Changes in growth and in uptake,distribution and translocation of phosphorus in susceptible and resistant alfalfa plants induced byCorynebacterium insidiosum

The weight of alfalfa plants, especially roots of susceptible strain, decreased when inoculated withCorynebacterium insidiosum. At the 6th week after inoculation the³²P uptake per plant and its translocation into the above-ground organs were considerably decreased in susceptible plants. On the other hand, the³²P uptake was increased and the radiophosphorus was accumulated in above-ground organs in resistant plants.     

Varietal differences in uptake of 32P labelled phosphate in clover plus ryegrass swards and monocultures

Lolium perenne cv. S.23, L. multiflorum cv. RvP, and Trifolium repens cvs S.184 and Olwen, were grown in mixed sward and monoculture during 1979. Whereas in mixtures grass roots absorbed more ³²P than clover roots, in monoculture clover generally absorbed more ³²P than grass roots. This showed that grass was a very strong competitor for uptake in mixed swards. Clover and grass monocultures absorbed most ³²P from 10 or 15 cm depth in the soil, while grass in mixtures absorbed most ³²P at 22.5 cm depth. Comparing varieties, in monocultures in June, Olwen was most active in absorbing ³²P at 15 cm. In August, Olwen absorbed more at 15 cm and 22.5 cm than S.184 or the grass varieties. Differences in absorption depth between varieties were less in mixtures than in monocultures. S.23 absorbed more ³²P in the late season than RvP, both in monoculture and in mixtures. Thus Olwen differed from S. 184 in depth and timing of uptake, whilst S.23 differed from RvP in time of uptake. Such varietal differences could be exploited by manipulation of depth and timing of fertiliser application to increase the precision of sward management.     

Traits related to differences in function among three arbuscular mycorrhizal fungi

Diversity in phosphorus (P) acquisition strategies was assessed among three species of arbuscular mycorrhizal fungi (AMF) isolated from a single field in Switzerland. Medicago truncatula was used as a test plant. It was grown in a compartmented system with root and root-free zones separated by a fine mesh. Dual radioisotope labeling (³²P and ³³P) was employed in the root-free zone as follows: ³³P labeling determined hyphal P uptake from different distances from roots over the entire growth period, whereas ³²P labeling investigated hyphal P uptake close to the roots over the 48 hours immediately prior to harvest. Glomus intraradices, Glomus claroideum and Gigaspora margarita were able to take up and deliver P to the plants from maximal distances of 10, 6 and 1 cm from the roots, respectively. Glomus intraradices most rapidly colonized the available substrate and transported significant amounts of P towards the roots, but provided the same growth benefit as compared to Glomus claroideum, whose mycelium was less efficient in soil exploration and in P uptake and delivery to the roots. These differences are probably related to different carbon requirements by these different Glomus species. Gigaspora margarita provided low P benefits to the plants and formed dense mycelium networks close to the roots where P was probably transiently immobilized. Numerical modeling identified possible mechanisms underlying the observed differences in patterns of mycelium growth. High external hyphal production at the root-fungus interface together with rapid hyphal turnover were pointed out as important factors governing hyphal network development by Gigaspora, whereas nonlinearity in apical branching and hyphal anastomoses were key features for G. intraradices and G. claroideum, respectively.     

Silver uptake, distribution, and effect on calcium, phosphorus, and sulfur uptake

Bean, corn, and tomato plants were grown in a nutrient solution labeled with ³²P, ⁴⁵Ca, or ³⁵S and varying concentrations of AgNO₃. Following a 6-hour treatment period, plants were harvested and analyzed. A low Ag⁺ concentration (50 nanomolar) inhibited the shoot uptake of the ions investigated. In the roots, Ca uptake increased whereas P and S uptake decreased.     

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.     

Light effects in mycorrhizal soybeans

Soybean (Glycine max. L. Merr.) plants were grown in an experiment with a 3 × 3 factorial design using different levels of light (170, 350, and 700 μE·m⁻²·s⁻¹) and P as factors. Plants were grown in a greenhouse in pot cultures using a soil low in plant-available P under three P regimes: no additional P, P added as KH₂PO₄, or P uptake enhanced by colonization of the host plant with the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus fasciculatum (Thaxt. sensu Gerd.) Gerd. and Trappe. Development of the VAM fungal endophyte and of plants under all three P regimes was depressed by limiting light. However, the growth response of VAM plants to increasing light relative to non-VAM plants in the absence of additional P increased while the response relative to non-VAM plants with additional P decreased slightly. The highly significant interaction between the factors (P < 0.001) of the experiment was due to differences in the magnitude and direction of simple effects of the factors. The implications of these differences in terms of source-sink relationships of the symbionts and the value of different non-VAM controls in interpreting VAM effects are discussed.     

A rapid method for the measurement of [γ-32P]ATP specific radioactivity in tissue extracts and its application to the study of 32Pi uptake in perfused rat heart

(i) A new, rapid method for the measurement of [γ-³²P]ATP specific radioactivity in tissue extracts in the presence of other ³²P-containing compounds is described. The deproteinized extract is incubated with phosphorylase b and phosphorylase kinase, and the incorporation of ³²P into protein from [γ-³²P]ATP is measured by precipitation on filter paper in trichloroacetic acid. No separation of ATP or other treatment of the extracts is required for the assay. (ii) ³²P_i uptake in perfused rat heart was found to be a relatively slow process, with a K_m of 0.084 mm, whereas equilibration between intracellular ³²P_i and [γ-³²P]ATP occurred rapidly.     

Effects of decenylsuccinic Acid on p uptake and translocation by barley and winter wheat

After 3 days of exposure to 10⁻³ and 10⁻⁴ M decenylsuccinic acid, winter wheat plants wilted and died. Decenylsuccinate at 10⁻³ M inhibited ³²P uptake by barley roots and wheat roots and resulted in significant (P ≤ 0.05) leakage of previously absorbed ³²P and total phosphorus (barley roots). Decenylsuccinate effects on ³²P uptake and retention were attributed to increased permeability resulting from injury. Decenylsuccinate at 10⁻⁴ M did not inhibit root uptake of ³²P but decreased movement into the shoot. This could be interpreted as an indication of reduced transpiration or inhibition of ³²P loading into the transpiration stream. Decenylsuccinate did not increase cold hardiness in winter wheat in a nonhardening environment.     

Phosphate transport by hyphae of field communities of arbuscular mycorrhizal fungi at two levels of P fertilization

This study was conducted to elucidate the effect of P fertilisation on the function of field communities of arbuscular mycorrhizal fungi (AMF) measured as P transport to flax. Two methods were applied to soil from a long-term field experiment with NaHCO₃-extractable soil P levels of 24 and 50 mg kg^-1in an experiment under controlled conditions: i) Measurement of plant growth and P uptake in the presence or absence of the fungicide benomyl and ii) measurement of hyphal P transport from a root-free compartment labelled with ³²P. Benomyl successfully prevented mycorrhizal function. The absolute contribution of AMF to plant P uptake was of the same magnitude with or without P fertilisation at 27 days after sowing. Therefore, even though plants grown at the higher soil P level had greater P uptake, the relative contribution of AMF to P uptake was greater at the lower P level than at the higher P level (77 and 49% of total P uptake, respectively). The AMF in P-fertilized soil transported less P³² from the root-free compartment to the plant after 23 days than the AMF in unfertilized soil, but this difference disappeared in plants harvested after 27 and 32 days. The production of hyphae was largely similar in both fertilization treatments, indicating that the capacity for P uptake and transport by hyphae of the two AMF communities was similar. This revised version was published online in June 2006 with corrections to the Cover Date.     

32P uptake in three submerged aquatic plant species

Summary Highest uptake of³²P by young shoots of three plant species was observed and lowest by old ones. The uptake of³²P was highest inHydrilla shoots, followed byVallisneria andPotamogeton.Kinetin (0.23 mM) pretreatment (24 h) increased the uptake of³²P, while 0.69 mM ethrel or 0.075 mM ABA decreased it in all species.³²P was transported to the largest extent to the young shoots of the submerged plants and to the smallest extent to the old ones by kinetin pretreatment. Kinetin enhanced the uptake of³²P most inHydrilla shoots, followed byVallisneria andPotamogeton. Ethrel diminished³²P uptake most inPotamogeton shoots and to the smallest extent inHydrilla, while ABA lowered it most inHydrilla shoots and to the smallest extent inPotamogeton. Kinetin, ethrel and ABA can modify the uptake of³²P of these aquatic plants.     

Involvement of na in active uptake of pyruvate in mesophyll chloroplasts of some c(4) plants : na/pyruvate cotransport

An artificial Na⁺ gradient across the envelope (Na⁺ jump) enhanced pyruvate uptake in the dark into mesophyll chloroplasts of a C₄ plant, Panicum miliaceum (NAD-malic enzyme type) (J Ohnishi, R Kanai [1987] FEBS Lett 219:347). In the present study, ²²Na⁺ and pyruvate uptake were examined in mesophyll chloroplasts of several species of C₄ plants. Enhancement of pyruvate uptake by a Na⁺ jump in the dark was also seen in mesophyll chloroplasts of Urochloa panicoides and Panicum maximum (phosphoenolpyruvate carboxykinase types) but not in Zea mays or Sorghum bicolor (NADP-malic enzyme types). In mesophyll chloroplasts of P. miliaceum and P. maximum, pyruvate in turn enhanced Na⁺ uptake in the dark when added together with Na⁺. When flux of endogenous Na⁺ was measured in these mesophyll chloroplasts preincubated with ²²Na⁺, pyruvate addition induced Na⁺ influx, and the extent of the pyruvate-induced Na⁺ influx positively correlated with that of pyruvate uptake. A Na⁺/H⁺ exchange ionophore, monensin, nullified all the above mutual effects of Na⁺ and pyruvate in mesophyll chloroplasts of P. miliaceum, while it accelerated Na⁺ uptake and increased equilibrium level of chloroplast ²²Na⁺. Measurements of initial uptake rates of pyruvate and Na⁺ gave a stoichiometry close to 1:1. These results point to Na⁺/pyruvate cotransport into mesophyll chloroplasts of some C₄ plants.     

The uptake,distribution, leakage,and incorporation of32P into organic compounds in alfalfa plants susceptible and resistant to the bacterial wilt and the effect ofCorynebacterium insidiosum upon these processes

Higher³²P uptake per plant was found in the healthy resistant (R) alfalfa (Medicago saliva L.) plants when compared with the healthy plants susceptible (S) to the bacterial wilt, following the exposure of the roots of intact plants to the radiophosphate solution. The bacterial infection markedly decreased³²P uptake and radioactivity levels per dry matter in most organs of the R-plants on the day 8 and 14 after inoculation withCorynebacterium insidiosum whereas in the S-plants a decrease in³²P uptake was only found on the day 8.³²P leakage rate from the infected R-plant roots to the nonradioactive nutrient solution was higher than from the healthy ones on the day 8. At the same time³²P content in the organic P fraction was somewhat increased due to the infection in the R-plant roots, whereas³²P content in DNA was decreased. After foliar application,³²P distribution pattern was similar in the tissues of both the S- and the R-plants and was not affected due to the infection in the course of the 3rd week after inoculation. However, the bacterial infection markedly increased³²P translocation from the primary leaf to the rest of the R-plant. An erratum to this article is available at .     

Potassium transport in two tomato species : lycopersicon esculentum and lycopersicon cheesmanii

The commercial tomato, lycopersicon esculentum Mill. cv Walter, and its wild relative, Lycopersicon cheesmanii ssp. minor (Hook.) C.H. Mull., were grown for 30 days under controlled conditions and in solution culture varying in its content of Na⁺ and K⁺. Subsequently, ⁸⁶Rb-labeled K⁺ uptake and distribution were studied. From all solutions, `Walter' consistently absorbed <sup>86</sup>Rb-labeled K<sup>+</sup> at a higher rate in micromoles per gram fresh weight per 30 minutes than L. cheesmanii. L. cheesmanii distributed a greater proportion of the absorbed K<sup>+</sup> from its root to its shoot. When 0.6 millimolar NaNO<sub>3</sub> replaced 0.6 millimolar KNO<sub>3</sub> in the pretreatment solution, intact plants of both genotypes followed a similar pattern as when they were pretreated with K<sup>+</sup> only, but a greater percentage of the absorbed K<sup>+</sup> remained in the roots. Leaf slices of L. cheesmanii plants deprived of K<sup>+</sup> for 6 days showed a greater rate of K<sup>+</sup> uptake than did slices from `Walter' plants pretreated the same way. Stem slices of L. cheesmanii, however, had a lower uptake rate than did those of `Walter'. Both leaf and stem slices of `Walter' plants, pretreated 6 days with 0.6 millimolar NaNO₃ substituting for 0.6 millimolar KNO₃ in their growth medium, had greater rates of ⁸⁶Rb-labeled K⁺ uptake from 0.5 and 20 millimolar KCl solutions than did slices of L. cheesmanii. These marked differences in patterns of ion uptake and translocation indicate that these genotypes of tomato have evolved different mechanisms to deal with K⁺ and Na⁺ in their environments.     

Uptake and transport of N,P and K in tomato supplied with nettle water and nutrient solution

Water extract of stinging nettle (Urtica dioica) has a growth stimulating effect on plants. This investigation elucidated effects of nettle water on uptake and transport of N, P and K. Tomato plants (Solanum lycopersicum L. cv. Dansk export) were grown in sand culture 6–8 weeks. Plants were supplied with nettle water and nutrient solution was used as a control medium. Uptake and transport of N, P and K⁺ were determined with isotopes (¹⁵N,³²P and⁸⁶Rb⁺ as a tracer for K⁺) and ion-selective electrodes and in exudation experiments. A 15% higher uptake of nitrogen (¹⁵N assay) was found after nettle water treatment compared with the nutrient solution control. The total amount of nitrogen was also higher in plants cultivated with nettle water. Transport of inorganic and organic nitrogen, measured in exudation experiments, was more than 50% higher for plants supplied with nettle water compared with plants supplied with nutrient solution. In contrast, nettle water had no effect on uptake, transport or total amount of phosphorus and potassium in the plants. Experiments in hydroculture showed that nettle water had a strong pH-elevating effect. Uptake of NH ₄ ⁺ was strongly stimulated by nettle water compared with nutrient solution. By holding pH at a constant level during the uptake period for 6 h, the uptake of NH ₄ ⁺ from nettle water was significantly lower when no adjustment of pH was made. Consequently a good deal of the NH ₄ ⁺ uptake enhancement by nettle water could be explained by pH-stimulation. Assays with the uncoupler/inhibitor 2,4-dinitrophenol (DNP) and dichlorophenyl-dimethyl-urea (DCMU) showed that uptake of nitrogen from nettle water was less metabolically-linked than uptake from a corresponding nutrient solution. All together, nettle water seems to stimulate the uptake of nitrogen, but not phosphorus or potassium.     

Radial salt transport in corn roots

Primary roots of solution-grown, 5-day-old or 6-day-old seedlings of corn (Zea mays L.) 10 to 14 cm in length were used to study radial salt transport. Measurements were made of the volume of root pressure exudation, salt concentration of the exudate, and rate of salt movement into the xylem exudate. The ³²P uptake, O₂ consumption, and dehydrogenase activity of the root cortex and stele also were studied.

These roots produced copious root pressure exudate containing 4 to 10 times the concentration of ³²P in the external solution. Freshly separated stele from 5-day-old roots accumulated ³²P as rapidly as the cortex from which it was separated and the stele of intact roots also accumulated ³²P. Separated stele has a higher oxygen uptake than cortex. It also shows strong dehydrogenase activity with the tetrazolium test. The high oxygen consumption, ³²P uptake and strong dehydrogenase activity indicate that the cells of the stele probably play a direct role in salt transport.

These data raise doubts concerning theories of radial salt transport into the xylem based on the assumption that the stele is unable to accumulate salt vigorously.

     

Changes in phosphorus metabolism in alfalfa plants induced by bacterial wilt

Radioactive phosphate was applied to the roots of intact alfalfa plants (Medicago sativa L.) on the 49th day after inoculation withCorynebacterium insidiosum (Me Culloch) Jensen and the³²P contents in different fractions of phosphoric compounds were determined. In inoculated plants, susceptible to bacterial wilt, the inorganio phosphate contents (³²Pinorg) was increased markedly and the³²P bound in organic compounds soluble in acids (³²Porg) decreased as compared with control. In roots of the same plants the³²P contents in phospholipid fraction and DNA were decreased. In tolerant inoculated plants the³²Pinorg increase and³²Porg decrease as compared with those changes in susceptible plants were less expressive. No expressive changes in determined³²P fractions have been proved in resistant plants without any visible disease symptoms.     

Transformations between organic and inorganic sediment phosphorus in Lake Balaton

In order to estimate microbial P content and biological P uptake in sediments, the tungstate precipitation method of Orrett & Karl (1987) was used in sediment extracts. This method allows a simple and rapid separation of organic and inorganic ³²P radioactivity. Either inorganic ³²P (as carrierfree H₃ ³²PO₄) or organic ³²P (as ³²P-labelled algal material) was added to surface sediment suspensions of shallow Lake Balaton. Inorganic ³²P was rapidly transformed into organic ³²P, and this process was completely inhibited by formaline. P content of living benthic microorganisms was estimated from steady state distribution of the radioactivity. Transformation of algal organic P into inorganic P could also be detected.In extremely P limited Lake Balaton benthic microorganisms were shown to supplement their high P requirements by inorganic P uptake. The velocity of the inorganic into organic P transformation, i.e. the rate of microbial P uptake, was comparable to P uptake in the water column. Microbial P uptake contributed significantly to total P fixation by sediments, particularly at low ( 100 µg P l^–1) phosphate additions.     

Long Distance Transport in Macrocystis integrifolia: II. Tracer Experiments with C and P

Discs from mature regions of Macrocystis blades picked up significantly more [³²P]phosphate from the ambient medium than similar discs from young meristematic regions, and this uptake was higher in light than in darkness. Double-labeling experiments with NaH¹⁴CO₃ and [³²P]phosphate, using intact fronds as well as cut frond segments, indicated that ³²P was translocated from mature blades to sink regions at velocities of 25 to 45 centimeters per hour, velocities comparable to ¹⁴C translocation velocity in the same material. There was a slight delay in transport of ³²P which may be due to a delay in loading or to a high metabolism of ³²P in the transporting channels. Histoautoradiography of stipe segments in the translocation pathway indicated that transport of label occurred in the peripheral parts of medulla. An analysis of ³²P-labeled compounds in the fed blade and in the sieve tube sap, collected from basal cut ends of stipes, indicated major differences in labeling patterns. In the blade, a high proportion of ³²P was recovered as inorganic phosphate and relatively small amounts were found in hexose mono- and diphosphates, UDPG and ATP. In the sieve tube sap, however, only a small amount of ³²P was present as inorganic phosphate, a large proportion was found in hexose mono- and diphosphates, and appreciable amounts were present in ATP and UDPG.     

Varietal differences in potassium uptake by barley

Potassium influx isotherms were obtained for 10 cultivars of barley using plants which had been grown with or without potassium (high K⁺ and low K⁺ plants, respectively), and the cultivars ranked with respect to K_m or V_max values for influx with a view to using these rankings as a predictive measure of long term performance under conditions of potassium-limited growth. Analyses of these rankings revealed significant differences between cultivars. Net uptake rates for low K⁺ plants, determined over a 24-hour period, confirmed the differences between upper (Herta) and lower (Conquest) ranked cultivars, and established similar differences in the rates of translocation to the shoot. Efflux analyses showed no differences in potassium efflux from the cytoplasm or from the vacuole for these cultivars. Growth rate studies under different conditions of potassium limitation indicated, with some exceptions, strong positive correlations between ranks accorded cultivars on the basis of influx kinetics and those based upon growth rates.     

Competitive Al Inhibition of Net Mg Uptake by Intact Lolium multiflorum Roots : II. Plant Age Effects

Rhizotoxicity of Al is more pronounced in younger plants. Effects of Al on nutrient uptake by plants of different age are poorly understood. The depletion technique was used to monitor net Mg²⁺ uptake from nutrient solutions by intact 15- and 35-day-old plants of two ryegrass (Lolium multiflorum Lam.) cultivars. Lowering the pH from 6.0 to 4.2 decreased the maximum net ion influx without affecting K_m. Aluminum at 6.6 micromolar Al³⁺ activity increased K_m indicating competitive inhibition. The effects of pH and 6.6 micromolar Al³⁺ on net Mg²⁺ uptake were much larger in 15- than in 35-day-old plants. Aluminum at 26 micromolar Al³⁺ activity competitively inhibited net Mg²⁺ uptake by 35-day-old plants, while causing time- and external Mg²⁺ activity-dependent net Mg²⁺ efflux from 15-day-old plants. The equilibrium constant (K_i) of a reversible combination of postulated plasmalemma Mg²⁺ transporter and Al³⁺ was calculated to be 2 and 5 micromolar Al³⁺ activity for 15-day-old plants of Wilo and Gulf ryegrass, respectively, and 21 micromolar Al³⁺ activity for 35-day-old plants of both cultivars. The Al³⁺-mediated increase in K_m was larger for 15-day-old plants of the Al-sensitive cultivar `Wilo' than of the more Al-tolerant cultivar `Gulf,' while Al³⁺ affected 35-day-old plants of both cultivars to the same extent.