Rapid responses of C14 clone of Eucalyptus globulus to root drought stress: Time-course of hormonal and physiological signaling (original) (raw)
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Tree physiology, 2014
Seasonal drought, typical of temperate and Mediterranean environments, creates problems in establishing plantations and affects development and yield, and it has been widely studied in numerous species. Forestry fast-growing species such as Eucalyptus spp. are an important resource in such environments, selected clones being generally used for production purposes in plantations in these areas. However, use of mono-specific plantations increases risk of plant loss due to abiotic stresses, making it essential to understand differences in an individual clone's physiological responses to drought stress. In order to study clonal differences in drought responses, nine Eucalyptus globulus (Labill.) clones (C14, C46, C97, C120, C222, C371, C405, C491 and C601) were gradually subjected to severe drought stress (<14% of field capacity). A total of 31 parameters, physiological (e.g., photosynthesis, gas exchange), biochemical (e.g., chlorophyll content) and hormonal (abscisic acid [ABA]...
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The genus Eucalyptus occurs in a wide range of environmental conditions, including rainforests, subalpine, arid/semi-arid and moist temperate zones. It includes species with the capacity to cope with extremely low water potential. This study aims to screen water stress tolerance in two Eucalyptus species under nursery conditions. Inter-specific variation in morphological, physiological, biochemical and molecular parameters in two Eucalyptus species (E. tereticornis and E. camaldulensis) with contrasting levels of tolerance to progressive short term water-deprived condition was evaluated. Water stress reduced growth measured in terms of root:shoot ratio and specific leaf area (SLA), photosynthetic parameters, leaf water potential and relative water content (RWC) in both genotypes. Biochemical parameters including total sugars, phenol, phytohormones (indole acetic acid and abscisic acid) and proline were found to significantly increase during stress in both genotypes. Water responsive...
Acta Physiologiae Plantarum
Drought stress promotes biochemical and physiological alterations in plant metabolism that limit growth and yield. This study investigated the accumulation of caminobutyric acid (GABA) in plant tissue, the stomatal conductance (gs) and changes in leaf anatomy in Eucalyptus following drought stress situation. In this study, eight Eucalyptus clones were evaluated under normal water supply (control) and drought stress conditions (stress). For the control treatment, plants were irrigated every day with an automated system until the soil was saturated, and for the stress treatment, drought stress was imposed by non-irrigation of plants, and pots were covered using plastic sheeting to avoid rainfall and humidity. This study has shown that:
Physiologia Plantarum, 2013
Eucalyptus plantations are among the most productive forest stands in Portugal and Spain, being mostly used for pulp production and, more recently, as an energy crop. However, the region's Mediterranean climate, with characteristic severe summer drought, negatively affects eucalypt growth and increases mortality. Although the physiological response to water shortage is well characterized for this species, evidence about the plants' recovery ability remains scarce. In order to assess the physiological and biochemical response of Eucalyptus globulus during the recovery phase, two genotypes (AL-18 and AL-10) were submitted to a 3-week water stress period at two different intensities (18 and 25% of field capacity), followed by 1 week of rewatering. Recovery was assessed 1 day and 1 week after rehydration. Drought reduced height, biomass, water potential, NPQ and gas exchange in both genotypes. Contrarily, the levels of pigments, chlorophyll fluorescence parameters (F v /F m and φ PSII), MDA and ABA increased. During recovery, the physiological and biochemical profile of stressed plants showed a similar trend: they experienced reversion of altered traits (MDA, ABA, E, g s , pigments), while other parameters did not recover (φ PSII , NPQ). Furthermore, an overcompensation of CO 2 assimilation was achieved 1 week after rehydration, which was accompanied by greater growth and re-establishment of oxidative balance. Both genotypes were tolerant to the tested conditions, although clonal differences were found. AL-10 was more productive and showed a more rapid and dynamic response to rehydration
Quercitol and osmotic adaptation of field-grown Eucalyptus under seasonal drought stress
Plant Cell and Environment, 2008
This study investigated the role of quercitol in osmotic adjustment in field-grown Eucalyptus astringens Maiden subject to seasonal drought stress over the course of 1 year. The trees grew in a native woodland and a farm plantation in the semi-arid wheatbelt region of south Western Australia. Plantation trees allocated relatively more biomass to leaves than woodland trees, but they suffered greater drought stress over summer, as indicated by lower water potentials, CO2 assimilation rates and stomatal conductances. In contrast, woodland trees had relatively fewer leaves and suffered less drought stress. Plantation trees under drought stress engaged in osmotic adjustment, but woodland trees did not. Quercitol made a significant contribution to osmotic adjustment in drought-stressed trees (25% of total solutes), and substantially more quercitol was measured in the leaves of plantation trees (5% dry matter) than in the leaves of woodland trees (2% dry matter). We found no evidence that quercitol was used as a carbon storage compound while starch reserves were depleted under drought stress. Differences in stomatal conductance, biomass allocation and quercitol production clearly indicate that E. astringens is both morphologically and physiologically ‘plastic’ in response to growth environment, and that osmotic adjustment is only one part of a complex strategy employed by this species to tolerate drought.
Physiological responses to water stress in Eucalyptus cloeziana and E. argophloia seedlings
Trees, 2004
Effects of water stress duration and intensity on gas exchange and leaf water potential were investigated in 7-month-old seedlings of a humid coastal provenance (Gympie) and a dry inland (Hungry Hills) provenance of E. cloeziana F. Muell. and in a dry inland (Chinchilla) provenance of E. argophloia Blakely supplied with 100% (T 100 ), 70% (T 70 ), 50% (T 50 ) of their water requirements, or were watered only after they were wilted at dawn (T 0 ). Seedlings of E. argophloia had the highest midday net photosynthetic rate (A), stomatal conductance (g s ), stomatal density and predawn leaf water potential (Y pd ) in all treatments. The E. cloeziana provenances did not differ in these attributes. The T 70 and T 50 treatments caused reductions in A of 30% in E. argophloia, and 55% in the E. cloeziana provenances. Under the T 0 treatment, E. argophloia maintained higher rates of gas exchange at all levels of water stress than E. cloeziana provenances. The estimates of Y pd and midday water potential (Y md ) at which plants remained wilted overnight were respectively: 2.7 and 4.1 MPa for E. cloeziana (humid), 2.8 and 4.0 MPa for E. cloeziana (dry) and, 3.7 and 4.9 MPa for E. argophloia. Following stress relief, both A and g s recovered more quickly in E. argophloia and in the dry provenance of E. cloeziana than in the humid provenance. We conclude that E. argophloia is more drought tolerant and has a potential for cultivation in the humid and semi humid climates, whilst E. cloeziana has greater potential in the humid subtropical climates.
Tree Physiology, 2018
Previous knowledge suggested the involvement of specific pathways/proteins that could be identified as potential molecular indicators linked to enhanced drought tolerance in Eucalyptus globulus. Here, we looked for specific variations in key transcripts of two Eucalyptus globulus clones (AL-18 and AL-13) exposed to water deficit and rehydration with two main goals: (i) to check if and how transcripts potentially associated with stress response and protection are modulated in a controlled experiment; and (ii) to verify if the transcript response is robust in a field case study. Our results showed that the controlled experiment induced a severe acute stress that resulted in a strong realignment of gene expression resulting from an overwhelming of physiological adjustments to water limitation. A number of transcripts exhibited altered abundance after the acute water stress: reduction of RuBisCO activase and mitochondrial glycine cleavage system H protein, and increase of isoflavone reductase. Malate dehydrogenase, catalase, dehydration response element B1A and potassium channel GORK showed a different abundance pattern in each clone. The stress in the field was more moderate and chronic and the plants were able to deal with the stress primarily through physiological adjustments resulting in much smaller changes in gene expression. The transcripts of clone AL-18 showed few alterations between irrigated and non-irrigated plants throughout the experiment, while the transcript changes found in clone AL-13 highlighted the impact of early rewatering rather than growing under extended drought typical of a Mediterranean summer. Although a few concurrent responses were found, the results obtained in the field study draw a very distinct picture when compared with the controlled experiment.
2002
Eucalyptus camaldulensis Dehnh., considered as a drought tolerant species, was examined in relation to some mechanisms linked to drought tolerance (cell-wall elastic adjustment and osmotic adjustment) and to the intraspecific variation related to those features. Rooted cuttings of five clones obtained from three different provenances from Australia (Gilgandra: 106, 109; Lake Albacutya: 119, 125; Condamine: 105) were gradually submitted to a water limitation regime. Water stress curtailed relative leaf area growth rate, pre-dawn relative water content (RWC) and noon stomatal conductance (gs) in all clones. Shoot water parameters were estimated at the end of the drought period by pressure-volume (P–V) analysis through a repeat pressurization method. The curves obtained were analyzed by Schulte’s P–V Curve Analysis Program. Drought decreased very significantly the osmotic potential at full turgor (χπFT) and at the turgor loss point (χπTLP), with a significant clone effect: 105 had the lowest values (–2.12±0.04 MPa and –2.39±0.05 MPa). Osmotic adjustment (OA) on average was 0.34±0.02 MPa. Drought increased maximum bulk modulus of elasticity (ɛMAX) by 6.60.7 MPa. There were no clonal differences in either OA or elastic adjustment.Water stress increased significantly turgor potential at full turgor (χFT), and differences between control and stress plants show that the OA recorded did not fully account for the positive changes in turgor of stressed plants. Drought decreased shoot turgid mass/dry mass ratio (TM/DM), again with a significant clone effect: 105 had the lowest value (2.66±0.11). Reduced shoot TM/DM combined with increases in ɛMAXduring stress were indicative of cell wall adjustment, reduced turgor-loss volumes and tightening of the cell walls around the protoplasts, suggesting a cell size reduction. No effects were observed on RWC at the turgor loss point. A regression model that considered ɛMAX and χπFT explained best the response patterns of stressed plants. The mechanisms observed in Eucalyptus camaldulensis that delay growth while maintaining turgor and water uptake allow us to consider it as a dehydration postponement species.