Influence Of Nitrogen Nutrition Research Articles

Productivity of sugar beet under alternative organic-mineral fertilization

Aim. Investigate the effect of doses and methods of applying nitrogen fertilizers, the use of micronutrients fertilizers on the productivity of sugar beet under an alternative organic-mineral fertilization system. Methods. Short-term field and analytical. Results. The results of research on the influence of nitrogen nutrition and micronutrients fertilizers on the productivity of sugar beet under alternative organic-mineral fertilization are presented. It was determined that the spring application of nitrogen fertilizers and foliar feeding with microfertilizers under plowing winter wheat straw into the soil increased the yield of roots - by 22.5−23.7 t/ha, stabilized sugar content at the level of 18.2−18.3% and ensured maximum sugar yield – 12.0−12.3 t/ha. Conclusions. It was found that in conditions of sufficient moisture on leached chernozem, the use of alternative organic-mineral fertilization systems increased sugar yield compared to the control without fertilizers by 3.1−4.4 t/ha. The application of nitrogen fertilizers in the fall under deep plowing against the background of alternative fertilization is determined to be less effective than their application in the spring under pre-sowing cultivation. Applying 5 t/ha of straw + N90P90K130 under plowing ensured the yield of roots – 60.4 t/ha, sugar yield – 11.0 t/ha, while 5 t/ha of straw + P90K130 under plowing + N90 under pre-sowing cultivation – 64, 5 and 11.6 t/ha, respectively. Application of 5 t/ha of straw + P90K130 under plowing + N90 under pre-sowing cultivation + foliar feeding with composite micronutrients fertilizer in the phase of leaf closure in rows and between rows was determined to be the most effective for sugar beet: yield of roots – 67.0 t/ha, sugar yield – 12.3 with an increase to the control without fertilizers by 23.7 and 4.4 t/ha.

The influence of nitrogen nutrition on the formation of the balance of nutrients in the agrocenosis of winter wheat

Аim. To study the influence of doses and methods of applying nitrogen fertilizers on the peculiarities of the use and balance of nutrients in the agrocenosis of winter wheat and to form a paradigm of an ecologically balanced fertilization system on leached chernozem. Меthods. Short-term field and analytical. Results. For the first time, under the conditions of sufficient moisture in the Forest Steppe of Ukraine, for the cultivation of winter wheat on leached chernozem, a fertilization system that forms a balanced balance of nutrients in the soil and ensures a grain yield of more than 6.5 t/ha has been substantiated. It was established that with a biological harvest, winter wheat takes the most nitrogen from the soil at the ratio N:P:K = 2.7:1:1.9. It was found that the formation of a balanced nitrogen balance in the soil depended mainly on the doses of nitrogen fertilizers and did not depend on the methods of their application. The potassium balance significantly depended on the removal of straw from the field and the doses of potash fertilizers, the phosphorus balance – on the doses of phosphorus fertilizers. Conclusions. Nitrogen was removed by plants mainly as part of grain yield, potassium – as part of by-products. In the control without fertilizers, removal of nitrogen by grain (4.77 t/ha) was 94 kg/ha, phosphorus – 33, potassium – 25, straw (5.35 t / ha) – 26, 10 and 57 kg/ha, respectively. The most ecologically stable fertilization system was that anticipated leaving winter wheat straw on the field and applying mineral fertilizers in a dose of N110Р60K60, where 60 kg / ha of nitrogen as ammonium sulfate was applied on the frozen soil surface, 30 kg/ha as ammonium nitrate on the soil surface or as urea foliarly in the phase of emergence into the tube (IVth stage of organogenesis) and 20 kg/ha as urea foliarly in the phase of milk-wax maturity (VIIIth stage of organogenesis) on the background of P60K60 applied under deep plowing. Under such conditions, an almost balanced balance of nutrients was achieved in the soil with nitrogen deficiency – 20–22 kg/ha and the accumulation of phosphorus and potassium reserves in the amount of 14–15 and 24 kg/ha, respectively. Obtaining a grain yield of more than 6.5 t/ha based on sustainability requires the application of mineral fertilizers in the dose of N130Р50K40 and under the condition that winter wheat straw remains on the field. In the case of removal of straw from the field, a deficiency of nitrogen and potassium was formed in the soil in the amount of 62–64 and 63 kg/ha with a balanced phosphorus balance, which is evidence of an ecologically unstable fertilization system.

Продуктивність лучних травостоїв за різних способів поверхневого поліпшення

Goal. To study the effect of surface improvement of meadow agro phytocoenoses by strip sowing of legumes in the existing grasslands, as well as the influence of the long-term application of different doses of mineral fertilizers on their productivity. Methods. Field — to determine the interaction of the object of study with weather and agronomic factors, measuring — to determine the yield and productivity of grass, statistical — to determine the reliability of the results of research. Results. The results of research in ways to increase the yield of meadow grasslands depending on surface improvement are presented. Application of phosphorus-potassium fertilizers (P60K90) and sowing of legume components increased productivity by 29% on short-term and 21% — long-term haymaking compared to the option without fertilizers. The main crop of meadows of different ages was formed under the influence of nitrogen nutrition, the use of which provided 60–109% growth. The lowest productivity was under control without fertilizers and amounted to 4.16 t/ha of hay on the short-term (5–9 years) phylogenesis, 2.6 t/ha of f.u., on the long-term (42–46 years) — 4.62 t/ha of hay, 2.0 t/ha of f.u. The application of phosphorus and potassium (P60K90) fertilizers made it possible to increase the yield of meadow grasslands from 21 to 29%. Conclusions. Feeding short-term grass with a nitrogen fertilizer at a dose of N60 (N30 for the first 2 mowing cycles) contributed to productivity growth up to 7.40 t/ha of dry matter and 5.65 t/ha of f.u. Uniform application of slightly lower doses of nitrogen N50 (25+25), with 2 times mowing of grasses provided 6.82 t/ha of hay with an increase to control of 64%, the collection of fodder units was 5.13 t/ha. The highest productivity of long-term (42–46-year-old) grassland (6.80 t/ha of f.u. and 0.98 t/ha of digestible protein) was provided by the use of mineral fertilizer (N90(30+30+30)P60K90) with uniform distribution of nitrogen fertilizers and 3 times mowing of meadow grasses.

Agroecological testing of rapeseed varieties in rice crop rotation in Kalmykia

The article deals with the effects of nitrogen nutrition on the production of spring rape varieties and row spacing on the linear growth of plants aimed at improving the rice yield. The experimental studies were carried out on the fields of the Federal State Unitary Enterprise “Harada” in the Oktyabrsk District of the Republic of Kalmykia located in the zone of the Sarpin irrigation system. The resource-saving technologies that can increase the yield without irrigation using residual moisture reserves are of great importance. Intermediate crops can accelerate the soil cultivation on rice fields and increase the rice yield. When spring rape is sown, the soil acquires an increased ability to restore the structure of the soil layer. The green mass is digestible and contains a small amount of fiber. With a high level of moisture, it can give several yields of green mass. With intensive growth of rapeseed after mowing crops, it can be used for grazing. Over the years of research, the yield of green mass varied from 14.8 to 22.9 t/ha. It was revealed that for Vizit variety, an increase in the row spacing from 15 to 30 cm does not reduce the yield of green mass, and with an increase from 30 to 60 cm, the yield decreases by 22 … 28%. For Ratnik variety, the best row spacing was 45 cm. An increase or decrease in row spacing reduces the green mass yield by 8 … 12%. The influence of nitrogen nutrition and sowing density on the production process and green mass yield was identified.

Effect of nitrogen and mineral composition of the high-concentrated wort made from starch-containing raw materials on the cultivation of yeast

We theoretically substantiated and experimentally confirmed the feasibility of enriching highly-concentrated wort made from starch-containing raw materials with nitrogen and mineral nutrition for yeast cells. The influence of nitrogen nutrition, as amine and ammoniac nitrogen, as well as mineral nutrition as nanoparticles and ions of metals was investigated. It was established experimentally that in the course of cultivating the yeast on wort with a concentration of 20, 28 % DS, a necessary precondition is the adjustment of nitrogen nutrition through additional introduction of glycine to serve as amine nitrogen, the concentration of 0.7 g/dm 3 of wort, and ammoniac nitrogen (to serve as carbamide) in the amount of 800 g/m 3 , which would make it possible to increase the concentration of yeast cells to 280−430 mln/cm 3 in the process of culturing the yeast depending on the concentration of wort and the type of nitrogen nutrition, respectively. Based on results of the present research on the influence of mineral nutrition in the nano- and ionic form on the yeast-generation process, it was determined that the largest positive effect on the synthesis of yeast cells was exerted by Zn and Mg and the mixtures of these metals, both in nano- and in ionic form, whose concentration was 1.2 mg/cm 3 and 50 g/m 3 , respectively; in this case, the number of yeast cells ranged from 360 to 480 mln/cm 3 depending on the concentration of wort and the type of mineral nutrition. We have proven the feasibility of cyclic use of mineral nutrition, both in ionic and in nano forms, when cultivating yeast, in order to obtain cells with high physiological-biochemical activity. The use of mineral and nitrogen nutrition allowed us not only to obtain a high concentration of yeast cells, but also reduce the duration of yeast-generation to 15–20 hours and ensure their high regenerative and physiological activity during fermentation of wort with high concentrations of dry substances

Influence of nitrogen nutrition on yield and growth of an everbearing strawberry cultivar (cv. Evie II)

ABSTRACTStrawberry plants are relatively unresponsive to nitrogen (N) fertilization. Supraoptimal N application also results in excessive vegetative growth, which competes to reproductive growth. Two strawberry field experiments were conducted for two consecutive years using fertigation to investigate the effect of different nitrogen (N) application rates on yield and growth of an everbearing strawberry (cv. Evie II). N was injected weekly into the drip irrigation system at 0, 0.5, 1, 3, and 6 kg N/ha/week the first year and 0, 1, 2, and 3 kg N/ha/week the next year. Fruit yield and fruit number were not affected the first year, but were increased the second year due to N application. However, there was no effect of N nutrition on average berry weight for both years. It was concluded that N fertilization may increase yield and fruit number, but average berry weight remains unaffected.

Influence of nitrogen nutrition on nitrate levels of strawberry leaf blades and petioles

ABSTRACTHydroponic and field experiments were conducted to assess the optimum nitrogen (N) levels in strawberry leaves for the appropriate management of its N nutrition under field or protected cultivation. Unlike the common view that leaf petiole is the right plant organ to sample for strawberries, the study showed that the leaf blade, of the most recently fully expanded leaf, is more responsive and therefore a better indicator of the N supply changes in the strawberry plant. This was attributed to the distinctive characteristic of strawberry plants to accumulate high concentrations of nitrates in leaf blades when there is luxury consumption of N.

The influence of nitrogen nutrition on the dynamics of growth and metabolism of endogenous growth regulators in Scotch pine (Pinus silvestris L.) seedlings

Pine seedlings were cultivated in sterile agar cultures containing nitrogen as NH4Cl. The most pronounced positive effect on the growth of seedlings was affected by N used at a concentration of 50 ppm. After 4 months was stated that nitrogen had only a slight effect on elongation, of .shoots but decreased the length of roots. Nitrogen increased the lenght and number of primary and secondary needles as well as the fresh and dry matter of sboots. It stimulated also the number of lateral roots and the fresh and dry matter of the root system. Stimulation of shoot growth and differentiation as a result of nitrogen treatment was correlated with the increase -of free gibberellins and auxins and decrease of the amount of bound gibberellins and ABA-like inhibitor in shoots. However the effect of N on growth of roots was connected with the increase of auxins, cytokinins and ABA-like inhibitor in these organs.

Redox states of photosystems I and II in irradiated leaves of wheat seedlings grown under different conditions of nitrogen nutrition

Changes in the redox states of photosystem I (PSI) and PSII in irradiated wheat leaves were studied after growing seedlings on a nitrogen-free medium or media containing either nitrate or ammonium. The content of P700, the primary electron donor of PSI was quantified using the maximum magnitude of absorbance changes at 830 nm induced by saturating white light. The highest content of P700 in leaves was found for seedlings grown on the ammonium-containing medium, whereas its lowest content was observed on seedlings grown in the presence of nitrate. At all irradiances of actinic light, the smallest accumulation of reduced QA was observed in leaves of ammonium-grown plants. Despite variations in light-response curves of P700 photooxidation and QA photoreduction, the leaves of all plants exposed to different treatments demonstrated similar relationships between steady-state levels of P700+ and QA−. The accumulation of oxidized P700 up to 40% of total P700 content was not accompanied by significant QA photoreduction. At higher extents of P700 photooxidation, a linear relationship was found between the steady-state levels of P700+ and QA−. The leaves of all treatments demonstrated biphasic patterns of the kinetics of P700+ dark reduction after irradiation by far-red light exciting specifically PSI. The halftimes of corresponding kinetic components were found to be 2.6–4 s (fast component) and 17–22 s (slow component). The two components of P700+ dark reduction were related to the existence of two PSI populations with different rates of electron input from stromal reductants. The magnitudes of these components differed for plants grown in the presence of nitrate, on the one hand, and plants grown either in the presence of ammonium or in the absence of nitrogen, on the other hand. This indicates the possible influence of nitrogen nutrition on synthesis of different populations of PSI in wheat leaves. The decrease in far-red light irradiance reduced the relative contribution of the fast component to P700+ reduction. The fast component completely disappeared at low irradiances. This finding indicates that the saturating far-red light must be applied to determine correctly the relative content of each PSI population in wheat leaves.

Influence of Nitrogen Nutrition on Tuber Quality of Potato with Special Reference to the Pathway of Nitrate Transport into Tubers

The influence of nitrogen (N) nutrition on tuber quality of potato (Solanum tuberosum L.), i.e., specific gravity, starch, nitrate, and protein content as well as ascorbic acid content was investigated in a pot experiment. As expected, specific gravity and starch content decreased with increasing fertilizer rates. Protein and especially nitrate content were positively related to nitrogen fertilization, while the effect on l-ascorbic acid content was relatively small. Only at the highest N level, which led to drastic yield depressions (3.8 g N pot−1), l-ascorbic acid content was significantly reduced. Since is considered phloem-immobile and xylem transport into the tubers is restricted (because of the tuber's low transpiration rate), the pathway of nitrate translocation into the tubers is unclear. For Ca2+, a direct uptake from the soil solution by the tuber surface is well documented. In order to check whether this pathway may also be of importance for , potato plants were cultivated in solution culture. The growing tubers were wrapped with paper tissue soaked with Ca(15NO3)2-labelled tuber medium, while contact of the tubers with the nonlabeled liquid growth medium was strictly avoided. 15N-content of tubers was measured on a mass spectrometer. The experiment demonstrated that with high concentration at the tuber surface, up to 40% of total tuber content can be taken up through the tuber skin.

Tolerance of wheat to Russian wheat aphids: Nitrogen fertilization reduces yield loss

Abstract The influence of nitrogen nutrition and Russian wheat aphid (Diuraphis noxia Mordvilko) infestation on morphology and grain yield of wheat (Triticum aestivum L.) was studied in growth chamber experiments. Plants were grown with nutrient solution containing 100, 50, 10, or 0 percent of the normal complement of nitrogen. Plants were infested with eight apterous adult Russian wheat aphids at the flag leaf stage (approximately 53 days after planting). The aphids remained on the plant for a period of 25 days. Aphid infestation reduced mature plant height across all nutrient solution nitrogen concentrations tested. Grain yield was reduced by aphid infestation under all nutrient solution nitrogen concentrations except 0 percent. However, the percentage of yield loss caused by aphid infestation was reduced by increased levels of nitrogen in the nutrient solution. These results suggest that nitrogen fertilization might be a useful strategy for limiting yield loss caused by Russian wheat aphid in plants th...

Influence of Nitrogen Nutrition on the Utilization of L-Phenylalanine for Building Flavonoids in Buckwheat Seedling Tissues

Summary In an attempt to elucidate metabolic mechanisms of the inhibitory effect of nitrogen feeding on the formation of phenolics, the influence of ammonium nitrate on the production of flavonoids, on the biosynthetic use of exogenous L-phenylalanine for their building, and on the functional capacity of the shikimic acid pathway in excised buckwheat cotyledons and hypocotyls was studied. In cotyledons the treatment caused, besides a marked decrease in the total production of flavonoids, a significant reduction of exogenous L-phenylalanine incorporation into these compounds while the activity of the shikimic acid pathway responsible for the primary synthesis of aromatic amino acids showed a slight increase. In hypocotyls, a decrease in the accumulation of flavonoids was accompained by an up to 30% inhibition of the shikimic acid pathway, but no change in the incorporation of L-phenylalanine exceeding the level of changes in its uptake could be observed. It was concluded that in buckwheat cotyledons, nitrogen-induced inhibition of flavonoid synthesis resulted from a shift in the distribution of L-phenylalanine in favour of protein biosynthesis, while in buckwheat hypocotyls a similar decrease in flavonoids was probably conditioned by an inhibition of the primary synthesis of L-phenylalanine via the shikimic acid pathway.

The influence of nitrogen nutrition on plant response to greenbug infestation1

Abstract The influence of nitrogen nutrition and greenbug (Schizaphis graminum Rondani) infestation on growth, chlorophyll content, soluble amino acids, and soluble protein of barley plants (Hordeum vulgare L.) was studied in growth chamber experiments. Plants were grown for 21 days using complete or minus nitrogen nutrient solution. First leaves were then fitted with cages containing eight apterous adult greenbugs. After 7 days, the greenbugs were removed and the plants harvested. The plants given complete nutrient solution grew more rapidly than those given minus nitrogen. Plants grown with minus nitrogen had fewer greenbugs per plant but had much higher numbers of greenbugs per square centimeter of total plant leaf area than plants given complete nutrient solution. All leaves of infested plants grown with minus nitrogen had decreased dry weight, decreased chlorophyll, and increased soluble amino acids when compared with minus nitrogen uninfested plants. Infestation of first leaves of plants grown on co...

The Influence of Nitrogen Nutrition on the Accumulation of Free Amino Acids in Root Tissue of <italic>Urtica dioica</italic> and their Apical Transport in Xylem Sap

The Influence of Nitrogen Nutrition on the Accumulation of Free Amino Acids in Root Tissue of <italic>Urtica dioica</italic> and their Apical Transport in Xylem Sap

Influence of nitrogen nutrition on the amount of hordein, protein Z and β-amylase messenger RNA in developing endosperms of barley

The amount of mRNA encoding hordein, protein Z and β-amylase was analyzed in developing endosperms of the barley variety Bomi and the high-lysine mutant Risø 56. Spikes were cultured in liquid media containing different amounts of ammonium nitrate and endosperms harvested between 15 and 25 days after anthesis. Levels of mRNA were determined by in vitro translations. In addition, B hordein and protein Z mRNA species were titrated by molecular hybridization to cDNAs encoding B hordein and protein Z polypeptides, respectively. Increasing amounts of mRNAs were found in response to increasing nitrogen application. The amount of mRNA for C hordein and protein Z increased linearly with increasing nitrogen concentrations in the medium, whereas the rise in β-amylase mRNA was slight. A concentration of 0.5g×l−1 nitrogen stimulated the transcription of B hordein mRNA, but further increases of nitrogen supply up to 2 g×l−1 resulted in little additional B hordein mRNA production. At high nitrogen levels C hordein and protein Z mRNA are preferentially transcribed whereby these proteins serve as major nitrogen sinks. Hordein and protein Z mRNA are effectively augmented by application of nitrogen after the onset of grain filling and storage protein synthesis. Removal of nitrogen in the medium during grain filling led to a short term decrease in the amounts of these mRNAs. Thus it is possible to modulate the mRNA levels by changing the nitrogen concentration in the medium. The absence of mRNA for B hordein polypeptides in the high-lysine mutant Risø 56, (hor 2 ca), does not influence the effect of nitrogen on the expression of the C hordein, protein Z and β-amylase genes.

The influence of nitrogen nutrition on the sensitivity of tomato plants to culture filtrates of Fusarium and to fusaric acid

High (420 and 630 ppm) and to a lesser extent very low (70 ppm) levels of fertilization with nitrate-nitrogen decreased the sensitivity of tomato plants to fusaric acid as well as to culture filtrates of Fusarium oxysporum f. sp. lycopersici R1. There was a positive correlation between the external symptoms produced (chlorosis, necrosis and epinasty) and the concentration of the toxin or culture filtrate used which varied with the nitrogen regime under which plants were grown. Leakage of electrolytes, from leaf discs of plants grown with various levels of nitrogen fertilization, was measured in the presence of fusaric acid. Membranes of cells from plants grown at high doses of nitrate-nitrogen were less sensitive to the toxin, and the variation in reaction of cells from plants grown with different levels of nitrate-nitrogen appeared to be directly correlated with the resistance of such plants to infection with F. oxysporum f sp. lycopersici. The decreased susceptibility of tissue to fungal infection is probably the consequence of the reduced sensitivity of the host plant membranes to toxic substances produced by the fungus. The importance of this type of non-specific resistance in pathogenesis is discussed.

Influence of nitrogen nutrition, daylength and temperature on contents of gibberellic and abscisic acid and on tuberization in potato plants

In water culture experiments, plants grown under inducing climatic conditions (20°C and 12 h) and continuous supply of N had a relatively low ABA and a high GA content in the shoot. These plants failed to form tubers. The combination of these same climatic conditons with interruption of the N supply led to an increase in the ABA and the simultaneous decrease in the GA content, i.e. a high ABA/GA ratio. Coincidently tuberization occurred. Restoration of the N supply caused an inversion of the ABA/GA ratio and was often accompanied by regrowth of tubers. Under non-inducing climatic conditions (30°C or 18 h) interruption of the N supply still increased the aBA content but failed to decrease the GA content. Under these conditions tuberization was not observed. The results indicate that N nutrition, like photoperiod and temperature, may control tuberization in potato plants mainly by changing the ABA/GA ratio.

The influence of nitrogen nutrition on the dynamics of growth and metabolism of endogenous growth regulators in Scotch pine (Pinus silvestris L.) seedlings

Pine seedlings were cultivated in sterile agar cultures containing nitrogen as NH4Cl. The most pronounced positive effect on the growth of seedlings was affected by N used at a concentration of 50 ppm. After 4 months was stated that nitrogen had only a slight effect on elongation, of .shoots but decreased the length of roots. Nitrogen increased the lenght and number of primary and secondary needles as well as the fresh and dry matter of sboots. It stimulated also the number of lateral roots and the fresh and dry matter of the root system. Stimulation of shoot growth and differentiation as a result of nitrogen treatment was correlated with the increase -of free gibberellins and auxins and decrease of the amount of bound gibberellins and ABA-like inhibitor in shoots. However the effect of N on growth of roots was connected with the increase of auxins, cytokinins and ABA-like inhibitor in these organs.

Einfluß von Stickstoffernährung und Wuchsstoffapplikation auf die Knolleninduktion bei Kartoffelpflanzen

Influence of nitrogen nutrition and application of growth regulators on tuber initiation in potato plantsIn water culture the effect of continuous and discontinuous N‐nutrition on tuber initiation was investigated. Additional applications of growth regulators on growing stolon tips were carried out.Continuous supply of nitrate or ammonium inhibited completely the tuber initiation in S. tuberosum varieties „Ostara”︁ and „Clivia”︁, The inhibition was compensated by application of CCC and ABA on the stolon tip. In contrast to this stolon application of kinetin and root application of CCC were ineffective. Temporarily damaging of the root system led to tuber initiation even when nitrogen was supplied continuously. In S. andigena grown under short day continuous N supply only delayed the tuber initiation but could not prevent it.Discontinuous N supply promotes tuber initiation in S. tuberosum. A sudden increase in N supply caused „re‐growth”︁ of the tuber, i.e. a stolon was formed on the tuber apex. GA3 application on the growing tuber had the same effect.The effect of N nutrition on tuber initiation can be explained via changing the balance of endogenous growth regulators in general and the physiological aging of the leaves in particular. Discontinuous N supply seems to reduce cytokinin production in roots and therefore accelerates the aging of the leaves. This in turn favours the formation of inhibitors and/or presumably reduces the GA production in the shoot, which will change the balance of the growth regulators in the stolon tip in favour to tuber initiation.

Some effects of the nitrogen supply on growth and development of Cirsium arvense

The influence of nitrogen nutrition on the growth and development of Canada thistle, Cirsium arvense (L.) Scop., was investigated by growing seedlings in sand culture under controlled conditions. A preliminary experiment showed that seedlings at the cotyledon stage were very susceptible to injury by high salt concentration; a 10 × dilution of Hoagland's solution was required for successful establishment. Nitrate-N at 210 ppm caused severe leaf necrosis and inhibition of shoot and root bud growth, but provision of ammonium-N eliminated these effects.When seedlings were supplied with NH4NO3 at levels that ranged from 5.25 to 420 ppm N, shoot dry weight and root bud growth increased up to 210 ppm but decreased at 420 ppm, probably as a result of ammonium toxicity. By clearing roots with lactic acid it was shown that while growth of the root buds increased with the N level, the number of buds initiated was significantly reduced. When plants were grown initially at a low N level, a subsequent increase in the N supply permitted the root buds to escape from inhibition and develop as leafy shoots. This response suggested that under the experimental conditions, bud inhibition was due to internal competition for a limiting N supply.