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.

Cortical Intracellular Electrical Potential in Roots of Unstressed and Stressed Sunflower Seedlings. II. Radial Profiles and Oscillations

1997 ◽  
Vol 24 (5) ◽  
pp. 651 ◽  
Author(s):  
P. M. Cortes
Keyword(s):  
Lateral Root ◽  
Electrical Coupling ◽  
Electrical Potential ◽  
Cortical Cell ◽  
Cortical Cells ◽  
Radial Profiles ◽  
Stressed Seedling ◽  
Seedling Roots ◽  
Cell Layers ◽  
Dry Soil

Various models have been proposed to explain how plants can extract water from dry soil against a gradient in water potential. According to one model, it is hypothesised that water uptake from dry soil is associated with a radial gradient in the intracellular electrical potential (Ec) of root cortical cells such that the potential in the outer cells is relatively hyperpolarised. As a partial test of this model, a microelectrode was used to measure radial profiles of Ec in intact roots of sunflower (Helianthus annuus) seedlings. The seedlings were subjected to either a control (unstressed) or one of two stress treatments. 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. There was a gradient in Ec in roots of unstressed plants with the potential of the outer cortical cells being relatively depolarised. The imposition of stress shifted the gradient in accordance with the hypothesis. Increasing the magnitude of the osmotic potential of the solution perfusing the measured portion of a lateral root of a stressed seedling resulted in a discontinuity in the profile between the second and third cortical layers. The gradients in the profile of Ec indicate there is a limitation in intercellular electrical coupling and the appearance of a discontinuity may indicate a decrease in coupling. Three types of occasional, spontaneous oscillations in Ec are characterised. One type of oscillation may be additional evidence that the electrical coupling between the cortical cell layers is variable and depends on the transport and status of water in the roots.

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.

Monitoring Crop Water Status and Irrigation Needs Using Multispectral Airborne Sensors

HortScience ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 905D-905
Author(s):  
Thomas R. Clarke ◽  
M. Susan Moran
Keyword(s):  
Water Stress ◽  
Near Infrared ◽  
Water Status ◽  
Canopy Cover ◽  
Stress Index ◽  
Crop Water ◽  
Vegetative Cover ◽  
Crop Water Stress Index ◽  
Water Stress Index ◽  
Subsurface Drip

Water application efficiency can be improved by directly monitoring plant water status rather than depending on soil moisture measurements or modeled ET estimates. Plants receiving sufficient water through their roots have cooler leaves than those that are water-stressed, leading to the development of the Crop Water Stress Index based on hand-held infrared thermometry. Substantial error can occur in partial canopies, however, as exposed hot soil contributes to deceptively warm temperature readings. Mathematically comparing red and near-infrared reflectances provides a measure of vegetative cover, and this information was combined with thermal radiance to give a two-dimensional index capable of detecting water stress even with a low percentage of canopy cover. Thermal, red, and near-infrared images acquired over subsurface drip-irrigated cantaloupe fields demonstrated the method's ability to detect areas with clogged emitters, insufficient irrigation rate, and system water leaks.

Infection by Phytophthora cinnamomi Rands of Roots of Eucalyptus calophylla R.Br. and Eucalyptus marginata Donn. ex Sm

1977 ◽  
Vol 25 (5) ◽  
pp. 483 ◽  
Author(s):  
N Malajczuk ◽  
AJ Mccomb ◽  
CA Parker
Keyword(s):  
Phytophthora Cinnamomi ◽  
Light And Electron Microscopy ◽  
Inhibitory Effect ◽  
Lateritic Soil ◽  
Root Damage ◽  
Mature Trees ◽  
Cortical Cells ◽  
Eucalyptus Marginata ◽  
Seedling Roots ◽  
Loam Soil

On lateritic podzolic soils in Western Australia Eucalyptus calophylla is resistant to Phytophthora cinnamomi whereas Eucalyptus marginata is susceptible and eventually killed by the pathogen. On loam soils both eucalypts are resistant. Possible mechanisms for resistance of E. calophylla in lateritic soil and the inhibitory action of loam soils were investigated. Aseptically raised eucalypt seedlings succumbed to infection in liquid culture tubes. The mechanism of infection was compared by light and electron microscopy which showed similar fungal invasion and penetration into roots of both eucalypt species. Vegetative hyphae initially penetrated intercellularly and proliferated rapidly within cortical and stelar tissue. Intracellular invasion of these tissues occurred 48hr after initial infection through dissolution of the host cell wall. Chlamydospores were formed within a number of cortical cells. Unsuberized roots of mature trees produced aseptically showed reactions to invasion similar to those of the eucalypt seedling roots. Suberized roots were not invaded. The addition of small quantities of lateritic soil to sterile sand so as to introduce soil micro-organisms without altering the chemical and physical status of the sand, and subsequent inoculation of the sand with P.cinnamomi, resulted in a reduction of root damage on both eucalypts when compared with seedlings raised in sterile sand. Roots of E.calophylla were less severely damaged than those of E.marginata. The addition of small quantities of loam soil significantly reduced root damage in seedlings of both species. These results parallel both pot experiments and field observations, and suggest that microorganisms of the rhizosphere may be an important factor in the resistance of E.calophylla to infection, and in the inhibitory effect of loam soil on P.cinnamomi.

scholarly journals In vitro and in vivo water stress in sunflower, Helianthus annuus L

Helia ◽  
2004 ◽  
Vol 27 (40) ◽  
pp. 227-236 ◽  
Author(s):  
H. Turhan ◽  
I. Baser
Keyword(s):  
Water Stress ◽  
Helianthus Annuus ◽  
Helianthus Annuus L

Estimation water status of the vineyard by calculating multispectral index from satellite images

2021 ◽  
Author(s):  
Marta Rodríguez-Fernández ◽  
María Fandiño ◽  
Xesús Pablo González ◽  
Javier J. Cancela
Keyword(s):  
Water Stress ◽  
Water Potential ◽  
Spectral Index ◽  
Satellite Images ◽  
Irrigation System ◽  
Water Status ◽  
Stress Index ◽  
Stem Water Potential ◽  
Stem Water ◽  
Water Potential Measurements

<p>The estimation of the water status in the vineyard, is a very important factor, in which every day the winegrowers show more interest since it directly affects the quality and production in the vineyards. The situation generated by COVID-19 in viticulture, adds importance to tools that provide information of the hydric status of vineyard plants in a telematic way.</p><p>In the present study, the stem water potential in the 2018 and 2019 seasons, is analysed in a vineyard belonging to the Rias Baixas wine-growing area (Vilagarcia de Arousa, Spain), with 32 sampling points distributed throughout the plot, which allows the contrast and validation with the remote sensing methodology to estimate the water status of the vineyard using satellite images.</p><p>The satellite images have been downloaded from the Sentinel-2 satellite, on the closets available dates regarding the stem water potential measurements, carried out in the months of June to September, because this dates are considered the months in which vine plants have higher water requirements.</p><p>With satellite images, two spectral index related to the detection of water stress have been calculated: NDWI (Normalized Difference Water Index) and MSI (Moisture Stress Index). Stem water potential measurements, have allowed a linear regression with both index, to validate the use of these multispectral index to determine water stress in the vineyard.</p><p>Determination coefficients of r<sup>2</sup>=0.62 and 0.67, have been obtained in July and August 2018 and 0.54 in June of 2019 for the NDWI index, as well as values of 0.53 and 0.63 in July 2018 and June 2019 respectively, when it has been analysed the MSI index.</p><p>Between both seasons, the difference observed, that implies slightly greater water stress in 2019, is reflected in the climate conditions during the summer months, with an average accumulated rainfall that doesn’t exceed 46 mm of water. Although, the NDWI index has allowed to establish better relationships in the 2018 season respect to the MSI index and the 2019 season, (r<sup>2</sup>=0.60 NDWI in 2018), as well as greater differences in terms of water stress presented in the vineyard.</p><p>With the spectral index calculated, it has been possible to validate the use of these index for the determination of the water stress of the vineyard plants, as an efficient, fast and less expensive method, which allows the application of an efficient irrigation system in the vineyard.</p>

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>

The Role of Ectomycorrhizal Symbiosis in the Resistance of Forests to Water Stress

2000 ◽  
Vol 29 (1) ◽  
pp. 63-69 ◽  
Author(s):  
Jean Garbaye
Keyword(s):  
Water Stress ◽  
Sustainable Management ◽  
Fine Roots ◽  
Forest Ecosystems ◽  
Water Status ◽  
Forest Trees ◽  
Direct Effects ◽  
Ectomycorrhizal Symbiosis ◽  
Protection Mechanisms

Forest trees live in enforced symbiosis with specialized fungi that form composite organs (ectomycorrhizas) with fine roots. This paper examines how this association contributes to the water status of trees and how it plays a major role in the protection mechanisms by which trees and forest stands resist drought-induced water stress. It shows how ectomycorrhizal symbiosis has both direct effects (at the uptake level) and indirect effects (at the regulation level) on the water status of trees. The facts presented are discussed in terms of forest adaptation to changing environmental conditions and the practical consequences for the sustainable management of forest ecosystems.

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