Allelopathic effect of Bromus spp. and Lolium spp. shoot extracts on some crops.

Allelopathy is an untapped resource for weed control in crops that could give good possibilities for environmentally sound, integrated crop production. Allelopathy is defined as the direct or indirect harmful or beneficial effects of one plant on another through the production of chemical compounds, called allelochemicals, which escape into the environment. Allelochemicals can be produced by weeds and affect crops, and the reverse is also true. Allelopathic interactions include weed-weed, weed-crop, and crop-crop. Allelopathy offers potential for selective biological weed control for instance weed-suppressing crops and the use of plant residues in cropping systems, allelopathic rotational crops, or companion plants with allelopathic potential. Bromus species occur in many habitats in temperate regions of the world, including America, Eurasia, Australia, and Africa. The genus Lolium is one of the most important forage grasses. The weed species usually grow in the same production zones as wheat and are considered weeds since they parasitize wheat fields. Some of the weed species in these two genus have been reported to have allelopathic effect. One of the methods that has been successful in studying allelopathic activity are bioassays. Laboratory experiments were conducted to determine allelopathic effect of watery shoot extracts of four weed species of the Poaceae family, namely Bromus rigidus, Bromus diandrus, Lolium multiflorum and Lolium temulentum on germination and growth of winter wheat (Triticum aestivum L.), spring barley (Hordeum vulgare L.), corn (Zea mays L), perennial ryegrass (Lolium perenne L.), bean (Phaseolus sp.) and sunflower (Helianthus annuus L.) and on each other. The experiment was carried out during the period March 2010 to October 2010. Twenty five seeds were put into one Petri-dish on filter paper, adding 15ml of extract to each in four repeats. The germination took place in a Binder-type thermostat in the dark. The timing of germination was checked in every two days and the rate of growth was estimated after a week, by counting the number of germinated seeds and measuring the length of the radicle and plumule. The measured data was statistically analyzed and the effect of the extracts on germination percentage and seedling length was evaluated.

Allelopathic effects of ragweed (Ambrosia artemisiifolia L.) on cultivated plants.

During the past years ragweed has been coming to the forefront of interest in Hungary and in other European countries as well because its serious health risk. Results of the 5th National Weed Survey has proven that ragweed is the most important weed species on Hungarian field lands, its coverage shows a rising tendency in cereals moreover it not only occurs in cultivated plants. Allelopathic effects of aqueous extracts derived from different parts of ragweed plants (air dried leafy stems, seeds) on the germination and growth of other cultivated plants [maize (Zea mays L.), winter wheat (Triticum aestivum L.), rye (Secale cereale L.), oat (Avena sativa L.)] were studied. The extracts made for the trials were prepared with distilled water. Petri dishes were used for the germination experiments and distilled water was used as a control treatment. The seven days long experiment was carried out within a Binder-type thermostat under dark conditions. The germination percentage was checked in every two days and the growth of sprouts was evaluated after a week counting the germinated seeds and measuring the length of the radicle and plumule. The measured data were statistically analysed and the effect of extracts on germinating and length of sprouts were assessed.

Study on weevil pests of oilseed rape at Keszthely, Hungary.

One of the most important pests of rape in early spring are weevils (Ceutorhynchus spp.). The aim of our studies was to identify the occurring weevil species and to study their emergence, swarming, mating and damage. Our observations were performed on an experimental plot at Keszthely (Hungary, Zala County) in early spring of four consecutive years. Following species were collected and identified: Ceutorhynchus pallidactylus MARSHAM, Ceutorhynchus obstrictus MARSHAM, Ceutorhynchus napi GYLLENHAL, Ceutorhynchus pleurostigma MARSHAM. The obvious dominance of C. pallidactylus and C. obstrictus was detected. Their frequency of occurrence was 88-90% among the identified adults. We found that C. obstrictus was the last species to settle. Complete developmental period was 68 +/- 7 days in case of C. pallidactylus and 70 +/- 7 days in case of C. obstrictus. Average number of eggs laid by one female was 176 +/- 23 in case of C. obstrictus and 21 +/- 6 in case of C. pallidactylus.

Examination of common ragweed's (Ambrosia artemisiifolia L.) allelopathic effect on some weed species.

In the last decades the importance of some weed species increased in Hungary. The common ragweed (Ambrosia artemisiifolia L.) also belongs to this group. The allelopathic effect of watery extract made from different plant parts of common ragweed (air dried leafy shoots, seeds) were studied on the germination and growth of some weed species. The extracts were prepared with tap water, chopped dry plant materials were added to water and 24 hours later the material was filtered. The germination took place in a Binder KBW type thermostat in dark. 25 seeds were put into one Petri-dish, adding 15 ml plant extract to each in four repeats. The timing of germination was checked in every two days and the rate of growth was estimated after a week, by counting the numbers of germinated seeds and measuring the length of the radicle and plumula. The measured data were statistically analysed and the effect of extracts on germinating ratio and seedling length were evaluated.

Effect of seed depth on germination and growth of velvetleaf (Abutilon theophrasti Medic.).

Importance of several weed species has been considerably increased during the last few decades in Hungary. Velvetleaf (Abutilon theophrasti Medic.) belongs to this spreading weed group as well. This weed species was in the 27th position in the course of the fourth Hungarian weed survey, but at the time of the fifth weed survey in 2007-2008 it stepped forward to the 10th position in the cornfields of Zala County. Requiring a warm climate, global climate warming plays a significant role in its rapid spread. Moreover, its effective reproduction strategy supports its occurrence and continuous spread in almost all field crops. Protection against velvetleaf can only be successful, if we know its biological and ecological characteristics. Comprehensive knowledge of the plant and selection of a proper application of weed control methods together can result velvetleaf free crop fields. The experiment was set up on the 29th of April 2009 at Keszthely where fifty seeds were sown into 50 litres volume plastic pots, in four replications with fifty pieces of seed per each plot. Germination percent of velvetleaf seeds and several growth indexes of seedlings (stem- and root length, leaf area, number of leaves, stem- and root fresh and dry weight) were measured on three different sampling dates.

Crop competitiveness influenced by seeding dates and top-dress nitrogen rates.

A competitive crop utilizes resources before they are available to the weeds. The essential steps of developing a competitive crop begin with good stand establishment. A vigorously growing crop is also important towards establishing a competitive stand. Components of establishing a good and vigorous crop stand include crop rotation, seedbed preparation, crop type and variety selection, seed quality and treatment, seeding rate (stand density), seeding date, fertilizer rate and placement, pest and disease control, etc. Failure to properly manage these components leads to poor germination, week seedlings with poor grows and vigor therefore promotes weed competition with the crop. Biomass production and density of weeds and winter wheat plants was studied in a seeding time and nitrogen application small-plot field trial. This trial was a perfect example of how the proper management practices help us to decrease weediness and increase competition of winter wheat. The trial included 3 planting date treatments (early, optimum and late) and 2 nitrogen rate treatments (56 kg N ha-1 and 110 kg N ha-1) in spring top-dressing application. The influence of treatments on the weed infestation and crop plant vs. weed competition was studied at beginning of steam extension (BBCH 32-33, two visible nodes on the steam) and after harvest on the stubble-field. The competitiveness of weeds and crop plants were evaluated by biomass production and also by nutrient content of plant samples. Biomass forming of weeds in wheat canopy was negligible compared to that of weeds, but it was strong on the stubble. Delayed planting Leaded to poorer wheat growth and better weed biomass production. The higher rate of nitrogen resuited in a less weediness on early and optimum time seeded plots, but the tendency was opposite in the late seeded treatment.

Nutrient absorbtion of weeds in maize.

Our study was carried out in Hungary at Keszthely, in 2007. The effect of different cultivation methods: no-till drill, disk tillage, conventional tillage (ploughing) and five increasing N doses were studied on the weediness. The bi-factorial trial was arranged in split plot design with four replications. Crop rotation: winter wheat-winter wheat-maize-maize. The seeding of maize was 23rd of April in 2007. The weed survey was made with Balázs-Ujvárosi coenological method on the 17th of May. In the experiment were found 21 weed species. We collected all plants of every weed species by plots. The sample area was 1 m2. Furthermore five maize plants per plot were sampled on the 22nd of May. Maize was at 3-4 leaves stage. For reason of competition studies no herbicides were applied on sampling sites. The aerial parts of weeds and maize plants were collected, and the fresh and dry matter weight was measured. We analyzed in detail, the occurrence of weed species, and the biomass production of weeds in comparison with maize. The effect of different cultivation methods markedly demonstrated the weed cover, the number of perennial and annual weeds and the number of occurring weed species.

Study on the seed production and germination dynamic of common milkweed (Asclepias syriaca L.).

The common milkweed causes considerable damages on the agricultural and nature conservation areas. The area occupied by this weed is continuously bigger. The common milkweed is spread over North-America between the 35th and 50th degree of western Latitude and 60th 103rd degree of longitude. Millions of hectares are polluted by this weed in the United States. Important is its spread also in Asia (Iraq), in Europe (Carpathian Basin, Poland, Bulgaria, Switzerland, France, Austria, Germany), as well as in the area of the former Soviet Union (Belorussia, The Baltic Countries, Caucasus, and the Ukraine). Though the basic biological characters of this plant are well known, still its control is a significant problem, the damages increase on the areas occupied by this weed. We collect seed samples from several Hungarian areas in 2007. After the sampling we determined the average sprout length and the number of follicle as well as the average seed numbers in the follicle. We determined also the weight of thousand seeds of the resultant seed samples. At natural circumstances the seedlings appear at a soil temperature of 15 degrees C during the end of April and first week of May. Under Laboratory circumstances the dormancy of the seeds ceases continuously from November on, germinate at a temperature of 20-30 degrees C, the maximum germination can be achieved in the first part of April. At January we started germination examinations with the seeds in Petri dish, among laboratory condition.

Study on the development of yellow nutsedge (Cyperus esculentus L.) with growth analysis.

Yellow nutsedge (Cyperus esculentus) is a cosmopolitan, tropical, subtropical plant. Nowadays, the Working Committee of Invasive Plants of the EPPO considers it as a highly damaging internationally important weed. During our work the development of the yellow nutsedge grown was examined until the end of flowering. The 5 repetition pot experiment has been started April 19 2007. Large-sized pots were filled with a mixture of mould and sandy loam in a ratio of 1:1, and planted in each pot 25 yellow nutsedge tuberlets. Weekly one plant and its progeny were harvested from each pot to measure their fresh and dry shoot and underground part (root, tuber and rhizome) weights and leaf area. Samplings were made at 16 occasions between 2007 26 of April and 24 of August. Results were considered by growth analysis. We studied RGR (relative growth rate), LAR (leaf area ratio), RLGR (relative leaf growth rate). Summarised it can be stated, that the beginning of the dynamic growing is 6 week after germination. The dry weight of the shoots is over the dry weight of the underground parts in the examined period. The RGR shows just a minimal change. The LAR was the highest between 17 May and 8 June.

Survey of weed composition befor maize sowing in long-term fertilization experiment.

The study was carried out in a long-term fertilization field experiment of the Experimental Station of University of Pannonia, Department of Crop Science and Soil Science in 2006. The Long-term fertilization experiment was set up in 1983. In the experiment, the success of the weeds ability to grow under the influence of NPK, NPK + FYM* and NPK + straw treatments was compared, and the effect of increasing Nitrogen dosing on weediness was studied. The bifactorial test was arranged in split plot design with three replications. Treatment A: nutrient: NPK, NPK + 35 t/ha FYM* and NPK + straw manure. Treatment B: N kg/ha(-1) N0-N4 (0, 70, 140, 210, 280), and 100 kg P2O5 ha(-1) & 100 kg K20. The weed survey was made on 2nd of May 2006. There were spraying no herbicide until the survey. For the weed survey the Balázs-Ujvárosi coenological method was applied. Altogether, we have found 23 weed species in the trial. In the NPK treatment there were 20 species, in the treatment NPK+organic manure there were 17 species and in the NPK+ stalk rest treatment there were 16 weed species. The most dominant of the weeds on the NPK and NPK+straw manure treatments was Veronica hederifolia while on the fertilizer + FYM, the A. theophrasti was most dominant. The average weed covering value of the treatment NPK + FYM was 1.36 times higher (10.87%) than that of treatment NPK only (7.97%) and 3.65 times higher than on the NPK + straw manure treatment.

Effect of fertilization on the weediness of maize in a long-term field experiment.

We carried our examination in a long-term fertilization field experiment in 2005. In the experiment we had opportunity to compare the weediness in NPK and NPK + FYM1 treatments, and we could study the effect of increasing N dosis on the weeds and maize. The bi-factorial trial was arranged in split plot design with three replications. The weed survey was made 25 days after seeding in the 27th of may. For the weed survey the Balázs-Ujvárosi method was applied. After the weed survey we collected all the weed species from the plots per 1-1 m2. We counted, mesured the fresh and dry matter weight of aerial shoots. We collected maize too, five pieces per plots. In the experiment were found 12 weed species, 9 annual: Abutilon theophrasti, Amaranthus chlorostachys, Ambrosia artemisiifolia, Chenopodium album, Chenopodium hybridum, Echinochloa crus-galli, Polygonum lapathifolium, Xantium strumarium, Veronica hederi-folia, and 3 perennial: Cirsium arvense, Convolvulus arvensis, Lathyrus tuberosus. On the NPK plots the Ch. album, on NPK + FYM treatments the A. theophrasti was the first in order of the dominance. The biomass production of weeds in the NPK + FYM treatments were 3 times higher than in the only NPK treatments.

Study on the weediness of winter wheat in a long-term fertilization field experiment.

The study was carried out in Keszthely, in the long-term fertilization field experiment in April of 2005. In the experiment we had opportunity to compare the weediness in NPK and NPK + FYM* treatments, and we could study the effect of increasing N dosis on the weeds and winter wheat. The weed survey was made on the 20th of April at the end of tillering. For the weed survey used the Balázs-Ujvárosi method. After that we collected all the weeds from the plots per 1 m2. We counted, measured the fresh and dry matter weight of aerial parts. Winter wheat sampels were taken also from all plots (1 running meter per plot). In the experiment 10 weed species were found, 9 annual: Ambrosia artemisiifolia, Consolida regalis, Galium aparine, Lamiunt amplexicaule, Matricaria inodora, Papaver rhoeas, Stellaria media, Veronica hederifolia, Veronica triphyllos, and 1 perennial: Cirsium arvense. Veronica hederifolia was the dominant species in both fertilized plots, Stellaria media has the second highest weed coverage. The manuring treatments, and the N-dosis has important and significantly effect to the weedeness and the biomass production of winter wheat. On the control plots was the relation of biomass weight of weeds the highest. This relation reduced to the effect of N treatments, wich had an favorable effect on the winter wheat.

Investigations on the germination depth of Johnson grass (Sorghum halepense [L.] pers).

The aim of our experiment was to gain data about the germination depth of Johnson grass, and to investigate the dynamics of germination at different sowing depths. These investigations have great importance in respect of effective weed control. The experiments were carried out in the summer of 2005, using pots, in glasshouses. 50 Sorghum halepense chaffy seeds per pot were sown at 1, 5, 10, 15, 20, 25 cm depth. Treatments were used in 4 repeats. Peat:sand mixture in 3:1 ratio was used in the experiments. From the first germination, weeds were counted in every second day for 3 weeks. Finally, we measured the length of sprouts, the fresh root and sprout weight of the weeds, and--after drying--the dry-matter weight as well. The results of the first experiment (carried out in July 2005) showed that 25% of the seeds came up from 15 cm. Most of the weeds (64%) came up from 1 cm depth. Answering to our expectations, the ratio of germination from 5 cm depth was also high: it was 56%. The ratio of germination from 10 cm depth was also good (58%). Another experiment was carried out in August 2005, where the germination of Sorghum halepense was investigated from 20 and 25 cm depth. The results show that in spite of the small size of its seeds (5-7 mm), Johnson grass is able to germinate from 20, 25 cm depth. 30% of the sown seeds germinated from 20 cm depth, and because of the slowing-down of the growth only 6% of them germinated from 25 cm depth.

Vegetative reproduction and chemical control with post-emergent herbicides of field bindweed (Convolvulus arvensis L.).

It is clearly seen from data that roots of Convolvulus arvensis L. have more and less intensive regenerative period during growing season. The more intensive period is in autumn, because in that time roots culminate nutrients, carbohydrate as starch and sugar. The less intensive regenerative or shoot-growing period is in spring, called "late spring bud dormancy". Experiments were conducted to get more information and further details about the regenerative capacity of roots close to and far from the collar of Convolvulus arvensis L. Root segments closer to collar have an intensive regenerative capacity than those ones further to collar. By data of Bakke et al. (1939) is well known, roots exhumed from deep soil layers are able to create shoots with low intensity. So finally we can exclaim that regenerative capacity is decreasing further to collar. Using mechanical weed control it is sufficient to till the upper layer of soil, but many times. Chemical treatments are most effective in the integrated weed control. It is clearly seen that auxin-type herbicide such as 2,4-D, fluroxipir, MCPA. dicamba give the best result. They gave 95% weed control effect used them separately or in combination with other herbicides. Combination of Banvel 480 S (dicamba) and Logran 75 WG (triasulfuron) introduced 95% weed control effect. Only one time got absolutely 100% weed control effect, in the case of Glyphosate active substance. Caused total plant destruction. Excellent result was given with the application of Pledge 50WP (flumioxazin). Herbicides mentioned above are absolutely allowed to take an important and significant part in chemical plant protection against Convolvulus arvensis L. Other herbicides like Granstar 75DF (tribenuron-methyl), Basis 75DF (rimsulfuron + tifensulfuron-methyl) and Huszár (jodosulfuron-methyl-sodium + mefenpir-diethyl) are not so effective against Convolvulus arvensis L., as compared to the previous ones.

Study on the weed-crop competition for nutrients in maize.

Considering the effect of crop-weed competition the rate of weed growing, the competitiveness of the occurring weed species and the duration of competition are determining factors. Experiments were carried out on fields in order to collect data on the effect of early weed competition on maize, including the competition for nutrients and the possible rate of nutrient removal by weeds. From 7 sampling areas of the 9.2 ha field weeds and maize samples were collected 1 month after the sowing of maize. We determined the total numbers and the species numbers of weeds by plots. The removed plant species and maize were weighed then dried until the weight balance was reached. The samples were tested for N, P, K and Ca. Comparison was done with the weight and nutrient element content of maize plants taken from the treated, weed-free area. At the same time comparative analyses were made with the mass and nutrient contents of maize plants. There were 12 occurring weed species in this experiment. Based on the rate of weed cover the following species were dominant: Datum stramonium L., Cannabis sativa L., Amaranthus chlorostachis Willd., Chenopodium album L., Chenopodium hybridum L. Our experiments revealed that in the areas being likely to produce high weed populations and showing a considerable high nutrient removal by weeds, the competition between weed plants and maize occurs at an earlier stage of the vegetation period of maize than on fields with moderate weed populations. Weeds have utilised significant amount of nutrients which has been many fold of maize in case of unit area.

Investigation of the effect of soil herbicides on the growth and nutrient uptake of potato.

In our experiments the effect of three preemergent herbicides was examined on potato varieties. The experiments were carried out under greenhouse conditions in pots with six Hungarian potato varieties. The following herbicides were applied: PATORAN 50 WP (metobromuron), SENCOR 70 WG (metribuzin) and COMMAND 48 EC (chlomazon). The results indicate that the variety Góliát showed the slowest growth. In the case of Lilla fresh and dry shoot weight was decreased by the application of PATORAN 50 WP and SENCOR 70 WG. Tuber weight showed a decrease with the application of SENCOR 70 WG in all varieties. The least tuber weight appeared with the varieties Kánkán and Szózszorszép. Nutrient concentration of potato and N, P and K uptake by potato were examined. In the case of White Lady, Százszorszép and Kánkán N concentration and uptake increase significantly because of SENCOR 70 WG. There was a significant increase in phosphorus concentration and uptake in White Lady, Hópehely and Kánkán varieties in all herbicide treatments. Potassium concentration increased in the case of all the six varieties because of herbicide treatments. Based on these experiments all varieties showed susceptibility against the used herbicides. The results show that important differences occur in the sensitivity and tolerance of varieties against herbicides, which are consequently significant for practical crop protection.

Changes in nutrient content of Cirsium arvense (L.) Scop. during the vegetation period.

Cirsium arvense /L/ Scop. nowadays is popular in all territory of Hungary, it can be found almost on every soil types. Cirsium arvense is one of the most difficulty eradicated weed of the fields, the ruderals, and also the roadsides. On the base of IV. Hungarian Weed Survey 1996-1997, it takes the fifth place in the dominance sequence of the weeds, with 1.8% average covering. In the interest of effective weed control we can know the biological characteristics of the weeds in detail. In our experiments we followed the nutrient uptake and its changing in Cirsium arvense plants. Nitrogen concentration of shoots altered between 1.5-3.6%. We established that plants can uptake potassium in a great quantity. Roots and shoots contained potassium in high concentration between 2.2-5.9%. The maximum of shoot production from the adventitious buds of the roots was in October and the minimum was in April and May.

Elevated levels of plasma and urine beta-thromboglobulin or thromboxane-B2 as markers of real platelet hyperactivation in diabetic nephropathy.

Serum creatinine, immunoreactive serum and urine beta 2-microglobulin, plasma and urine thromboglobulin, plasma thromboxane-B2 levels and daily protein excretion were determined in 61 insulin-treated diabetic patients, comparing the different patient groups (complication free, nephropathy without and with azotaemia) with control subjects. In the groups of diabetic patients, plasma and urine beta-thromboglobulin (BTG) and plasma thromboxane-B2 levels were higher than in the controls. There was a significant positive correlation between urine BTG and beta 2-microglobulin in the group without complication, and between the plasma BTG and beta 2-microglobulin, and plasma BTG and thromboxane levels in the diabetic group with azotaemia. In contrast to some previous assumptions, the increased level of plasma BTG reflects a real platelet hyperactivation in patients with diabetic nephropathy. At the same time, urine BTG also increases. Determination of urine BTG is more simple with less possibility of methodological error.

[Plasma and urine beta-thromboglobulin determination in the detection of thrombocyte hyperactivation in diabetic nephropathies]. / A plasma és a vizelet béta-thromboglobulin meghatározás a diabeteses nephropathiát kísérö thrombocyta hyperaktiváció kimutatásában.

Serum creatinine, immunoreactive serum and urine beta-2-microglobulin, plasma and urine thromboglobulin, plasma thromboxane-B2 levels and daily protein excretion were determinated in 61 insulin treated diabetic patients, comparing the different patient groups (complication free, nephropathy without azotaemia and nephropathy with azotaemia) with the control subjects. In the groups of all diabetic patients plasma and urine beta-thromboglobulin and plasma thromboxane-B2 levels were higher that in the controls. There was a positive significant correlation between urine beta-thromboglobulin and beta-2-microglobulin in the group without complication, and between the plasma beta thromboglobulin and beta-2-microglobulin, and plasma beta thromboglobulin and thromboxane levels in the diabetic group with azotaemia. In contradiction to some previous assumptions, the increased level of plasma beta-thromboglobulin reflects a real platelet hyperactivation also in patients with diabetic nephropathy. At the same time urine beta-thromboglobulin also increases. Determination of urine beta-thromboglobulin is more simple with less possibility of methodological error.

Tubular transport and urinary excretion of phosphate after renal denervation in the anesthetized rat.

Tubular transport of phosphate (Pi) was studied using clearance and tracer microinjection techniques in Inactin-anesthetized male rats subjected to left kidney denervation. Experiments were conducted in the following groups: i) acute denervation (AD); ii) chronic denervation (CD); iii) acute denervation plus thyroparathyroidectomy (AD + TPTX); iv) microinjection with AD. Besides a marked diuresis and natriuresis with no difference in GFR between innervated (inn) and denervated (den) kidneys, unilateral renal denervation resulted in an increased urinary excretion and decreased tubular reabsorption of inorganic phosphate. Maximum tubular reabsorption of Pi (TmPi) calculated per unit GFR was (means +/- SE): AD, inn: 2.38 +/- 0.04, den: 1.98 +/- 0.06 mumol/ml; CD, inn: 2.66 +/- 0.10, den: 2.19 +/- 0.11 mumol/ml; AD + TPTX, inn: 4.78 +/- 0.06, den: 4.26 +/- 0.08 mumol/ml. Thus, differences in TmPi between the two sides were of the same magnitude in the three groups. Fractional recovery of 32Pi from microinjections in control (C) and postdenervation (D) periods was: early proximal, C: 53.0 +/- 0.81, D: 61.3 +/- 1.07%; late proximal, C: 77.0 +/- 0.81, D: 70.6 +/- 0.60%; early distal, C: 93.7 +/- 0.75, D: 03.5 +/- 0.72%. It is concluded that renal sympathectomy depresses tubular transport of inorganic phosphate in anesthetized rats by a primary action on the proximal convoluted tubule and with a partial compensation in the loop of Henle.