• Drought-induced variations of water relations

    Drought-induced variations of water relations

    Skip to main content. Authors B. Dichio, V. Nuzzo, C. Xiloyannis, G. Celano, K. Abstract The aim of this study was to determine the effects of water stress on total water potential components, tissue water content, maximum elastic modulus and osmoregulation capacity evaluated by means of the pressure-volume curves technique.

    The trial was conducted using two year-old ownrooted olive trees, cv. Osmotic potentials at saturation were Osmotic adjustment determined a broadening of the range within which turgor potentials remained positive. At incipient plasmolysis, osmotic potential 0 in fact varied from The maximum elastic modulus calculated at full turgor was High osmotic adjustment values and the rigidity of the cell wall induced high potential gradients between leaves and roots, making for water absorption through roots even at low soil water potentials.

    Citation Dichio, B. Acta Hortic. Keywords Olive tree, total potential, osmotical and turgor potentials, maximum elastic modulus, osmoregulation. Facebook Careers YouTube.To browse Academia.

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    Skip to main content. Log In Sign Up. Drought-induced variations of water relations parameters in Olea europaea Giuseppe Celano.

    Drought-induced variations of water relations parameters in Olea europaea. Plant and Soil —, Printed in the Netherlands.

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    Accepted in revised form 11 July Key words: elastic modulus, osmotic adjustment, pressure-volume curve, relative water content, soluble carbo- hydrates, turgor pressure Abstract The effects of water stress on water potential components, tissue water content, mean elastic modulus and the osmoregulation capacity of olive Olea europaea L. Coratina leaves was determined.

    Natural variation and gene regulatory basis for the responses of asparagus beans to soil drought

    Artificial rehydration of olive leaf tissues altered the P-V relationships so that a plateau phenomenon occurred. In the corrected P-V relationship, an osmotic adjustment was found in drought-stressed leaf tissues. Osmotic adjustment values obtained from the P-V curves agreed with those obtained using an osmometer.

    An active osmotic adjustment of 1. Mannitol is the main carbohydrate involved in osmotic potential decrease in all treatments. The maximum elastic modulus increased from Introduction to this method, the fresh weight at full turgor TW of a sample is required to calculate relative water One of the mechanisms by which plants adapt to content R following artificial rehydration, and then drought-stress is by osmoregulation.

    In this way plants back-extrapolation of the linear region of the moisture can tolerate temporary or long-term periods of high release curve flesh weight FW vs water potential soil water deficit Hsiao et al. In some cases however, and justment has been reported for several woody plants particularly in drought-hardy plants, artificial rehydra- Grammatikopoulos, ; Huang et al.

    The Campbell et al. This results in an erroneous solutes that accumulate in plants during water stress estimate of tissue elasticity and osmotic potential and and contribute to active osmotic adjustment can be sol- masks seasonal variations and responses to water de- uble carbohydrates, inorganic cations, organic acids or ficit Eamus and Narayan, ; Kubiske and Ab- free amino acids Huang et al.

    Parker and Pallardy, and as a method for estimating various tissue-water rela- in Pseudotsuga menziesii L Kubiske and Abrams, tions parameters Tyree and Jarvis, According b. E-mail dichio unibas. It is characterised by a significant chamber. Chartzoulakis et al. However, adjustment and the elastic modulus of tissues were there are not sufficient data to elucidate the drought calculated by means of P-V curves analysis in 8—10 resistance mechanism.

    The leaves The purposes of the present study are, 1 to were collected predawn at The tissues were parameters characterizing leaf water status. The beakers were estimated from P-V analysis in olive leaves. Full rehydra- tion was, on average, achieved in 24—48 h.The —20 Southern Africa drought is an ongoing period of drought taking place in Southern Africa. The drought began in late Octoberand is negatively affecting food security in the region. As a region, Southern Africa has historically been at high risk of droughts; a probability due to several meteorological and sociological factors.

    The Southern African climate is affected by strong seasonal rainfall patterns; the majority of the region's annual rainfall is deposited by storms from early November to March, forming what is considered Southern Africa's wet season.

    The wet months of rainfall saturate the region's soil, providing moisture that persists for the drier months of the year. As noted by sources, Southern Africa's low level of economic development and reliance on agriculture —namely cereal crops and livestock —leaves the region highly susceptible to droughts.

    The next five-six months are considered the "lean" season, during which time stockpiled food is consumed while the concurrent "wet" season rains nourish the next year's crops. However, if the usual rains are disrupted by a weather anomaly, planting is delayed until November or early December, resulting in a longer "lean" season before crops can be harvested.

    If the region's weather patterns are disrupted enough to cause a drought, the lack of rainfall and eventual loss of moisture from soil often results in a noteworthy decline in Southern Africa's agricultural production; the resulting detrimental economic conditions leads to social unrest and a decline in the level of regional food security.

    Periods of drought effect Southern Africa' s various biomes and wildlife, while reduced water levels in rivers can cause hydroelectric dams to operate at reduced capacity.

    In August and Septemberseveral organizations began to warn farmers about the possibility of an oncoming drought.

    drought-induced variations of water relations

    In August the Southern African Development Community advised farmers to avoid selling some of their stockpiled food from the previous season, [10] and in September the United Nations Food and Agriculture Organization FAO issued a warning to Southern African countries about the formation of conditions for a drought.

    The first effect of this disruption was a delayed sowing date, which was pushed back from late October to early November. The drought continued to with multiple regions in Southern Africa seeing significantly reduced levels of rainfall. A report [12] from FAO noted that, while rainfall had picked up in late Decemberseveral areas within the region were suffering from a severe drought and accompanying effects. As of Aprilparts of Southern Africa remain affected by the ongoing drought. Rates of hunger in the region have risen, and are expected to continue to rise.

    In MayNamibia declared a state of emergency in response to the drought, [18] and extended it by additional 6 months in October The drought was re-declared as national emergency in South Africa 4 March From Wikipedia, the free encyclopedia. Retrieved The Independent.Much is known about the physiological control of stomatal aperture as a means by which plants adjust to water availability. By contrast, the role played by the modulation of stomatal development to limit water loss has received much less attention.

    The control of stomatal development in response to water deprivation in the genus Populus is explored here. Drought induced declines in stomatal conductance as well as an alteration in stomatal development in two genotypes of Populus balsamifera. Leaves that developed under water-deficit conditions had lower stomatal indices than leaves that developed under well-watered conditions.

    Drought-Induced Carbon and Water Use Efficiency Responses in Dryland Vegetation of Northern China

    Transcript abundance of genes that could hypothetically underpin drought-responsive changes in stomatal development was examined, in two genotypes, across six time points, under two conditions, well-watered and with water deficit.

    The findings highlight the role that could be played by stomatal development during leaf expansion as a longer term means by which to limit water loss from leaves. Water availability is a key determinant of plant growth and survival. In keeping with this, plants have evolved mechanisms to modulate physiological and developmental processes so as to match water use and retention with water availability.

    Stomata, the pores found on plant surfaces, play a key role in regulating water movement and retention in response to the prevailing environmental conditions. For example, episodic water deficit can invoke a decrease in stomatal aperture with a concomitant decrease in water loss from the plant body Cowan and Farquhar, ; Chaves et al. Although reduction in stomatal aperture in response to drought limits photosynthesis and affects water-use efficiency, it is a short-term response that enables plants to contend with fluctuating water supply Chaves et al.

    drought-induced variations of water relations

    Plants can also mount more lasting stomatal-based responses to persistent water deficit i. Lower stomatal density restricts the number of sites for water loss, with an attendant decrease in water loss.

    Changes in stomatal density are brought about by modulating stomatal development during leaf formation. Much is known about stomatal development in Arabidopsis thaliana. Stomatal development proceeds from the asymmetric division of epidermal meristemoid mother cells to the final terminal differentiation of the guard cells that will form the stomate early in leaf development.

    Many of the components of the regulatory network underlying this terminal differentiation pathway have been characterized for a review see Bergmann and Sack, ; Casson and Hetherington, Downstream of the aforementioned receptors, a mitogen activated protein MAP kinase signalling cascade is implicated.

    The stomatal development signalling network, based on current literature.The effects of water stress on water potential components, tissue water content, mean elastic modulus and the osmoregulation capacity of olive Olea europaea L.

    Coratina leaves was determined. Artificial rehydration of olive leaf tissues altered the P-V relationships so that a plateau phenomenon occurred. In the corrected P-V relationship, an osmotic adjustment was found in drought-stressed leaf tissues.

    Osmotic adjustment values obtained from the P-V curves agreed with those obtained using an osmometer. An active osmotic adjustment of 1. Mannitol is the main carbohydrate involved in osmotic potential decrease in all treatments. The maximum elastic modulus increased from This is a preview of subscription content, log in to check access. Rent this article via DeepDyve. Google Scholar.

    Hort Sci. Acta Hortic. Vitis 23 1 Mechanisms of diurnal osmotic potential changes. Plant Physiol. Grammatikopoulos G Mechanisms for drought tollerance in two mediterranean seasonal dimorphic shrubs. Gucci R, Lombardi L and Tattini M Analysis of leaf water relation in leaves of two olive Olea europaea cultivars differing in tolerance to salinity.

    Tree Physiol. Holbrook N M and Putz F E From epiphyte to tree: Differences in leaf structure and leaf water relation associated with the transition in growth form in eight species of hemiepiphytes. N R Baker et al. Karamanos A J Ways of detecting adaptive responses of cultivated plants to drought.The requirements of the water transport system of small herbaceous species differ considerably from those of woody species.

    Despite their ecological importance for many biomes, knowledge regarding herb hydraulics remains very limited. We compared key hydraulic features vulnerability to drought-induced hydraulic decline, pressure-volume relations, onset of cellular damage, in situ variation of water potential, and stomatal conductance of three Ranunculus species differing in their soil humidity preferences and ecological amplitude.

    In species with narrow ecological amplitude, the drought-exposed Ranunculus bulbosus was less vulnerable to desiccation analyzed via loss of k leaf and turgor loss point than the humid-habitat Ranunculus lanuginosus.

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    Accordingly, water stress-exposed plants from the broad-amplitude Ranunculus acris revealed tendencies toward lower vulnerability to water stress e. We show that small herbs can adjust to their habitat conditions on interspecific and intraspecific levels in various hydraulic parameters. Reversible recovery of hydraulic conductance, desiccation-tolerant seeds, or rhizomes may allow them to prioritize toward a more efficient but vulnerable water transport system while avoiding the severe effects that water stress poses on woody species.

    The resistance of terrestrial plant species to water stress is an important determinant of their spatial distribution Engelbrecht et al. The hydraulic vulnerability to drought-induced embolism in woody species is adjusted to their environmental conditions on a global scale Choat et al.

    While many studies have dealt with the hydraulics of woody species Maherali et al. Yet, herbs play an important ecological role in many biomes, such as grasslands and the alpine zone Billings and Mooney, ; Gilliam, ; Scholz et al.

    The requirements of the water transport system of herbs differ in several ways from those of woody species Mencuccini, First, transport distances and supported leaf areas are much smaller in herbs, and reversible extraxylary limitations Brodribb and Holbrook, ; Kim and Steudle, may have a stronger effect on hydraulic conductivity. Second, herbs often do not feature an essential, lignified main axis designed for long-term functioning, in which hydraulic failure may mean whole-plant mortality.

    Thus, herbs may not be as threatened by drought-induced failure as taller woody species. Hydraulic failure occurs when vulnerability thresholds are exceeded under water stress and the xylem tension is suddenly released as water is replaced by air, effectively blocking water transport in the affected conduits Tyree and Zimmermann, Vulnerability to drought-induced embolism can thus be analyzed hydraulically by measuring decreases in conductance during increasing water stress Sperry et al.

    However, the usability of UE analysis to noninvasively study hydraulic vulnerability remains under discussion Sandford and Grace, ; Kikuta, ; Wolkerstorfer et al.

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    On the leaf level, desiccation may induce turgor loss, decreases in mesophyll conductance Kim and Steudle, ; Scoffoni et al. When water stress increases further, living cells may incur damage resulting in tissue and leaf mortality. In this study, we compared key hydraulic features vulnerability to drought-induced loss of conductance as measured via hydraulic flow and xylem staining, pressure-volume relations, and the onset of cellular damage of three species from the genus Ranunculuswhich is distributed almost worldwide and contains species adapted to dry and humid habitats as well as species with broad ecological amplitude.

    We hypothesized that herbaceous species would be more vulnerable to water stress than woody species but also would show interspecific and intraspecific adjustments in hydraulic vulnerability based on the water availability of their respective habitats. Namely, the hydraulics of species with narrow ecological amplitude were hypothesized to reflect their respective habitat conditions, and broad-amplitude species should show adequate intraspecific variation to enable growth in dry and humid habitats.

    Volumetric soil water content SWC at field capacity was The low field capacity SWC of the second humid site was due to the soil composition thin layer of humus and litter on top of gravel substrateyet the SWC remained constant due to the humid conditions inside the gorge.

    drought-induced variations of water relations

    Ecological indicator values for the study species and cooccurring species at the sampling sites supported the observed differences in water availability: averaged humidity values were 4. At the dry site, Ranunculus bulbosus humidity index of 3; indicator for dry sites and R.

    In contrast, at the humid sites, R. The turgor loss point TLP was least negative in R. In contrast, the modulus of elasticity was lowest i. Maximum whole-leaf hydraulic conductance k leaf max was between Thresholds were computed after fitting the reparameterized Weibull function Ogle et al. Vertical lines indicate fitted hydraulic vulnerability parameters P k50 solid and P k88 dashed. Curves were extrapolated using the same equation and parameters used for vulnerability curves Eq.

    Conductive xylem staining in R. Stained leaf laminas and petiole cross sections of R. Conducting elements appear red, while embolized conduits remain unstained.Previous studies demonstrated that ammonium nutrition results in higher water uptake rate than does nitrate nutrition under water stress, and thus enhances the tolerance of rice plants to water stress.

    However, the process by which water uptake is related to nitrogen form under water stress remains unknown. A hydroponic experiment with simulated water stress induced by polyethylene glycol PEG was conducted in a greenhouse to study the relationship between root aerenchyma formation and water uptake rate, such as xylem sap flow rate and hydraulic conductance, in two different rice cultivars cv.

    The results showed that root aerenchyma tissue increased in water-stressed plants of both cultivars fed by nitrate. It was concluded that aerenchyma that formed in the root cortex impeded the radial transport of water in the root cylinder and decreased water uptake in water-stressed rice plants fed by nitrate.

    Water transport occurred mainly through Hg-sensitive water channels in rice roots supplied with ammonium. Water stress is a primary limitation to plant growth and production LawlorTuberosa et al. Many studies have focused on the relationship between nutritional status and drought resistance and the integrated effects of nutrients and water status on photosynthesis and water relationships Shangguan et al.

    Rice plants have a higher ammonium assimilation capacity than other plant species and can avoid ammonium toxicity or may exhibit a growth preference for ammonium nutrition Britto et al. Maintenance of plant growth and water uptake rate in water-stressed rice plants supplied with ammonium indicates that ammonium nutrition enhances the tolerance of rice seedlings to water stress Guo et al.

    The essential function of roots is to supply shoots with nutrients and water from the root medium Steudle and Peterson Plant roots constitute the largest hydraulic resistance to water flow in the soil—plant—atmosphere continuum.

    Water flux from the root surface to the root xylem can be calculated by the root hydraulic conductivity and water potential gradient across the pathway Fan et al. Root morphology and anatomy are generally closely related to water and nutrient uptake.

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    In addition to the Casparian band, the number of passage cells in the endodermis, suberization of the endodermis or exodermis, root diameter, root cortical width and aerenchyma may also cause variability in root hydraulic conductivity Melchior and SteudleRieger and Litvin In a well-aerated solution culture, aerenchyma is observed in the adventitious roots of rice when N or P is omitted from the nutrient solution He et al.

    Zhu et al. We have demonstrated previously that ammonium nutrition enhances drought tolerance and maintains water uptake in water-stressed rice seedlings Guo et al. In this study, we investigated whether the root aerenchyma and water uptake of water-stressed rice are related to both nitrogen and water stress. We further analyzed the relationship between root aerenchyma and root hydraulic conductivity in rice seedlings supplied with different forms of nitrogen under water stress.

    Water stress significantly increased the root-to-shoot ratio under ammonium and nitrate nutrition. Compared with no-water stress, tillers were depressed under water stress and nitrate nutrition, whereas no depression was found in plants fed ammonium Table 1.

    2018–20 Southern Africa drought

    Shanyou 63 and cv. Yangdao 6. Regardless of water stress, hybrid indica rice seedlings had a higher biomass and more tillers than indica rice seedlings fed both N forms Table 1. No significant difference in aerenchyma formation was observed between plants under the two N forms of nutrition in the non-water-stressed condition Fig.

    Scanning electron micrographs of transverse sections from newly formed adventitious roots of rice plants. Effects of nitrogen form and water stress on aerenchyma formation a and root porosity b in rice plants cv.

    Aerenchyma formation was determined from the electron micrographs in Fig. Data represent means of three replicates. Bars indicate the SD.


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