Variation of Leaf Characteristics With Level of Insertion on a Grass Tiller. III. Tissue Water Relations

1977 ◽  
Vol 4 (5) ◽  
pp. 733 ◽  
Author(s):  
JR Wilson
Keyword(s):  
Water Content ◽  
Water Relations ◽  
Osmotic Potential ◽  
Water Status ◽  
Physiological Age ◽  
Wall Material ◽  
Panicum Maximum ◽  
Stomatal Frequency ◽  
Matric Potential ◽  
Potential Component

Plants of a grass, green panic (Panicum maximum var. trichoglume) were grown under controlled environmental and nutritional regimes. Throughout the growth of the plants, leaves from varying levels of insertion on the main stem were sampled at comparable physiological age (viz, when just fully expanded) and their water relations characteristics measured over a range from full turgidity to a moderately stressed condition to determine whether there were inherent differences between leaves on the shoot. Leaf water potential, osmotic potential, and pressure potential fell in a similar manner for the leaves from each insertion level as leaf relative water content declined. A small increase in the average water and osmotic potential, and also in the average matric potential component, estimated for a common reIative water content, was evident with increasingly higher level of leaf insertion. Despite marked increases in the proportion of cell wall material and a trend towards increasing lignification in leaves of higher insertion, the bulk coefficient of elasticity of the tissues showed no gradient of change, and the overall change in the matric potential component was small. Various other chemical and morphological characteristics showed definite gradients with insertion level: for example, stomatal frequency increased from 91 to 287 mm-2 from leaf 5 to the flag leaf. There was no evidence of a progressive variation with insertion level in the water status of leaves sampled fresh from the plants, and thus no support for the theory that upper leaves on a tiller develop under inherently higher water stress, which could account for their xeromorphic chemical, anatomical and morphological features. It appears that in green panic at least, the water relations characteristics measured, with the exception of stomatal frequency, exhibit no strong inherent gradients with insertion level of leaves which could seriously confound comparisons of water status between plants in different treatments.

Adaptation to Water Stress of the Leaf Water Relations of Four Tropical Forage Species

1980 ◽  
Vol 7 (2) ◽  
pp. 207 ◽  
Author(s):  
JR Wilson ◽  
MM Ludlow ◽  
MJ Fisher ◽  
E Schulze
Keyword(s):  
Water Stress ◽  
Water Content ◽  
Water Relations ◽  
Bound Water ◽  
Leaf Tissue ◽  
Dry Weight ◽  
Panicum Maximum ◽  
Soil Drying ◽  
Buffel Grass ◽  
Heteropogon Contortus

Three tropical grasses, green panic (Panicum maximum var, trichoglume), spear grass (Heteropogon contortus) and buffel grass (Cenchrus ciliaris) and the tropical legume siratro (Macroptilium atropurpureum), were grown in plots in a semi-arid field environment. The water relations characteristics of leaves from plants subjected to a soil drying cycle were compared with those of unstressed leaves from plants in irrigated plots. Minimum water potentials attained in the stressed leaves were c. -44, - 38, - 33 and - 13 bar for the four species, respectively. The grass leaves adjusted osmotically to water stress, apparently through accumulation of solutes, so that there was a decrease in osmotic potential at full turgor (Ψπ100) of 5.5, 3.9 and 7.1 bar, and in water potential at zero turgor (Ψ0) of 8.6, 6.5 and 8.6 bar for green panic, spear grass and buffel respectively. Water stress appeared to increase slightly the proportion of bound water (B) and the bulk modulus of elasticity (ε) of the grass leaves, but it did not alter the relative water content at zero turgor (RWC0) or the ratio of turgid water content to dry weight of the tissue. The Ψπ100 and Ψ0 of stressed siratro leaves decreased by 2.5-4 bar and 3-5 bar respectively when subjected to soil drying cycles. These changes could be explained by the marked decrease in the ratio of turgid water content to dry weight of the leaf tissue rather than by accumulation of solutes. The values of RWC0 and ε for siratro leaves were not altered by stress but, in contrast to the grasses, B was apparently decreased although the data exhibited high variability. Adjustments in Ψπ100 and Ψ0 of stressed leaves of buffel grass and siratro were largely lost within 10 days of rewatering.

Influence of water stress on parameters associated with herbage quality of Panicum maximum var. trichoglume

1975 ◽  
Vol 26 (1) ◽  
pp. 127 ◽  
Author(s):  
JR Wilson ◽  
TT Ng
Keyword(s):  
Cell Wall ◽  
Water Stress ◽  
Dry Matter ◽  
Stem Elongation ◽  
Physiological Age ◽  
Wall Material ◽  
Panicum Maximum ◽  
Dry Matter Digestibility ◽  
Influence Of Water

Plants of Panicum maximum var. trichoglume grown in soil in pots under a controlled environment were subjected to water stress and the effect on forage quality was assessed. Stress was applied as a series of drying and re-wetting cycles, and harvests of total laminae, stem, root, and also specific laminae, were taken 5, 10, 17, 27 and 57 days after the commencement of stress treatment. When compared with control plants of similar chronological age, the dry matter digestibility (estimated by an in vitro technique) of the stressed plants was lower in leaves 4, 6 and 8, similar in total green laminae and in leaves 10 and 12, and higher in stem and dead laminae. The cell wall content of various tissues of the stressed plants was lower than that of the controls. Water stress delayed stem elongation and flowering. It is postulated that stress also delayed the normal ontogenetical changes of the leaves. If comparison was made on a physiological age basis then stress markedly lowered the dry matter digestibility but had little effect on the cell wall content. The broader implication of delayed ontogeny is briefly discussed. The decrease in dry matter digestibility in stressed plants was not associated with changes in the proportions of cellulose, hemicellulose or lignin, but reflected a decline in digestibility of cell wall material.

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

2004 ◽  
Vol 82 (2) ◽  
pp. 273-281 ◽  
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 pressure–volume 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, pressure–volume curves, yield, mineral content.

Effects of Temperature, Soil Water Status and Depth of Planting on Germination and Emergence of Maize (Zea Mays) Adapted to Semi-Arid Eastern Kenya

1993 ◽  
Vol 29 (3) ◽  
pp. 351-364 ◽  
Author(s):  
J. K. Itabari ◽  
P. J. Gregory ◽  
R. K. Jones
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Water Status ◽  
Soil Water Potential ◽  
Thermal Time ◽  
Controlled Environment ◽  
Base Temperature ◽  
Matric Potential ◽  
Effects Of Temperature ◽  
Time Required

SUMMARYThe effects of temperature and soil water potential on maize germination were investigated in controlled environment conditions and the effects of depth of planting and a mulch on maize emergence were studied in a field experiment in eastern Kenya. The rate of germination increased to an optimum temperature of 33.6°C above a base temperature of 6.1°C and decreased above the optimum to zero germination at 42.9°C. The thermal time for median germination increased from 51.5°Cd to 56.4°Cd as soil matric potential decreased from -5 to -40 kPa. Soil water content, depth of planting, and their interaction had significant (P < 0.001) effects on final germination and emergence but mulch, or any interactions involving mulch, had no such effects. Increasing depth of planting by 1 cm increased the thermal time required for emergence by 2.8°Cd, and decreasing water content by 1% increased the thermal time required for emergence by 3.2°Cd.Germinación y emergencia del maíz

Water Relations of Laticifers in Nerium oleander

1981 ◽  
Vol 8 (3) ◽  
pp. 329 ◽  
Author(s):  
WJS Downton
Keyword(s):  
Water Potential ◽  
Water Relations ◽  
Osmotic Potential ◽  
Water Status ◽  
Turgor Pressure ◽  
Death Valley ◽  
Nerium Oleander ◽  
Laboratory Measurements ◽  
Hydrocarbon Sources ◽  
Daily Changes

The water relations of laticifers in N. oleander were examined for plants growing in Death Valley, California, USA. Osmotic potential of laticifers in well watered plants paralleled the daily changes in leaf water potential. The turgor pressure of laticifers was usually less than bulk leaf turgor. Laticifer turgor was maintained in the absence of positive leaf turgor in severely water stressed plants (Ψw ͭ6 -7.0 MPa) and latex exuded when leaves were cut. The recovery in water status of leaves and laticifers following watering of the plants is described. Laboratory measurements confirmed that laticifer turgor differed from bulk leaf turgor and that it was maintained over a range of water potentials. These observations may have relevance for some of the latex-bearing plants currently being considered as future hydrocarbon sources.

Leaf and root osmotic adjustment in drought-stressed Quercusalba, Q. macrocarpa, and Q. stellata seedlings

1988 ◽  
Vol 18 (1) ◽  
pp. 1-5 ◽  
Author(s):  
William C. Parker ◽  
Stephen G. Pallardy
Keyword(s):  
Water Potential ◽  
Water Content ◽  
Water Relations ◽  
Osmotic Adjustment ◽  
Osmotic Potential ◽  
Root Tissue ◽  
Tissue Elasticity ◽  
Tissue Water ◽  
Before And After ◽  
Relative Water

The leaf and root tissue water relations of Quercusalba L., Quercusmacrocarpa Michx., and Quercusstellata Wang. seedlings before and after drought were examined to evaluate the occurrence and comparative extent of osmotic adjustment in seedlings of these species. Drought resulted in active osmotic adjustment in leaves of all three species, with decreases in osmotic potential at full tissue hydration and at the turgor loss point from 0.25 to 0.60 MPa. Active osmotic adjustment in Q. stellata, and increased root tissue elasticity in Q. macrocarpa and Q. alba, resulted in turgor loss of roots occurring at a water potential 0.36 to 0.66 MPa lower in drought-stressed than in well-watered seedlings. Species differed in tissue water relations only before drought, with Q. stellata exhibiting lower osmotic potentials than Q. alba and Q. macrocarpa. Estimates of the osmotic potential at full saturation were generally lower in leaves than in roots, but the osmotic potential at turgor loss was similar. Roots exhibited turgor loss at lower values of relative water content and experienced a more gradual decrease in water potential per unit water content during dehydration than did leaves. This response indicates greater relative tissue capacitance in roots than in leaves in these species.

Water relations in Azospirillum-inoculated wheat seedlings under osmotic stress

1998 ◽  
Vol 76 (2) ◽  
pp. 238-244 ◽  
Author(s):  
Cecilia M Creus ◽  
Rolando J Sueldo ◽  
Carlos A Barassi
Keyword(s):  
Cell Wall ◽  
Osmotic Stress ◽  
Water Relations ◽  
Osmotic Potential ◽  
Modulus Of Elasticity ◽  
Growth Promotion ◽  
Water Status ◽  
Water Volume ◽  
Wheat Seedlings ◽  
Water Fraction

Azospirillum has been shown to improve coleoptile growth in seedlings growing in darkness under osmotic stress. However, the changes in water relations that may occur in this experimental system have not yet been studied. Two-centimetre long Triticum aestivum cv. Buck Pucará and Triticum durum cv. Balcarceño-INTA seedlings were inoculated with viable or autoclaved (control) Azospirillum brasilense Sp. 245 bacteria, at approximately 108 cells per seedling. Three days after inoculation, seedlings were exposed to osmotic stress by immersing their roots in 20% polyethylene glycol 6000 for up to 72 h. Germination and seedling growth were at 20°C in darkness. Shoots were excised after 72 h of stress, and water-status parameters were determined through pressure-volume analyses. While osmotic potential at full turgor remained constant, Azospirillum-stimulated growth in Buck Pucará seedlings was accompanied by significant decreases in osmotic potential and relative water content at zero turgor, in volumetric cell wall modulus of elasticity, and in absolute symplastic water volume and by a significant rise in apoplastic water fraction parameters. Except for a constant volumetric cell wall modulus of elasticity, similar results were obtained with Balcarceño-INTA seedlings. However, bacterial growth promotion was evident only in the less tolerant cv. Buck Pucará. Turgor at low water potential was higher in inoculated seedlings in both wheat cultivars under osmotic stress. These results are consistent with a better water status in Azospirillum-inoculated wheat seedlings under water stress, where both effects on cell wall elasticity and (or) apoplastic water are evident.Key words: Azospirillum, drought, seedlings, water status, wheat.

Sensitivity of root and leaf water status in maize (Zea mays) subjected to mild soil dryness

1998 ◽  
Vol 25 (3) ◽  
pp. 307 ◽  
Author(s):  
U. Schmidhalter ◽  
Z. Burucs ◽  
K.H. Camp
Keyword(s):  
Zea Mays ◽  
Osmotic Potential ◽  
Water Status ◽  
Mild Stress ◽  
Diurnal Changes ◽  
Matric Potential ◽  
Leaf Water Status ◽  
Diurnal Courses ◽  
Relative Water ◽  
Soil Dryness

The aim of this work was to test the sensitivity of the water potential (Ψw), osmotic potential (Ψs) and turgor (Ψp) of roots and leaves of maize seedlings (Zea mays L. cv. Carla) subjected to a mild stress in drying soil in a growth chamber. To the best of our knowledge there are no experimental data which describes diurnal courses of Ψw in soil, roots, and leaves and the parallel changes in the osmotic potential (Ψs) and turgor (Ψp) of roots and leaves from plants grown in moist and drying soil. Root and leaf Ψw varied diurnally, the amplitude being much more marked in leaves than in roots. Root and leaf Ψw did not achieve equilibrium at predawn with the bulk soil matric potential (Ψm) but became higher. Our results are at variance with data indicating root Ψw is a sensitive indicator of soil dryness. Root Ψw in the well-watered and drought-stressed treatments did not differ, whereas daytime leaf Ψw in the droughted treatment was lower 6 days after water was withheld. Diurnal changes in Ψs and Ψp were more marked in leaves than in roots. Withholding water lowered leaf Yp, whereas root Ψp substantially increased after only 3 days of withholding water. Early mild stress can be more easily and more quickly identified by changes in root Ψs, increases in root Ψp, or the divergence in root and leaf Ψp than by a lower Ψw of root or leaf. Relative water contents of roots and leaves measured in the light period indicated also sensitively falling Ψm.

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

1996 ◽  
Vol 28 (3) ◽  
pp. 257-266 ◽  
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.

scholarly journals Water relations in seed biology

1998 ◽  
Vol 55 (spe) ◽  
pp. 98-101 ◽  
Author(s):  
F. A. Villela
Keyword(s):  
Water Potential ◽  
Water Content ◽  
Seed Development ◽  
Water Relations ◽  
Water Status ◽  
Regulatory Role ◽  
Seed Biology

The water relations play a fundamental role in seed biology. Thus, the purpose of the present paper was to analyze the performance of water status in seed development and germination. The researches have suggested that the water potential of the seed or seed structures provides a better indicator of the seed water status than water content. The seed water status plays a regulatory role in seed development and germination.

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