Frost Resistance in .Eucalyptus nitens (Deane & Maiden) Maiden: Physiological Aspects of Hardiness

1987 ◽  
Vol 35 (3) ◽  
pp. 235 ◽  
Author(s):  
WN Tibbits ◽  
JB Reid
Keyword(s):  
Water Stress ◽  
Frost Resistance ◽  
Water Status ◽  
The Other ◽  
Plant Water ◽  
Eucalyptus Nitens ◽  
Critical Temperatures ◽  
Daily Amount ◽  
Seedling Roots ◽  
Resistance Rates

The effects of photoperiod, temperature regime and differential root and shoot temperatures on frost resistance were examined in both hardening and dehardening Eucalyptus nitens seedlings. Frost resist- ance was primarily determined by measuring the relative loss of electrolytes from frosted leaf discs. This method of assessing frost resistance compares favourably with the frosting of whole seedlings since the critical temperatures producing 50% leaf death in whole seedlings and the leakage of 50% of cellular electrolytes (T50) agreed to within 0.6°C after 14 and 28 days' hardening. Unhardened seedlings had T50 values of - 3.4°C. Seedlings hardening over a 56 day period, at night temperatures of 3°C for 16 h and days of 13-25°C, steadily increased in frost resistance to T50 values of -7.5°C. Reducing the daily amount of hardening temperature from 16 to 8 h produced seedlings that were over 1.0°C less frost resistant at the end of 42 days' hardening. On the other hand, seedlings exposed to a constant 3°C, day and night, suffered considerable water stress and were unable to harden beyond -5.8°C, even after 77 days. Heating seedling roots to between 6 and 18°C throughout the 3°C regime maintained high plant water status but did not confer any increased frost resistance. Rates of dehardening in well hardened seedlings increased with increasing day and 1 or night tempera- ture in the range 6-20°C. Seedlings exposed to 14 h nights at 6.0°C, just 3°C warmer than the hardening temperatures used, were unable to maintain T50 levels of -7.5°C and dehardened by 2.5°C over a 3-week period. The dehardening rate of leaves from seedlings exposed to an air temperature of 18°C day and night was significantly reduced if roots were exposed to 3°C.

Single hyperspectral bands are highly sensitive to water stress in adult mandarin trees

2021 ◽  
Author(s):  
Pablo Berríos ◽  
Abdelmalek Temnani ◽  
Susana Zapata ◽  
Manuel Forcén ◽  
Sandra Martínez-Pedreño ◽  
...  
Keyword(s):  
Water Stress ◽  
Water Deficit ◽  
Phase Ii ◽  
Irrigation Water ◽  
Water Status ◽  
Irrigation Scheduling ◽  
Plant Water Status ◽  
Phase Iii ◽  
Plant Water ◽  
Severe Water Stress

<p>Mandarin is one of the most important Citrus cultivated in Spain and the sustainability of the crop is subject to a constant pressure for water resources among the productive sectors and to a high climatic demand conditions and low rainfall (about 250 mm per year). The availability of irrigation water in the Murcia Region is generally close to 3,500 m<sup>3</sup> per ha and year, so it is only possible to satisfy 50 - 60% of the late mandarin ETc, which requires about 5,500 m<sup>3</sup> per ha. For this reason, it is necessary to provide tools to farmers in order to control the water applied in each phenological phase without promoting levels of severe water stress to the crop that negatively affect the sustainability of farms located in semi-arid conditions. Stem water potential (SWP) is a plant water status indicator very sensitive to water deficit, although its measurement is manual, discontinuous and on a small-scale.  In this way, indicators measured on a larger scale are necessary to achieve integrating the water status of the crop throughout the farm. Thus, the aim of this study was to determine the sensitivity to water deficit of different hyperspectral single bands (HSB) and their relationship with the midday SWP in mandarin trees submitted to severe water stress in different phenological phases. Four different irrigation treatments were assessed: i) a control (CTL), irrigated at 100% of the ETc throughout the growing season to satisfy plant water requirements and three water stress treatments that were irrigated at 60% of ETc throughout the season – corresponding to the real irrigation water availability – except  during: ii) the end of phase I and beginning of phase II (IS IIa), iii) the first half of phase II (IS IIb) and iv) phase III of fruit growth (IS III), which irrigation was withheld until values of -1.8 MPa of SWP or a water stress integral of 60 MPa day<sup>-1</sup>. When these threshold values were reached, the spectral reflectance values were measured between 350 and 2500 nm using a leaf level spectroradiometer to 20 mature and sunny leaves on 4 trees per treatment. Twenty-four HVI and HSB were calculated and a linear correlation was made between each of them with SWP, where the ρ940 and ρ1250 nm single bands reflectance presented r-Pearson values of -0.78** and -0.83***, respectively. Two linear regression curves fitting were made: SWP (MPa) = -11.05 ∙ ρ940 + 7.8014 (R<sup>2</sup> =0.61) and SWP (MPa) = -13.043 ∙ ρ1250 + 8.9757 (R<sup>2</sup> =0.69). These relationships were obtained with three different fruit diameters (35, 50 and 65 mm) and in a range between -0.7 and -1.6 MPa of SWP. Results obtained show the possibility of using these single bands in the detection of water stress in adult mandarin trees, and thus propose a sustainable and efficient irrigation scheduling by means of unmanned aerial vehicles equipped with sensors to carry out an automated control of the plant water status and with a suitable temporal and spatial scale to apply precision irrigation.</p>

Stomatal conductance and growth of five Alnusglutinosa clones in response to controlled water stress

1988 ◽  
Vol 18 (4) ◽  
pp. 421-426 ◽  
Author(s):  
T. C. Hennessey ◽  
E. M. Lorenzi ◽  
R. W. McNew
Keyword(s):  
Water Stress ◽  
Stomatal Conductance ◽  
Drought Tolerance ◽  
Leaf Area ◽  
Water Status ◽  
Height Growth ◽  
Plant Water ◽  
Black Alder ◽  
Severe Water Stress ◽  
Progressive Water Stress

An experiment to quantify the response of unnodulated, fertilized European black alder (Alnusglutinosa (L.) Gaertn.) seedlings to progressive water stress showed contrasting drought tolerance among five clones, using stomatal conductance, leaf area, and height as indices of drought sensitivity. In particular, one rapidly growing clone (AG 8022-14) showed the ability to moderate changes in water stress more efficiently than the more slowly growing clones. After 30 days of moderate levels of water stress, clones that had higher stomatal conductance also had greater leaf area and height growth. Leaf area and height were both sensitive to plant water status, although no threshold of stress associated with a cessation of leaf area or height expansion was found even though stomatal conductance decreased to 0.05 cm s−1 under severe water stress.

Development of a Continuous Leaf Monitoring System to Predict Plant Water Status

2017 ◽  
Vol 60 (5) ◽  
pp. 1445-1455 ◽  
Author(s):  
Rajveer S. Dhillon ◽  
Shrini K. Upadhaya ◽  
Francisco Rojo ◽  
Jed Roach ◽  
Robert W. Coates ◽  
...  
Keyword(s):  
Water Stress ◽  
Data Collection ◽  
Water Status ◽  
Irrigation Scheduling ◽  
Leaf Temperature ◽  
Plant Water Status ◽  
Mesh Network ◽  
Plant Water ◽  
Plant Water Stress ◽  
Precision Irrigation

Abstract. There is increased demand for irrigation scheduling tools that support effective use of the limited supply of irrigation water. An efficient precision irrigation system requires water to be delivered based on crop needs by measuring or estimating plant water stress. Leaf temperature is a good indicator of water stress. In this study, a system was developed to monitor leaf temperature and microclimatic environmental variables to predict plant water stress. This system, called the leaf monitor, monitored plant water status by continuously measuring leaf temperature, air temperature, relative humidity, ambient light, and wind conditions in the vicinity of a shaded leaf. The system also included a leaf holder, a solar radiation diffuser dome, and a wind barrier for improved performance of the unit. Controlled wind speed and consistent light conditions were created around the leaf to reduce the effect of nuisance variables on leaf temperature. The leaf monitor was incorporated into a mesh network of wireless nodes for sensor data collection and remote valve control. The system was evaluated for remote data collection in commercial orchards. Experiments were conducted during the 2013 and 2014 growing seasons in walnut () and almond () orchards. The system was found to be reliable and capable of providing real-time visualization of the data remotely, with minimal technical problems. Leaf monitor data were used to develop modified crop water stress index (MCWSI) values for quantifying plant water stress levels. Keywords: Almonds, CWSI, Infrared sensor, Irrigation scheduling, Leaf temperature, Nut crops, Plant water stress, Precision irrigation, Stem water potential, Walnuts, Wireless mesh network.

Cortical Intracellular Electrical Potential in Roots of Unstressed and Stressed Sunflower Seedlings. I. Dependence on Water Status

1997 ◽  
Vol 24 (5) ◽  
pp. 643 ◽  
Author(s):  
P. M. Cortes
Keyword(s):  
Water Stress ◽  
Helianthus Annuus ◽  
Nutrient Solution ◽  
Lateral Root ◽  
Water Status ◽  
Electrical Potential ◽  
Cortical Cells ◽  
Seedling Roots ◽  
Low Levels ◽  
Intact Roots

The intracellular electrical potential (Ec) was measured with a microelectrode in cortical cells of intact roots of sunflower (Helianthus annuus) seedlings subjected to differing levels of water stress and illumination. Water stress was rapidly imposed and relieved by lowering and raising the level of nutrient solution in a tank which contained all the seedling roots except the lateral root in which Ec was measured. The base value of Ec for unstressed, illuminated seedlings was –120 mV. When placed in the dark, a small reversible depolarisation of approximately 10 mV could be measured in roots of seedlings grown under low levels of radiation but was not evident in seedlings grown under high levels of radiation. The imposition of and relief from extreme water stress (leaves and apex severely wilted) resulted in a reversible depolarisation of approximately 50 mV. The effect of water stress was greatly reduced by the presence of sucrose and glucose in the nutrient solution perfusing the 30 mm portion of the lateral root in which Ec was measured. It appears likely that the variation in potential was mediated by a reduction in the supply of photosynthate to the roots.

scholarly journals Effect of Fall Irrigation Level in `Mauritius' and `Floridian' Lychee on Soil and Plant Water Status, Flowering Intensity, and Yield

1998 ◽  
Vol 123 (1) ◽  
pp. 150-155 ◽  
Author(s):  
R.A. Stern ◽  
M. Meron ◽  
A. Naor ◽  
R. Wallach ◽  
B. Bravdo ◽  
...  
Keyword(s):  
Water Stress ◽  
Water Potential ◽  
Shoot Growth ◽  
Water Status ◽  
Plant Water ◽  
Stem Water Potential ◽  
Irrigation Level ◽  
Irrigation Control ◽  
Stem Water ◽  
Flowering Intensity

The effect of fall irrigation level in `Mauritius' and `Floridian' lychee (Litchi chinensis Sonn.) on soil and plant water status, flowering intensity, and yield the following year was studied in a field during 2 consecutive years. At the end of the second vegetative flush after harvest (1 Oct. 1994 and 10 Oct. 1995), four irrigation treatments were initiated: 0.5, 0.25, 0.125, and 0 Class A pan evaporation coefficients designated 100%, 50%, 25%, and 0%. The three lower irrigation levels effectively stopped shoot growth, suggesting the 50% treatment to be the threshold for shoot growth cessation in both years. For both years, flowering intensity and yield in the 100% treatment were lower than those following the other three treatments. Soil and plant water-stress indicators responded to the water-stress irrigation treatments. However soil water-potential values were highly variable relative to plant water potentials. Stem water potential differed more markedly between treatments than leaf water potential. Midday stem water potential appeared to be the best water-stress indicator for irrigation control. Midday stem water potential in both years was correlated with midday vapor-pressure deficit, suggesting that the threshold for irrigation control should take into account evaporative demand.

scholarly journals Root Growth and Water Status of Container-grown Photinia ×fraiseri Dress Transplanted into a Landscape

HortScience ◽  
1994 ◽  
Vol 29 (11) ◽  
pp. 1295-1297 ◽  
Author(s):  
R.C. Beeson
Keyword(s):  
Water Stress ◽  
Root Growth ◽  
Water Status ◽  
Growth Index ◽  
Plant Water ◽  
Root Mass ◽  
Trunk Diameter ◽  
Plant Water Potential ◽  
Daily Water ◽  
Similar Growth

Photinia plants produced in 11.4-liter polyethylene containers using a pine bark-based medium were transplanted into a well-drained sand and irrigated on alternate days. Polyethylene barriers were placed under half the root balls at transplanting to limit gravitational water loss. Plant water potential was measured diurnally between irrigations, and root growth was determined at 4-month intervals. Plants with barriers averaged higher cumulative daily water stress than control plants over the year, although predawn and minimum water potentials were similar. Growth index and trunk diameter were similar for the plants over barriers and controls, but the former were taller after 1 year. Plants with barriers had twice the horizontal root growth into the landscape site as control plants, resulting in twice the root mass in the landscape after 1 year.

Sensitivity and variability of soil and plant water stress indicators in response to withholding and resuming irrigation cycles in sweet cherry trees 

2021 ◽  
Author(s):  
Pedro José Blaya-Ros ◽  
Víctor Blanco ◽  
Roque Torres-Sánchez ◽  
Rafael Domingo
Keyword(s):  
Water Stress ◽  
Sweet Cherry ◽  
Water Status ◽  
Plant Water Status ◽  
Plant Water ◽  
Crop Water Stress Index ◽  
Stress Indicators ◽  
Drought Period ◽  
Stress Indicator ◽  
Cherry Trees

<p>Reduced water availability is the main limiting factor for crop production in semi-arid and arid regions. For this reason, irrigation water management needs to be based on reliable information and data that are rapidly and easily acquired. The aim of the present study was to assess the sensitivity and variability of several soil and plant water status indicators in response to two cycles of withholding and resuming irrigation in sweet cherry trees. The experiment was carried out during the summers of 2018 and 2019 in an experimental orchard of sweet cherry trees [<em>Prunus avium</em> (L.) ‘Lapins’] in SE Spain. Three irrigation treatments were studied: control, CTL, irrigated to ensure non-limiting soil water conditions (115% ETc) and two water stress treatments, medium water stress, MS, and severe water stress, SS. The threshold values of midday stem water potential (Ψ<sub>stem</sub>) proposed to the first and second drought period for MS trees were -1.3 and -1.7 MPa and for SS trees were -1.6 and -2.5 MPa. After every irrigation withholding period, MS and SS trees were fully irrigated until reaching Y<sub>stem</sub> values of CTL trees. The experimental design was a completely randomized block design with three blocks per treatment. Soil and plant water status were assessed by measuring the soil volumetric water content (θv), the Ψ<sub>stem</sub>, the daily trunk growth rate (TGR), the maximum daily trunk shrinkage (MDS), the temperature of the canopy (Tc), the difference between Tc and air temperature (ΔT) and the crop water stress index (CWSI). The signal intensity (SI), the coefficient of variation (CV) and the sensitivity (S = SI/CV) of θv, Ψ<sub>stem</sub>, MDS and Tc were determined.</p><p>θv at 25 cm dropped significantly during the drought periods. Ψ<sub>stem</sub> of MS and SS trees reached minimum values close to those thresholds proposed both years of study. MDS and TGR had a rapid response to the irrigation regimen applied. Tc, ΔT and CWSI increased as an effect of the stomatal closure. Ψ<sub>stem</sub> and Tc were the water stress indicators with the highest sensitivity. MDS showed SI values greater than that of Ψ<sub>stem</sub> and Tc, although it also had greater variability (CV<sub>MDS</sub> ≈ 29%). Ψ<sub>stem</sub> showed high SI values and low CV both study years. When the linear relationships between Ψ<sub>stem</sub> and the other plant water status indicators were calculated, it was observed that the Pearson correlation coefficients exceeded 0.75 in all cases, except for TGR. The relationship obtained between MDS and Ψ<sub>stem</sub> was linear from −0.5 MPa to a threshold value of around −1.3 MPa, from that value onwards, Ψ<sub>stem</sub> decreases were not related to MDS values. In contrast, ΔT and CWSI were always linearly related to Ψ<sub>stem</sub>. These results suggest that: i) MDS could be used as a water stress indicator up to moderate water deficit; ii) Ψ<sub>stem</sub> is a sensitive water stress indicator with low variability; and iii) the thermal indicators (Tc, ΔT and CWSI) can rapidly and easily assess sweet cherry tree water status.</p><p>This study was funded by the Spanish Economy and Competitiveness Ministry (AGL2013-49047-C2-1-R; AGL2016-77282-C33-R).</p>

scholarly journals Grazing winter wheat relieves plant water stress and transiently enhances photosynthesis

2010 ◽  
Vol 37 (8) ◽  
pp. 726 ◽  
Author(s):  
Matthew T. Harrison ◽  
Walter M. Kelman ◽  
Andrew D. Moore ◽  
John R. Evans
Keyword(s):  
Water Stress ◽  
Leaf Area ◽  
Water Status ◽  
Leaf Water ◽  
Plant Water ◽  
Rubisco Activity ◽  
Leaf Water Status ◽  
Area Index ◽  
Plant Water Stress ◽  
The Impact

To model the impact of grazing on the growth of wheat (Triticum aestivum L.), we measured photosynthesis in the field. Grazing may affect photosynthesis as a consequence of changes to leaf water status, nitrogen content per unit leaf area (Na) or photosynthetic enzyme activity. While light-saturated CO2 assimilation rates (Asat) of field-grown wheat were unchanged during grazing, Asat transiently increased by 33–68% compared with ungrazed leaves over a 2- to 4-week period after grazing ended. Grazing reduced leaf mass per unit area, increased stomatal conductance and increased intercellular CO2 concentrations (Ci) by 36–38%, 88–169% and 17–20%, respectively. Grazing did not alter Na. Using a photosynthesis model, we demonstrated that the increase in Asat after grazing required an increase in Rubisco activity of up to 53%, whereas the increase in Ci could only increase Asat by up to 13%. Increased Rubisco activity was associated with a partial alleviation of leaf water stress. We observed a 68% increase in leaf water potential of grazed plants that could be attributed to reduced leaf area index and canopy evaporative demand, as well as to increased rainfall infiltration into soil. The grazing of rain-fed grain cereals may be tailored to relieve plant water stress and enhance leaf photosynthesis.

The course and magnitude of water stress in Lolium perenne and Dactylis glomerata

1974 ◽  
Vol 82 (1) ◽  
pp. 19-27 ◽  
Author(s):  
D. K. Jackson
Keyword(s):  
Water Stress ◽  
Lolium Perenne ◽  
Water Status ◽  
Plant Stress ◽  
Dactylis Glomerata ◽  
Leaf Water ◽  
Minor Effect ◽  
Plant Water ◽  
Evaporative Demand ◽  
Leaf Water Status

SUMMARYSimulated swards of Dactylis glomerata (var. S.37) and Lolium perenne (var. S.23) were grown in large lysimeters or vertical pipes of 15 cm diameter, both sufficiently deep to allow largely unrestricted root development.Rainfall was excluded, and the effect of a drying cycle on the plant water balance was compared with irrigated controls in a sequence of sampling harvests at increasing soil water deficits.Leaf water potential (ΨL) fell during the day, both in treatments and controls, to levels which might be expected to reduce extension growth and, frequently, stomatal diffusion. Rapid recovery occurred in the evening to levels which might allow normal functioning of growth processes not dependent on sunlight. Defoliation reduced plant stress and stomatal restriction.The amelioration of plant water stress appeared to require a reduction in atmospheric evaporative demand, and irrigation had relatively little effect. The possibility is discussed that the major benefits of irrigation are other than through the relief of water stress within the plant. The significance of this is considered in relation to conventional irrigation techniques.The leaf water status was more sensitive to drought, transpiration was reduced more, and the root system extended more slowly in Dactylis than in Lolium. Consequently, the onset of permanent wilting due to exhaustion of water from the profile was delayed compared with Lolium. It is deduced that this characteristic might enhance the survival of Dactylis in prolonged drought, but prove disadvantageous in terms of growth during short droughts, when reduced stomatal opening might limit CO2 uptake. This would not be an impediment, however, if investigations suggesting that partial closure has a minor effect on CO2 uptake compared with that on transpiration were to be confirmed.

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