Xylem Sap from Actinidia chinensis: Apparent Differences in Sap Composition Arising from the Method of Collection

Large differences in composition were found between xylem sapcollected from Actinidia chinensis (Chinese gooseberry or kiwifruit) as bleeding sap and sap collected by vacuum extraction.A comparison of saps collected by the two methods has littlemeaning, however, unless the position on the plant from whichsap was collected and the prior treatment of the plant are specified.Furthermore the composition of bleeding sap changes rapidlywith time, probably because of marked gradients in concentrationof individual solutes in the xylem sap from the base to thetop of the plant. Contamination of vacuum-extracted sap by cellularcontents was shown to be insignificant. Sap collected as bleeding sap and by vacuum extraction are ofsomewhat different origins. It would be difficult to predictthe composition of bleeding sap simply from a knowledge of vacuum-extractedsap: it may be similarly unwise to predict the composition ofthe transpiration stream from that of vacuum extracted sap. Actinidia chinensis, kiwi fruit, Chinese gooseberry, xylem sap, bleeding sap, vacuum-extraction     

Chemical Composition of Phloem Sap from the Uppermost Internode of the Rice Plant

The chemical composition of phloem sap from the uppermost internodeof rice plants (Oryza sativa L., var. Kantou), one week afteranthesis, was compared with that of phloem sap from the leafsheath of a young seedling. The pure phloem sap from rice plantswas collected by an insect laser technique. The phloem sap from the uppermost internode contained a highlevel of sucrose (573.8 mM) which was the only sugar detected.The concentrations of total amino acids, potassium and ATP were124.8 mM, 40.4 mM and 1.76 mM, respectively. The concentrationof sucrose was three times higher and the potassium level wasone third as high in the internode sap as in the phloem sapfrom the leaf sheath. The total concentration of amino acidswas almost the same, but the relative amount of each amino acidwas quite different. The ratios of levels of Glu to Gln andof levels of Asp to Asn in the phloem sap from the uppermostinternode were smaller than those in the phloem sap from theleaf sheath. The adenylate energy charge was 0.92–0.93in both types of phloem sap. The amino acid composition of the phloem sap from the uppermostinternode was compared with that of the phloem sap of the flagleaf and the endosperm sap of the same plant, one week afteranthesis. The differences in composition along the phloem pathwaysuggest the selective translocation of amino acid. (Received July 21, 1989; Accepted December 11, 1989)     

Terpenoids are transported in the xylem sap of Norway spruce

Norway spruce is a conifer storing large amounts of terpenoids in resin ducts of various tissues. Parts of the terpenoids stored in needles can be emitted together with de novo synthesized terpenoids. Since previous studies provided hints on xylem transported terpenoids as a third emission source, we tested if terpenoids are transported in xylem sap of Norway spruce. We further aimed at understanding if they might contribute to terpenoid emission from needles. We determined terpenoid content and composition in xylem sap, needles, bark, wood and roots of field grown trees, as well as terpenoid emissions from needles. We found considerable amounts of terpenoids—mainly oxygenated compounds—in xylem sap. The terpenoid concentration in xylem sap was relatively low compared with the content in other tissues, where terpenoids are stored in resin ducts. Importantly, the terpenoid composition in the xylem sap greatly differed from the composition in wood, bark or roots, suggesting that an internal transport of terpenoids takes place at the sites of xylem loading. Four terpenoids were identified in xylem sap and emissions, but not within needle tissue, suggesting that these compounds are likely derived from xylem sap. Our work gives hints that plant internal transport of terpenoids exists within conifers; studies on their functions should be a focus of future research.     

Changes in the amino acid composition and protein modification in phloem sap of rice

Pure phloem sap was collected from insects feeding on rice (Oryza sativa L.) leaves by a laser technique similar to the aphid stylet technique. Rapid circulation of nitrogen in the sieve tubes was demonstrated directly using ¹⁵N as a tracer. Application to the roots of the metabolic inhibitors of amino acids, aminooxyacetate and methioninesulfoximine, changed the amino acid composition in the sieve tubes. Feeding methionine to leaf tips resulted in its bulk transfer into the sieve tubes. In vitro experiments confirmed the existence of protein kinases in the pure rice phloem sap. The phosphorylation status of the sieve tube sap proteins was affected by the light regime. The possibility that changes in chemical composition or protein modification such as phosphorylation in the sieve tubes might affect plant growth are discussed.Analysis of pure phloem sap collected from rice plants by insect laser technique has shown dynamic changes in the chemical composition and the quality of proteins in the sap.     

Amino Acid Composition Along the Transport Pathway during Grain Filling in Wheat

The amino acid composition of endosperm cavity sap and of sieve tube saps from the flag leaf, peduncle, rachis, grain pedicel, and grain were determined for wheat plants just past the mid-half of grain filling. On a mole percent basis, glutamine accounted for almost half of the amino acids in sieve tube sap from the peduncle and ear. Other protein amino acids, plug γ-aminobutyrate, were present in varying, but mostly low (a few mole percent) proportions. The amino acid composition of phloem exudate resembled that of the mature wheat grain. The proportions of amino acids in the endosperm cavity were generally similar to those of the sieve tube sap supplying the grain. Cysteine, however, while virtually absent from sieve tube sap, comprised 1 to 2 mole percent of amino acids in the endosperm cavity, suggesting it is transported in a different form. Also, alanine and, to a lesser extent, glutamate were relatively more prominent in endosperm cavity sap than in the sieve tube sap. Thus, while most amino acids were more concentrated in the sieve tube sap than in the endosperm cavity sap, alanine and glutamate appeared to be moving from the sieve tube to the endosperm cavity in the absence of, or perhaps even against, their concentration gradients.     

Evaluation of the most adequate organ of reference for sap analysis in the tomato plant

The most adequate organ of reference for sap analysis is studied during the phenological stage corresponding to the fructification of the second flower bud in the tomato plant grown in hydroponic culture with normal nutrient solution. Thus, the composition of the sap extracted from petioles of leaves in different stages of growth is studied. The results obtained indicate that the sap extracted from the petioles of fully grown young leaves is the best for achieving a nutritional study of the tomato plant.     

Characterization of the maize xylem sap proteome

The xylem in plants has mainly been described as a conduit for water and minerals, but emerging evidence also indicates that the xylem contains protein. To study the proteins in xylem sap, we characterized the identity and composition of the maize xylem sap proteome. The composition of the xylem sap proteome in maize revealed proteins related to different phases of xylem differentiation including cell wall metabolism, secondary cell wall synthesis, and programmed cell death. Many proteins were found to be present as multiple isoforms and some of these isoforms are glycosylated. Proteins involved in defense mechanisms were also present in xylem sap and the sap proteins were shown to have antifungal activity in bioassays.     

Seasonal and spatial variation of carbohydrates in mistletoes (Viscum album) and the xylem sap of its hosts (Populus x euamericana and Abies alba)

In the present field study we analysed the seasonal pattern of carbohydrate composition and contents in the xylem sap of Viscum album and the xylem sap of a deciduous ( Populus × euramericana ) and a coniferous ( Abies alba ) host tree species. The results were compared with the soluble carbohydrate composition and contents of mistletoe tissues. On both hosts significant amounts of glucose, fructose, and sucrose were found in the xylem sap of Viscum throughout the seasons. The general seasonal pattern of sugar contents, i.e. high concentrations in spring and lower concentrations in other seasons on Populus , and intermediate concentrations throughout the year on Abies , largely reflected the xylem sap carbohydrate composition and contents of the respective host. These observations provide indirect evidence for carbohydrate flux from the xylem sap of the host into the mistletoe. However, in both hosts xylem sap seems to be deviated into the mistletoe without specific control of carbohydrate flux. Differences observed between the seasonal pattern of xylem sap carbohydrate concentrations in Viscum on Populus and Abies may originate from the different time of leaf development of these species. A clear-cut seasonal pattern of soluble carbohydrates was not observed in the leaves of Viscum on both hosts. Still soluble carbohydrates seem to be reallocated from the senescing to the newly developed leaves of Viscum indicating that the seasonal requirement of carbohydrate for growth and development can only completely be met by carbohydrate acquisition from the host and their own photosynthesis.     

Composition of the Xylem Sap of Tea Plants (Camellia sinensis L.)

A modified method for the collection of xylem sap from tea plantsis described. In multistemmed tea plants a marked differencein the composition of the sap collected from different branchesof comparable diameter on the same plant was found. The possibilitythat the variation could be due to root disease or mechanicaldamage on one side of the tree was eliminated byusing V-stemsfrom a main branch. The sap contained a small quantity of asubstance which showed gibberellin-like activity.     

Seasonal and spatial variation of reduced sulphur compounds in mistletoes (Viscum album) and the xylem sap of its hosts (Populus × euramericana and Abies alba)

In the present field study with adult trees inhabited by Viscum album , the question was addressed as to whether European mistletoes are able to remove reduced sulphur from the xylem sap of its hosts. For this purpose the reduced sulphur composition and content of the xylem sap of Viscum album and the corresponding hosts Populus  ×  euramericana and Abies alba were analysed. The xylem sap of Viscum was enriched in reduced sulphur compared to the hosts but still reflected the higher reduced sulphur content of Populus compared to Abies . Despite similar xylem sap composition of the hosts with glutathione as the dominating thiol, Viscum on Populus contained predominantly cysteine, Viscum on Abies predominantly glutathione in its xylem sap. These findings suggest selective and different removal of reduced sulphur from these hosts. Still the amount of reduced sulphur removed was too small to result in changes of the concentration of thiols in the xylem sap of the hosts that are statistically significant, probably due to the high variability encountered under field conditions. Despite the differences in the reduced sulphur composition and contents of the xylem sap between Viscum on Populus and Viscum on Abies , total thiol content as well as thiol composition of Viscum leaves on the two hosts were similar throughout the seasons. The seasonal pattern in the thiol composition and contents of Viscum leaves showed high levels in spring and autumn and low levels in summer. The significance of these seasonal changes is discussed.     

Lipids in xylem sap of woody plants across the angiosperm phylogeny

Lipids have been observed attached to lumen-facing surfaces of mature xylem conduits of several plant species, but there has been little research on their functions or effects on water transport, and only one lipidomic study of the xylem apoplast. Therefore, we conducted lipidomic analyses of xylem sap from woody stems of seven plants representing six major angiosperm clades, including basal magnoliids, monocots and eudicots, to characterize and quantify phospholipids, galactolipids and sulfolipids in sap using mass spectrometry. Locations of lipids in vessels of Laurus nobilis were imaged using transmission electron microscopy and confocal microscopy. Xylem sap contained the galactolipids di- and monogalactosyldiacylglycerol, as well as all common plant phospholipids, but only traces of sulfolipids, with total lipid concentrations in extracted sap ranging from 0.18 to 0.63 nmol ml⁻¹ across all seven species. Contamination of extracted sap from lipids in cut living cells was found to be negligible. Lipid composition of sap was compared with wood in two species and was largely similar, suggesting that sap lipids, including galactolipids, originate from cell content of living vessels. Seasonal changes in lipid composition of sap were observed for one species. Lipid layers coated all lumen-facing vessel surfaces of L. nobilis, and lipids were highly concentrated in inter-vessel pits. The findings suggest that apoplastic, amphiphilic xylem lipids are a universal feature of angiosperms. The findings require a reinterpretation of the cohesion-tension theory of water transport to account for the effects of apoplastic lipids on dynamic surface tension and hydraulic conductance in xylem.     

Effects of iron deficiency on the composition of the leaf apoplastic fluid and xylem sap in sugar beet. Implications for iron and carbon transport

The effects of iron deficiency on the composition of the xylem sap and leaf apoplastic fluid have been characterized in sugar beet (Beta vulgaris Monohil hybrid). pH was estimated from direct measurements in apoplastic fluid and xylem sap obtained by centrifugation and by fluorescence of leaves incubated with 5-carboxyfluorescein and fluorescein isothiocyanate-dextran. Iron deficiency caused a slight decrease in the pH of the leaf apoplast (from 6.3 down to 5.9) and xylem sap (from 6.0 down to 5.7) of sugar beet. Major organic acids found in leaf apoplastic fluid and xylem sap were malate and citrate. Total organic acid concentration in control plants was 4.3 mM in apoplastic fluid and 9.4 mM in xylem sap and increased to 12.2 and 50.4 mM, respectively, in iron-deficient plants. Inorganic cation and anion concentrations also changed with iron deficiency both in apoplastic fluid and xylem sap. Iron decreased with iron deficiency from 5.5 to 2.5 microM in apoplastic fluid and xylem sap. Major predicted iron species in both compartments were [FeCitOH](-1) in the controls and [FeCit(2)](-3) in the iron-deficient plants. Data suggest the existence of an influx of organic acids from the roots to the leaves via xylem, probably associated to an anaplerotic carbon dioxide fixation by roots.     

Nitrogen and Cation Nutrition of Three Ecologically Different Plant Species

Apple rootstocks M.7 were given a nitrogen application either in the spring or in the preceding autumn. At the time of the spring application some rootstocks were ringed. During the 50-day experimental period from bud-break, shoot growth and the amount of nitrogen incorporated into the new shoots were slightly reduced in the spring-treated trees and strongly reduced in the ringed trees of both treatments. Roots of unringed autumn-fertilized trees showed higher levels of total and amino nitrogen than those of similar trees in the spring treatment; to a lesser degree, the reverse held for xylem sap from the stem. Ringing increased the amino-nitrogen level in the roots, which suggests a reduced translocation rate. The nitrogen treatments led to marked differences in the percentage composition of the amino-nitrogen fraction of roots and xylem sap. The distribution of amino acids and amides in the roots and that in xylem sap of the same trees was divergent, but arginine and asparagine often were the most important constituents. Aspartic acid was rather abundant in xylem sap. Ringing did not affect the composition of the amino-nitrogen fraction in the roots quantitatively but increased the proportion of arginine in the sap. The possible relationship between the composition of xylem sap and soluble nitrogen in the roots is discussed. It is argued that especially in spring-fertilized trees appreciable amounts of nitrogen must be translocated via the phloem in addition to the transport in the xylem.     

Xylem Sap from Actinidia chinensis: seasonal Changes in Composition

Seasonal variation was followed in the content of total a-aminoacids, arginine, calcium, total carbohydrate, ß-galactosidaseactivity, magnesium, nitrate, phosphatase activity, phosphateand sulphate in vacuum-extracted xylem sap from Actinidia chinensisvar. hispida, the Chinese gooseberry or kiwifruit. There wasa marked increase in the concentration of most sap componentsjust prior to leaf emergence followed by a rapid decrease afterthe leaves had expanded. Experiments with excised extensionshoots showed that much of this spring-time increase in concentrationsof sap components was due to mobilization of nutrients withinthe shoot itself. Sap from the trunk and the older brancheschanged less in composition than did sap from the younger partsof the plant. The amplitude and direction of trends in concentrationof sap from the different parts of the plant varied with nutrientand with time. Analysis of vacuum-extracted xylem sap collectedduring periods of rapid transpiration from early summer onwardsgives a reliable indication of the composition of the transpirationstream. Actinidia chinensis, Chinese gooseberry, kiwifruit, storage reserves, xylem sap, amino acids, arginine, calcium, carbohydrate, ßgalactosidase, magnesium, nitrate, phosphatase, phosphate, potassium, sulphate     

Free amino Acid composition of leaf exudates and Phloem sap : a comparative study in oats and barley

Comparisons were made between the free amino acid composition in leaf exudates and that in pure phloem sap, using twin samples taken from a single leaf of two oat (Avena sativa L.) and three barley (Hordeum vulgare L.) varieties. Leaf exudate was collected in a 5 mm EDTA-solution (pH 7.0) from cut leaf blades and phloem sap was obtained through excised aphid (Rhopalosiphum padi L.) stylets. Fluorescent derivatives of amino acids were obtained using 9-fluorenylmethyl chloroformate and were separated by means of high performance liquid chromatography. The total concentration of free amino acids varied considerably in the exudate samples. There was no correlation between the total amino acid content in the exudate samples and that of the corresponding phloem sap samples, but the amino acid composition of the corresponding samples was highly correlated (median R²-value 0.848). There was only limited between-plant variation in phloem sap amino acid composition. Nevertheless, in comparisons involving all samples, many of the amino acids showed significant correlations between their relative amounts in exudate and phloem sap. The results presented here indicate that the exudate technique holds great promise as an interesting alternative to the laborious and time-consuming stylet-cutting technique of obtaining samples for comparative studies of phloem sap.     

Collection of Pure Phloem Sap from Wheat and its Chemical Composition

Wheat Phloem sap was collected without contamination from thestylets of small brown planthopper severed by a YAG laser beam.The sugar, amino acid and inorganic ion composition was determinedusing only one µl of the sap. The sap had a high sucrose level (251 mM), and also a high K⁺level (299 mM). Total amino acid compounds in the sap reached262 mM. The dominant amino acids were glutamic acid, asparticacid and serine, while r-amino butylic acid was absent. Themajor anion in the sap was Cl^– and its concentration was25.1 mM. Nitrate was also present at a concentration of 8.1mM. These results suggested that the sap obtained from the cut endof the stylets of the small brown planthopper was a phloem originof wheat. (Received May 21, 1986; Accepted August 7, 1986)     

Relationships between xylem sap constituents and leaf conductance of well-watered and water-stressed maize across three xylem sap sampling techniques

Many different techniques have been used for xylem sap collection, but few direct comparisons of techniques have been conducted and few comparisons have been based on comprehensive analyses of xylem sap. Moreover, the suitability of extraction techniques for use on plants grown under water-stress conditions has not been addressed. Xylem sap was extracted from both well-watered and water-stressed Zea mays plants using three different techniques. The main aim was to determine how the extraction method altered the correlations between sap constituents and stomatal conductance in order to determine which relationships change with extraction technique. A 'root pressure' technique was the simplest method of extracting large volumes of sap, but the low sap delivery rates altered the composition of sap. Two pressurization techniques that varied in the position from which sap was collected were tested. The pressurization techniques allowed for the control of delivery rates that influence sap constituent concentrations. The position from which xylem sap was collected on the plant was also found to be important. All three techniques produced consistent correlations between ABA and chloride delivery rates and changes in stomatal conductance, suggesting that each technique could be applied to identify certain putative xylem-borne signals.     

Proteomic analysis of Chelidonium majus milky sap using two-dimensional gel electrophoresis and tandem mass spectrometry

Milky sap, a milky-like orange fluid, isolated from the Greater Celandine (Chelidonium majus L.), family Papaveraceae, serves as a rich source of various biologically active substances such as alkaloids, several flavonoids, phenolic acids and proteins. The objective of this study was to separate Ch. majus milky sap extract proteins using two-dimensional gel electrophoresis (2-DE) to demonstrate for the first time the protein composition in the sap and to identify them using liquid chromatography-tandem mass spectrometry analysis (LC-ESI-MS/MS). It was possible to identify 21 proteins, which comprise disease/defence-related, signalling, Krebs cycle, nucleic acid binding and other proteins. The majority of the identified proteins can be linked to direct and indirect stress and defence reactions, e.g. against different pathogens. The specific protein composition of the milky sap suggests an important role of these proteins for the whole plant physiology and development.     

How nutritionally imbalanced is phloem sap for aphids?

Aphids harbour intracellular symbionts (Buchnera) that provide their host with amino acids present in low amounts in their diet, phloem sap. To find out the extent to which aphids depend on their symbionts for synthesis of individual essential amino acids, we have evaluated how well phloem sap amino acid composition matches the aphids' needs. Amino acid compositions of the ingested phloem sap were compared to amino acids in aphid body proteins and also to available information about optimal diet composition for other plant feeding insects. Phloem sap data from severed stylets of two aphid species, Rhopalosiphum padi (L.) (Homoptera: Aphididae) feeding on wheat, and Uroleucon sonchi (L.) (Homoptera: Aphididae) feeding on Sonchus oleraceus (L.), together with published information on phloem sap compositions from other plant species were used.Phloem sap has in general only around 20% essential amino acids, with a range from 15–48%. Aphid body proteins and optimal diets for two other plant feeding insects have around 50%. The phloem sap of early flowering S. oleraceus ingested by U. sonchi contained 48%, which seems to be exceptional. Aphids feeding on different plants appear to be very differently dependent on their symbionts for their overall essential amino acid synthesis, due to the large variation in proportion of essential amino acids in phloem sap from different plants.The profile of the essential amino acids in phloem sap from different plant species corresponds rather well to profiles of both aphid body proteins and optimal diets determined for plant feeding insects. However, methionine and leucine in phloem sap are in general low in these comparisons, suggesting a higher dependence on the symbiont for synthesis of these amino acids. Concentrations of several essential amino acids in phloem from different plant species seem to vary together, suggesting that levels of symbiont provisioning of different amino acids are adjusted in parallel.     

THE BASE COMPOSITION OF RIBONUCLEIC ACID IN LAMPBRUSH CHROMOSOMES, NUCLEOLI, NUCLEAR SAP, AND CYTOPLASM OF TRITURUS OOCYTES

The base composition of RNA's extracted from chromosomes, nucleoli, nuclear sap, and cytoplasm of Triturus oocytes has been determined by microelectrophoresis. The chromosomal RNA has a content of guanine+cytosine equal to that of DNA, but there is no complementarity in the composition as for DNA. Nuclear sap contains a highly variable RNA with a tendency towards high uracil values. Nucleolar and cytoplasmic RNA's are similar in composition and both are of the guanine-cytosine rich type. The chromosomes and nucleoli contain roughly equivalent amounts of RNA, somewhat less than is present in the nuclear sap. The RNA/DNA ratio of the whole chromosomes is about 10. However, the ratio in the synthetically active regions, the loops, is much higher, since the loops contain all the chromosomal RNA but only a small fraction of the DNA.