SHORT-TERM EFFECTS OF SALINITY ON SOME PHYSIOLOGICAL PARAMETERS OF YOUNG OLIVE TREES OF ARBEQUINA, COBRANÇOSA AND GALEGA VARIETIES

SHORT-TERM EFFECTS OF SALINITY ON SOME PHYSIOLOGICAL PARAMETERS OF YOUNG OLIVE TREES OF ARBEQUINA, COBRANÇOSA AND GALEGA VARIETIES Ana Elisa Rato1,4, Renato Coelho1, Margarida Vaz1, Teresa Carola2, Dália Barbosa2, Nádia Silva1, José dos Santos2, Lourenço Machado2, João Godinho2, Luzia Ruas2, Margarida Barradas2, Hernani Pereira2, Sara Porfírio4 1 ICAAM, Universidade de Évora, Apartado 94, 7002-554 Évora, Portugal 2 Master students, Universidade de Évora, Apartado 94, 7002-554 Évora, Portugal 3 Ph.D. student, Universidade de Évora, Apartado 94, 7002-554 Évora, Portugal 4 aerato@uevora.pt Due to the desertification in some regions, the interest in plant’s tolerance to salinity has been increasing, as this response is determining for plant survival in stress conditions. This work reports the investigation of tolerance to salt in two year-old olive trees (Olea europaea L.) of three varieties, Arbequina, Cobrançosa and Galega vulgar. Plants were grown in 10 L plastic pots containing approximately 9 Kg of a sandy granitic soil, on a greenhouse. For 3 months (from the beginning of February to the end of April 2012), they were subjected to three levels of salinity in the irrigation water, 0 mM, 80 mM and 200 mM NaCl (6 plants per salinity level in a total of 18 plants of each variety),. Stomatal conductance (gs) and relative leaf chlorophyll content were assessed on each plant in February, March and April. Mid-day leaf water potential () and soil salinity were measured at the end of the experiment (April). On average, concerning all treatments and dates of determination, stomatal conductance of Arbequina and Galega vulgar was quite similar, around 40 mmol m-2 s-1, but Cobrançosa had a value of gs 36% higher, almost 50% higher (61 mmol m-2 s-1) when compared with the controls (0 mM salt) of the other two varieties. In percentage of controls, there was little difference in gs between varieties and between salinities during February and March. In contrast, in April, after about 90 days of exposure to salt, there was a clear decrease in gs with salt irrigation, proportional to salt concentration. Compared with controls, plants irrigated with 200 mM salt showed around 80% (Arbequina) or 85% (Cobrançosa and Galega vulgar) decrease in gs. Chlorophyll content of leaves showed less than 5% difference between varieties on the average of all treatments and dates of determination. During the course of this experiment, the salinity levels used did not show any relevant effect on chlorophyll content. Overall, at the end of the experimental period (April), leaf water potential () at midday was significantly higher in Cobrançosa (-1,4 MPa) than in Galega vulgar (-1,7 MPa) or Arbequina (-1,8 MPa), and salt decreased  of control plants (-1,25 MPa) by an average 30% (with 80 mM) and 65% (with 200 mM). At the end of the experiment, salinity in the soil irrigated with 0 mM, 80 mM or 200 mM NaCl was, on average of all varieties, 0,2 mS, 1,0 mS or 2,0 mS, respectively. Soil salinity was quite similar in Arbequina and Galega vulgar but about 35% lower in the pots of Cobrançosa, on average of all salt-irrigation levels. Plants of Cobrançosa had higher stomatal conductance, however they showed higher water potential and lower salinity in the soil. These apparently contradictory results seem to suggest that Cobrançosa responds to salt differently from the other two varieties. This issue needs further investigation.

Response to salinity in young olive trees of three Iberian varieties

Soil salinization is a problem in the Mediterranean region. This paper reports a research on the response to salt in two year-old olive trees (Olea europaea L.) of three Iberian varieties: Arbequina, Cobrançosa and Galega Vulgar. Plants were grown in plastic pots containing approximately 9 Kg of a sandy granitic soil, on a greenhouse at the University of Évora since February 2010. The experiment went from February to April 2012. As a rule, plants were watered every other day alternating salt solution (0 mM, 80 mM or 200 mM NaCl) or tap water. After three months irrigation with the different NaCl solutions, soil electric conductivity and soil water content were significantly higher on salt-irrigated pots. Salt also decreased significantly stomatal conductance (gs) and mid-day leaf water potential (), Cobrançosa having in general higher gs and but lower SLA than the two other varieties. Chlorophyll content of leaves was not affected by salt after this three months exposure to NaCl but was significantly higher on Arbequina and lower on Cobrançosa. In general, hyperspectral reflectance indexes did not show significant correlations with salt irrigation, except for the Photochemical Reflectance Index (PRI) which was clearly lower on plants of all three varieties irrigated with salt. Interestingly, Cobrançosa showed frequently vegetation indexes different from the other two varieties.

Influence of Soil and Irrigation Management on the Quality of Seedless Crimson Table Grapes

The market for table grapes is moving into mass production of specialty seed-less grapes in covered areas, aiming at obtaining premium prices with early or late production of high quality products. Production of quality seedless grapes is not straightforward since it is requires the correct combination of various independent characteristics, such as color, sugars, size and quantity at the right moment for successful harvesting and marketing. The present study was carried out at the two largest Portuguese producers located in Alentejo, and has the objective of studying the effect of irrigation management strategies and two different soils on the various relevant parameters for successful production and marketing. The management strategies were the application of ten day stress at the end of the cycle, in order to promote early maturing of the grapes. Three different timings of the stress were applied. Soil moisture, sap flow, bark thickness, as well as leaf water potential, stomatal conductance and chlorophyll content were measured regularly during the production season. The results indicate that the roots explore a rather large soil volume and the plants can successfully withstand reasonable periods of drought without significant changes to the plant physiology. Additionally late rains can mask the effect of any farmer applied drought and invalidate any farmer induced stress to the plants. Water-logged soils tend to cause early onset of maturity, but cause the ripening stage to extend over a longer period of time, and thus, in effect result in a delay in the harvest date. Topography also has some effect on the ripening, since hot air tends to accumulate under the plastic at the higher areas of the field. This work is funded by PRODER, 4.1, within the scope of project MORECRIMSON

Analyse de l'effet de la contamination du sol sur la croissance et la physiologie de 11 cultivars de Salix

Mon mémoire de maîtrise a été réalisé dans le cadre du projet Génorem (www.genorem.ca), un projet multidisciplinaire qui réunit différents chercheurs de l'Université de Montréal et de l'Université McGill dans le but d'améliorer les techniques utilisées en bioremédiation. Dans le cadre de l'étude, des saules à croissance rapide (Salix sp.) ont été utilisés comme plantes modèles dans l'étude. Ainsi, 11 cultivars de saule ont été suivis afin de déterminer leur potentiel à produire un bon rendement de biomasse, à tolérer des conditions de stress sévère causé par la présence de HAPs (hydrocarbures aromatiques polycycliques) , BPCs (biphényles polychlorés) et d'hydrocarbures pétroliers C10-C50. L'expérimentation consistait en une plantation de saule à forte densité qui a été mise en place en 2011 sur le site d'une ancienne industrie de pétrochimie à Varennes, dans le sud du Québec. Les boutures des génotypes sélectionnés ont été plantées sur une superficie d'environ 5000 m2. Les plantes ont été suivies pendant les deux saisons de croissance suivant le recépage et une série de paramètres de croissance et de mesures physiologiques ont été récoltés (surface foliaire, taux de chlorophylle, conductance stomatique et statut nutritionnel) dans le but d'évaluer et de comparer les performances de chaque génotype sur un sol pollué. Les analyses statistiques ont démontré que le cultivar S. miyabeana (SX61) était le meilleur producteur de biomasse sur le site contaminé, tandis que S. nigra (S05) et S. acutifolia (S54) présentaient la meilleure capacité photosynthétique. S. dasyclados (SV1), S. purpurea (‘Fish Creek’) et S. caprea (S365) ont semblé particulièrement affectés par la présence de contaminants. La capacité d'établissement et la croissance de S. nigra (S05), S. eriocephala (S25) and S. purpurea x S. miyabeana (‘Millbrook’) indiquent une tolérance globale supérieure à la pollution . Cette analyse comparative des différentes réponses physiologiques des saules cultivés sur un sol contaminé pourra guider le processus de sélection de plantes et les techniques de bioremédiation dans les futurs projets de phytoremédiation.

Water relations, growth and gas exchange in Acacia auriculiformis under experimental and natural conditions

Investigations on the water relations and gas exchange of/tcacia aun'culiji_2rmis were carried out in natural and controlled environments. The experiments were performed in both seedlings and five year old trees. Different sets of experiments were conducted in Acacia plantations, at Kothachira, Palakkad District and in .seedlings, at KFRI campus nursery mainly during the summer months. Investigations were also extended to seedlings of A.mangium, Aaulacocarpa and /Lholocericea, which are also phyllodinous species with the intention of comparing their physiology with Acacia auriculifomus. Potted seedlings of four species of Acacia viz., A. auriculi/E)/7r:i.r, /I. aulacocarpa, A. holocericea and A. mangium were used for the study. Measurements of relative water content (RWC), water potential, photosynthetic rate, transpiration, stomatal conductance, water use efficiency etc. of phyllodes were measured diumally in plants subjected to three stress conditions namely, drought, salinity and flooding

Illustration of micro-scale advection using grid-pattern mini-lysimeters

Twenty-five small soil-filled perspex boxes arranged in a square, with dwarf sunflowers growing in them, were used to study micro-scale advection. Hydrological heterogeneity was introduced by applying two different amounts of irrigation water (low-irrigation, L, versus high-irrigation, H). The nine central boxes (4 H, 4 L and I bare box) were precision weighing lysimeters, yielding diurnal measurements of evaporation. After the onset of soil water stress, a large difference in latent heat flux (up to 4-fold) was observed between the lysimeters of the H and L treatments, mainly caused by large differences between H and L stomatal conductance values. This resulted in micro-advection, causing H soil-sunflower systems to evaporate well above equilibrium latent heat flux. The occurrence of micro-advective enhancement was reflected in large values of the Priestley-Taylor constant (often larger than 2.0) and generally negative values of sensible heat flux for the H treatment. (c) 2005 Elsevier B.V. All rights reserved.

Effects of cultural system (organic and conventional) on growth, photosynthesis and yield components of sweet corn (zea mays L.) under semi-arid environment

Organic sweet maize consists of a new industrial crop product. Field experiment was conducted to determine the effects of cultural systems on growth, photosynthesis and yield components of sweet maize crop (Zea mays L. F-1 hybrid 'Midas'). A randomized complete block design was employed with four replicates per treatment (organic fertilization: cow manure (5, 10 and 20 t ha(-1)), poultry manure (5, 10 and 20 t ha(-1)) and barley mulch (5, 10 and 20 t ha(-1)), synthetic fertilizer (240 kg N ha(-1)): 21-0-0 and control). The lowest dry weight, height and leaf area index and sod organic matter were measured in the control treatment. Organic matter content was proportionate to the amount of manure applied. The control plots had the lowest yield (1593 kg ha(-1)) and the double rate cow manure plots the had,greatest one. (6104 kg ha(-1)). High correlation between sweet corn yield and organic matter was registered. Moreover, the lowest values of 1000-grain weight were obtained with control plot. The fertilizer plot gave values which were similar to the full rate cow manure treatment. The photosynthetic race of the untreated control was significantly lower than that of the other treatments. The phorosynthetic rate increased as poultry manure and barley mulch ram decreased and as cow manure increased. Furthermore the untreated control had the lowest stomatal conductance and chlorophyll content. Our results indicated that sweet corn growth and yield in the organic plots was significantly higher than those in the conventional plots.

Water use of a bioenergy plantation increases in a future high CO2 world

Fast-growing poplar trees may in future be used as a source of renewable energy for heat, electricity and biofuels such as bioethanol. Water use in Populus x euramericana (clone I214), following long-term exposure to elevated CO2 in the POPFACE (poplar free-air carbon dioxide enrichment) experiment, is quantified here. Stomatal conductance was measured and, during two measurement campaigns made before and after coppicing, whole-tree water use was determined using heat-balance sap-flow gauges, first validated using eddy covariance measurements of latent heat flux. Water use was determined by the balance between leaf-level reductions in stomatal conductance and tree-level stimulations in transpiration. Reductions in stomatal conductance were found that varied between 16 and 39% relative to ambient air. Whole-tree sap flow was increased in plants growing under elevated CO2, on average, by 12 and 23%, respectively, in the first and in the second measurement campaigns. These results suggest that future CO2 concentrations may result in an increase in seasonal water use in fast-growing, short-rotation Populus plantations.

Regulated irrigation of woody ornamentals to improve plant quality and precondition against drought stress

Regulated irrigation has the potential to improve crop quality in woody ornamentals by reducing excessive vigour and promoting a more compact habit. This research aimed to compare the effectiveness and the mode of action of two techniques, regulated deficit irrigation (RDI) and partial root drying (PRD), when applied to container-grown ornamentals through drip irrigation. Results showed that RDI and PRD reduced growth in Cotinus coggygria 'Royal Purple', but in Forsythia x intermedia 'Lynwood', significant reductions were recorded only with RDI. Physiological measurements in Forsythia indicated that reductions in stomatal conductance (g(s)) occurred in both treatments, but those in the RDI tended to be more persistent. Reduced g(s) in PRD was consistent with the concept that chemical signals from the root can regulate stomatal aperture alone; however, the data also suggested that optimising the growth reduction required a moderate degree of shoot water deficit (i.e. a hydraulic signal to be imposed). As RDI was associated with tissue water deficit, it was used in a second experiment to determine the potential of this technique to precondition container-grown plants against subsequent drought stress (e.g. during retail stages or after planting out). Speed of acclimation would be important in a commercial context, and the results demonstrated that both slow and rapid imposition of RDI enabled Forsythia plants to acclimate against later drought events. This article discusses the potential to both improve ornamental plant quality and enhance tolerance to subsequent adverse conditions through controlled, regulated irrigation.

Shoot dieback in clipped young Golden Leyland (Cupressocyparis leylandii) trees - a physiological mechanism?

Shoot dieback is a problem in frequently trimmed Leyland hedges and is increasingly affecting gardeners’ choice of hedge trees, having a negative effect on a conifer nursery industry. Some damage can be attributed to the feeding by aphids, but it is unclear if there are also underlying physiological causes. In this study, we tested the hypothesis that shoot-clipping of conifer trees during adverse growing conditions (i.e. high air temperature and low soil moisture) could be leading to shoot ‘dieback’. Three-year-old Golden Leyland Cypress (x Cupressocyparis leylandii ‘Excalibur Gold’) plants were subjected to either a well-watered or droughted irrigation regime and placed in either a ‘hot’ (average day temperature = 40°C) or a ‘cool’ (average day temperature = 27°C) glasshouse compartment. Half of the plants from each glasshouse were clipped on Day 14 and again on Day 50. Measurements of soil moisture content (SMC), net CO2 assimilation rate (A), stomatal conductance (gs), branchlet xylem water potential (XWP), plant height and foliage colour were made. Within the clipped and unclipped treatments of both glasshouse compartments, plants from the droughted regime had significantly lower values for A, gs and XWP than those from the well-watered regime. However, there was no difference in these parameters between the hot and cool glasshouse compartments. The trends seen for A, gs and XWP of all treatments generally mirrored changes in SMC indicating a direct effect of water supply on these parameters. By the end of the experiment the overall foliage colour of plants from the hot glasshouse was darker than that of plants from the cool glasshouse and the overall foliage colour was also darker following shoot clipping. In general, shoot clipping led to increases in A, gs XWP and SMC. This may be due to the reduction in total leaf area leading to a greater supply of water for the remaining leaves. No shoot ‘dieback’ was observed in any treatment in response to drought stress or shoot-clipping.

Root pruning as a means to encourage root growth in two ornamental shrubs, Buddleja davidii ‘Summer Beauty’ and Cistus ‘Snow Fire'

The inability of a plant to grow roots rapidly upon transplanting is one of the main factors contributing to poor establishment. In bare-rooted trees, treatments such as root pruning or application of the plant hormone auxin [e.g., indole butyric acid (IBA)] can promote root growth and aid long-term establishment. There is little information on ornamental containerised plants, however, other than the anecdotal notion that 'teasing' the roots out of the rootsoil mass before transplanting can be beneficial. In the present study we tested the ability of various root-pruning treatments and application of IBA to encourage new root and shoot growth in two shrub species, commonly produced in containers - Buddleja davidii 'Summer Beauty' and Cistus 'Snow Fire'. In a number of experiments, young plants were exposed to root manipulation (teasing, light pruning, or two types of heavy pruning) and/or treatment with IBA (at 500 or 1,000 mg l-1) before being transplanted into larger containers containing a medium of 1:1:1 (v/v/v) fine bark, sand and loam. Leaf stomatal conductance (gl) was measured 20 min, and 1, 2, 4 and 6 h after root manipulation. Net leaf CO2 assimilation (A) was measured frequently during the first week after transplanting, then at regular intervals up to 8 weeks after transplanting. Plants were harvested 8 weeks after transplanting, and root and shoot weights were measured. In both species, light root pruning alone, or in combination with 500 mg l-1 IBA, was most effective in stimulating root growth. In contrast, teasing, which is commonly used, showed no positive effect on root growth in Buddleja, and decreased new root growth in Cistus. The requirement for exogenous auxin to encourage new root growth varied between experiments and appeared to be influenced by the age and developmental stage of the plants. There were no consistent responses between root treatments and net CO2 assimilation rates, and changes in root weight were not closely correlated with changes in assimilation. The mechanisms whereby new root growth is sustained are discussed.

Idealized model for changes in equilibrium temperature, mixed layer depth, and boundary layer cloud over land in a doubled CO2 climate

An idealized equilibrium model for the undisturbed partly cloudy boundary layer (BL) is used as a framework to explore the coupling of the energy, water, and carbon cycles over land in midlatitudes and show the sensitivity to the clear‐sky shortwave flux, the midtropospheric temperature, moisture, CO2, and subsidence. The changes in the surface fluxes, the BL equilibrium, and cloud cover are shown for a warmer, doubled CO2 climate. Reduced stomatal conductance in a simple vegetation model amplifies the background 2 K ocean temperature rise to an (unrealistically large) 6 K increase in near‐surface temperature over land, with a corresponding drop of near‐surface relative humidity of about 19%, and a rise of cloud base of about 70 hPa. Cloud changes depend strongly on changes of mean subsidence; but evaporative fraction (EF) decreases. EF is almost uniquely related to mixed layer (ML) depth, independent of background forcing climate. This suggests that it might be possible to infer EF for heterogeneous landscapes from ML depth. The asymmetry of increased evaporation over the oceans and reduced transpiration over land increases in a warmer doubled CO2 climate.

Sub-irrigation of Petunia: benefits in dry summers

With the increasing frequency and magnitude of warmer days during the summer in the UK, bedding plants which were a traditional part of the urban green landscape are perceived as unsustainable and water-demanding. During recent summers when bans on irrigation have been imposed, use and sales of bedding plants have dropped dramatically having a negative financial impact on the nursery industry. Retaining bedding species as a feature in public and even private spaces in future may be conditional on them being managed in a manner that minimises their water use. Using Petunia x hybrida ‘Hurrah White’ we aimed to discover which irrigation approach was the most efficient for maintaining plants’ ornamental quality (flower numbers, size and longevity), shoot and root growth under water deficit and periods of complete water withdrawal. Plants were grown from plugs for 51 days in wooden rhizotrons (0.35 m (h) x 0.1 m (w) x 0.065 m (d)); the rhizotrons’ front comprised clear Perspex which enabled us to monitor root growth closely. Irrigation treatments were: 1. watering with the amount which constitutes 50% of container capacity by conventional surface drip-irrigation (‘50% TOP’); 2. 50% as sub-irrigation at 10 cm depth (‘50% SUB’); 3. ‘split’ irrigation: 25% as surface drip- and 25% as sub-irrigation at 15 cm depth (‘25/25 SPLIT’); 4. 25% as conventional surface drip-irrigation (‘25% TOP’). Plants were irrigated daily at 18:00 apart from days 34-36 (inclusive) when water was withdrawn for all the treatments. Plants in ‘50% SUB’ had the most flowers and their size was comparable to that of ‘50% TOP’. Differences between treatments in other ‘quality’ parameters (height, shoot number) were biologically small. There was less root growth at deeper soil surface levels for ‘50% TOP’ which indicated that irrigation methods like ‘50% SUB’ and ‘25/25 SPLIT’ and stronger water deficits encouraged deeper root growth. It is suggested that sub-irrigation at 10 cm depth with water amounts of 50% container capacity would result in the most root growth with the maximum flowering for Petunia. Leaf stomatal conductance appeared to be most sensitive to the changes in substrate moisture content in the deepest part of the soil profile, where most roots were situated.

Profiling dehydrin gene sequence and physiological parameters in drought tolerant and susceptible spring wheat cultivars.

Physiological and yield traits such as stomatal conductance (mmol m-2s-1), Leaf relative water content (RWC %) and grain yield per plant were studied in a separate experiment. Results revealed that five out of sixteen cultivars viz. Anmol, Moomal, Sarsabz, Bhitai and Pavan, appeared to be relatively more drought tolerant. Based on morphophysiological results, studies were continued to look at these cultivars for drought tolerance at molecular level. Initially, four well recognized primers for dehydrin genes (DHNs) responsible for drought induction in T. durum L., T. aestivum L. and O. sativa L. were used for profiling gene sequence of sixteen wheat cultivars. The primers amplified the DHN genes variably like Primer WDHN13 (T. aestivum L.) amplified the DHN gene in only seven cultivars whereas primer TdDHN15 (T. durum L.) amplified all the sixteen cultivars with even different DNA banding patterns some showing second weaker DNA bands. Third primer TdDHN16 (T. durum L.) has shown entirely different PCR amplification prototype, specially showing two strong DNA bands while fourth primer RAB16C (O. sativa L.) failed to amplify DHN gene in any of the cultivars. Examination of DNA sequences revealed several interesting features. First, it identified the two exon/one intron structure of this gene (complete sequences were not shown), a feature not previously described in the two database cDNA sequences available from T. aestivum L. (gi|21850). Secondly, the analysis identified several single nucleotide polymorphisms (SNPs), positions in gene sequence. Although complete gene sequence was not obtained for all the cultivars, yet there were a total of 38 variable positions in exonic (coding region) sequence, from a total gene length of 453 nucleotides. Matrix of SNP shows these 37 positions with individual sequence at positions given for each of the 14 cultivars (sequence of two cultivars was not obtained) included in this analysis. It demonstrated a considerable diversity for this gene with only three cultivars i.e. TJ-83, Marvi and TD-1 being similar to the consensus sequence. All other cultivars showed a unique combination of SNPs. In order to prove a functional link between these polymorphisms and drought tolerance in wheat, it would be necessary to conduct a more detailed study involving directed mutation of this gene and DHN gene expression.

Genotypic variation in photosynthetic and leaf traits in cocoa

The photosynthetic characteristics of eight contrasting cocoa genotypes were studied with the aim of examining genotypic variation in maximum (light-saturated) photosynthetic rates, light-response curve parameters and water use efficiency. Photosynthetic traits were derived from single leaf gas exchange measurements using a portable infra-red gas analyser. All measurements were conducted in a common greenhouse environment. Significant variation was observed in light-saturated photosynthesis ranging from 3.4 to 5.7 µmol CO2 m-2 s-1 for the clones IMC 47 and SCA 6, respectively. Furthermore, analyses of photosynthetic light response curves indicated genotypic differences in light saturation point and quantum efficiency (i.e. the efficiency of light use). Stomatal conductance was a significant factor underlying genotypic differences in assimilation. Genotypic variation was also observed in a number of leaf traits, including specific leaf area (the ratio of leaf area to leaf weight), chlorophyll concentration and nitrogen content. There was a positive correlation between leaf nitrogen per unit area and light-saturated photosynthesis. Water use efficiency, defined as the ratio of photosynthetic rate to transpiration rate, also varied significantly between clones (ranging from 3.1 mmol mol-1 H2O for the clone IMC 47 to 4.2 mmol mol-1 H2O for the clone ICS 1). Water use efficiency was a negative function of specific leaf area, suggesting that low specific leaf area might be a useful criterion for selection for increased water use efficiency. It is concluded that both variation in water use efficiency and the photosynthetic response to light have the potential to be exploited in breeding programmes.