Differences In Stem Water Potential Research Articles

Development and application of an inexpensive open-source dendrometer for detecting xylem water potential and radial stem growth at high spatial and temporal resolution.

There is currently a need for inexpensive, continuous, non-destructive water potential measurements at high temporal resolution (<1min). We describe here the development and testing of an entirely open-source dendrometer that, when combined with periodic Scholander pressure chamber measurements, provides sub-minute resolution estimates of water potential when placed on tissues exhibiting little or no secondary growth (petioles, monocotyledon stems). The dendrometer can also be used to measure radial growth of stems and branches when placed on dicotyledon and gymnosperm species. The dendrometer can be interfaced directly with a computer in real time in the lab or greenhouse, or connected to a datalogger for long periods of use in the field on batteries. We tested this device on a herbaceous dicotyledon (Helianthus annuus) (petioles and stems) and a monocotyledon (Zea mays) species (stems) for 1 week during dehydration and re-watering treatments under laboratory conditions. We also demonstrated the ability of the device to record branch and trunk diameter variation of a woody dicotyledon (Rhus typhina) in the field. Under laboratory conditions, we compared our device (hereafter 'contact' dendrometer) with modified versions of another open-source dendrometer (the 'optical' dendrometer). Overall, contact and optical dendrometers were well aligned with one another, with Pearson correlation coefficients ranging from 0.77 to 0.97. Both dendrometer devices were well aligned with direct measurements of xylem water potential, with calibration curves exhibiting significant non-linearity, especially at water potentials near the point of incipient plasmolysis, with pseudo R2 values (Efron) ranging from 0.89 to 0.99. Overall, both dendrometers were comparable and provided sufficient resolution to detect subtle differences in stem water potential (ca. 50 kPa) resulting from light-induced changes in transpiration, vapour pressure deficit and drying/wetting soils. All hardware designs, alternative configurations, software and build instructions for the contact dendrometers are provided.

Hydric Behavior: Insights into Primary Metabolites in Leaves and Roots of Cabernet Sauvignon and Grenache Grapevine Varieties under Drought Stress

The classification of grapevine cultivars into isohydric and anisohydric categories depends on their ability to close stomata under conditions of low soil water availability or high atmospheric demand. This study aimed to compare the responses of Grenache, classified as isohydric, and Cabernet Sauvignon, classified as anisohydric, both grafted onto Richter 110 rootstock, and subjected to severe drought stress. Three cycles of drought stress were applied, followed by watering, while a well-watered treatment served as the control. Stomatal conductance and stem water potential were measured at predawn and midday during the drought cycles, and primary metabolites were analyzed in leaves and roots using gas chromatography. We found that Grenache had significantly higher stomatal conductance than Cabernet Sauvignon under both well-watered and water-stressed conditions. There were no significant differences in stem water potential between the two varieties, but the control treatment maintained a higher stem water potential at predawn and midday for both varieties. Primary metabolite analysis showed that both varieties accumulated sugars and polyols in their leaves and roots under drought stress, while organic acids were more abundant in leaves than in roots. Overall, the results suggest that the hydric behavior of grapevines depends on the intensity and duration of drought stress. In this study, both varieties exhibited near-isohydric behavior by regulating stomatal closure under drought stress. The metabolites identified in this study may serve as potential biomarkers of water drought stress in Grenache and Cabernet Sauvignon grapevines under the conditions of this experiment.

Unraveling the Physiological Mechanisms Underlying the Intracultivar Variability of Water Use Efficiency in Vitis vinifera “Grenache”

Selecting genotypes with a better capacity to respond and adapt to soil water deficits is essential to achieve the sustainability of grapevine cultivation in the context of increasing water scarcity. However, cultivar changes are very poorly accepted, and therefore it is particularly interesting to explore the intracultivar genetic diversity in water use efficiency (WUE). In previous studies, the cultivar "Grenache" has shown up to 30% variability in WUE. This research aimed to confirm the intracultivar variability and to elucidate the traits underlying this variability in the response to a water deficit by analyzing the growth rates, water relations, osmotic potential, leaf morphology, leaf gas exchange and carbon isotope discrimination in nine "Grenache" genotypes grown in pots during two seasons. The results showed lower differences in WUE and carbon isotope ratio than in previous field studies, but fairly good consistency in genotype ranking. Leaf mass area and osmotic potential did not underlie differences in stem water potential and in stomatal conductance. Overall, stomatal regulation and photosynthetic capacity seem to underlie differences in WUE among genotypes with an important environmental influence. These results confirm the ability to select clones with higher WUE and present an opportunity for the genetic improvement of WUE in grapevines.

Effect of mixed substrate with different mycorrhizal fungi concentrations on the physiological and productive response of three varieties of tomato

The application of arbuscular mycorrhizal fungi (AMF) in a mixed substrate is a vegetable production practice capable of improving plant productivity and sustainability of agricultural ecosystems. This study was conducted to determine the effect of a mixed substrate (agricultural soil with coconut fiber substrate) not enriched (S0) and enriched with 100 and 300 g m−3 of the fungus Glomus iranicum var. Tenuihypharum (S100 and S300) in water relations, photosynthetic and nutritional capacity, as well as production and fruit quality in three tomato varieties “H4”, “H3” (susceptible to mycorrhization) and “Jacaranda” not susceptible to mycorrhization). Plants irrigated with moderately saline water (EC: 2.35 dS m-1) in a commercial greenhouse in Mediterranean climate conditions were used for this study. Results showed that plants grown in substrate S100 showed an increase of AMF colonization, leaf phosphorus concentration, leaf total carbon and total nitrogen content compared with those grown in S0 and S300, which induced an increase in photosynthesis and stomatal conductance. This positive response was less evident by the application of substrate S300. Variety “H3” had a decrease in leaf sodium content, as well as higher photosynthesis values. There were no differences in stem water potential between factors. The lowest fruit production was observed in the “H4” variety, while fruit firmness decreased by AMF concentration and in variety “Jacaranda”. Root and aerial biomass increased in plants grown in S100 and S300, with respect to S0. Therefore, the improvements in the physiological and nutritional behaviour of these plants resulted in increased vegetative growth, but not in increased production. Varieties susceptible to AMF infection were more colonized than “Jacaranda”, but there were not improvements in yield and fruit quality. These results suggest that aspects related to the composition of the selected substrate, enzymatic AMF activity, fruit nutrition, as well as molecular mechanisms that control the plant-AMF interaction should be studied in depth.

Differences in stem water potential during oil synthesis determine fruit characteristics and production but not vegetative growth or return bloom in an olive hedgerow orchard (cv. Arbequina)

Although oil synthesis in fruits of cv. Arbequina starts at the end of pit hardening (beginning of July in central Spain) most oil is synthesized from late summer (end August) until harvest (end October). An experiment was established in two nearby high-density olive orchards (C and L) trained in 4-m spaced hedgerows (2.3 m tall) and maintained over three successive seasons (2011–2013) to determine the effect of irrigation treatments during oil synthesis on stem water potential (Ψstem), fruit characteristics, production, water productivity (production per irrigation amount + effective rainfall), flowering and fruit-set and next-year growth. The control treatments (C1 and L1) were irrigated to maintain the “wetted” bulb near field capacity throughout the season. Three deficit-irrigation treatments were established in each orchard. In orchard C, treatments C2, C3 and C4 received 64, 38, 14% of the water applied to C1, while in orchard L, treatments L2, L3 and L4 received 71, 41, 18% of water applied to L1. The treatments produced significant differences in Ψstem that were lower in Orchard C (mean C4 value −4.91 MPa) than L (L4 −2.58 MPa) due to differences in soil depth and drip emitter spacing. At the two orchards, individually, the stressed trees were not significantly affected in terms of shoot length, flowering, fruit set, fruit abscission and consequently fruit number. While deficit irrigation significantly reduced size, oil and water content of fruit, and hence olive and oil production in Orchard C, there was no response in Orchard L. Analysis revealed that individual fruit parameters were maintained constant as Ψstem decreased during oil synthesis in response to treatment until a threshold value was reached. Oil content (% fresh weight-FW) was the least sensitive parameter (threshold −4.11 MPa) with a positive linear relationship between water and oil fruit content (R2 = 0.81). Olive production was more sensitive to Ψstem (threshold −1.82 MPa) than oil production (−2.21 MPa). Indicating that moderate stress can be applied during oil synthesis by irrigating such that Ψstem declines to the threshold value −2.21 MPa without reduction of oil production. This value corresponds to a water-stress integral of 130 MPa day−1. Maximum water productivity was achieved by irrigating at Ψstem −2.31 MPa with lower values obtained at higher or lower Ψstem. Our results indicate that Ψstem should be maintained higher than −2.21 MPa during oil synthesis for maximum production, but higher values of the water productivity will be achieved at −2.31 MPa.

Assessing Spatial Variability of Grape Skin Flavonoids at the Vineyard Scale Based on Plant Water Status Mapping.

Plant water stress affects grape (Vitis vinifera L. cv. Cabernet Sauvignon) berry composition and is variable in space due to variations in the physical environment at the growing site. We monitored the natural variability of grapevine water stress by stem water potential (Ψstem) and leaf gas exchange in an equi-distant grid in a commercial vineyard. Spatial differences were measured and related to topographical variation by modeling. Geospatial analysis and clustering allowed researchers to differentiate the vineyard block into two distinct zones having severe and moderate water stress where it varied by 0.2 MPa. Differences in stem water potential affected stomatal conductance, net carbon assimilation, and intrinsic water use efficiency that were different in all measurement dates. The two zones were selectively sampled at harvest for measurements of berry chemistry. The water status zones did not affect berry mass or yield per vine. Significant difference in total soluble solids was observed (3.56 Brix), and in titratable acidity, thus indicating a direct effect of water stress on ripening acceleration. Berry skin flavonol and anthocyanin composition and concentration were measured by C18 reversed-phased high-performance liquid chromatography (HPLC). The anthocyanins were most affected by the two water stress zones. The dihydroxylated anthocyanins were more affected than trihydroxylated; therefore, the ratio of the two forms increased. Flavonols were different in total amounts, but hydroxylation patterns were not affected. Proanthocyanidin isolates were characterized by acid catalysis in the presence of excess phloroglucinol followed by reversed-phase HPLC. Proanthocyanidins showed the least significant difference, although (+)-catechin terminal subunits were important predictors in a partial least square model used to summarize the multivariate relationships, predicting Ψstem or the management zone. The results provide fundamental information on vineyard water status to discriminate harvest or direction to vineyard operators to modify irrigation management to equilibrate berry composition at harvest.

Usefulness of stem dendrometers as continuous indicator of loquat trees water status

Postharvest regulated deficit irrigation (RDI) is an effective strategy to hasten flowering and harvest in loquat (Eriobotrya japonica Lindl.) trees, which in the Mediterranean countries has been related to an increase in the economic return. The success of an RDI strategy, however, depends on the duration and severity of the water stress reached by the trees. When RDI is applied, then, it is important to regularly monitor the plant water status. The measurement of the trunk diameter variations by means of stem dendrometers, which can be automated to remotely determine the plant water status, is a proven method for many fruit trees. In loquat, however, its use has not been yet assessed. In this experiment performed in a loquat orchard planted with the cv. ‘Cardona’ during the summer of 2009, the suitability of using stem dendrometers to detect plant water stress was assessed by taking measurements in fully irrigated and trees subjected to a drought cycle of 47 days. Results showed that at the beginning of the drought cycle period there was an increase in the maximum daily trunk shrinkage (MDS) in non-irrigated trees even before that clear differences in stem water potential (Ψs) could be detected between treatments. However, when plant water stress became more severe (Ψs lower than −1.4MPa), MDS did not increase further. The maximum trunk diameter (MXTD) evolution in control trees showed a steadily increase in trunk growth during the whole experimental period. In non-irrigated trees, however, MXTD remained stable until the end of the treatment when irrigation was resumed. The Ψs was the most sensitive indicator to water stress due to its very low tree-to-tree variability in comparison with the other indicators. Overall results show that trunk diameter variations have some limitations to monitor plant water status in loquat RDI orchards and therefore new alternatives should be explored.

Effects of deficit irrigation applied during fruit growth period of late mandarin trees on harvest quality, cold storage and subsequent shelf-life

The quality traits of fruit harvested from ‘Fortune’ mandarin trees (Citrus clementina Hort. Ex. Tanaka×C. reticulata Blanco) subjected to different irrigation strategies was studied at harvest, during cold storage (33 d at 5°C), and after an additional shelf-life period of 5 d at 25°C. Plant water status was also determined in the pre-harvest period. Irrigation treatments consisted of a control irrigated at 100% of crop evapotranspiration throughout the season, and two deficit irrigation treatments irrigated during the fruit growth period to maintain the ratio between the fruit growth rate (FGR) of the control trees and those of the water deficit treatment (signal intensity, SIFGR) at two different water stress levels: (i) Severe (DI10) when this ratio was around 1.1 (SIFGR), and (ii) moderate (DI5) when it was around 1.05. The amount of water applied in DI10 and DI5 represented a reduction of 40% and 29%, respectively, compared with the control. No negative effects on the yield parameters studied were observed. During the second fruit growth stage, differences in stem water potential at midday of around 0.4 and 0.9MPa in DI5 and DI10 treatments, respectively, respect control promoted a significant decrease in FGR. Overall, both DI treatments improved fruit quality at harvest due to increased total soluble solids and juice proline content, fruit maintained their quality longer during storage than the control. Cold stored fruit of both DI treatments presented similar fruit hardness values but a higher juice proline content, total soluble solids and titratable acidity, and, as a consequence, a lower maturity index than the control. At the end of storage, DI fruit showed a thicker skin and lower commercial losses due to chilling injury.

Soil water depletion in irrigated mature pecans under contrasting soil textures for arid Southern New Mexico

Relationship between plant water stress and soil water depletion (SWD) is not investigated thoroughly for irrigated pecans of southern New Mexico. In this study, transient soil water contents, rootzone SWD, and midday stem water potential (SWP) were monitored in mature pecan orchards in sandy loam (Site 1) and silty clay loam (Site 2) soils near Las Cruces, New Mexico. Corresponding to transient variations of soil water content at different depths, daily SWD varied with soil depth but not spatially. The SWD within the rootzone (0–80 cm) was higher in the shallow depths (0–40 cm) where root length density (RLD) was also higher than in the deeper depths (40–80 cm). The SWD at Site 1 was higher compared to Site 2 due to the higher clay content of the latter. The SWD patterns at outside the tree driplines were similar to those under-canopy locations because of similar RLD at the shallow depths. At both pecan orchards, differences in SWP at 2.5, 4.5, and 7.6 m tree heights were evident particularly 10–14 days after irrigation. This was due to the stress caused by decreasing soil water contents at different depths, which were generally significantly correlated with SWP. Midday air temperature was as useful as midday atmospheric vapor pressure deficit for interpreting SWP. Combined influence of soil water content (0–40 cm) and air temperature on midday SWP was significant at both orchards, which can be used as an adjunct for the clear interpretation of SWP to help refine irrigation scheduling.

Effects of cluster thinning and irrigation amount on water relations, growth, yield and fruit and wine composition of Tempranillo grapes in Extemadura (Spain)

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Aim&lt;/strong&gt;: The effects of cluster thinning and irrigation regime on vine performance and grape and wine quality of Tempranillo grapevines were studied in a field experiment carried out in Extremadura in Spain.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Methods and results&lt;/strong&gt;: Treatments were combinations of two irrigation doses (25% and 100% of estimated crop evapotranspiration) and two crop levels (thinned and unthinned vines). Cluster thinning was performed just before veraison to retain five clusters per m2 of vine leaf area. Results showed that irrigation amount produced important differences in stem water potential, leaf area index and berry growth but cluster thinning did not significantly affect these parameters. However, cluster thinning independently of the irrigation amount, advanced by seven days grape maturity and largely affected the main grape quality parameters, increasing total soluble solids concentration, pH, total anthocyanins and phenolic content and reduced must yield. Wines made from grapes of the thinned treatments also had higher contents of anthocyanins, tanins and colour index. This increasing effect was more noticeable in the lower irrigation dose. Similarly, the higher irrigation amount reduced phenolic content of wines.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Conclusion&lt;/strong&gt;: Both, lower irrigation rates and cluster thinning, despite decreased yield, improved wine composition. Overall thinning had a larger impact on grape and wine composition than irrigation.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Significance and impact of study&lt;/strong&gt;: In the semi-arid environment of the Extremadura region of Spain, irrigation in Tempranillo is important to obtain economically sound yield. However, the irrigation dose to apply might vary depending on the desired wine style. Irrigation to replace potential evapotranspiration should be avoided for premium wine production and, in these cases; deficit irrigation is probably preferred as a tool to increase yields but minimizing the negative effects on fruit and wine quality. Cluster thinning, performed just before veraison, can be also applied to accelerate ripening improving the overall fruit phenolic composition.&lt;/p&gt;

Transpiration of the 'Rebula' cuttings (Vitis vinifera L.) grafted on three different rootstocks (Vitis sp.)

The purpose of the investigation was to determine the use of water in grafted vines (Vitis vinifera L.) in dependence on the vine (Vitis sp.) rootstocks. The local vine variety 'Rebula' was grafted on three different rootstocks (Vitis sp.): (1) on the 'Rebula' (Vitis vinifera L.) vine itself, (2) on the rootstock 196/17 Castel' [(Vitis vinifera 'Mourvèdre' x Vitis rupestris '1202 Couderc') x Vitis riparia 'Gloire'] and (3) on the rootstock 'Börner' (Vitis riparia x Vitis cinerea). Daily transpiration was calculated as a difference in the pot mass between the day of measurement and the previous day. Daily differences in the use of water were compared with leaf area and meteorological data (temperature, duration of sun light). Stem water potential (SWP) and, at the end of the trial, leaf area and mass of individual parts of plant (roots, shoot) were determined using destructive method. The dynamics of water used per leaf area unit showed the trend of reduction and the response to the changing meteorological conditions. No statistically significant differences in SWP, leaf area and water used were noticed between rootstocks, however, they existed in the final mass of shoot and roots.

Transpiration of the ‘Rebula’ cuttings (Vitis vinifera L.) grafted on three different rootstocks (Vitis sp.)

The purpose of the investigation was to determine the use of water in grafted vines (Vitis vinifera L.) in dependence on the vine (Vitis sp.) rootstocks. The local vine variety 'Rebula' was grafted on three different rootstocks (Vitis sp.): (1) on the 'Rebula' (Vitis vinifera L.) vine itself, (2) on the rootstock 196/17 Castel' [(Vitis vinifera 'Mourvedre' x Vitis rupestris '1202 Couderc') x Vitis riparia 'Gloire'] and (3) on the rootstock 'Borner' (Vitis riparia x Vitis cinerea). Daily transpiration was calculated as a difference in the pot mass between the day of measurement and the previous day. Daily differences in the use of water were compared with leaf area and meteorological data (temperature, duration of sun light). Stem water potential (SWP) and, at the end of the trial, leaf area and mass of individual parts of plant (roots, shoot) were determined using destructive method. The dynamics of water used per leaf area unit showed the trend of reduction and the response to the changing meteorological conditions. No statistically significant differences in SWP, leaf area and water used were noticed between rootstocks, however, they existed in the final mass of shoot and roots.

Olive oil production as influenced by different quantities of applied water

Irrigation management can have a profound influence on olive oil production. We initiated a 2-year study in the spring of 2002 to identify the optimal level of applied water on a super high tree-density (spacing 1.5 m × 3.9 m) olive ( Olea europaea L.‘Arbequina I-18’) orchard. Irrigation water was applied by drip irrigation to produce different water-application treatments of 15, 25, 40, 57, 71, 89, and 107% ET of non-stressed trees in 2002 and 28, 33, 55, 74, 93, 117, and 140% ET in 2003. Tree growth was monitored by changes in trunk diameter and branch length and their increases over the season were very responsive to irrigation treatments. Mid-day stem water potentials (SWP) were measured periodically throughout the season and values ranged between −0.2 and −4.1 MPa. Differences in stem water potential were consistent with the irrigation treatments and decreased with reduced water applications after stored soil water was depleted. Stable isotope discrimination was an effective indicator of seasonal tree-stress experience and increased in a second order function to the applied water. Fruits were harvested at two different times at the end of each season to evaluate treatment effect in relation to harvest date. At each harvest, fruit production (kg/ha) followed a second order relationship ( r 2 = 0.79–0.99) with applied water. Olive oil was extracted using the Abencor method and the percentage of oil extracted from the fruit decreased linearly ( r 2 = 0.91–0.93) with increased applied water for three out of the four harvests. The overall quantity of oil extracted per area followed a second order function ( r 2 = 0.71–0.94) in three of the four harvests. In 2003, there was a poorer correlation ( r 2 = 0.56) between oil yields and irrigation treatment for the earlier harvest. However, for the second harvest, total oil yield per tree increased with applied water reaching a maximum at 408 mm (75% ET). Data from both harvests in 2002, on the other hand, indicate that an optimum oil extraction is achieved over a wide range of treatments (i.e. 196–491 mm (ET c 40–89%)). Therefore, our data indicate that oil yields can be maximized over a rather broad range of applied water because increases in fruit yield with increased applied water can be off-set to a large extent by the reduction in the percentage of oil extracted. Oil quality must also be considered when optimizing the amount of applied water.

Optimization of irrigation water use in grapevines using the relationship between transpiration and plant water status

Abstract The study was carried out in order to evaluate the thresholds of grapevine internal water status as well as to propose an irrigation management technique that permits the uninterrupted photosynthetic process under drought conditions. The relationships between water relation, gas exchange parameters and sap flow measurements were examined in field grown grapevines ( Vitis vinifera L., cv. Malagouzia) subjected to various levels of water stress. The differences in stem water potential were greater between the treatments compared to leaf water potential indicating that stem water potential represents a more reliable indicator of plant water status. Stomatal conductance and photosynthetic rate were significantly lower in stressed treatments while stomatal sensitivity to changes in vapor pressure deficit seems to be higher in stressed than in well-watered treatment. Maximum diurnal sap flow rates were recorded early in the morning in all treatments and decreased in water stressed treatments over the stress cycle. The SF Ti /SF T1 ratio (SF T1 = mean daily sap flow of the fully irrigated plants; SF Ti = mean sap flow of the stressed plants) also decreased in water stressed treatments. The close relationship between the SF Ti /SF T1 ratio and stem water potential values could be used in developing a sap flow based technique for automatically controlling the irrigation system in field grown grapevines.