Movement In Xylem Research Articles

Root Absorption and Xylem Movement of Ethephon in Tomato

Although ethephon is commonly used as a plant growth regulator during commercial production of horticultural crops, information on its movement within plants is limited. In this study, we developed a method to detect ethephon in plant tissues, and determined ethephon localization and movement using tomato (Solanum lycopersicum L.) as a model system. Tissues were ground in an acidic buffer that preserved ethephon intact. Ethylene was released from the extracts by adding sodium hydroxide and was determined subsequently by gas chromatography. Ethephon was detected in leaves within 1 hour of application to peat-based root zones and within 10 minutes in hydroponics. In a pulse–chase experiment, ethephon levels increased initially, then decreased after the plants were returned to ethephon-free solutions. Ethephon was present in directly collected xylem fluid; fluid collected from petiole stumps (after leaf blade excision) had similar ethephon levels between the different petioles. Stem girdling had no effect on ethephon accumulation in leaves. Together, these data indicate ethephon is readily mobile in the xylem stream and provides insight into the commercial use of ethephon as a root zone-applied growth regulator.

Translocation, Leaf Distribution, and Nutritional Status of Manganese in Cucumber Plants as Affected by Foliar Application of Exogenous Amino Acids

The present study was carried out to investigate the effect of exogenous amino acids (AAs) on leaf apoplastic retention and symplastic absorption, leaf distribution, translocation, and nutritional status of manganese (Mn) in cucumber plants. Results showed that application of AAs increased the symplastic to apoplastic Mn proportion in leaves of cucumber. Furthermore, a greater part of Mn applied with AAs accumulated in the internal area of newly growing leaves suggesting the transport of Mn mostly in the phloem in the presence of AAs. In contrast, Mn preferentially accumulated in the marginal area of treated leaves indicating the Mn movement in xylem according to the transpiration stream. The AAs used in the present study also increased the relative translocation of Mn from treated leaves to the upper leaves and roots. More time was needed for long-distance translocation of Mn from treated leaves to the upper leaves than that to the roots. Application of AAs mainly increased the transport of Mn in the phloem. The leaf PO (peroxidase) activity was the better marker to index the nutritional status of Mn than PPO (polyphenoloxidase) activity. In conclusion, exogenous AAs especially lysine (Lys) promoted the mobility and bioavailability of applied Mn as foliar spray.

Effect of arsenic on concentrations and translocations of mineral elements in the xylem of rice

ABSTRACTBy using Particle-Induced X-ray Emission (PIXE) technique, the effect of arsenic (As) on the mineral contents and translocation in the xylem of rice (Oryza sativa L. cv. ‘Akihikari’) was studied. The results suggest that exogenous As increased the concentrations of phosphorus (P), calcium (Ca) magnesium (Mg), sulfur (S), and manganese (Mn) in xylem, while the concentrations of potassium (K) remained unchanged. The highest concentration of As to the rice roots did not have any clear effect on the translocation of P, Ca, S, and chlorine (Cl) in the xylem, indicating that the increasing concentrations of the minerals may be due to a condensation effect, resulting from the repression of water movement in xylem by As-toxicity. Among the metal micronutrients, As decreased the concentrations and translocations of iron (Fe), zinc (Zn), and copper (Cu).

Living cells in wood. 1. Absence, scarcity and histology of axial parenchyma as keys to function

The diversity of expression in axial parenchyma (or lack of it) in woods is reviewed and synthesized with recent work in wood physiology, and questions and hypotheses relative to axial parenchyma anatomy are offered. Cell shape, location, abundance, size, wall characteristics and contents are all characteristics for the assessment of the physiological functions of axial parenchyma, a tissue that has been neglected in the consideration of how wood histology has evolved. Axial parenchyma occurrence should be considered with respect to mechanisms for the prevention and reversal of embolisms in tracheary elements. This mechanism complements cohesion–tension-based water movement and root pressure as a way of maintaining flow in xylem. Septate fibres can substitute for axial parenchyma (‘axial parenchyma absent’) and account for water movement in xylem and for the supply of carbohydrate abundance underlying massive and sudden events of foliation, flowering and fruiting, as can fibre dimorphism and the co-occurrence of septate fibres and axial parenchyma. Rayless woods may or may not contain axial parenchyma and are informative when analysing parenchyma function. Interconnections between ray and axial parenchyma are common, and so axial and radial parenchyma must be considered as complementary parts of a network, with distinctive but interactive functions. Upright ray cells and more numerous rays per millimetre enhance interconnection and are more often found in woods that contain tracheids. Vesselless woods in both gymnosperms and angiosperms have axial parenchyma, the distribution of which suggests a function in osmotic water shifting. Water and photosynthate storage in axial parenchyma may be associated with seasonal changes and with succulent or subsucculent modes of construction. Apotracheal axial parenchyma distribution often demonstrates storage functions that can be read independently of osmotic water shifting capabilities. Axial parenchyma may serve to both enhance mechanical strength or, when parenchyma is thin-walled, as a tissue that adapts to volume change with a change in water content. Other functions of axial parenchyma (contributing resistance to pathogens; a site for the recovery of physical damage) are considered. The diagnostic features of axial parenchyma and septate fibres are reviewed in order to clarify distinctions and to aid in cell type identification. Systematic listings are given for particular axial parenchyma conditions (e.g. axial parenchyma ‘absent’ with septate fibres substituting). A knowledge of the axial parenchyma information presented here is desirable for a full understanding of xylem function.

11C-imaging: methyl jasmonate moves in both phloem and xylem, promotes transport of jasmonate, and of photoassimilate even after proton transport is decoupled

The long-distance transport and actions of the phytohormone methyl jasmonate (MeJA) were investigated by using the short-lived positron-emitting isotope 11C to label both MeJA and photoassimilate, and compare their transport properties in the same tobacco plants (Nicotiana tabacum L.). There was strong evidence that MeJA moves in both phloem and xylem pathways, because MeJA was exported from the labeled region of a mature leaf in the direction of phloem flow, but it also moved into other parts of the same leaf and other mature leaves against the direction of phloem flow. This suggests that MeJA enters the phloem and moves in sieve tube sap along with photoassimilate, but that vigorous exchange between phloem and xylem allows movement in xylem to regions which are sources of photoassimilate. This exchange may be enhanced by the volatility of MeJA, which moved readily between non-orthostichous vascular pathways, unlike reports for jasmonic acid (which is not volatile). The phloem loading of MeJA was found to be inhibited by parachloromercuribenzenesulfonic acid (PCMBS) (a thiol reagent known to inhibit membrane transporters), and by protonophores carbonyl cyanide 3-chlorophenylhydrazone (CCCP) and 2,4-dinitrophenol (DNP) suggesting proton co-transport. MeJA was found to promote both its own transport and that of recent photoassimilate within 60 min. Furthermore, we found that MeJA can counter the inhibitory effect of the uncoupling agent, CCCP, on sugar transport, suggesting that MeJA affects the plasma membrane proton gradient. We also found that MeJA's action may extend to the sucrose transporter, since MeJA countered the inhibitory effects of the sulfhydryl reagent, PCMBS, on the transport of photoassimilate.

Effects of transverse movement of water in xylem on patterns of water transport within current‐year shoots of kudzu vine, Pueraria lobata

Summary This study investigated the effects on water transport patterns of the transverse water movement in xylem, on a whole‐shoot scale, using current‐year shoots of kudzu vine (Pueraria lobata (Willd.) Ohwi). The connections between xylem vessels were detected by dye injection and were found to be distributed throughout the internode. This means that short internodes limit the connections between vessels. The hydraulic conductance of the internode‐to‐petiole path decreased with successive cutting of the internodes. To estimate hydraulic patterns at the whole‐shoot scale, the hydraulic conductance of the shoot base‐to‐petiole path (KBP) were measured. These were compared with two mathematical models representing extreme examples of connections between vessels – the interconnected model and the independent model. The former model assumes a high capacity for the transverse movement of water in xylem tissues. The KBP values measured were explained more accurately by the interconnected model than by the independent model. These results suggest that kudzu vine has a large capacity for the transverse movement of water in xylem, which contributes to the effective transport of water from internodes to leaves that offsets sectored transport at the whole‐shoot scale.

A unified nomenclature for quantification and description of water conducting properties of sapwood xylem based on Darcy's law

The literature dealing with the water conducting properties of sapwood xylem in trees is inconsistent in terminology, symbols and units. This has resulted from confusion in the use of either an analogy to Ohm's law or Darcy's law as the basis for nomenclature. Ohm's law describes movement of electricity through a conductor, whereas Darcy's law describes movement of a fluid (liquid or gas) through a porous medium. However, it is generally not realized that, in their full notation, these laws are mathematically equivalent. Despite this, plant physiologists have failed to agree on a convention for nomenclature. As a result, the study of water movement through sapwood xylem is confusing, especially for scientists entering the field. To improve clarity, we suggest the adoption of a single nomenclature that can be used by all plant physiologists when describing water movement in xylem. Darcy's law is an explicit hydraulic relationship and the basis for established theories that describe three-dimensional saturated and unsaturated flow in porous media. We suggest, therefore, that Darcy's law is the more appropriate theoretical framework on which to base nomenclature describing sapwood hydraulics. Our proposed nomenclature is summarized in a table that describes conventional terms, with their formulae, dimensions, units and symbols; the table also lists the many synonyms found in recent literature that describe the same concepts. Adoption of this proposal will require some changes in the use of terminology, but a common rigorous nomenclature is needed for efficient and clear communication among scientists.

TOMATO PHOTOSYNTHESIS MONITORING IN INVESTIGATIONS ON TOLERANCE TO LOW TEMPERATURES

At the Physiology Laboratory of the Lithuanian Institute of Horticulture investigation is carried out on tolerance to low temperatures of tomato species and hybrids in greenhouses. In trials with the help of an automatic plant investigation system 'Ecoplant-11' the following physiological parameters are observed: photosynthesis intensity, xylem movement, stem diameter, difference in leaf and air temperatures, parameters of microclimate factors. We observed tomato variety Svara and hybrids Sveikutis F 1 and Pirmutis F 1 that were developed at the LIH. The analysis of investigation data showed that under autumn lighting conditions in Lithuania integral lighting affects the intensity of greenhouse tomato photosynthesis most significantly. Other important factors are temperature and CO 2 amount in the environment. The investigated variety and hybrids distinguish themselves for tolerance to low temperatures, especially the variety Svara. CO 2 assimilation is still observed over the compensation point, at 6-8°C. However, intensity of the process increases when temperature rises. In any case the level of lighting intensity and lighting of separate leaves are most important. Observations of leaf temperature stem diameter changes and dynamics of xylem movement under different temperatures revealed that the variety Svara has greater plasticity when adapting to low temperature conditions. Nearly in all cases the plants of the new hybrid Pirmutis F 1 distinguished themselves for greater photosynthesis intensity, especially when integral lighting was increasing along with other environmental factors changing to optimum. It is possible to suppose that the hybrid will meet the requirements of an intensive tomato crop. The phytomonitoring investigation shows that by selection it is possible to develop tomato forms tolerant to low temperature.

Effects of cadmium on the longitudinal and lateral xylem movement of citric acid through tomato stem internodes

SUMMARY Short-term experiments (2.5 h) were performed to gain insight in the effects of cadmium (Cd) on the longitudinal and lateral xylem movement of 14C-citric acid through tomato stem internodes (Lycopersicon esculentum, Mill, cv. Tiny Tim). The behaviour of citric acid was expressed by the concentrations of citric acid sorbed to the xylem walls (apparent anion exchange capacity AEC), and by the rate constant k for citric acid lateral escape. For 0.05 mM citric acid applications, the presence of 1.0 mM cadmium resulted in approximately 2-fold increases in values for apparent AEC and k; for the 9.5 mM citric acid concentrations, cadmium resulted in less than 2-fold increase in AEC, but here k did not change. In the presence of Cd, the stem-length profile of absorbed citric acid was shown to be in accordance with stem-length profiles of Cd xylem concentrations, rather than with the xylem concentrations of citric acid itself. These results were discussed in the light of the expected presence of Cd—citric acid complexes in the xylem sap; effects on k values were discussed with consideration for the possible processes of escape rate limitation in the stem.

Nitrate movement in xylem of lucerne plants

Nitrate content in lucerne stems and leaf blades immersed by cut ends in distilled water or in KNO3 solution increased with the increase in KNO3 concentration and with the duration of exposure under irradiance of 100 or 230 W m-2 PAR. The nitrate content increased from basal stem parts to apical stem parts and leaves. Nitrate was transported mainly with transpiration stream. Some flow variations occurred in stems causing time changes in nitrate content in different parts of stems.

Dye and Calcium Ascent in Dogwood Trees

How calciuim imioves in the transpiration strean of plants is not fully uinderstood. Biddulph et al. (2) com.pared movemenllt of 4'Ca and tritiated water in bean plants and fotund that xylem operated essentially as an exchange coluimn for calciutm. After additional experiments, Bell and Biddiilph (1) concludifed that caleiuim movement in xylem occurred in 2 phases: a) After calciuim enteredl the transpiration stream, it xA as boundcl on exchanige sites and theni ascenlded with aid of the transpiratiOln streanm xx-heln it was replaced by other :o0ns: h) Calcilm was removed from exchange sites to more immol)ile positions dule to ioIn uitilizationi by metabolizing cells anid depositioni in calciuim oxalate crystals. Emmert (4) founiid this explanation satisfactory to interpret upwar(l movemenit of stronitiunm ini bean plants. NMorris,on and Heine (9) id nloit believe that this mechanism explaine(l movemient of all polyvalent catiolns, an,d O'Leary (10) foundi(i that the mass flow itheory could liOt be entirely discarded as an explaniationi forcalcilm ascenit in bean plants. As part of an investigation of cycling of calciuim by floxvering dogwood trees, experiments xvere condiucted tr) (letermine the pattern of the transptiration stream and the slhort-term distribuition of stem-inocilaited ca-ldciluTml.

Absorption of Herbicides by Roots

Crafts, A. S., and S. Yamaguchi. (U. California, Davis.) Absorption of herbicides by roots. Amer. Jour. Bot. 47(4): 248—255. Illus. 1960.—Many herbicides are used through soil. When 2,4-D*2 was applied to culture-solution barley, bean, cotton, and Zebrina plants, there was evidence that the herbicide is held at high concentration by the roots. Very little of the labeled compound moved into the tops of barley, Zebrina and bean; a fair quantity was found in cotton foliage. Barley seedlings allowed to absorb 2,4-D*, ATA*, MH*, urea*, monuron*, dalapon*, simazin*, P32 and IAA* showed interesting differences. All chemicals were highly sorbed by roots, 2,4-D* was moved to tops in least amount, urea was next; the other seven were moved in larger quantities. ATA*, MH*, IAA*, P32, and dalapon* seemed readily phloem mobile; monuron* and simazin* seemed limited to xylem movement. Results are discussed in relation to the mechanism of root uptake.

ABSORPTION OF HERBICIDES BY ROOTS

Crafts, A. S., and S. Yamaguchi. (U. California, Davis.) Absorption of herbicides by roots. Amer. Jour. Bot. 47(4): 248—255. Illus. 1960.—Many herbicides are used through soil. When 2,4‐D*2 was applied to culture‐solution barley, bean, cotton, and Zebrina plants, there was evidence that the herbicide is held at high concentration by the roots. Very little of the labeled compound moved into the tops of barley, Zebrina and bean; a fair quantity was found in cotton foliage. Barley seedlings allowed to absorb 2,4‐D*, ATA*, MH*, urea*, monuron*, dalapon*, simazin*, P32 and IAA* showed interesting differences. All chemicals were highly sorbed by roots, 2,4‐D* was moved to tops in least amount, urea was next; the other seven were moved in larger quantities. ATA*, MH*, IAA*, P32, and dalapon* seemed readily phloem mobile; monuron* and simazin* seemed limited to xylem movement. Results are discussed in relation to the mechanism of root uptake.

The behaviour of systemic insecticides in plants: A survey of results obtained with 32P‐labelled schradan and demeton‐s

AbstractExperiments on the behaviour under glasshouse conditions of schradan and demeton‐S applied to different species of plants are reviewed.Following application of schradan to leaves, some was absorbed and some evaporated. Absorption occurred both in light and darkness but higher temperatures accelerated initial absorption. Whilst the two surfaces of broad bean and Coleus leaves were equally absorptive, the lower surface of apple and chrysanthemum leaves absorbed more than their upper surface. Application of demeton‐S to leaves was followed by three processes—evaporation, change into less volatile, toxic derivatives, and absorption, and the chemical was effectively removed from the leaf surface within a few hours. The products derived from demeton‐S were also absorbed but at a slower rate. The evaporation of demeton‐S gave rise to a fumigant effect.Translocation of schradan from treated leaves to other parts of the plant occurred, mainly in an upward direction and in amounts sufficient to kill aphids. Schradan was also found in the nectar of borage and mustard flowers following leaf application before the flowers had opened. The schradan appeared to be translocated in the phloem. Translocation from leaves treated with demeton‐S was never sufficient to kill aphids feeding elsewhere on the plant, and no unchanged demeton‐S and only small amounts of its toxic derivatives were found in untreated leaves or nectar.Species differences were found in the rate of breakdown of schradan after absorption from leaves and in the relative rate of breakdown of schradan in treated leaves and in those receiving schradan by translocation. The primary derivatives of demeton‐S were retained for several weeks, especially within treated leaves. The breakdown rates of both schradan and demeton‐S slowed down towards the end of the growing season.Following root application to broad beans in sand or soil, unchanged demeton‐S was absorbed and detected in the shoot tip where concentrations of demeton‐S and its primary derivatives were present in amounts sufficient to kill Aphis fabae. Movement in xylem following root application seems to occur freely.