Apoplastic water fraction and rehydration techniques introduce significant errors in measurements of relative water content and osmotic potential in plant leaves

Abstract Background Non-contact resonant ultrasound spectroscopy (NC-RUS) has been proven as a reliable technique for the dynamic determination of leaf water status. It has been already tested in more than 50 plant species. In parallel, relative water content (RWC) is highly used in the ecophysiological field to describe the degree of water saturation in plant leaves. Obtaining RWC implies a cumbersome and destructive process that can introduce artefacts and cannot be determined instantaneously. Results Here, we present a method for the estimation of RWC in plant leaves from non-contact resonant ultrasound spectroscopy (NC-RUS) data. This technique enables to collect transmission coefficient in a [0.15–1.6] MHz frequency range from plant leaves in a non-invasive, non-destructive and rapid way. Two different approaches for the proposed method are evaluated: convolutional neural networks (CNN) and random forest (RF). While CNN takes the entire ultrasonic spectra acquired from the leaves, RF only uses four relevant parameters resulted from the transmission coefficient data. Both methods were tested successfully in Viburnum tinus leaf samples with Pearson’s correlations between 0.92 and 0.84. Conclusions This study showed that the combination of NC-RUS technique with deep learning algorithms is a robust tool for the instantaneous, accurate and non-destructive determination of RWC in plant leaves.

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Genotypic variation for drought stress response traits in soybean. I. Variation in soybean and wild Glycine spp. for epidermal conductance, osmotic potential, and relative water content

Australian Journal of Agricultural Research ◽

10.1071/ar07159 ◽

2008 ◽

Vol 59 (7) ◽

pp. 656 ◽

Cited By ~ 27

Author(s):

A. T. James ◽

R. J. Lawn ◽

M. Cooper

Keyword(s):

Water Content ◽

Wild Species ◽

Osmotic Potential ◽

Relative Water Content ◽

Stomatal Closure ◽

Genotypic Variation ◽

Soil Water Potential ◽

Genotypic Differences ◽

Relative Water ◽

Soybean Genotypes

Studies were undertaken to assess genotypic variation in soybean and related wild species for traits with putative effects on leaf turgor maintenance in droughted plants. Traits of interest were (i) epidermal conductance (ge) which influences the rate of water loss from stressed leaves after stomatal closure; (ii) osmotic adjustment (OA) as indicated by tissue osmotic potential (π), which potentially affects the capacity to withdraw water at low soil water potential; and (iii) relative water content (RWC) at incipient leaf death (critical relative water content, RWCC), which is a measure of the dehydration tolerance of leaf tissue. The germplasm comprised a diverse set of 58 soybean genotypes, 2 genotypes of the annual wild species G. soja and 9 genotypes representing 6 perennial wild Glycine spp. indigenous/endemic to Australia. Seedling plants were grown in soil-filled beds in the glasshouse and exposed to terminal water deficit stress from the second trifoliolate leaflet stage (21 days after sowing). Measurements were made on well watered plants, moderately stressed plants, and at incipient plant death, in 2 separate studies. In both studies, there were significant genotypic differences in all 3 traits in the stressed plants. However, across the 3 sample times, ge decreased and the absolute magnitude of π increased, indicating that the expression of these traits changed as the plants acclimated to the stress. RWC was therefore used as a covariate to adjust the genotypic values of π and ge in order to facilitate comparison at a consistent plant water status of 70% RWC. There was statistically significant genotypic variation for the adjusted values, ge70 and π70, in both studies, and genotypic correlations between the 2 studies were significant (P < 0.05) and positive for all 3 traits: ge70 (r = 0.48), π70 (r = 0.50), and RWCC (r = 0.53). Among the soybean genotypes, there was at least a 2-fold range in ge70, a 0.7 MPa range in π70, and a 12 percentage point range in RWCC. Some of the perennial wild genotypes exhibited lower values of ge and RWCC and greater OA than soybean and G. soja, consistent with adaptation to drier environments. While the repeatability of measurement between experiments was variable among genotypes, the studies confirmed the existence of genotypic differences for ge, OA, and RWCC in cultivated soybean, with a wider range among the wild germplasm.

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Water relations and yield inAzospirillum-inoculated wheat exposed to drought in the field

Canadian Journal of Botany ◽

10.1139/b03-119 ◽

2004 ◽

Vol 82 (2) ◽

pp. 273-281 ◽

Cited By ~ 152

Author(s):

Cecilia M Creus ◽

Rolando J Sueldo ◽

Carlos A Barassi

Keyword(s):

Grain Yield ◽

Water Potential ◽

Water Content ◽

Water Relations ◽

Relative Water Content ◽

Mineral Content ◽

Water Status ◽

Water Fraction ◽

Relative Water ◽

And Control

There are scarce data connecting water relations in Azospirillum-inoculated wheat suffering drought during anthesis with the yield and mineral content of grains. Azospirillum brasilense Sp245-inoculated seeds of Triticum aestivum 'Pro INTA Oasis' were sown in nonirrigated and control plots. Water potential, water content, and relative water content were determined on flag leaves. Plant water status was calculated from pressurevolume curves. At maturity, grain yield and its components were determined. P, Ca, Mg, K, Fe, Cu, and Zn were determined in dried grains. Even though the cultivar underwent osmotic adjustment, significantly higher water content, relative water content, water potential, apoplastic water fraction, and lower cell wall modulus of elasticity values were obtained in Azospirillum-inoculated plants suffering drought. Grain yield loss to drought was 26.5% and 14.1% in noninoculated and Azospirillum-inoculated plants, respectively. Grain Mg and K diminished in nonirrigated, noninoculated plots. However, grains harvested from Azospirillum-inoculated plants had significantly higher Mg, K, and Ca than noninoculated plants. Neither drought nor inoculation changed grain P, Cu, Fe, and Zn contents. A better water status and an additional "elastic adjustment" in Azospirillum-inoculated wheat plants could be crucial in promoting higher grain yield and mineral quality at harvest, particularly when drought strikes during anthesis.Key words: Azospirillum, wheat, drought, pressurevolume curves, yield, mineral content.

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A Gene Controlling Differences in Osmoregulation in Wheat

Functional Plant Biology ◽

10.1071/pp9910249 ◽

1991 ◽

Vol 18 (3) ◽

pp. 249 ◽

Cited By ~ 48

Author(s):

JM Morgan

Keyword(s):

Water Content ◽

Osmotic Potential ◽

Relative Water Content ◽

Flag Leaf ◽

Single Gene ◽

Recessive Gene ◽

Single Chromosome ◽

Relative Water ◽

Environment Chamber ◽

Response To Water

Evidence is presented for a single gene controlling differences in osmoregulation in wheat in response to water stress, confirming earlier results. Analyses of osmoregulation were made on the flag leaves of wheat plants which were grown in pots in the glasshouse and stressed in a controlled environment chamber by withholding water after the flag leaf had fully emerged. Osmoregulation was derived from responses of osmotic potential to relative water content or from responses of relative water content and osmotic potential to water potential. Usable estimates of osmoregulation were obtained for 67 F2 lines derived from contrasting parents, to test for gene number, and for one substitution series with contrasting parents, to determine chromosomal location. The F2 frequency response, which consisted of two overlapping distributions, was compatible with a single recessive gene, the estimated ratio being 2.79 : 1 (low: high osmoregulation). This confirmed previous measurements made on F1s and F4s Results for the substitution series were also compatible with these results in indicating a single chromosome, 7A, which had an identical response to the low osmoregulation parent, Red Egyptian. The effects of the gene were confined to solute accumulations at water potentials above, but not below, zero turgor.

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Studies on the Impact of Water Deficit on Plant Height, Relative Water Content, Total Chlorophyll, Osmotic Potential and Yield of Banana (Musa spp.,) Cultivars and Hybrids

International Journal of Horticulture ◽

10.5376/ijh.2013.03.0011 ◽

2013 ◽

Cited By ~ 1

Author(s):

K. Krishna Surendar ◽

D. Durga Devi ◽

I. Ravi ◽

P. Jeyakumar ◽

S. Ramesh Kumar ◽

...

Keyword(s):

Water Content ◽

Plant Height ◽

Water Deficit ◽

Osmotic Potential ◽

Relative Water Content ◽

Total Chlorophyll ◽

Relative Water ◽

The Impact

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Genotypic variation for drought stress response traits in soybean. III. Broad-sense heritability of epidermal conductance, osmotic potential, and relative water content

Australian Journal of Agricultural Research ◽

10.1071/ar07161 ◽

2008 ◽

Vol 59 (7) ◽

pp. 679 ◽

Cited By ~ 8

Author(s):

A. T. James ◽

R. J. Lawn ◽

M. Cooper

Keyword(s):

Water Content ◽

Osmotic Potential ◽

Relative Water Content ◽

Genotypic Variation ◽

Broad Sense ◽

Broad Sense Heritability ◽

Relative Water ◽

Rainout Shelter ◽

Additive Gene ◽

Leaf Survival

The broad-sense heritability of 3 traits related to leaf survival in severely stressed plants was studied in several hybrid soybean populations. The 3 traits were epidermal conductance (ge), osmotic potential (π), and relative water content (RWC). The populations were generated by hybridising unrelated parental genotypes previously shown to differ in the 3 traits. ge (mm/s) was measured on well watered plants from 10 populations involving all combinations of 5 parental lines, grown in soil-filled beds in the glasshouse. π (MPa) and RWC (%) were measured on severely stressed plants of 3 populations involving all combinations of 3 different parents, growing into a terminal water deficit under a rainout shelter in the field. Broad-sense heritability for ge was significantly different from zero (P < 0.05) in all 10 populations and ranged from 60% to 93%. Heritability estimates for π70 (the tissue osmotic potential at 70% RWC) ranged from 33% to 71%. Only two estimates were statistically significant (P < 0.05) because of large standard errors and the fact that parental differences were smaller than previously observed. Broad-sense heritability for RWC of severely stressed plants ranged from 40% to 74%, and was statistically significant (P < 0.05) for 2 of the 3 populations. For all 3 traits, F2 progeny distributions were consistent with quantitative inheritance with a high degree of additive gene action. It was concluded that capacity exists to breed varieties with low ge, low π70, and high RWC in stressed plants. However, in the case of osmotic potential, genotypes with lower π70 combined with greater precision of measurement would be needed than proved possible in these studies. Further, specific strategies would be needed to select for the critical RWC, the minimal RWC at which leaf tissues die and which provides a measure of tissue dehydration tolerance. More research is also needed to characterise the dynamic relations between ge, π, and RWC in influencing leaf survival in soybean, before they could be confidently used in a breeding program to improve drought tolerance.

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Genotypic variation for drought stress response traits in soybean. II. Inter-relations between epidermal conductance, osmotic potential, relative water content, and plant survival

Australian Journal of Agricultural Research ◽

10.1071/ar07160 ◽

2008 ◽

Vol 59 (7) ◽

pp. 670 ◽

Cited By ~ 22

Author(s):

A. T. James ◽

R. J. Lawn ◽

M. Cooper

Keyword(s):

Drought Stress ◽

Water Content ◽

Osmotic Potential ◽

Relative Water Content ◽

Genotypic Variation ◽

Genotypic Differences ◽

Plant Survival ◽

Turgor Maintenance ◽

Relative Water ◽

Rate Of Decline

As part of a project exploring the potential for using leaf physiological traits to improve drought tolerance in soybean, studies were conducted to explore whether epidermal conductance (ge), osmotic potential (π), and relative water content (RWC) influenced turgor maintenance and ultimately the survival of droughted plants. In a glasshouse study, plants of 8 soybean genotypes that showed different expression of the traits were grown in well watered soil-filled beds for 21 days and then exposed to terminal water deficit stress. The trends in each trait were then monitored periodically until plant death. Genotypic differences were observed in the rate of decline in RWC as the soil dried, in the temporal patterns of change in ge and π, in the duration of survival after watering ceased, and in the critical relative water content (RWCC) at which plants died. In general, ge became smaller and π became more negative as RWC declined and plants acclimated to the increasing stress. Genotypic differences in ge remained broadly consistent as RWC declined. In contrast, the genotypic rankings for π in stressed plants were poorly correlated with those for well watered plants, indicating differential genotypic capacity for osmotic adjustment (OA) in response to stress. Survival times among genotypes after stress commenced ranged from 27 to 41 days, while RWCC ranged from 49% down to 41%. The differences in survival time among the genotypes were able to be explained by genotypic differences in the rate of decline in RWC and in the RWCC, using a multiple linear regression relationship (R 2 = 0.94**). In turn, genotypic differences in the rate of decline in RWC were positively correlated (r = 0.75*) with ge at 70% RWC, and with OA over the drying period (r = 0.98**). In a second study in a controlled environment facility, leaf area retention at 90% soil water extraction was greatest in the one genotype that combined low ge, high OA, and low RWCC. Overall, the responses from the two studies were consistent with the hypothesis that turgor maintenance and ultimately leaf and plant survival of different genotypes during advanced stages of drought stress are enhanced by low ge, high OA capacity, and low RWCC.

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Some Aspects of the Water Relations of the Lichen Parmotrema Tinctorum Measured Using Thermocouple Psychrometry

The Lichenologist ◽

10.1006/lich.1996.0023 ◽

1996 ◽

Vol 28 (3) ◽

pp. 257-266 ◽

Cited By ~ 8

Author(s):

R. P. Beckett

Keyword(s):

Bulk Modulus ◽

Water Potential ◽

Water Content ◽

Water Relations ◽

Osmotic Potential ◽

Relative Water Content ◽

Thermocouple Psychrometer ◽

Relative Water ◽

Parmotrema Tinctorum

AbstractThe thermocouple psychrometer was used to determine water potential, Ψ and its components in the lichen Parmotrema tinctorum. Data suggested that using conventional pressure-volume curves to study the water relations of lichens may give anomalous results, possibly because lichens may contain appreciable amounts of intercellular water. A way of correcting pressure-volume curves to remove the effect of intercellular water is discussed. Parmotrema tinctorum had a very low osmotic potential at full turgor (c. −2.5 MPa), and a low bulk modulus of elasticit (c. 2.1 MPa). As a result, P. tinctorum lost turgor only when the relative water content dropped below 0.47. Likely benefits of this for the lichen are discussed.

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The Method of Plant Water Status Measurement in Sweet Potato (Ipomoea Batatas (L) Lam.)

Beccariana Botanical Research Bulletin ◽

10.30862/bbrp.v7i1.274 ◽

2010 ◽

Vol 7 (1) ◽

Author(s):

Saraswati Prabawardani

Keyword(s):

Water Content ◽

Sweet Potato ◽

Relative Water Content ◽

Water Status ◽

Plant Water Status ◽

Equilibration Time ◽

Plant Water ◽

Font Size ◽

Potato Leaf ◽

Relative Water

The measurement of plant water status such as leaf water potential (LWP) and leaf relative water content (RWC) is important part of understanding plant physiology and biomass production. Preliminary study was made to determine the optimum amount of leaf abrasion and equilibration time of sweet potato leaf inside the thermocouple psychrometer chambers. Based on the trial, the standard equilibration time curve of a Peltier thermocouple for sweet potato leaf was between 2 and 3 hours. To increase the water vapour conductance across the leaf epidermis the waxy leaf cuticle should be removed or broken by abrasion. The result showed that 4 times leaf rubbings was accepted as the most effective way to increase leaf vapour conductance of sweet potato in the psychrometer chambers. In calculating the leaf relative water content, unstressed water of sweet potato leaves require 4 hours imbibition, whereas water stressed of sweet potato leaves require 5 to 6 hours to reach the saturation time. Either leaf water potential or relative water content can be used as a parameter for plant water status in sweet potato.

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Palmer Amaranth (Amaranthus palmeri) Competition for Water in Cotton

Weed Science ◽

10.1614/ws-d-15-00062.1 ◽

2015 ◽

Vol 63 (4) ◽

pp. 928-935 ◽

Cited By ~ 11

Author(s):

Sarah T. Berger ◽

Jason A. Ferrell ◽

Diane L. Rowland ◽

Theodore M. Webster

Keyword(s):

Water Content ◽

Relative Water Content ◽

Yield Loss ◽

Linear Trend ◽

Palmer Amaranth ◽

Cotton Production ◽

Excess Water ◽

Relative Water ◽

Competition For Light ◽

Daily Water

Palmer amaranth is a troublesome weed in cotton production. Yield losses of 65% have been reported from season-long Palmer amaranth competition with cotton. To determine whether water is a factor in this system, experiments were conduced in 2011, 2012, and 2013 in Citra, FL, and in Tifton, GA. In 2011, infrequent rainfall lead to drought stress. The presence of Palmer amaranth resulted in decreased soil relative water content up to 1 m in depth. Cotton stomatal conductance (gs) was reduced up to 1.8 m from a Palmer amaranth plant. In 2012 and 2013 higher than average rainfall resulted in excess water throughout the growing season. In this situation, no differences were found in soil relative water content or cottongsas a function of proximity to Palmer amaranth. A positive linear trend was found in cotton photosynthesis and yield; each parameter increased as distance from Palmer amaranth increased. Even in these well-watered conditions, daily water use of Palmer amaranth was considerably higher than that of cotton, at 1.2 and 0.49 g H20 cm−2d−1, respectively. Although Palmer amaranth removed more water from the soil profile, rainfall was adequate to replenish the profile in 2 of the 3 yr of this study. However, yield loss due to Palmer amaranth was still observed despite no change ings, indicating other factors, such as competition for light or response to neighboring plants during development, are driving yield loss.

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