Midday Stem Water Potential Values Needed to Maintain Photosynthesis and Leaf Gas Exchange Established for Pecan

Demand for New Mexico’s limited water resources coupled with periodic drought has increased the necessity for tree water status monitoring to guide irrigation scheduling of pecan (Carya illinoinensis) orchards. The objectives of this study were to assess the impact of water status developed during the flood irrigation dry-down cycles on photosynthesis (Pn), and gas exchange [stomatal conductance (gS) to H2O (gH2O), transpiration (E), and intercellular CO2 (ci)] and to establish values of midday stem water potential (Ψsmd) that are needed to maintain Pn and gas exchange of pecan. We conducted the study simultaneously on two southern New Mexico mature pecan orchards from 2011 through 2013. Flood irrigation as determined by grower practice was used on both orchards and Pn, gH2O, E, and ci were assessed at Ψsmd of –0.4 to –2.0 MPa. Photosynthesis and gas exchange were higher in pecan trees shortly after irrigation than trees exhibiting water deficit near the end of a flood irrigation dry-down cycle. The decline in Pn was markedly noticeable when Ψsmd dropped below –0.9 MPa. We attributed the reduction in Pn mostly to stomatal limitation. The decline in Pn and gH2O exceeded 50% when Ψsmd ranged from –1.5 to –2.0 MPa. For those reasons, we recommended that pecan orchards be maintained at Ψsmd higher than –0.90 MPa to prevent significant reductions in carbon assimilation and gas exchange.

Download Full-text

Partial rootzone drying improves almond tree leaf-level water use efficiency and afternoon water status compared with regulated deficit irrigation

Functional Plant Biology ◽

10.1071/fp10247 ◽

2011 ◽

Vol 38 (5) ◽

pp. 372 ◽

Cited By ~ 24

Author(s):

Gregorio Egea ◽

Ian C. Dodd ◽

María M. González-Real ◽

Rafael Domingo ◽

Alain Baille

Keyword(s):

Gas Exchange ◽

Water Potential ◽

Leaf Gas Exchange ◽

Water Status ◽

Stem Water Potential ◽

Regulated Deficit Irrigation ◽

Leaf Level ◽

Use Efficiency ◽

Stem Water ◽

Partial Rootzone Drying

To determine whether partial rootzone drying (PRD) optimised leaf gas exchange and soil–plant water relations in almond (Prunus dulcis (Mill.) D.A. Webb) compared with regulated deficit irrigation (RDI), a 2 year trial was conducted on field-grown trees in a semiarid climate. Five irrigation treatments were established: full irrigation (FI) where the trees were irrigated at 100% of the standard crop evapotranspiration (ETc); three PRD treatments (PRD70, PRD50 and PRD30) that applied 70, 50 and 30% ETc, respectively; and a commercially practiced RDI treatment that applied 50% ETc during the kernel-filling stage and 100% ETc during the remainder of the growth season. Measurements of volumetric soil moisture content in the soil profile (0–100 cm), predawn leaf water potential (Ψpd), midday stem water potential (Ψms), midday leaf gas exchange and trunk diameter fluctuations (TDF) were made during two growing seasons. The diurnal patterns of leaf gas exchange and stem water potential (Ψs) were appraised during the kernel-filling stage in all irrigation regimes. When tree water relations were assessed at solar noon, PRD did not show differences in either leaf gas exchange or tree water status compared with RDI. At similar average soil moisture status (adjudged by similar Ψpd), PRD50 trees had higher water status than RDI trees in the afternoon, as confirmed by Ψs and TDF. Although irrigation placement showed no effects on diurnal stomatal regulation, diurnal leaf net photosynthesis (Al) was substantially less limited in PRD50 than in RDI trees, indicating that PRD improved leaf-level water use efficiency.

Download Full-text

Tolerance of lowbush blueberries (Vaccinium angustifolium Ait.) to drought stress. II. Leaf gas exchange, stem water potential and dry matter partitioning

Canadian Journal of Plant Science ◽

10.4141/p03-028 ◽

2005 ◽

Vol 85 (4) ◽

pp. 919-927 ◽

Cited By ~ 3

Author(s):

V. M. Glass ◽

D. C. Percival ◽

J. T.A. Proctor

Keyword(s):

Soil Moisture ◽

Drought Stress ◽

Gas Exchange ◽

Water Potential ◽

Stomatal Density ◽

Leaf Gas Exchange ◽

Water Status ◽

Stem Water Potential ◽

Vaccinium Angustifolium ◽

Stem Water

A 2-yr field study examining the effect of soil moisture on plant water status, photosynthesis and gas exchange parameters in lowbush blueberry (Vaccinium angustifolium Ait.) was conducted at the Nova Scotia Wild Blueberry Institute (NSWBI), Debert, NS. Drought and irrigation treatments were applied over two years in either or both the vegetative and cropping years of production. Midday stem water potential values indicated that all treatments resulted in drought stress. Mean stem water potential values ranged from -1.41 to -1.45 MPa. Predawn stem water potentials in the vegetative growth season indicated that although some recharging and recovery of water loss occurred overnight, the drought-stressed plants did not fully return to pre-stress levels under the moisture-limiting conditions. Higher chlorophyll a and b levels were observed in the single-season drought treatment. Leaves of irrigated plants in both sprout and crop years had the highest stomatal density. There were no differences in photosynthetic rate (Pn) among treatments despite the lower stomatal conductance resulting from limited soil moisture. Key words: Photosynthesis, stomate, stem water potential

Download Full-text

Microtensiometers Accurately Measure Stem Water Potential in Woody Perennials

Plants ◽

10.3390/plants10122780 ◽

2021 ◽

Vol 10 (12) ◽

pp. 2780

Author(s):

Victor Blanco ◽

Lee Kalcsits

Keyword(s):

Water Potential ◽

Leaf Gas Exchange ◽

Water Status ◽

Full Range ◽

Canopy Temperature ◽

Plant Water ◽

Stem Water Potential ◽

Woody Tissue ◽

Woody Perennials ◽

Stem Water

Stem water potential (Ψstem) is considered to be the standard measure of plant water status. However, it is measured with the pressure chamber (PC), an equipment that can neither provide continuous information nor be automated, limiting its use. Recent developments of microtensiometers (MT; FloraPulse sensors), which can continuously measure water tension in woody tissue of the trunk of the tree, can potentially highlight the dynamic nature of plant water relations. Thus, this study aimed to validate and assess the usefulness of the MT by comparing the Ψstem provided by MT with those same measurements from the PC. Here, two irrigation treatments (a control and a deficit treatment) were applied in a pear (Pyrus communis L.) orchard in Washington State (USA) to capture the full range of water potentials in this environment. Discrete measurements of leaf gas exchange, canopy temperature and Ψstem measured with PC and MT were made every two hours for four days from dawn to sunset. There were strong linear relationships between the Ψstem-MT and Ψstem-PC (R2 > 0.8) and with vapor pressure deficit (R2 > 0.7). However, Ψstem-MT was more variable and lower than Ψstem-PC when Ψstem-MT was below −1.5 MPa, especially during the evening. Minimum Ψstem-MT occurred later in the afternoon compared to Ψstem-PC. Ψstem showed similar sensitivity and coefficients of variation for both PC and MT acquired data. Overall, the promising results achieved indicated the potential for MT to be used to continuously assess tree water status.

Download Full-text

Correlations among Predawn Leaf, Midday Leaf, and Midday Stem Water Potential and their Correlations with other Measures of Soil and Plant Water Status in Vitis vinifera

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.127.3.448 ◽

2002 ◽

Vol 127 (3) ◽

pp. 448-454 ◽

Cited By ~ 143

Author(s):

L.E. Williams ◽

F.J. Araujo

Keyword(s):

Vitis Vinifera ◽

Water Potential ◽

Leaf Water Potential ◽

Leaf Gas Exchange ◽

Water Status ◽

Linear Regression Analysis ◽

Leaf Water ◽

Stem Water Potential ◽

Stem Water ◽

Water Potential Measurements

A study was conducted to compare three measurements of determining water status of grapevines (Vitis vinifera L.) in the field. Predawn leaf water potential (ΨPD), midday leaf water potential (Ψl), and midday stem water potential (Ψstem) were measured on `Chardonnay' and `Cabernet Sauvignon' grapevines grown in Napa Valley, California late in the 1999 growing season. Both cultivars had been irrigated weekly at various fractions (0, 0.5, and 1.0 for `Chardonnay' and 0, 0.5, 0.75, and 1.5 for `Cabernet') of estimated vineyard evapotranspiration (ETc) from approximately anthesis up to the dates of measurements. Predawn water potential measurements were taken beginning at 0330 hr and completed before sunrise. Midday Ψl and Ψstem measurements were taken only between 1230 and 1330 hr. In addition, net CO2 assimilation rates (A) and stomatal conductance to water vapor (gs) were also measured at midday. Soil water content (SWC) was measured in the `Chardonnay' vineyard using a neutron probe. Values obtained for ΨPD, Ψl, and Ψstem in this study ranged from about -0.05 to -0.8, -0.7 to -1.8, and -0.5 to -1.6 MPa, respectively. All three measurements of vine water status were highly correlated with one another. Linear regression analysis of Ψl and Ψstem versus ΨPD resulted in r2 values of 0.88 and 0.85, respectively. A similar analysis of Ψl as a function of Ψstem resulted in an r2 of 0.92. In the `Chardonnay' vineyard, all three methods of estimating vine water status were significantly (P < 0.01) correlated with SWC and applied amounts of water. Lastly, ΨPD, Ψl, and Ψstem were all linearly correlated with measurements of A and gs at midday. Under the conditions of this study, ΨPD, Ψl, and Ψstem represent equally viable methods of assessing the water status of these grapevines. They were all correlated similarly with the amount of water in the soil profile and leaf gas exchange as well as with one another.

Download Full-text

Variation in scion water relations mediated by two newly released Geneva series rootstocks

10.1101/2021.07.20.453132 ◽

2021 ◽

Author(s):

Erica Casagrande Biasuz ◽

Lee Kalcsits

Keyword(s):

Stomatal Conductance ◽

Gas Exchange ◽

Water Potential ◽

Water Relations ◽

Isotope Composition ◽

Water Status ◽

Physiological Traits ◽

Stem Water Potential ◽

Carbon And Oxygen Isotope ◽

Stem Water

Dwarfing rootstocks are used to control tree vigor allowing for increased densities that increase apple production. Although there is considerable variation among rootstocks in dwarfing capacity, the mechanisms by which rootstocks affect vigor in apple scions remains unclear. Here, Honeycrisp apple growth and water relations were compared among three rootstocks; M-9 as the industry standard and two less studied Geneva series rootstocks; G.87 and G. 814 in Washington, USA. Trees were acquired from a commercial nursery and planted in 2017. In 2018 and 2019, scion physiological, isotopic and morphological traits were measured to better understand the link between rootstock-driven vigor and physiological traits. Rootstock affected scion shoot growth (P <0.001), stomatal conductance (P< 0.01) and stem water potential (P <0.001). Rootstocks with low vegetative vigor like M.9 also had lower stomatal conductance and enriched leaf δ13C and δ18O isotope composition. Plant growth was positively correlated with stomatal conductance and stem water potential. Rootstocks also affected plant water status and net gas exchange. Here, we report an association between rootstock-induced vigor and scion physiological traits such as gas exchange, stem water potential, and leaf carbon and oxygen isotope composition. This research has implications for the understanding of the mechanisms of dwarfing by rootstocks in apple.

Download Full-text

Physiological Response of Carambola Trees to Soil Water Depletion in Krome Soils

HortScience ◽

10.21273/hortsci.39.4.857b ◽

2004 ◽

Vol 39 (4) ◽

pp. 857B-857

Author(s):

Rashid Al-Yahyai* ◽

Bruce Schaffer ◽

Frederick S. Davies

Keyword(s):

Stomatal Conductance ◽

Gas Exchange ◽

Water Potential ◽

Soil Water ◽

Leaf Gas Exchange ◽

Stem Water Potential ◽

Soil Water Depletion ◽

Water Depletion ◽

Loam Soil ◽

Stem Water

The effect of soil water depletion on plant water potential and leaf gas exchange of carambola (Averrhoa carambola L. cv. Arkin) in Krome very gravelly loam soil was studied in an orchard and in containers in the field and in a greenhouse. The rate of soil water depletion was determined by continuously monitoring soil water content with multi-sensor capacitance probes. Stem water potential and leaf gas exchange of carambola in containers were reduced when the soil water depletion level fell below 50% (where field capacity = 100%). Although there was a decrease in the rate of soil water depletion in the orchard as the soil dried, soil water depletion did not go below an average of 70%. This was presumably due to sufficient rainfall and capillary movement of water in the soil. Therefore, soil water content did not decline sufficiently to affect leaf gas exchange and leaf and stem water potential of orchard trees. A decline in soil water depletion below 40% resulted in a concomitant decline in stem water potential of the container trees in the field and greenhouse to below -1.0 MPa. Stomatal conductance, net CO2 assimilation, and transpiration declined significantly when stem water potential was below -1.0 MPa. The reduction of net CO2 assimilation and transpiration was proportional to the decline in stomatal conductance of container trees in the field and greenhouse. Thus, soil water depletion in Krome very gravelly loam soil must be less than 50% before water potential or leaf gas exchange of carambola is affected. Based on these results, irrigation scheduling should be based on physiological variables such as stem water potential and stomatal conductance or the amount rather than the rate of soil water depletion.

Download Full-text

593 A Lightweight, Hand-operated Pressure Chamber for Determining Plant Water Status

HortScience ◽

10.21273/hortsci.35.3.499b ◽

2000 ◽

Vol 35 (3) ◽

pp. 499B-499

Author(s):

Ken Shackel ◽

David Paige

Keyword(s):

Water Potential ◽

Water Status ◽

Irrigation Management ◽

Nitrogen Pressure ◽

Irrigation Scheduling ◽

Pressure Chamber ◽

Plant Water ◽

Stem Water Potential ◽

Stem Water ◽

Time Required

In a number of tree crops, we have found that the water potential of lower canopy, nontranspiring leaves, measured with the pressure chamber at midday (midday stem water potential), is an excellent index of plant water stress and can be used for irrigation scheduling. Because stem water potential is typically much higher than transpiring leaf water potential, a lower pressure is required for the measurement, allowing us to design and build a lightweight device that could be easily operated by hand. The prototype was designed for pressures up to 2 MPa, which is sufficient for most irrigation conditions. A number of design features were incorporated into the sealing gland to eliminate the need for retightening during the pressurization process, reduce the amount of tissue external to the pressure chamber, and allow a greater visibility of the petiole. Identical values to those obtained with the standard, compressed nitrogen pressure chamber were obtained over the entire 2-MPa range, and the time required using either device under field conditions was the same (about 1 min per measurement). A number of alternative protocols were tested, and we found that even substantial recutting of the petiole had no influence on the measured water potential, contrary to popular belief. We also found that the same sample could be remeasured multiple times (five), with no net change in the water potential, allowing the measurement to be checked if necessary. This device should be of great utility in field irrigation management.

Download Full-text

Rapid Equilibration of Leaf and Stem Water Potential under Field Conditions in Almonds, Walnuts, and Prunes

HortTechnology ◽

10.21273/horttech.11.4.609 ◽

2001 ◽

Vol 11 (4) ◽

pp. 609-615 ◽

Cited By ~ 36

Author(s):

Allan Fulton ◽

Richard Buchner ◽

Cyndi Gilles ◽

Bill Olson ◽

Nick Bertagna ◽

...

Keyword(s):

Sample Size ◽

Water Potential ◽

Water Status ◽

Irrigation Management ◽

Irrigation Scheduling ◽

Field Conditions ◽

Equilibration Time ◽

Diurnal Changes ◽

Stem Water Potential ◽

Stem Water

Covering a plant leaf with a reflective, water impervious bag ensures that equilibrium is reached between the nontranspiring leaf and the stem, and appears to improve the accuracy of determining plant water status under field conditions. However, the inconvenience of covering the leaf for 1 to 2 hours before measuring stem water potential (SWP) has constrained on-farm adoption of this irrigation management technique. A second constraint has been that the requirement of midafternoon determinations limits the area that can be monitored by one person with a pressure chamber. This paper reports findings from field studies in almonds (Prunus dulcis),prunes (P. domestica), and walnuts (Juglans regia) demonstrating modified procedures to measure midday SWP, making it a more convenient and practical tool for irrigation management. For routine monitoring and irrigation scheduling, an equilibration period of 10 min or longer appears to be suitable to provide accurate SWP measurements. Based on the large sample sizes in this study, we estimate that measurement error related to equilibration time for SWP can be reduced to an acceptable level [0.05 MPa (0.5 bar)] with a sample size of about 10 leaves when using a 10-min equilibration period. Under orchard conditions where tree growth and health appears uniform, a sample of one leaf per tree and 10 trees per irrigation management unit should give an accurate mean indicator of orchard water status. Under more variable orchard conditions a larger sample size may be needed. Midmorning and midday SWP both exhibited similar seasonal patterns and responded alike to irrigation events. On some occasions, midday SWP was accurately predicted from midmorning SWP and the change in air vapor pressure deficit (VPD) from midmorning to midday, but both over- and underestimate errors [to 0.3 MPa (3.0 bar)] appeared to be associated with unusually low or high diurnal changes in VPD, respectively. Hence, direct measurement of SWP under midday conditions (about 1300 to 1500 hr) is still recommended.

Download Full-text

An Index for User-Friendly Proximal Detection of Water Requirements to Optimized Irrigation Management in Vineyards

Agronomy ◽

10.3390/agronomy11020323 ◽

2021 ◽

Vol 11 (2) ◽

pp. 323

Author(s):

Ana Fernandes de Oliveira ◽

Massimiliano Giuseppe Mameli ◽

Mauro Lo Cascio ◽

Costantino Sirca ◽

Daniela Satta

Keyword(s):

Water Potential ◽

Leaf Gas Exchange ◽

Water Status ◽

Water Productivity ◽

Linear Regression Analysis ◽

Plant Water Status ◽

Plant Water ◽

Stem Water Potential ◽

Water Requirements ◽

Stem Water

We propose an index for proximal detection of water requirements to optimize the use of water resources in arid and semi-arid wine growing regions. To test the accuracy and representativeness of the proposed irrigation need index (IIN), plant water status and physiological performances were monitored during seasons 2019 and 2020 in two grapevine varieties with different anisohydric degree (Vermentino and Cannonau) grown in 3 sites in Sardinia (Italy). Daily leaf gas exchange curves and stem water potential were recorded. Canopy temperature was monitored, using both thermistor sensors (Tc) and infrared thermometry (IR). Meteorological data, including dry and wet bulb temperatures were collected to compute and parametrize IIN, based on energy balance equation. Vineyard water balance, thermal time and irrigation water productivity were characterized. Linear regression analysis allowed to validate IIN for both varieties and to establish target thresholds for mild, moderate and severe water deficit to optimize irrigation for high yield and quality objectives. IIN well represents plant water status, using either Tc or IR, and allows rapid and easy detection of water and heat stress condition, even when a stricter stomatal control determines slighter variation and lower response of stem water potential, as in plants with low anisohydric degree.

Download Full-text

Physiological Effects of Mechanical Harvesting in Citrus Trees

HortScience ◽

10.21273/hortsci.39.4.885c ◽

2004 ◽

Vol 39 (4) ◽

pp. 885C-885

Author(s):

Kuo-Tan Li* ◽

James P. Syvertsen

Keyword(s):

Gas Exchange ◽

Water Potential ◽

Leaf Gas Exchange ◽

Fluorescence Emission ◽

Stem Water Potential ◽

Long Term Effects ◽

Significant Treatment ◽

Linear Type ◽

Stem Water ◽

Citrus Trees

Mechanical harvesting of citrus trees by trunk or canopy shakers can cause leaf and twig removal, bark injury and root exposure. Such problems have restricted the adoption of mechanical harvesting in Florida citrus. We assessed physiological responses of citrus trees that were mechanically harvested with a linear-type trunk shaker, operating at 4 Hz, 70.8 kg mass weight, and 6.5 cm displacement, for 10 or 20 seconds. We measured fruit recovery efficiency, leaf and shoot removal, mid-day stem water potential, leaf gas exchange, and leaf fluorescence emission of mature `Hamlin' and `Valencia' orange trees under restricted or normal irrigation. Shaking treatments effectively removed 90% to 94% of fruit without bark damage. Compared to harvesting by hand, trunk shaking removed 10% more leaf area and twigs, and caused some visible exposure of fibrous roots at the soil surface. There were no significant treatment differences on mid-day stem water potential, leaf gas exchange, and leaf photosystem efficiency. Excessively shaken trees for 20-30 seconds can temporary induce stress symptoms resembling that in trees without irrigation. Trees may have benefited from the low levels of leaf and twig loss after trunk shaking that compensated for any root loss. Long-term effects of trunk shaking will be assessed by tree growth, return bloom, subsequent yield, and carbohydrate reserves.

Download Full-text