journals Summer drought stress: differential effects on cane anatomy and non-structural carbohydrate content in overwintering Cabernet Sauvignon and Syrah vines

2019 ◽  
Vol 13 ◽  
pp. 03007 ◽  
Author(s):  
Rachele Falchi ◽  
Elisa Petrussa ◽  
Marco Zancani ◽  
Valentino Casolo ◽  
Paola Beraldo ◽  
...  
Keyword(s):  
Water Stress ◽  
Drought Stress ◽  
Biochemical Characterization ◽  
Carbon Allocation ◽  
Starch Accumulation ◽  
Cabernet Sauvignon ◽  
Severe Drought ◽  
Summer Drought ◽  
Long Term Effects ◽  
Experimental Conditions

Grapevines store non-structural carbohydrates (NSC) during late summer to sustain plant development at the onset of the following spring’s growth. Starch is the main stored carbohydrate, found in the wood-ray parenchyma of roots and canes. Although the relationship between hydraulic and plant photosynthetic performance is well-recognized, little research has been done on the long-term effects of drought in grapevines adopting different strategies to cope with water stress (i.e. isohydric and anisohydric). We performed our study by exposing two different grape cultivars (Syrah and Cabernet Sauvignon) to a short but severe drought stress, at two stages of the growing season (July and September). No marked differences in the physiological and hydraulic responses of the two varieties were found, probably due to our experimental conditions. However, anatomical and biochemical characterization of overwintering canes pointed out several interesting outcomes. We found a significant and parallel increase of starch and medullar ray number in both cultivars exposed to early water stress. We hypothesize that stressed vines limited their carbon allocation to growth, while shifting it to starch accumulation, with a most evident effect in the period of intense photosynthetic activity. We also speculate that a different aptitude to osmotic adjustment may underlay variation in starch increase and the specific involvement of bark NSC in the two cultivars.

Summer dormancy in Festuca arundinacea Schreb.; the influence of season of sowing and a simulated mid-summer storm on two contrasting cultivars

2006 ◽  
Vol 57 (12) ◽  
pp. 1267 ◽  
Author(s):  
M. R. Norton ◽  
F. Volaire ◽  
F. Lelièvre
Keyword(s):  
Festuca Arundinacea ◽  
Water Status ◽  
Severe Drought ◽  
Summer Drought ◽  
Full Irrigation ◽  
Leaf Elongation ◽  
Aerial Growth ◽  
Summer Dormancy ◽  
Summer Storm ◽  
Moisture Conditions

Due to the shortage of information on summer dormancy in tall fescue (Festuca arundinacea, syn. Lolium arundinaceum), we tested the response of 2 cultivars of differing dormancy expression and growth stage to a range of summer moisture conditions, including full irrigation, drought, and a simulated mid-summer storm and analysed whether traits associated with summer dormancy conferred better survival under severe field drought. Autumn-sown reproductive and younger, spring-sown plants of 2 cultivars, claimed to exhibit contrasting summer dormancy, were established and then tested in summer 2002 under either long drought, drought + simulated mid-summer storm, or full irrigation. The autumn-sown reproductive plants of cv. Flecha exhibited traits that can be associated with partial summer dormancy since under summer irrigation they reduced aerial growth significantly and exhibited earlier herbage senescence. Moreover, cv. Flecha used 35% less soil water over the first summer. However, the water status of leaf bases of young vegetative tillers of both cultivars was similar under irrigation and also throughout most of the drought (leaf potential and water content maintained over –4 MPa and at approx. 1 g H2O/g DM, respectively). The summer-active cv. Demeter did not stop leaf elongation even in drought and produced twice as much biomass as Flecha under irrigation. Cultivar Demeter responded to the simulated storm with a decline in dehydrin expression in leaf bases, whereas no decline occurred in Flecha, presumably because it remained partially dormant. The younger, spring-sown swards of both cultivars had similar biomass production under summer irrigation but whereas Demeter regrew in response to the simulated storm, cv. Flecha did not, indicating that dormancy, although only partially expressed, was reinforced by summer drought. In all trials, cv. Flecha out-yielded Demeter in autumn regrowth. In particular, the severe drought in 2003 caused a 25% loss of the basal cover in cv. Demeter, whereas Flecha fully maintained its sward allowing it to produce a higher post-drought autumn yield. This work links summer dormancy with higher persistence over long, dry summers.

Water transfer in a mature oak stand (Quercuspetraea): seasonal evolution and effects of a severe drought

1993 ◽  
Vol 23 (6) ◽  
pp. 1136-1143 ◽  
Author(s):  
N. Bréda ◽  
H. Cochard ◽  
E. Dreyer ◽  
A. Granier
Keyword(s):  
Stomatal Conductance ◽  
Potential Evapotranspiration ◽  
Stomatal Closure ◽  
Time Lag ◽  
Xylem Sap ◽  
Water Shortage ◽  
Hydraulic Conductance ◽  
Canopy Conductance ◽  
Severe Drought ◽  
Order Of Magnitude

The reactions of sessile oak (Quercuspetraea (Mattuschka) Liebl.) to drought were studied under natural conditions in a 32-year-old stand near Nancy (northeastern France) during the summers of 1989 (strongly rain deficient) and 1990. A plot of five trees was subjected to imposed water shortage, while a group of irrigated trees was used as a control. Measurements of xylem sap flows and water potential enabled the computation of plot transpiration, canopy conductance, and specific hydraulic conductance in the soil–tree continuum. Stomatal conductance was measured directly with a porometer. Specific hydraulic conductance of our oaks was of the same order of magnitude as that reported for other species. It decreased significantly during spring because of a time lag between cambial growth and leaf area expansion. Measured transpiration was close to potential evapotranspiration, except during days with high vapor pressure deficits, which promoted stomatal closure in the absence of soil water deficits. Imposed drought caused predawn leaf water potentials to reach values as low as −2.0 MPa and a progressive decline in hydraulic conductance, which was probably attributable to modifications in hydraulic properties at the soil–root interface. This gradual decline in conductance was attributed to their deep rooting (1.40 m). This study revealed that Q. petraea may be considered as drought tolerant because of adaptations like deep rooting, efficient and safe xylem sap transport, maintenance of significant stomatal conductance, and significant transpiration, even during strong drought stress.

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