Water relations and xylem anatomy of ferns

1985 ◽  
Vol 86 ◽  
pp. 81-92 ◽  
Author(s):  
A. C. Gibson ◽  
H. W. Calkin ◽  
D. O. Raphael ◽  
P. S. Nobel
Keyword(s):  
Water Potential ◽  
Water Flow ◽  
Water Relations ◽  
Unit Length ◽  
Potential Gradient ◽  
Hydraulic Conductance ◽  
Xylem Anatomy ◽  
Potential Gradients ◽  
Water Potential Gradient ◽  
Poiseuille Equation

SynopsisThe entire soil-plant-atmosphere continuum must be analysed to elucidate how xylem anatomy relates to water flow in plants. Measurements of water potential gradients and volume of water flow per unit time are needed to obtain values of hydraulic conductance per unit length. By comparing values of hydraulic conductance per unit length along the plant, the regions where xylem structure restricts water flow can be determined. Previous studies of fern water relations demonstrated that very large water potential gradients occurring in stipes of certain ferns were closely correlated with reduced conducting area of stipe xylem. A new study on Cyrtomium falcatum showed that the water potential gradient was relatively small and constant along the stipe and rachis; however, a much larger gradient occurred from the rachies into the pinnae. Hydraulic conductance per unit length varied with the leaf area to be supplied, leading to the fairly constant water potential gradient along the rachis.. The measured hydraulic conductance per unit length was only half the value predicted from the Hagen-Poiseuille equation. Although the Hagen-Poiseuille equation overestimated the measured value by a factor of 2, it did support the assumption that conduit number and lumen diameter are the principal determinants of water conductance in the xylem.

scholarly journals 275 Water Relations of Fruit Cracking in Single-truss Tomato Plants

HortScience ◽  
1999 ◽  
Vol 34 (3) ◽  
pp. 489E-489
Author(s):  
Takashi Ikeda ◽  
Kunio Okano ◽  
Yuka Sakamoto ◽  
Shin-ichi Watanabe
Keyword(s):  
Water Potential ◽  
Water Relations ◽  
Water Status ◽  
Potential Gradient ◽  
Culture Solution ◽  
Tomato Plants ◽  
Fruit Flesh ◽  
Fruit Cracking ◽  
Fruit Skin ◽  
Water Potential Gradient

This study was undertaken to investigate the water relations of tomato (Lycopersicon esculentum Mill.) fruit cracking for single-truss tomato plants. The tomato plants were cultured on a closed hydroponic system in greenhouse. Water status of culture solution and plant tissues was measured with psychrometers. Water potential of the culture solution for the stressed plant was changed from -0.06 MPa (control plants) to -0.36 MPa at 24 days after anthesis. Hardness of the fruit skin was not different significantly between the stressed plants and the control plants. Fruit cracking occurred frequently in the control plants, but not in the stressed plants. Water potential gradient between the tissue of fruit flesh and water source for the control plants was bigger than that of the stressed plants. Turgors were increased at the tissues of fruit flesh and fruit skin at the control plants between predawn and morning but not at the stressed plants. These results indicated that the water potential gradient and the increased turgor in these tissues might be a trigger for the occurrence of fruit cracking on single-truss tomato plants.

scholarly journals Direct evidence for dynamics of cell heterogeneity in watercored apples: turgor-associated metabolic modifications and within-fruit water potential gradient unveiled by single-cell analyses

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Hiroshi Wada ◽  
Keisuke Nakata ◽  
Hiroshi Nonami ◽  
Rosa Erra-Balsells ◽  
Miho Tatsuki ◽  
...  
Keyword(s):  
Water Potential ◽  
Volatile Compounds ◽  
Water Relations ◽  
Freezing Point ◽  
Potential Gradient ◽  
Pressure Probe ◽  
Ionization Mass ◽  
Cell Water ◽  
Water Potential Gradient ◽  
Osmotic Potentials

AbstractWatercore is a physiological disorder in apple (Malus × domestica Borkh.) fruits that appears as water-soaked tissues adjacent to the vascular core, although there is little information on what exactly occurs at cell level in the watercored apples, particularly from the viewpoint of cell water relations. By combining picolitre pressure-probe electrospray-ionization mass spectrometry (picoPPESI-MS) with freezing point osmometry and vapor pressure osmometry, changes in cell water status and metabolisms were spatially assayed in the same fruit. In the watercored fruit, total soluble solid was lower in the watercore region than the normal outer parenchyma region, but there was no spatial difference in the osmotic potentials determined with freezing point osmometry. Importantly, a disagreement between the osmotic potentials determined with two methods has been observed in the watercore region, indicating the presence of significant volatile compounds in the cellular fluids collected. In the watercored fruit, cell turgor varied across flesh, and a steeper water potential gradient has been established from the normal outer parenchyma region to the watercore region, retaining the potential to transport water to the watercore region. Site-specific analysis using picoPPESI-MS revealed that together with a reduction in turgor, remarkable metabolic modifications through fermentation have occurred at the border, inducing greater production of watercore-related volatile compounds, such as alcohols and esters, compared with other regions. Because alcohols including ethanol have low reflection coefficients, it is very likely that these molecules would have rapidly penetrated membranes to accumulate in apoplast to fill. In addition to the water potential gradient detected here, this would physically contribute to the appearance with high tissue transparency and changes in colour differences. Therefore, it is concluded that these spatial changes in cell water relations are closely associated with watercore symptoms as well as with metabolic alterations.

Hydraulic Conductance and Xylem Structure in Tracheid-Bearing Plants

IAWA Journal ◽  
1985 ◽  
Vol 6 (4) ◽  
pp. 293-302 ◽  
Author(s):  
Arthur C. Gibson ◽  
Howard W. Calkin ◽  
Park S. Nobel
Keyword(s):  
Water Flow ◽  
Unit Length ◽  
Hydraulic Conductance ◽  
Distal Portion ◽  
Pteris Vittata ◽  
Root Tips ◽  
Xylem Structure ◽  
Pit Membrane ◽  
Potential Gradients ◽  
Uniform Diameter

To understand water flow in tracheary elements, hydraulic conductances per unit length were measured and then compared with theoretical values calculated from xylem anatomical measurements using the Hagen -Poiseuille relation for nine species of pteridophytes, including Psilotum and eight species of ferns. In ferns the water potential gradients were essentially constant from the root tips to the distal portion of the leaf rachises, although somewhat larger gradients were found from the petiolule onward. Although tracheid number and diameter apparently controlled water flow in xylem, estimates of hydraulic conductance per unit length predicted from tracheid numbers and diameters were generally twice those actually measured from plants under steady-state conditions. A model was developed to account for this discrepancy for Pteris vittata, indicating that pit membrane resistances may contribute 70% of the total resistance to water flow in this fern. This may account for the generally observed deviation of tracheid performance from that predicted for ideal capillaries of uniform diameter.

scholarly journals Molecular mechanisms mediating root hydrotropism: what we have observed since the rediscovery of hydrotropism

2019 ◽  
Vol 133 (1) ◽  
pp. 3-14
Author(s):  
Yutaka Miyazawa ◽  
Hideyuki Takahashi
Keyword(s):  
Arabidopsis Thaliana ◽  
Water Potential ◽  
Water Availability ◽  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Potential Gradient ◽  
Regulatory Mechanisms ◽  
Directional Growth ◽  
Plant Adaptation ◽  
Water Potential Gradient

AbstractRoots display directional growth toward moisture in response to a water potential gradient. Root hydrotropism is thought to facilitate plant adaptation to continuously changing water availability. Hydrotropism has not been as extensively studied as gravitropism. However, comparisons of hydrotropic and gravitropic responses identified mechanisms that are unique to hydrotropism. Regulatory mechanisms underlying the hydrotropic response appear to differ among different species. We recently performed molecular and genetic analyses of root hydrotropism in Arabidopsis thaliana. In this review, we summarize the current knowledge of specific mechanisms mediating root hydrotropism in several plant species.

The decline in xylem flow to mango fruit at the end of its development is related to the appearance of embolism in the fruit pedicel

2015 ◽  
Vol 42 (7) ◽  
pp. 668 ◽  
Author(s):  
Thibault Nordey ◽  
Mathieu Léchaudel ◽  
Michel Génard
Keyword(s):  
Hydraulic Conductivity ◽  
Water Potential ◽  
Fruit Development ◽  
Hydraulic Properties ◽  
Potential Gradient ◽  
Mango Fruit ◽  
Xylem Flow ◽  
Water Potential Gradient ◽  
The Impact ◽  
Late Growth

The decline in xylem flow during the late growth stage in most fruits may be due either to a decrease in the water potential gradient between the stem bearing the fruit and the fruit tissues or to a decrease in the hydraulic conductivity of xylem vessels, or both. In this study, we analysed changes in xylem flows to the mango Mangifera indica L. fruit during its development to identify the sources of variation by measuring changes in the water potential gradient and in the hydraulic properties of the fruit pedicel. The variations in xylem and transpiration flows were estimated at several stages of mango fruit development from the daily changes in the fresh mass of detached and girdled fruits on branches. The water potential gradient was estimated by monitoring the diurnal water potential in the stem and fruit. The hydraulic properties of the fruit pedicel were estimated using a flow meter. The results indicated that xylem flow increased in the early stages of fruit development and decreased in the late stage. Variations in xylem flow were related to the decrease in the hydraulic conductivity of xylem vessels but not to a decrease in the water potential gradient. The hydraulic conductivity of the fruit pedicel decreased during late growth due to embolism caused by a decrease in the fruit water potential. Further studies should establish the impact of the decrease in the hydraulic conductivity of the fruit pedicel on mango growth.

Water relations of winter wheat: 2. Soil water relations

1978 ◽  
Vol 91 (1) ◽  
pp. 103-116 ◽  
Author(s):  
P. J. Gregory ◽  
M. McGowan ◽  
P. V. Biscoe
Keyword(s):  
Winter Wheat ◽  
Water Potential ◽  
Soil Water ◽  
Water Relations ◽  
Unit Length ◽  
Soil Water Potential ◽  
Rooting Depth ◽  
Wheat Crop ◽  
Deep Roots ◽  
Volumetric Soil Water Content

SummaryVolumetric soil water content and soil water potential were measured beneath a winter wheat crop during the 1975 growing season. Almost no rain fell between mid-May and mid-July and the soil dried continuously until the potential was less than – 20 bars to a depth of 80 cm. Evaporation was separated from drainage by denning an ‘effective rooting depth’ at which the hydraulic gradient was zero.Rates of water uptake per unit length of root (inflow) were calculated for the whole soil profile and for individual soil layers. Generally, inflow decreased throughout the period of measurement from a maximum of 2·5 × 10–3 to a minimum of 0·66 × 10–3 ml water/cm root/day. Values in individual layers were frequently higher than the mean inflow and the importance of a few deep roots in taking up water during a dry season is emphasized. A similar correlation between inflow and soil water potential was found to apply for the 0–30 cm and 30–60 cm layers during the period of continual soil drying. This relationship represents the maximum inflow measured at a given soil water potential; actual inflow at any particular time depends upon the interrelationship of atmospheric demand, soil water potential and the distribution of root length in the soil.

Simultaneous measurements of tomato fruit and stem water potentials using in situ stem hygrometers

1989 ◽  
Vol 67 (8) ◽  
pp. 2352-2355 ◽  
Author(s):  
D. R. Lee ◽  
M. A. Dixon ◽  
R. W. Johnson
Keyword(s):  
Water Potential ◽  
Tomato Fruit ◽  
Potential Gradient ◽  
Diurnal Changes ◽  
Stem Water Potential ◽  
Simultaneous Measurements ◽  
Water Potentials ◽  
Stem Water ◽  
Water Potential Gradient

Simultaneous measurements were made of the water potentials of the stem and fruit of intact tomato plants (Lycopersicon esculentum Mill. var. Heinz 2653) using in situ temperature-corrected stem psychrometers. Water potential of the fruit remained consistently lower than the water potential of the stem except when the plant had been subjected to prolonged water stress. Stem water potential recovered quickly with rewatering, increasing by approximately 0.5 MPa in 1 h, but the water potential of the fruit remained consistently near −1.0 MPa. The results indicate a significant resistance to water flow between the stem and the fruit and a substantial hydraulic capacitance represented by the volume of the fruit. Diurnal changes in dimensions of tomato fruit were also measured. Fruit diameter expanded at night and contracted during the day even when the water potential gradient favoured flow towards the fruit. This indicates that bidirectional flow (to and from the fruit) is not responsible for the observed diurnal changes in the fruit dimensions.

STEADY STATE RESISTANCE TO WATER FLOW IN CORN UNDER WELL WATERED CONDITIONS

1975 ◽  
Vol 55 (4) ◽  
pp. 941-948 ◽  
Author(s):  
P. A. DUBÉ ◽  
K. R. STEVENSON ◽  
G. W. THURTELL ◽  
H. H. NEUMANN
Keyword(s):  
Water Potential ◽  
Water Flow ◽  
Leaf Water Potential ◽  
Water Movement ◽  
Leaf Water ◽  
In Vivo Detection ◽  
Staining Techniques ◽  
Total Plant ◽  
Potential Gradients

Determinations of plant resistance to water flow from measurements of leaf water potential at steady transpiration rates were made on different lines of corn (Zea mays L.). Two inbreds, Q188, a wilting mutant, and DR1, an inbred line shown to have at least some heat and drought tolerance under field conditions, were compared to a commercial single-cross hybrid, United 106. The purpose of the experiment was to isolate the cause of the wilting characteristic of Q188. A linear relationship was found between leaf water potential and transpiration rate for all lines. No water potential gradients were found at zero transpiration. Low total plant resistances were observed in United 106 and DR1, with the major resistance being in the root system in both genotypes. Although the resistance to water movement through the roots and lower stalk in Q188 did not appear to differ from those of the other lines, a much larger resistance was found in the upper stalk of Q188; resistance to water movement through the lower stalk (up to node 5) decreased as the plants matured from 55 to 70 days of age but no comparable changes occurred in the upper portions of the stem. In vivo detection of the xylem vessels with staining techniques confirmed the observed differences in resistances.

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