Influence de i’acide abscissique sur le transport d’ions inorganiques chez la pomme de terre (solanum tuberosum cv. Bintje). etude comparée avec quelques autres phytohormones

Using detached leaves of potato plants (Solanum tuberosum cv. Bintje) it was shown that abscisic acid (ABA) induced an oriented transport of ions (⁸⁶Rb,³²P and^3SS) towards the hormone-treated leaflet. In order to understand the hormone effect on cell permeability, pretreatment of discs with hormonal solution was conducted. The pretreatment with ABA stimulated the uptake of K⁺ simultaneously with the decrease of efflux. The effect of ABA on ion uptake is compared with the action of other hormones, benzylaminopurine (BAP), gibberellic acid (GA₃) known to act over a long distance transport, too. Three kinds of specificity are underlined: - hormonal specificity (stimulation by ABA and inhibiton by BAP of K⁺ uptake by foliar tissues); - ionic specificity (ABA increase⁸⁶Rb influx, but inhibits³²P and^3SS influx); - tissue specificity shown by a comparative study between foliar tissues (source) and tuber tissues (sink). The autoradiography of foliar discs demonstrated that a treatment of foliar discs can be used, at least for Rb⁺ (K), to study role of ABA in long-distance transport.      

Effect of iron and manganese on65Zn absorption and translocation in soybean seedlings

Summary Short-term experiments were conducted to determine the effect of varying levels of iron and manganese on⁶⁵Zn absorption by roots and translocation to shoots in soybean seedlings. In 11 hours uptake duration, both iron and manganese depressed the⁶⁵Zn absorption by roots and translocation to shoots. The depression was of higher magnitude at higher levels of iron and manganese (5.0 ppm) in the medium coupled with highest level (5.0 ppm) of zinc concentration. It is concluded that interactions between zinc and iron as well as zinc and manganese occur during absorption and translocation processes.Publication No.1185 under Journal Series of the G.B. Pant University of Agriculture and Technology, Experiment Station, Pantnagar     

2,4-Dichlorophenoxyacetic acid inhibition of potassium transport in barley seedlings

Growth, potassium uptake and translocation as well as transpiration rates were measured in intact low-salt barley seedlings ( Hordeum vulgare L. cv. Union) in the presence of different 2,4-D concentrations at pH 6.5. Growth was only affected at 10^-3 M .
Above 10^-7 M 2,4-D both uptake by the roots and transport to the shoots were inhibited. The inhibition at 10^-5 M remained constant for at least 24 h. Furthermore inhibition of uptake was measurable within 1 h. Excised roots and roots of intact plants showed the same uptake pattern.
It is suggested that the observed effects were caused by 2,4-D-induced changes in uptake and translocation systems in the roots. Pre-treatment with 10^-5 M 2,4-D had no effect upon subsequent potassium uptake. Transpiration was reduced within 1 h in 10^-4 or 10^-3 M 2,4-D, probably due to changes in water transport or root permeability.     

Phosphorus transport to the xylem and its regulation by water flow

Summary The effects of water flow on phosphorus uptake by roots and on its subsequent translocation to shoots were separated by giving short-term pulses of ³²P-labelled nutrient to intact tomato plants. At the end of a 5 min pulse, all the ³²P taken up by the plants was confined to the roots. Only about half of this ³²P was later translocated to shoots; there was very little translocation after 4 hours.Experiments after long-term labelling showed that only a small part of the total P in the root is readily translocated to shoots. This P appears to be in part of the symplast and contributes about 75% of the P transported to the xylem sap. The rest is presumably derived by leakage from vacuoles.A slow rate of water flow reduced both uptake into the symplast and the translocation to the shoots of P which had already been absorbed by the roots. This was conclusively demonstrated by giving a ³²P pulse before reducing the rate of water flow; ³²P not translocated to shoots was partly retained by the roots and partly lost to the external solution. Water flow also accelerates transport to the xylem of previously-absorbed P in excised roots.It is concluded that the major effect of water flow on phosphorus transport to shoots occurs after phosphorus uptake by the roots, probably during radial transport to the xylem.     

Mechanism of phosphorus-induced zinc deficiency in cotton. II. Evidence for impaired shoot control of phosphorus uptake and translocation under zinc deficiency

Cotton (Gossypium hirsutum L. cv. Deltapine 15/21) plants were precultured for 19 to 25 days under controlled climatic conditions in nutrient solutions with different levels of Zn. With the onset of visual Zn-deficiency symptoms the pH of the nutrient solution decreased from 6.0 to about 5.0. In contrast, Zn-sufficient plants raised the pH of the nutrient solution to about 7.0. In short-term studies it could be demonstrated that the Zn nutritional status of the plants remarkably influenced the uptake and translocation rates of mineral nutrients. Compared to Zn-sufficient plants, P uptake rate in severely Zn-deficient plants was increased by a factor of 2 to 3, whereas the uptake rates of K, Ca and particularly NO₃ decreased. The accumulation of P in the roots of Zn-deficient plants was either not affected or even lower than in Zn-sufficient plants. Thus, Zn deficiency had a specific enhancement effect on root to shoot transport of P. This enhancement effect of Zn deficiency on uptake and transport of P was similar at nutrient solution pH values of 7.0 and 5.8; i.e. it was not the result of acidification of the nutrient solution. After application of ³⁶CI, ⁸⁶Rb and ³²P to plant stems, basipetal transport of ³⁶CI and ⁸⁶Rb was not affected by the Zn nutritional status of the plants. However, in Zn-deficient plants, only 7.8% of the ³²P was translocated basipetally compared to 34% in the Zn-sufficient plants. A resupply of Zn for 19 h to Zn-deficient plants enhanced basipetal ³²P transport. The results indicate that a feedback mechanism in the shoots is impaired in Zn-deficient plants which controls the P uptake by roots and especially the P transport from roots to shoots. As a result of this impairment toxic concentrations of P accumulate in the leaves. The mechanism responsible is likely the retranslocation of P in the phloem from shoots to roots.     

The effect of plant hormones on phosphate uptake and translocation in maize roots

In short-term (1 h) uptake experiments GA₃(10^-5M) stimulated P_i uptake into maize root cortex cells by 28.7 %, Ethrel (10^-3M) inhibited it by 18.5 % and BA, IAA, and ABA were inactive. In long-term (5 h) experiments ABA remained inactive, GA₃ lost its stimulatory effect, and BA (5. 10^-6M), IAA (10^-4 -10^-5M), and Ethrel (10^-3 -5. 10^-4M) decreased P_i uptake. When the hormones were present only during 3 h preincubation (“augmentation”) period ABA was inactive, GA₃ slightly raised and BA, IAA, and Ethrel slowed down subsequent P_i uptake. BA(10^-7 –10^-5M) decreased xylem sap volume flow and P_i translocation. ABA in all tested concentrations (10^-8 –10^-5M) reduced exudation rate and P_i translocation, its effect declining with time. IAA effect strongly depended on concentration used and on application time and varied from strong inhibition to moderate stimulation of both volume flow and P_i translocation. GA₃ (10^-7M) slightly stimulated xylem volume flow but inhibited phosphate translocation. Ethrel (10^-4 and 10^-5M) increased both parameters, but P_i transloeation much more than volume flow. IAA, BA, and ABA influenced volume flow and P transloeation to the same extent leaving P_i concentration in the xylem sap unchanged. GA₃ and Ethrel influence P_i concentration in the xylem sap and it is thus probable that these hormones regulate release of phosphate ions into the xylem sap.     

Enantioselective Uptake and Translocation of a Novel Chiral Neonicotinoid Insecticide Cycloxaprid in Youdonger (Brassica campestris subsp. Chinensis)

For a novel potential commercial chiral pesticide, an independent study on the fate characteristics and residues of each stereoisomer is essential if the application rates for the pesticide and human exposure are to be reduced. The absorption and translocation behavior of a chiral insecticide, cycloxaprid, in plants treated by root immersion and blade smearing was studied using ¹⁴C‐labeling tracer techniques. With the root treatment, total absorption of (1R;8S)‐cycloxaprid (RS) (12.39%) was much greater than that of (1S;8R)‐cycloxaprid (SR) (3.31%) at 192 h after treatment (HAT). The mass concentrations ( RS / SR ) of cycloxaprid in the roots, cotyledons, leaf 1, leaf 2, and leaf 3 were 37.0/16.8, 8.3/2.8, 11.7/6.5, 5.1/4.8, and 8.0/4.7 mg kg^‐1 (fresh weight), respectively, at 192 HAT at an initial concentration 1.6 mg kg^‐1. With the foliar application treatment, no significant difference was observed between the total absorption of RS (3.11%) and SR (4.03%) at the end of the treatment. Both acropetal and basipetal transport of absorbed ¹⁴C occurred and more than 71.83% of absorbed RS and 82.42% of SR remained in the treated leaf. Stereoselective absorption was observed during root uptake but not during foliar absorption. Chirality 25:686–691, 2013. © 2013 Wiley Periodicals, Inc.     

The uptake,translocation and release of phosphorus by Elodea densa

Short-term (16 h) laboratory studies of ³²P uptake by Elodea densa rooted in sediment demonstrated both foliar and root uptake, and that translocation occurred acropetally and basipetally. Root absorption is projected to provide 83–85% of total phosphorus uptake during 12–16 h photoperiod days. Measured foliar uptake and excretion rates suggest that there would be no net leakage of phosphorus into the water by undamaged actively-growing E. densa. Foliar uptake decreased and root uptake increased in the dark relative to rates under light.     

Zinc compartmentation in root, transport into xylem, and absorption into leaf cells in the hyperaccumulating species of Sedum alfredii Hance

Sedum alfredii Hance can accumulate Zn in shoots over 2%. Leaf and stem Zn concentrations of the hyperaccumulating ecotype (HE) were 24- and 28-fold higher, respectively, than those of the nonhyperaccumulating ecotype (NHE), whereas 1.4-fold more Zn was accumulated in the roots of the NHE. Approximately 2.7-fold more Zn was stored in the root vacuoles of the NHE, and thus became unavailable for loading into the xylem and subsequent translocation to shoot. Long-term efflux of absorbed ⁶⁵Zn indicated that ⁶⁵Zn activity was 6.8-fold higher in shoots but 3.7-fold lower in roots of the HE. At lower Zn levels (10 and 100 μM), there were no significant differences in ⁶⁵Zn uptake by leaf sections and intact leaf protoplasts between the two ecotypes except that 1.5-fold more ⁶⁵Zn was accumulated in leaf sections of the HE than in those of the NHE after exposure to 100 μM for 48 h. At 1,000 μM Zn, however, approximately 2.1-fold more Zn was taken up by the HE leaf sections and 1.5-fold more ⁶⁵Zn taken up by the HE protoplasts as compared to the NHE at exposure times >16 h and >10 min, respectively. Treatments with carbonyl cyanide m-chlorophenylhydrazone (CCCP) or ruptured protoplasts strongly inhibited ⁶⁵Zn uptake into leaf protoplasts for both ecotypes. Citric acid and Val concentrations in leaves and stems significantly increased for the HE, but decreased or had minimal changes for the NHE in response to raised Zn levels. These results indicate that altered Zn transport across tonoplast in the root and stimulated Zn uptake in the leaf cells are the major mechanisms involved in the strong Zn hyperaccumulation observed in S. alfredii H.     

Uptake,Translocation, Distribution and Persistence of 14C-Metalaxyl in Pearl Millet (Pennisetum americanum) [L.] Leeke)1

Time course absorption and desorption of metalaxyl by seeds of pearl millet was analysed by following chemical kinetics equations. Uptake of metalaxyl through roots, leaves and seed, its translocation and distribution in different plant parts and persistence following seed application were studied in pearl millet using ¹⁴C-metalaxyl. Both uptake and efflux of metalaxyl by pearl millet seeds were complex and compartmentalized. Distribution inside the seed was not uniform. A major part of applied fungicide remained within the treated plant part, particularly after seed and foliar applications. Metalaxyl was ambimobile inside the plant and was found to get accumulated at apex and margins of leaf blade. No metalaxyl could be detected in grains, harvested from plants grown from metalaxyl treated seeds.     

Effect of calcium on the absorption and translocation of heavy metals in excised barley roots: Multi-compartment transport box experiment

Summary The effect of Ca on the absorption and translocation of Mn, Zn and Cd in excised barley roots was studied using a multi-compartment transport box technique. A radioisotope (⁵⁴Mn,⁶⁵Zn or^115mCd)-labelled test solution was supplied to the apexes of excised roots and the distribution pattern in the roots was examined in the absence or presence of Ca. Results obtained were as follows. Addition of Ca to the test solution reduced the absorption of Mn and inhibited drastically its translocation in excised roots. With increasing concentrations of Ca in test solutions, its inhibitory effects on the absorption and translocation of Mn became severe. Similar results were observed for the absorption and translocation of Zn. Ca in the test solution decreased the absorption and inhibited drastically the translocation of Zn; as in the case of Mn, higher concentrations of Ca had severe effects on these functions. It was also evident that the addition of Ca to the test solution reduced the absorption of Cd at all levels of Cd concentration (1, 10, and 100 μM). Cd absorption decreased with increasing concentrations of Ca in the test solution. However, Ca accelerated the translocation of Cd in excised roots supplied with test solutions containing up to 10μM Cd. At 100μM Cd, addition of Ca caused a negligibly small acceleration of Cd translocation. The accelerating effect of Ca on Cd translocation, especially “xylem exudation”, decreased markedly with the addition of 2,4-dinitrophenol, but not with the addition of chloramphenicol or p-chloromercuribenzene sulphonic acid. When barley plants were supplied with only CaSO₄ during the entire growing period, that is, plants were not supplied with nutrient solution on the last day of this period, Ca had no accelerating effect on Cd translocation in excised roots.     

Effects of root and foliar applications of exogenous NO on alleviating cadmium toxicity in lettuce seedlings

The effects of sodium nitroprusside (SNP, a donor of NO) on cadmium (Cd) toxicity in lettuce seedlings were studied. SNP was added into hydroponic systems or sprayed directly on the leaves of plants grown with and without Cd. Excess supply of Cd (100 μM) caused growth inhibition, dramatically increased Cd accumulation in both leaves and roots, and inhibited the absorption of Ca, Mg, Fe and Cu. Excess Cd also decreased activities of superoxide dismutase peroxidase and catalase in leaves and roots, and increased the accumulation of superoxide anion (O ₂ ^·? ), hydrogen peroxide (H₂O₂) and malondialdehyde (MDA). Root or foliar applications of exogenous NO alleviated Cd-induced growth suppression, especially root application of 250 μM SNP and foliar addition of 500 μM SNP. Addition of SNP promoted the chlorophyll synthesis suggesting that the photosynthesis was up-regulated. Exogenous NO increased Cd-decreased activities of antioxidant enzymes and markedly diminished Cd-induced reactive oxygen species (ROS) and MDA accumulation. Moreover, the absorption of Ca, Mg, Fe and Cu was increased, indicating that exogenous NO stimulated H⁺-ATPase activity to promote sequestration or uptake of ions. In addition, exogenous NO also inhibited Cd transfer from roots to shoots, which may indicate that Cd retention in roots induced by NO plays a significant role in Cd tolerance in lettuce seedlings. These data suggest that under Cd stress, exogenous NO improves photosynthesis by increasing chlorophyll synthesis, protects lettuce seedlings against oxidative damage by scavenging ROS, helps to maintain the uptake of nutrient elements, and inhibits Cd transferred to shoots effectively.     

Mise en évidence de déplacements de 86Rb à grande vitesse,dans le phloème de Tradescantia viridis

Summary An autoradiographic study of the rooted shoots of Tradescantia viridis (=T. albiflora Kunth emend. Brueckn.) showed a high speed translocation of ⁸⁶Rb applied to a leaf for short periods of time (5 to 2.5 min).The speed of this translocation (between 840 and 1.440 cm h^-1) speaks for the existence of a very rapid phloem component translocating ions to an active sink, represented here by the growing roots.Pretreatment with cycloheximide (48 h, 50 mg l^-1) decreases the quantity of this long distance transport but not the velocity.

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Abbreviations FD leuille donatrice - CHM cycloheximide     

Sodium and potassium compartmentation and transport in the roots of intact lettuce plants

In this report, we consider the accumulation in roots, and transport to the shoot, of Na⁺ and K⁺ in intact lettuce plants (Lactuca sativa cv Black-seeded Simpson). Plants were grown in modified Hoagland medium supplemented with 10 moles NaCl per cubic meter. At this salinity, significant levels of Na⁺ were accumulated in roots and shoots, but there was no reduction in plant growth. Transport characteristics for both Na⁺ and K⁺ were qualitatively similar to those previously reported, for Spergularia marina, indicating that the results obtained with these experimental protocols are not limited to one unconventional experimental plant. The most pronounced difference in transport of the two ions was evident when transport was followed in a chase period after a 10 minute uptake pulse. For Na⁺, there was an initially rapid, but small, loss of label to the medium, and very little movement to the shoot. For K⁺, little label was lost from the plants, but translocation to the shoot proceeded for at least 60 minutes. The transport systems were further distinguished by treating the roots during labeling with 20 micrograms per milliliter cycloheximide. For K⁺, both uptake and translocation were reduced by about 50%. For Na⁺, root accumulation was stimulated more than five-fold, while transport to the shoot was reduced about 20%. Cycloheximide also modified the Na⁺ transport characteristics such that continued translocation occurred during the chase period of pulse-chase studies.     

THE ABSORPTION AND TRANSLOCATION OF C14-LABELED PROTEINS IN YOUNG TOMATO PLANTS

The uptake of C¹⁴-labeled proteins (lysozyme, hemoglobin, lactoglobulin, and ovalbumin) from solution by tomato plants with sterile roots was studied. It was found that C¹⁴-compounds (proteins and/or protein-degradation products) were translocated to the foliage if the roots had undergone minor mechanical injury or if the plants were subjected to temporary wilting, i.e., physiological damage. C¹⁴-lysozyme was not transported to foliar tissue in healthy plants; C¹⁴-hemoglobin showed radioactivity in leaves of both healthy and injured plants, but there was evidence of a breakdown of the molecule; C¹⁴-ovalbumin gave a faint labeling of foliar tissues of some plants in which wilting or mechanical damage was below the threshold of detection. It is concluded, however, that translocation of proteins from roots in nutrient solution to tomato leaves does not occur in significant amounts in healthy plants in spite of the large uptake of proteins by root cortex, as found in earlier studies.     

Ginsenoside Rb1 exerts antidiabetic action on C2C12 muscle cells by leptin receptor signaling pathway

Context: Ginsenoside Rb1 improves insulin sensitivity and glucose uptake in muscle cells via different signaling pathways; however, it is not clear that it has any effect on leptin signaling in skeletal muscle.

Objectives: The aim of this study was to investigate the effect of ginsenoside Rb1 on leptin receptors expression and main signaling pathways of leptin (STAT3, PI3 kinase and ERK kinase) in C2C12 skeletal muscle cells.

Materials and methods: C2C12 myotubes were incubated with various concentrations of Rb1 (0.1, 1 and 10?μM) for different incubation times (1–12?h). Leptin receptors expression and GLUT-4 translocation were analyzed using realtime PCR and western blot analyses, respectively. PI3 and ERK kinases were blocked using their specific inhibitors (wortmannin and PD98059) in the presence and absence of RB1 to determine the main signaling pathway related to leptin receptor activation in C2C12 cells.

Results: Rb1 could maximally stimulate both leptin receptors (OBRa and OBRb) mRNA and protein expression and phosphorylation of STAT3, PI3K and ERK2 in C2C12 myotubes at 10?μM for 3?h. Rb1 induced GLUT4 translocation was inhibited by the silencing of OBRb mRNA, demonstrated that glucose uptake was mediated via leptin receptor activation. GLUT4 recruitment to the cell surface induced by Rb1 was inhibited by wortmannin, an inhibitor of PI3K in combination with OBRb siRNA, but not by PD98059 an ERK2 kinase-1 inhibitor, indicating that GLUT4 translocation induced by Rb1 was associated with the leptin receptor upregulation and subsequent activation of PI3K.

Conclusions: Our results suggest that Rb1 promote translocation of GLUT4 by upregulation of leptin receptors and activation of PI3K.     

Wheat leaf properties affecting the absorption and subsequent translocation of foliar-applied phosphoric acid fertiliser

Background and aims

Although foliar fertilisation using liquid forms of phosphorus (P) is not a new concept, its adoption has been hindered by a limited understanding of the variability in performance of fluid forms of foliar P applied to broadacre crops. There is a need to identify how the surface structure of leaves influences the absorption and subsequent translocation of foliar-applied P in above ground plant parts.

Methods

This study examined the surface properties of wheat leaves using scanning electron microscopy and measured the recovery of foliar-applied fertiliser that was labelled with either ³²P or ³³P from both the adaxial (upper) and abaxial (lower) leaf sides into untreated plant parts.

Results

We found that the adaxial leaf surface absorbed and translocated more foliar-applied P away from the treated leaf than the abaxial surface, likely related to the higher abundance of trichomes and stomata present on that side of the leaf. The recovery of the foliar-applied fertiliser varied with rate and timing of application; ranging from <30 % to as much as 80 % of the adaxial-applied fertiliser translocated from the treated leaf into the wheat ear.

Conclusions

This study demonstrated that the differences in surface morphological features between leaf sides influenced the combined absorption and subsequent translocation of foliar-applied P in the above ground plant parts. This is due to a direct effect on the foliar pathway and/or due to differences in wettability affecting both the leaf coverage and drying time of fertilisers on the leaves. Although foliar fertilisation in this study contributed less than 10 % of the total P in the plant, it provided a more efficient pathway for P fertilisation than soil-applied P.     

Uptake and Translocation of Benthiocarb Herbicide by Plants

The uptake and translocation of ¹⁴C-benthiocarb labelled at benzyl methylene by rice plant, bamyardgrass, wild amaranth, smart weed and lambsquarters were investigated, ¹⁴C-Benthiocarb was absorbed through the roots and the radioactivity was translocated into whole plants. The rate of absorption and translocation varied by the kind of plants. The translocation was occurred not only from roots into leaves, but from a leaf into other leaves, and even into roots of some kinds of plant. The absorption and translocation was more easy in barnyard-grass than in rice plant. Benthiocarb was rapidly absorbed by seeds and accumulated mostly in the embryo. The uptake of benthiocarb by seedlings decreased with the order of mesocotyl (bamyardgrass only), coleoptyl, root and leaf. Benthiocarb was degraded rapidly in plants.     

Dual mechanisms of ion absorption in relation to long distance transport in plants

The characteristics of ion transport to the shoots of young corn seedlings were studied with respect to the nature of the isotherm through a wide concentration range, the competitive influence of closely related ions upon the transport of a given ion, and the influence of the counter-ion. Both with respect to ³⁶Cl and ⁸⁶Rb transport, the characteristics of the process in every way resemble uptake by non-vacuolate root tips wherein the plasma membrane is the only membrane involved in absorption, and where system 1 — of the 2 systems which can be shown to participate in absorption by vacuolate tissue — is the only system operative. Net ion uptake by the roots per se was shown to display both the high affinity (system 1) and low affinity (system 2) mechanisms. It is concluded that the symplastic theory of ion movement to the xylem is valid, and that the contention that system 1 operates at the plasma membrane while system 2 functions at the tonoplast is strengthened.     

Salicylic acid can regulate phloem unloading in the root tip

In three-day-old maize (Zea mays L.) seedlings, we removed the endosperm, coleoptile with leaflets, and adventitious roots. Primary roots were exposed to 0–10⁻³ M salicylic acid (SA) for 1–5 h; scutellum, to 10⁻² M 2-desoxy-D-glucose (2dG). 2dG-sucrose synthesized from 2dG was transported from scutella to the roots along the phloem. Its accumulation in 5-mm-long root tips was the measure of phloem unloading. At the concentrations higher than 10⁻⁴ M, SA suppressed unloading. Simultaneously, the uptake of ¹⁴C-5,5-dimethyloxazolidinedione (DMO) by root segments was inhibited, indicating cytoplasm acidification. 10⁻³ M SA also inhibited root respiration and growth. The lower SA concentrations (10⁻⁵ and 10⁻⁶ M) activated unloading under conditions of weak sucrose phloem transport to the root. They did not affect DMO uptake, respiration, and growth. 10⁻⁴ M SA stimulated unloading during 1- or 2-h exposure but did not affect it at longer treatments. A dependence of SA action on its concentration and exposure duration implies its involvement in the control of phloem unloading in the root tip.