Effects of Slowly and Rapidly Permeating Osmotica on Permeability of Excised Roots of Zea mays

1974 ◽  
Vol 1 (2) ◽  
pp. 247 ◽  
Author(s):  
H Greenway
Keyword(s):  
Zea Mays ◽  
Ethylene Glycol ◽  
Water Potential ◽  
Free Space ◽  
Cell Membranes ◽  
Cellular Activity ◽  
Root Tissues ◽  
Three Phases

Excised roots of Z. mays were treated at a water potential of – 20.8 atm, using slowly and rapidly permeating solutes both as osmotica (800 mM ) and as permeants (10 mM ) . The temperature during all experiments was 2�C. The solutes were mannitol, glycerol, and ethylene glycol. In highly vacuolated root tissues there were at least three phases for the influx and efflux of the permeants. These phases presumably represented the free space, the 'cytoplasm', and the 'vacuoIe'. Treatment with slowly permeating osmotica increased the free space of both highly and slightly vacuolated tissues. In highly vacuolated tissues all osmotica doubled the rate of exchange for the 'cytoplasm', but had very little effect on the rate of exchange for the 'vacuole'. The latter observation suggests that the permeability of the tonoplast changed little during plasmolysis. In contrast to highly vacuolated tissues, exposure of slightly vacuolated tissue to osmotica decreased the rates of exchange of the permeant mannitol. Removal of slowly permeating osmotica dramatically increased the permeability of highly vacuolated tissues. Moreover, permeability to rapidly permeating ethylene glycol increased much less than permeability to slowly permeating mannitol and glycerol. These observations suggest that deplasmolysis changed the structure of cell membranes. Permeability of slightly vacuolated tissues was not greatly increased by removal of osmotica. These different effects on the permeability of highly and slightly vacuolated tissues are consistent with earlier results, which showed that removal of slowly permeating osmotica restored metabolism of slightly vacuolated tissues, while it strongly depressed cellular activity of highly vacuolated tissues.

Lateral Stresses in Membranes at Low Water Potential

1987 ◽  
Vol 14 (3) ◽  
pp. 311 ◽  
Author(s):  
J Wolfe
Keyword(s):  
Osmotic Stress ◽  
Water Potential ◽  
Cell Membranes ◽  
Cellular Damage ◽  
Biological Cells ◽  
Severe Dehydration ◽  
Stress Strain ◽  
Stress Measurements ◽  
Different Levels ◽  
Water Contents

Severe dehydration of biological cells can produce large stresses and substantial strains in the membranes of some organelles. Water contents and water potentials which are critical for cellular damage in rather dry tissues may reflect a limiting stress characteristic of cell membranes. Different levels of tolerance of extreme dehydration may therefore be a result of different cellular osmotic pressures or of different stress-strain characteristics of the cellular membranes. In this paper, data from phospholipid osmotic stress measurements are used to model the stresses generated in membranes in dehydrated phases.

NET CO2 EXCHANGE RATE AS A SENSITIVE INDICATOR OF PLANT WATER STATUS IN CORN (Zea mays L.)

1988 ◽  
Vol 68 (3) ◽  
pp. 597-606 ◽  
Author(s):  
R. CEULEMANS ◽  
I. IMPENS ◽  
M. C. LAKER ◽  
F. M. G. VAN ASSCHE ◽  
R. MOTTRAM
Keyword(s):  
Zea Mays ◽  
Exchange Rate ◽  
Water Stress ◽  
Water Potential ◽  
Soil Water ◽  
Leaf Water Potential ◽  
Zea Mays L ◽  
Leaf Water ◽  
Water Capacity ◽  
Available Water Capacity

With the objective to evaluate and compare different physiological plant parameters as indicators of water stress, net CO2 exchange rate (NCER), leaf temperature, predawn and daytime leaf water potential were monitored diurnally on last fully expanded leaves of corn (Zea mays L.) plants under two different soil water treatments (stressed and nonstressed) during a 10-d period at anthesis in a semi-arid region in South Africa. Profile available water capacity (PAWC) was used to express the soil water contents during the experiments. A significant decrease in NCER was noticed as soon as 30% of PAWC was extracted, i.e. 2 or 3 d after irrigation. Although the results were limited to a short, well-defined measuring period, NCER, and especially NCER at noon, seemed to be a more sensitive and more reliable indicator of corn water stress than, for example, predawn or daytime leaf water potential, at least under the conditions studied here. This reduction in NCER might have a significant impact on total biomass, rooting density, flower and ear formation.Key words: Corn, irrigation scheduling, photosynthesis, leaf water potential, profile available water capacity, soil water content

scholarly journals Osmotic Behavior of Oat Coleoptile Tissue in Relation to Growth

1963 ◽  
Vol 47 (1) ◽  
pp. 83-101 ◽  
Author(s):  
Peter M. Ray ◽  
Albert W. Ruesink
Keyword(s):  
Water Potential ◽  
Osmotic Pressure ◽  
Free Space ◽  
Traditional Method ◽  
Turgor Pressure ◽  
Immersion Method ◽  
Osmotic Swelling ◽  
Equilibrium Response ◽  
Large Water ◽  
Osmotic Behavior

Efforts were made to estimate the water potential difference that is required, between rapidly growing oat coleoptile cylinders and dilute medium, to support the rate of water uptake involved in elongation, (a) by the traditional method of determining the concentration of mannitol in which the tissue neither gains nor loses water, and (b) by measuring the rates of osmotic exchanges induced by treating the tissue with different hypotonic mannitol concentrations. Both methods indicated large water potential differences (3 to 10 atm), in some cases approaching the osmotic pressure of the cells. However, indication was obtained that the rates of osmotic exchanges induced by mannitol solutions, and presumably also the equilibrium response sought in (a), are governed by the rate of diffusional exchange of mannitol with the free space rather than by the permeability of the tissue to water. Osmotic swelling of the tissue measured by immersing it in water after its turgor pressure had been reduced by evaporation, was at least two to four times more rapid than when mannitol was involved. The permeability to water estimated by the evaporation-immersion method indicated that rapidly elongating cylinders have water potentials between -0.8 and -2.5 atm, or between 10 and 25 per cent of their osmotic pressure.

A thermodynamic analysis of the feasibility of water secretion into xylem vessels against a water potential gradient

2015 ◽  
Vol 42 (9) ◽  
pp. 828 ◽  
Author(s):  
Lars H. Wegner
Keyword(s):  
Free Energy ◽  
Water Potential ◽  
Thermodynamic Analysis ◽  
Cell Membranes ◽  
Chemical Potential ◽  
Potential Gradient ◽  
Energy Status ◽  
Hordeum Vulgare L ◽  
Water Potential Gradient ◽  
Water Secretion

A series of recent publications has launched a debate on trans-membrane water secretion into root xylem vessels against a water potential gradient, energised by a cotransport with salts (e.g. KCl) that follow their chemical potential gradient. Cation–chloride–cotransporter -type transporters that function in this way in mammalian epithelia were detected in root stelar cells bordering on xylem vessels. Using literature data on barley (Hordeum vulgare L.) seedlings, one study confirmed that K+ and Cl– gradients across stelar cell membranes favour salt efflux. Moreover, the energetic costs of putative water secretion into the xylem (required for maintaining ionic gradients) would amount to just 0.12% of the energy captured by photosynthetic C assimilation if transpirational water flow relied exclusively on this mechanism. Here, a detailed thermodynamic analysis of water secretion into xylem vessels is undertaken, including an approach that exploits its analogy to a desalinisation process. Water backflow due to the passive hydraulic conductivity of stelar cell membranes is also considered. By comparing free energy consumption by putative water secretion with (i) the free energy pool provided by root respiration and (ii) stelar ATPase activity, the feasibility of this mechanism is confirmed but is shown to depend critically on the plant’s energy status.

Effects of No-tillage and Ploughing on Efficiency of Water Use in Maize and Cowpea

1978 ◽  
Vol 14 (2) ◽  
pp. 113-119 ◽  
Author(s):  
R. Lal ◽  
P. R. Maurya ◽  
S. Osei-Yeboah
Keyword(s):  
Zea Mays ◽  
Water Use Efficiency ◽  
Water Potential ◽  
Water Use ◽  
Leaf Water Potential ◽  
Vigna Unguiculata ◽  
Sprinkler System ◽  
Leaf Water ◽  
No Tillage ◽  
Use Efficiency

SUMMARYWater use efficiency of maize (Zea mays) and cowpea (Vigna unguiculata) was investigated, with and without tillage, under four irrigation frequencies in which 12 mm of water was applied at 2, 4, 8 and 12 day intervals, using a sprinkler system. Both maize and cowpea under no-tillage yielded more than with conventional ploughing. Water use efficiency of maize without tillage was 18·3, 17·5, 57·8 and 100% greater than with tillage at irrigation frequencies of 2, 4, 8 and 12 days respectively. Whereas the leaf water potential of cowpea was not affected by tillage, that of maize was generally higher for no-tillage compared with conventional ploughing.

Emerging effects of selected rhizosphere properties on transpiration and leaf water potential of two Zea mays L. genotypes in semi-arid environments

2020 ◽  
Author(s):  
Tina Köhler ◽  
Daniel-Sebastian Moser ◽  
Ákos Botezatu ◽  
Jana Kholova ◽  
Andrea Carminati ◽  
...  
Keyword(s):  
Zea Mays ◽  
Water Potential ◽  
Leaf Water Potential ◽  
Zea Mays L ◽  
Root Hairs ◽  
Leaf Water ◽  
Soil Drying ◽  
Wild Type ◽  
Stomatal Regulation ◽  
Semi Arid

<p>Understanding the mechanisms that control water use of plants exposed to soil drying and increasing vapour pressure deficit (VPD) has important implications for crop growth in semi-arid regions with low-input agriculture. In particular, the effect of belowground processes on transpiration and stomatal regulation remains controversial. Objective of this study was to understand the role of soil properties and root hairs (as an example of rhizosphere traits) on transpiration and leaf water potential. We hypothesize that root hairs facilitate the water extraction from drying soils, particularly at high VPD, and that this impacts the relation between transpiration rate and leaf water potential. We further hypothesize that stomatal regulation attenuates the drop in leaf water potential when the soil water flow cannot match the transpiration demand and thus emphasizes the importance of root hairs on transpiration rates during soil drying.</p><p>We compared maize (Zea mays L.) with (wild-type) and without (mutant) root hairs in three different soil substrates (Alfisol, Vertisol and Sandy Soil). Transpiration and leaf water potential were monitored at varying VPD and soil moistures during soil drying. The hairless mutant showed a higher transpiration in wet soils but declined transpiration at greater water contents as compared to the wild-type. Under well-watered conditions, both genotypes had the highest transpiration rates in Vertisol. In Vertisol, both genotypes closed their stomata at relatively higher water content levels. The relation between transpiration and soil moisture strongly varied between soils. No obvious differences between the genotypes were visible in the relationship between leaf water potential and transpiration. This is explained by the prompt closure of stomata. This study provides experimental evidence of the strong link between stomatal regulation and soil-root hydraulic properties.</p>

scholarly journals The morphological, physiological and biochemical responses of sweet corn to foliar application of amino acids biostimulants sprayed at three growth stages

2019 ◽  
Vol 13 ((03) 2019) ◽  
pp. 412-417 ◽  
Author(s):  
Maher J. Tadros ◽  
Omari, Munir A. Turk
Keyword(s):  
Amino Acids ◽  
Zea Mays ◽  
Water Potential ◽  
Protein Content ◽  
Sweet Corn ◽  
Foliar Application ◽  
Growth Stages ◽  
Biochemical Characteristics ◽  
Physiological And Biochemical ◽  
Nitrogen Phosphorus

Corn (Zea mays L.) is one of the most important cereal crops in many countries due to its high nutritive value and a raw material for many industrial products. This research was conducted to determine the optimum concentration of the foliar application of amino acids biostimulants at appropriate growth stage for achieving more efficient use of the foliar application on sweet corn (Zea mays saccharata) var. merkur. The foliar application used in this study was the commercial product (PerfectoseTM, liquid) which is a well known product and commonly used for different crops in Jordan. The experiment was conducted at the greenhouse during the summer of 2015. Corn plants were sprayed with four different concentrations: 1, 2, 3 and 4ml/L at three different growth stages: 7th leaf, tasseling and milk stage, while the control plants were sprayed with distilled water only. The morphological characteristics (plant height, root length and ear length), physiological characteristics (leaf relative water content and leaf water potential), and biochemical characteristics (chlorophyll content, nitrogen, phosphorus, potassium and protein content) were recorded during the experiment. The results indicated that the corn plant height, leaf water potential, chlorophyll content, nitrogen, phosphorus, potassium and protein content were significantly affected by the foliar application treatments, while the rest of the parameters studied were not significant. The treatments 4ml/L at milk stage and 1ml/L and 2ml/L at 7th leaf stage were most effective in the majority of parameters studied. It can be concluded that using foliar application of amino acids biostimulants could positively enhance sweet corn morphological, physiological and biochemical characteristics.

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