Ions In Xylem Sap Research Articles

Osmotic regulation mediates embolism vessel refilling via bark water uptake in Salix Matsudana

The aim of this study was to understand the role of bark water uptake in xylem embolism vessel refilling in Salix matsudana. Isolated branch segments of Salix matsudana were soaked in deionized water. Next, the percent loss of conductivity (PLC), the volume, the osmotic potential (Ψs), the concentrations of soluble sugar and ions in xylem sap and the concentration of NSC in the xylem were measured after 2, 4 and 6 h. The PLC decreased, and the volume of xylem sap increased, compared with initial values after soaking for 2, 4, and 6 h. Moreover, the osmotic potential (Ψs) of xylem sap decreased. The concentrations of ions and soluble sugar in the xylem sap increased significantly compared with the initial concentrations after soaking. Based on our findings, water not only entered the xylem vessels through the bark but also repaired the embolism of branches in a certain time. These findings will contribute to the understanding of the physiological and molecular mechanisms between bark water uptake and embolism repair.

Cytosolic Glutamine Synthetase1;2 is Responsible for the Primary Assimilation of Ammonium in Rice Roots

Among three genes for cytosolic glutamine synthetase (OsGS1;1, OsGS1;2 and OsGS1;3) in rice (Oryza sativa L.) plants, the OsGS1;2 gene is known to be mainly expressed in surface cells of roots, but its function was not clearly understood. We characterized knock-out mutants caused by the insertion of an endogenous retrotransposon Tos17 into exon 2 of OsGS1;2. Homozygously inserted mutants showed severe reduction in active tiller number and hence panicle number at harvest. Other yield components, such as spikelet number per panicle, 1,000-spikelet weight and proportion of well ripened grains, were nearly identical between the mutants and wild-type plants. When the contents of free amino acids in roots were compared between the mutants and the wild type, there were marked reductions in contents of glutamine, glutamate, asparagine and aspartate, but a remarkable increase in free ammonium ions in the mutants. Concentrations of amino acids and ammonium ions in xylem sap behaved in a similar fashion. Re-introduction of OsGS1;2 cDNA under the control of its own promoter into the knock-out mutants successfully restored yield components to wild-type levels as well as ammonium concentration in xylem sap. The results indicate that GS1;2 is important in the primary assimilation of ammonium ions taken up by rice roots, with GS1;1 in the roots unable to compensate for GS1;2 functions.

Mineral content of excreta from the spittlebug Philaenus spumarius closely matches that of xylem sap

Summary Analysis of xylem sap from intact transpiring plants is possible using excreta of xylem feeding insects. However, the extent to which the inorganic composition of ingested sap is altered by its passage through the insect has not been fully evaluated. The impact of the xylem feeding insect Philaenus spumarius (meadow spittlebug) on the inorganic composition of ingested sap from tomato (Lycopersicon esculentum) is reported here. Two nondestructive experimental approaches were used. Sap exuding due to root pressure from a cut tomato stem was compared with excreta from a caged insect feeding just below the cut surface. A second method involved pumping a solution of inorganic ions through a section of tomato stem upon which an adult insect was caged. The composition of insect excreta was compared with that of the input and output solutions. Overall, the concentrations of inorganic ions were similar in ingested fluid and excreta except for ammonium, which was generally elevated in excreta samples. It is demonstrated that excreta of P. spumarius can be used for continual monitoring of most inorganic ions in xylem sap of intact transpiring plants, and that stem perfusion is a useful tool for quantifying the effect of the insect on solutions of known composition.

Investigation of the transported heavy metal ions in xylem sap of cucumber plants by size exclusion chromatography and atomic absorption spectrometry

An ‘off-line’ high performance liquid chromatography–graphite furnace atomic absorption spectrometry (HPLC–GF-AAS) method using a size exclusion chromatography (SEC) column was developed to investigate heavy metal ions in xylem sap samples of cucumber plants grown in hydroponics containing iron as Fe(III)-ethylenediaminetetraacetate (Fe(III) EDTA), Fe(III) citrate or FeCl 3 and exposed to lead, nickel or vanadium contamination. The SEC chromatogram of the samples contained the peak of nitrate ions (in significant concentration ≈1400 μg/ml) and some small, unidentified compounds with molecular weight lower than 700 Da. The results indicate that Cu and Mn — which were added to the hydroponics as nutrient elements — determined in the collected fractions during the chromatographic runs are transported in the xylem vessels together with small inorganic ions like nitrate ions. In case of nickel other low-molecular weight compounds eluting earlier than the nitrate ions may take part in its transport toward the shoots. Lead could not be detected in the above mentioned fractions. Determination of vanadium in the fractions was not expected since it could not be detected in the sap samples.

The Chemical Composition of Xylem Sap inVitis viniferaL. cv. Riesling During Vegetative Growth on Three Different Franconian Vineyard Soils and as Influenced by Nitrogen Fertilizer

Cuttings of grapevine (<i>Vitis vinifera</i> L. cv. Riesling clone B 68) grafted on SO4 (Selection Oppenheim No. 4) rootstocks were grown in pots with three different soils from Franconian vineyards derived from different geological formations (namely, Loess, Muschelkalk (shell lime), or Keuper). Additionally, the influence of N-fertilizer treatment was investigated. From the midrib of leaves six to eight of the sole shoot, xylem sap was collected simultaneously by pressurizing the rhizosphere during the vegetative growth phase. The chemical composition of xylem sap was determined and compared with that of the aqueous soil extract. In Muschelkalk soil, carbon, nitrogen, and calcium were present in the greatest concentrations. Sulfur, boron, magnesium, sodium, and potassium were greatest in Keuper, and the concentrations in Loess soil were intermediate. Aqueous extraction of the soils resulted in a two-fold greater concentration of total solutes in Keuper extract compared with Muschelkalk, and more than threefold than in Loess. The apparent volume flow was greatest in the middle leaves along the shoot and in plants grown on Keuper; additionally there was a tendency for fertilizer treatment to increase flow. The concentrations of mineral ions in xylem sap were the same in all the leaves of a shoot of grapevine. An important exception was the supply to the leaves of amino acids, which increased in concentration along the transpiration stream and were greatest in the youngest leaves (particularly in non-fertilized plants). Potassium was the dominant cation in xylem sap and was greatest in plants grown on Keuper. Concentrations of sodium and calcium were increased in non-fertilized plants, but not significantly in vines grown on Muschelkalk. In xylem sap, nitrate was the major anion, followed by malate. Nitrate concentration was greatest in plants grown on Muschelkalk, while malate was greater in plants grown on Keuper. Chloride, sulfate, and phosphate concentration in sap were increased by fertilizer treatment. Abscisic acid was markedly increased in xylem sap of non-fertilized plants grown on Loess and Muschelkalk and was discussed as a signal for nutrient limitation. If Keuper was the substrate it was also increased by fertilizer treatment. Of the organic N-compounds, glutamine was the largest fraction. On the basis of the relation of nitrate to total N in xylem sap, it could be assumed that about 40% to 75% of nitrate reduction took place in the shoots. In general, soil type had only a moderate effect on the chemical composition of the xylem sap compared with the effect of N-fertilizer.

Calcium in the xylem and its influence on the behaviour of stomata

Calcium is known to play an important role in regulating guard cell turgor and the movements of stomata. The concentrations of calcium ions in xylem sap are often higher than 1 mol m -3 , which would be sufficient to influence, or interfere with, stomatal function if such concentrations were delivered to points of evaporation in the vicinity of the guard cells. This paper presents some recent experimental evidence concerning the way in which a plant’s calcium status affects the amount of free calcium in the xylem, and the effect this may have on the diurnal pattern of stomatal behaviour. Changes in the rhizospheric supply of calcium have a major influence on the concentrations in the xylem. In Commelina communis an eightfold increase in rhizospheric calcium led to an increase in the xylem sap in the shoot of approximately sixfold. Very high concentrations of xylem calcium were associated with reduced stomatal opening, and injection of a pulse of calcium ions into the xylem via a catheter caused stomatal closure. Calcium-induced suppression of stomatal aperture does not inflict permanent damage upon the guard cells, because stomatal aperture recovered quickly when the calcium concentration in the xylem was reduced. The experimental data presented suggest that the amount of calcium delivered by the transpiration stream to points of evaporation needs to be regulated if interference with stomatal behaviour is to be avoided. This regulation is likely to occur in tissues such as the mesophyll. The roots may also play an important part in controlling the delivery of calcium into the xylem and evidence is presented of malfunctioning of the regulatory mechanism in roots when plants are exposed to high calcium in the rhizosphere. Some of the data presented are for a calcifuge, Lupinus luteus , and the possibility is discussed that disturbances in stomatal behaviour contribute to the physiological problems of such plants in the presence of high rhizospheric calcium.

Effect of high external NaCl concentrations on ion transport within the shoot of Lupinus albus. I. Ions in xylem sap

Abstract. Xylem sap was collected from individual leaves of intact transpiring lupin plants exposed to increasing concentrations of NaCl by applying pneumatic pressure to the roots. Concentrations of Na+ and Cl− in the xylem sap increased linearly with increases in the external NaCl concentration, averaging about 10% of the external concentration. Concentrations of K+ and NO3−, the other major inorganic ions in the sap, were constant at about 2.5 and 1.5 mol m−3, respectively. There was no preferential direction of Na + or Cl− to either young or old leaves: leaves of all ages received xylem sap having similar concentrations of Na+ and Cl−, and transpiration rates (per unit leaf area) were also similar for all leaves. Plants exposed to 120–160 mol m−3 NaCl rapidly developed injury of oldest leaves; when this occurred, the Na+ concentration in the leaflet midrib sap had increased to about 40 mol m−3 and the total solute concentration to 130 osmol m−3. This suggests that uptake of salts from the transpiration stream had fallen behind the rate of delivery to the leaf and that salts were building up in the apoplast.

Xylem sap analysis for determining the nutrient status and growth of Pinusponderosa

Natural variation in the ion concentration of the xylem sap of ponderosa pine (Pinusponderosa Laws.) in Montana was studied relative to tree height, crown aspect, age, time of day and year, species, tree to tree (within-stand variation), soil chemistry, and growth prediction. Xylem sap was extracted from branches at 2.4–2.7 MPa. The sap was analyzed chemically for 13 ions and total nitrogen. Extraction and analysis are fast and inexpensive. The top third of the crowns of P. ponderosa normally had higher ion concentrations in the sap for all but four ions. Crown aspect has little effect on the ion concentrations in sap. Age is a significant factor in xylem sap ion concentrations. Trees to be compared should be within 10 years in age. Time of day causes significant changes in ion concentration in the sap, but two stands can be compared over the same 2 to 8 sunlight hours. Xylem sap can be collected easily in the winter from frozen branches or in the summer when transpiration should be measured as well. Most ions decrease in concentration in the sap from the time of flush through hardening off. Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) sap has higher Ca than P. ponderosa sap. Slowly growing P. ponderosa had low Ca, Mn, K, P, and N, but high Mg and Si in the sap, compared with more rapidly growing trees. Xylem sap shows promise as a means of simultaneously evaluating the water, nutrient, and energy stress of trees and may be useful as a rapid means of predicting various parameters of tree growth.