Sap Exudation Research Articles

Relationships between sap exudation and sapwood temperature in Acer mono and Acer rufinerve trees

Relationships between sap exudation and sapwood temperature in <i>Acer mono</i> and <i>Acer rufinerve</i> trees

Variation rule of EDTA-Na2 in grape shoots based on trellis and phenological period

To better understand the physiological processes involved in responses of trellises to the transportation and distribution of nutrient within shoots of grapevines, analysis method of disodium ethylenediamine tetraacetate (EDTA - Na2) was employed at the whole development stages of vine. In the trial, the traditional independent long-stem pruning (ILSP) was taken as control to compare the effect of new single crawled cordon training (SCCT) on the transportation and distribution of phloem sap on the experimental material Ecolly. Thus the consumption level of phloem sap in the grapevine shoots of various trellises was analyzed by EDTA-Na2 phloem sap exudation technique during the whole development. Results was that the consumption rate of EDTA - Na2 solution in the SCCT and ILSP shoots increased before August 15 (15.130 g–16.216 g in SCCT and 10.653 g–15.042 g in ILSP, respectively) including 16.348–20.809 g in SCCT and 11.912–19.593 g in ILSP from August 25 to September 4 as well as decreased in August 15–25 (17.216–16.348 g in SCCT and 15.042–11.912 g in ILSP, respectively) and after September 4 (20.809–7.669 g in SCCT and 19.593–4.072 g in ILSP), respectively, and values of SCCT were always higher than that of ILSP during the whole growth. In addition, EDTA - Na2 consumption content in the phloem sap per shoots in SCCT kept almost around 16 g, more than that in ILSP, from 21 July to 25 August. Therefore, SCCT was more advantageous to accumulate nutrient compared with ILSP, and ensured an even distribution of phloem sap in the grape shoots from berry growth to maturity.

Comparison of sap exudation between Acer pictum and A. rufinerve and the observation of environmental changes

Comparison of sap exudation between <i>Acer pictum</i> and <i>A. rufinerve</i> and the observation of environmental changes

Asparagine and sugars are both required to sustain secondary axis elongation after bud outgrowth in Rosa hybrida

Nitrogen is required for optimal plant growth, especially in young organs such as secondary axes (axes II) after axillary bud outgrowth. Several studies have shown an increase of nitrogen concentration in xylem sap concomitantly with bud outgrowth, but the relation between nitrogen, sugars and plant hormones in axis II still remains unclear. We investigated in Rosa hybrida the involvement of nitrogen nutrition in axis II elongation in relation with sugars and cytokinins using 15N-labeled nitrate and sugars, amino acids and cytokinin quantifications. Besides, we measured the effect of the exogenous supply of these compounds on axis II elongation using in vitro excised bud culture. We demonstrated that nitrogen in the axis II comes mainly from new root uptake after decapitation. Asparagine, which concentration increases in sap exudates and tissues during axis II elongation, was the sole amino acid able to sustain an efficient elongation in vitro when supplied in combination with sucrose.

Observed compression of in situ tree stems during freezing

Freezing temperatures can influence the material properties of trees. Understanding how forest biometeorological interactions respond to freezing temperatures is important for forest science and management, as its effects can cascade through coupled hydrological and ecological processes including limitations on tree growth, changes to canopy interception, and influences on atmospheric turbulence. This short communication details the effect of sub-freezing temperatures on the mechanical displacement of three in situ Pinus contorta Douglas (lodgepole pine) stems during a winter season (2013–2014) at Niwot Ridge Mountain Research Station (CO, USA). Although previous research on harvested trees suggests longitudinal stem expansion should occur as temperatures decrease below freezing, we observed longitudinal compression in live stems below −3°C that linearl y correlated with sub-zero air temperatures ranging down to −22°C. Freeze-related compression of stems frequently achieved displacement magnitudes comparable to applying 55kN of compressive force (800μm). Hypotheses are proposed to explain the significant mechanical displacement observed due to freezing: (1) internal gas release as freezing fronts propagate through stems; (2) short-term relocation of water via sap exudation or preferential ice crystal growth. As the observed stem compression response to freezing is substantial, future work on underlying processes and consequences is merited. The measurement technique used here may prove useful to others interested in the dynamics of stem freezing.

A two-scale Stefan problem arising in a model for tree sap exudation

The study of tree sap exudation, in which a (leafless) tree generates elevated stem pressure in response to repeated daily freeze-thaw cycles, gives rise to an interesting multi-scale problem involving heat and multiphase liquid/gas transport. The pressure generation mechanism is a cellular-level process that is governed by differential equations for sap transport through porous cell membranes, phase change, heat transport, and generation of osmotic pressure. By assuming a periodic cellular structure based on an appropriate reference cell, we derive an homogenized heat equation governing the global temperature on the scale of the tree stem, with all the remaining physics relegated to equations defined on the reference cell. We derive a corresponding strong formulation of the limit problem and use it to design an efficient numerical solution algorithm. Numerical simulations are then performed to validate the results and draw conclusions regarding the phenomenon of sap exudation, which is of great importance in trees such as sugar maple and a few other related species. The particular form of our homogenized temperature equation is obtained using periodic homogenization techniques with two-scale convergence, which we investigate theoretically in the context of a simpler two-phase Stefan-type problem corresponding to a periodic array of melting cylindrical ice bars with a constant thermal diffusion coefficient. For this reduced model, we prove results on existence, uniqueness and convergence of the two-scale limit solution in the weak form, clearly identifying the missing pieces required to extend the proofs to the fully nonlinear sap exudation model. Numerical simulations of the reduced equations are then compared with results from the complete sap exudation model.

Observation of environmental conditions and relationships between sap exudation and sap flow in Acer pictum Thumb. subsp. mono

Observation of environmental conditions and relationships between sap exudation and sap flow in <i>Acer pictum</i> Thumb. subsp. <i>mono</i>

Identification of the fitness determinants of budding yeast on a natural substrate.

The budding yeasts are prime models in genomics and cell biology, but the ecological factors that determine their success in non-human-associated habitats is poorly understood. In North America Saccharomyces yeasts are present on the bark of deciduous trees, where they feed on bark and sap exudates. In the North East, Saccharomyces paradoxus is found on maples, which makes maple sap a natural substrate for this species. We measured growth rates of S. paradoxus natural isolates on maple sap and found variation along a geographical gradient not explained by the inherent variation observed under optimal laboratory conditions. We used a functional genomic screen to reveal the ecologically relevant genes and conditions required for optimal growth in this substrate. We found that the allantoin degradation pathway is required for optimal growth in maple sap, in particular genes necessary for allantoate utilization, which we demonstrate is the major nitrogen source available to yeast in this environment. Growth with allantoin or allantoate as the sole nitrogen source recapitulated the variation in growth rates in maple sap among strains. We also show that two lineages of S. paradoxus display different life-history traits on allantoin and allantoate media, highlighting the ecological relevance of this pathway.

Sap volatile components in relation to susceptibility of anthracnose and Aspergillus rot of mangoes (Mangifera indica L.)

ABSTRACTSap burn injury and postharvest diseases are major causes of mango fruit quality deterioration, resulting in considerable postharvest losses in many countries. Susceptibility of selected cultivars of mango in Sri Lanka to sap burn injury and the incidence of anthracnose and Aspergillus rot of mango were examined in this study. Volatile components of non-aqueous (oil) phase were investigated using GC-MS, and artificial inoculation studies were carried out to assess disease resistance with Colletotrichum queesnlandicum (KC 820802) and Aspergillus niger (KC 820801). It was observed that the popular ‘Karuthakolumban’ and ‘Willard’ mangoes with high sap flow at harvest and high sap burn incidence were more susceptible to sap burn injury compared with ‘Chembaddan’ and ‘Ambalavi’ mangoes. Cultivar variations in susceptibility to Aspergillus rot of mangoes are reported for the first time in this study, where ‘Willard’ mangoes were more resistant to Aspergillus rot than other cultivars. The sap exudates of ‘Ambalavi’ and ‘Karuthakolumban’ mangoes were observed to contain the preformed antifungal compounds 5-pentadecyl resorcinol and 5-(Heptadeca-8,11- dienyl) benzene1,3-diol, with variety ‘Ambalavi’ showing a high resorcinol level. These cultivars were found to be resistant to anthracnose disease. These results suggest that presence of sap volatiles is cultivar dependent and could be used to identify cultivars resistant to postharvest diseases and sap burn.

Genetic variability of the phloem sap metabolite content of maize (Zea mays L.) during the kernel-filling period

Using a metabolomic approach, we have quantified the metabolite composition of the phloem sap exudate of seventeen European and American lines of maize that had been previously classified into five main groups on the basis of molecular marker polymorphisms. In addition to sucrose, glutamate and aspartate, which are abundant in the phloem sap of many plant species, large quantities of aconitate and alanine were also found in the phloem sap exudates of maize. Genetic variability of the phloem sap composition was observed in the different maize lines, although there was no obvious relationship between the phloem sap composition and the five previously classified groups. However, following hierarchical clustering analysis there was a clear relationship between two of the subclusters of lines defined on the basis of the composition of the phloem sap exudate and the earliness of silking date. A comparison between the metabolite contents of the ear leaves and the phloem sap exudates of each genotype, revealed that the relative content of most of the carbon- and nitrogen-containing metabolites was similar. Correlation studies performed between the metabolite content of the phloem sap exudates and yield-related traits also revealed that for some carbohydrates such as arabitol and sucrose there was a negative or positive correlation with kernel yield and kernel weight respectively. A posititive correlation was also found between kernel number and soluble histidine.

Nighttime evaporative demand induces plasticity in leaf and root hydraulic traits.

Increasing evidence suggests that nocturnal transpiration rate (TRN ) is a non-negligible contributor to global water cycles. Short-term variation in nocturnal vapor pressure deficit (VPDN ) has been suggested to be a key environmental variable influencing TRN . However, the long-term effects of VPDN on plant growth and development remain unknown, despite recent evidence documenting long-term effects of daytime VPD on plant anatomy, growth and productivity. Here we hypothesized that plant anatomical and functional traits influencing leaf and root hydraulics could be influenced by long-term exposure to VPDN . A total of 23 leaf and root traits were examined on four wheat (Triticum aestivum) genotypes, which were subjected to two long-term (30 day long) growth experiments where daytime VPD and daytime/nighttime temperature regimes were kept identical, with variation only stemming from VPDN , imposed at two levels (0.4 and 1.4 kPa). The VPDN treatment did not influence phenology, leaf areas, dry weights, number of tillers or their dry weights, consistently with a drought and temperature-independent treatment. In contrast, vein densities, adaxial stomata densities, TRN and cuticular TR, were strongly increased following exposure to high VPDN . Simultaneously, whole-root system xylem sap exudation and seminal root endodermis thickness were decreased, hypothetically indicating a change in root hydraulic properties. Overall these results suggest that plants 'sense' and adapt to variations in VPDN conditions over developmental scales by optimizing both leaf and root hydraulics.

Characterization of a pumpkin mRNA encoding a Cyclin-Dependent Protein Kinase (CDK) potentially involved in phloem development

The phloem is involved in the delivery of nutrients but also of long-range signals that regulate diverse processes. Several different RNAs have been found in the phloem translocation stream, which could have a role in signaling. In a previous work, we have found several RNAs in pumpkin phloem sap exudates in response to viral infection, among them a transcript encoding a potential cyclindependent protein kinase (CDK). In this study, we report the further characterization of the aforementioned CDK mRNA. The complete sequence of this mRNA, which we termed CmCDKP (for Cucurbita maxima CDK from Phloem), was obtained (GenBank no. AIQ82912.1). The phylogenetic analysis of the virtual translation of this sequence showed that CmCDKP is closely related to those involved in transcriptional regulation via RNA polymerase II CTD phosphorylation, or splicing control. The mRNA accumulated to highest levels in pollen tissue. Interestingly, the mRNA localized to the companion cell-sieve element complex in the phloem, developing phloem, and also in isolated cells in the shoot apical meristem, suggesting a role in early phloem development.

Effects of arbuscular mycorrhizae on tomato yield, nutrient uptake, water relations, and soil carbon dynamics under deficit irrigation in field conditions

Plant strategies to cope with future droughts may be enhanced by associations between roots and soil microorganisms, including arbuscular mycorrhizal (AM) fungi. But how AM fungi affect crop growth and yield, together with plant physiology and soil carbon (C) dynamics, under water stress in actual field conditions is not well understood. The well-characterized mycorrhizal tomato (Solanum lycopersicum L.) genotype 76R (referred to as MYC+) and the mutant nonmycorrhizal tomato genotype rmc were grown in an organic farm with a deficit irrigation regime and control regime that replaced evapotranspiration. AM increased marketable tomato yields by ~25% in both irrigation regimes but did not affect shoot biomass. In both irrigation regimes, MYC+ plants had higher plant nitrogen (N) and phosphorus (P) concentrations (e.g. 5 and 24% higher N and P concentrations in leaves at fruit set, respectively), 8% higher stomatal conductance (gs), 7% higher photosynthetic rates (Pn), and greater fruit set. Stem water potential and leaf relative water content were similar in both genotypes within each irrigation regime. Three-fold higher rates of root sap exudation in detopped MYC+ plants suggest greater capacity for water uptake through osmotic driven flow, especially in the deficit irrigation regime in which root sap exudation in rmc was nearly absent. Soil with MYC+ plants also had slightly higher soil extractable organic C and microbial biomass C at anthesis but no changes in soil CO2 emissions, although the latter were 23% lower under deficit irrigation. This study provides novel, field-based evidence for how indigenous AM fungi increase crop yield and crop water use efficiency during a season-long deficit irrigation and thus play an important role in coping with increasingly limited water availability in the future.

Nodulation control of crack fertilization technique reduced the growth inhibition of soybean caused by short-term waterlogging at early vegetative stage

Waterlogging is the constraint for soybean growth and yield, because soybean is often cultivated in upland fields converted from paddy in Japan. However, efficient cultivation techniques for alleviating the adverse effects have not been developed. We have proposed the new soybean cultivation technique named crack fertilization which enables yield increase due to enhancing new root growth and N acquisition by increasing nodulation. Waterlogging induces N deficiency due to the suppression of nutrient uptake by the inhibition of root growth and nodule activity. Thus, it is hypothesized that crack fertilization would be effective to alleviate the inhibition of soybean growth and yield. The soybean cultivar of Sachiyutaka was planted in 1/5000 a Wagner pots and root boxes. Two separate waterlogging treatments were imposed to soybean plants at different growth stages, V1 and R4, and crack fertilization was done at V3. After these treatments, soybean plants were sampled at R5 in 2012 and 2013 experiments, respectively. Waterlogging at V1 and R4 inhibited the growth and yield of soybean and nodule growth, and the decreases in physiological parameters of soybean such as photosynthesis, chlorophyll content, and xylem sap exudation rate were observed. The adverse effects of waterlogging at V1 were alleviated by crack fertilization at V3, whereas crack fertilization could not alleviate the adverse effects of waterlogging at R4. Thus, crack fertilization after waterlogging at early vegetative stage would be the cultivation technique that enables to alleviate the adverse effects.

Stem‐galling moths provide cetoniine beetles with feeding sites via sap exudation of invasive alien plants

AbstractThe alien moth Epiblema sugii (Lepidoptera: Tortricidae) induces stem galls on an invasive alien weed, Ambrosia trifida. During summer, along riverbanks in central Japan, the native insects Protaetia brevitarsis, P. orientalis submarumorea (Coleoptera: Scarabaeidae: Cetoniinae), and Camponotus vitiosus (Hymenoptera: Formicidae) feed on the sap exuded from the galls. The cetoniine beetles are highly aggregated among the galls and make wounds on the galls to facilitate sap exudation. Feeding on gall sap may be beneficial to the beetles due to the efficient intake of water and sugar, and the beetles’ inflicting wounds and feeding on the sap seem to have little effect on the gallers. This is a unique finding, where alien plant–galler interaction provides a feeding site for native insects.

Root aquaporins contribute to whole plant water fluxes under drought stress in rice (Oryza sativa L.).

Aquaporin activity and root anatomy may affect root hydraulic properties under drought stress. To better understand the function of aquaporins in rice root water fluxes under drought, we studied the root hydraulic conductivity (Lpr) and root sap exudation rate (Sr) in the presence or absence of an aquaporin inhibitor (azide) under well-watered conditions and following drought stress in six diverse rice varieties. Varieties varied in Lpr and Sr under both conditions. The contribution of aquaporins to Lpr was generally high (up to 79% under well-watered conditions and 85% under drought stress) and differentially regulated under drought. Aquaporin contribution to Sr increased in most varieties after drought, suggesting a crucial role for aquaporins in osmotic water fluxes during drought and recovery. Furthermore, root plasma membrane aquaporin (PIP) expression and root anatomical properties were correlated with hydraulic traits. Three chromosome regions highly correlated with hydraulic traits of the OryzaSNP panel were identified, but did not co-locate with known aquaporins. These results therefore highlight the importance of aquaporins in the rice root radial water pathway, but emphasize the complex range of additional mechanisms related to root water fluxes and drought response.

A comprehensive strategy for identifying long-distance mobile peptides in xylem sap.

There is a growing awareness that secreted pemediate organ-to-organ communication in higher plants. Xylem sap peptidomics is an effective but challenging approach for identifying long-distance mobile peptides. In this study we developed a simple, gel-free purification system that combines o-chlorophenol extraction with HPLC separation. Using this system, we successfully identified seven oligopeptides from soybean xylem sap exudate that had one or more post-transcriptional modifications: glycosylation, sulfation and/or hydroxylation. RNA sequencing and quantitative PCR analyses showed that the peptide-encoding genes are expressed in multiple tissues. We further analyzed the long-distance translocation of four of the seven peptides using gene-encoding peptides with single amino acid substitutions, and identified these four peptides as potential root-to-shoot mobile oligopeptides. Promoter-GUS analysis showed that all four peptide-encoding genes were expressed in the inner tissues of the root endodermis. Moreover, we found that some of these peptide-encoding genes responded to biotic and/or abiotic factors. These results indicate that our purification system provides a comprehensive approach for effectively identifying endogenous small peptides and reinforce the concept that higher plants employ various peptides in root-to-shoot signaling.

Multiscale model of a freeze-thaw process for tree sap exudation.

Sap transport in trees has long fascinated scientists, and a vast literature exists on experimental and modelling studies of trees during the growing season when large negative stem pressures are generated by transpiration from leaves. Much less attention has been paid to winter months when trees are largely dormant but nonetheless continue to exhibit interesting flow behaviour. A prime example is sap exudation, which refers to the peculiar ability of sugar maple (Acer saccharum) and related species to generate positive stem pressure while in a leafless state. Experiments demonstrate that ambient temperatures must oscillate about the freezing point before significantly heightened stem pressures are observed, but the precise causes of exudation remain unresolved. The prevailing hypothesis attributes exudation to a physical process combining freeze-thaw and osmosis, which has some support from experimental studies but remains a subject of active debate. We address this knowledge gap by developing the first mathematical model for exudation, while also introducing several essential modifications to this hypothesis. We derive a multiscale model consisting of a nonlinear system of differential equations governing phase change and transport within wood cells, coupled to a suitably homogenized equation for temperature on the macroscale. Numerical simulations yield stem pressures that are consistent with experiments and provide convincing evidence that a purely physical mechanism is capable of capturing exudation.

Differential responses of grapevine rootstocks to water stress are associated with adjustments in fine root hydraulic physiology and suberization.

Water deficits are known to alter fine root structure and function, but little is known about how these responses contribute to differences in drought resistance across grapevine rootstocks. The ways in which water deficit affects root anatomical and physiological characteristics were studied in two grapevine rootstocks considered as low-medium (101-14Mgt) and highly (110R) drought resistant. Rootstocks were grown under prolonged and repeated drying cycles or frequent watering ('dry' and 'wet' treatments, respectively), and the following parameters were evaluated: root osmotic and hydrostatic hydraulic conductivity (Lp os and Lp hyd, respectively), suberization, steady-state root pressure (P rs), sap exudation rates, sap osmotic potential, and exosmotic relaxation curves. For both rootstocks, the 'dry' treatment reduced fine root Lp, elicited earlier root suberization and higher sap osmotic potential, and generated greater P rs after rewatering, but the rootstocks responded differently under these conditions. Lp os, Lp hyd, and sap exudation rates were significantly higher in 110R than in 101-14Mgt, regardless of moisture treatment. Under 'dry' conditions, 110R maintained a similar Lp os and decreased the Lp hyd by 36% compared with 'wet' conditions, while both parameters were decreased by at least 50% for 101-14Mgt under 'dry' conditions. Interestingly, build-up of P rs in 110R was 34% lower on average than in 101-14Mgt, suggesting differences in the development of suberized apoplastic barriers between the rootstocks as visualized by analysis of suberization from fluorescence microscopy. Consistent with this pattern, 110R exhibited the greatest exosmotic Lp os (i.e. Lp os of water flowing from roots to the soil) as determined from relaxation curves under wet conditions, where backflow may have limited its capacity to generate positive xylem pressure. The traits studied here can be used in combination to provide new insights needed for screening drought resistance across grapevine rootstocks.

A Highly Selective Biosensor with Nanomolar Sensitivity Based on Cytokinin Dehydrogenase

We have developed a N 6-dimethylallyladenine (cytokinin) dehydrogenase-based microbiosensor for real-time determination of the family of hormones known as cytokinins. Cytokinin dehydrogenase from Zea mays (ZmCKX1) was immobilised concurrently with electrodeposition of a silica gel film on the surface of a Pt microelectrode, which was further functionalized by free electron mediator 2,6-dichlorophenolindophenol (DCPIP) in supporting electrolyte to give a bioactive film capable of selective oxidative cleavage of the N 6- side chain of cytokinins. The rapid electron shuffling between freely diffusible DCPIP and the FAD redox group in ZmCKX1 endowed the microbiosensor with a fast response time of less than 10 s. The immobilised ZmCKX1 retained a high affinity for its preferred substrate N 6-(Δ2-isopentenyl) adenine (iP), and gave the miniaturized biosensor a large linear dynamic range from 10 nM to 10 µM, a detection limit of 3.9 nM and a high sensitivity to iP of 603.3 µAmM−1cm−2 (n = 4, R2 = 0.9999). Excellent selectivity was displayed for several other aliphatic cytokinins and their ribosides, including N 6-(Δ2-isopentenyl) adenine, N 6-(Δ2-isopentenyl) adenosine, cis-zeatin, trans-zeatin and trans-zeatin riboside. Aromatic cytokinins and metabolites such as cytokinin glucosides were generally poor substrates. The microbiosensors exhibited excellent stability in terms of pH and long-term storage and have been used successfully to determine low nanomolar cytokinin concentrations in tomato xylem sap exudates.