The effect of phosphorus and nitrogen deficiency on growth of seedlings of spring barley in dependence on irradiance: Content of chlorophyll,nitrogen and phosphorus

Seedlings of spring barley,Hordeum vulgare L. cv. Mirena, were grown in complete mineral solution (Richter’s solution: R) or in solution lacking either phosphorus (R-P) or nitrogen (R-N) at low (LI: 28 W m^?2) or high (HI: 122 W m^?2) irradiance. Plants were kept in controlled environment chamber with 16 h photoperiod and 20 °C/15 °C day/night temperature. The experiment was terminated after 15 days when plants grown under R -N nad HI conditions died. The content of chlorophyll was estimated during the plant growth and content of nitrogen and phosphorus was determined at the end of the experiment. Deficiency of N and P induced higher chlorophyll formation at low irradiance. The efficiency of nitrogen and phosphorus utilization,i.e. ratio of plant dry mass/weight of N and P, respectively, per plant, was higher at HI in all experimental variants. Extremely high value of P utilization was found in plants grown under P-deficiency (850) as compared to the control (80). Understanding of interactions between the irradiance and deficiency of mineral nutrients is necessary for optimization of fertilization and understanding the mechanisms of action of mineral substances on plant structures and functions.     

The effect of phosphorus and nitrogen deficiency on growth of seedlings of spring barley in dependence on irradiance: Growth analysis

Seedlings of spring barley,Hordeum vulgare L. cv. Mirena, were grown in a controlled environment chamber at high (HI: 122 Wm^?2) and low (LI: 28 Wm^?2) irradiance in the complete Richter’s nutrient solution (R) or in solution lacking either phosphorus (R -P) or nitrogen (R -N). The experiment was terminated 15 days after sowing when plants (R-N) at HI ceased to grow. At that time the dry mass of one plant was 449.8 mg, 145.7 mg and 116.8mg at HI and 203.4 mg, 110.1 mg and 91.0 at LI for R, (R-P) and (R-N), respectively. Deficiency of P and especially N reduced the size of loaf area more under HI than under LI conditions. Specific dry mass of leaves was the highest in R-N plants. The values of relative growth rate and assimilation rate are presented. Interaction of the effects of deficiency of mineral nutrients and irradiance during cultivation should be analyzed in further experiments for determination of optimum conditions for utilization of mineral nutrients.     

Effect of Nitrogen Deficiency upon Translocation of C in Sugarcane

Withholding nitrogen decreased the percentages of nitrogen and chlorophyll in the blades; reduced the total fixation of radioactive carbon dioxide at 15, 37, and 178 seconds; and changed the relative composition of fixation products. Translocation of radioactive photosynthate from the fed part down the attached blade and into the stalk was less in the plants deprived of nitrogen than in the control plants supplied with nitrogen. Both the percentage of total activity translocated and the velocity of transport were decreased by nitrogen deficiency. During a translocation period of 90 minutes the minus nitrogen blade retained more ¹⁴C-sucrose than the control in the fed part and the blade below the fed part, but it sent less ¹⁴C-sucrose to the sheath of the fed leaf. Thus translocation decreased with nitrogen deficiency not for lack of sucrose but for some other reason. Although withholding nitrogen decreased translocation of labeled carbon in and from attached blades, there was no effect upon transport in detached blades. The effect of nitrogen deficiency upon translocation may be indirect and secondary to the effect upon growth of the plant as a whole.     

Plant nitrogen metabolism and calcium or potassium Deficiency

The content and distribution of nitrogen substances in wheat, pumpkin and pea seedlings in complete (NS) or deficient ( - Ca²⁺ or - K⁺) nutrient solutions were studied with the aim of establishing whether impairments in the synthesis of nitrogen substances in vegetative tissues due to the deficiencies may be compensated for by storage nitrogenous substances. Pumpkin and pea seedlings were found to accumulate nitrogen mainly from depots of the seed stores. Both the accumulation and the synthesis of nitrogen substances were inhibited by the cation deficiencies, especially by that of calcium. Concomitant morphological deformations were probably the direct cause of the impairments in the mobilization and hence also in the utilization of the substances. With wheat, on the other hand, no morphological changes resulted from the deficiences and nitrogen was accumulated intensively even from the cultivation solution. Still, the rate of the synthesis of the nitrogenous substances was significantly reduced. Under the conditions of calcium or potassium deficiency in the outer nutrient solution the possibility or utilizing the ions from the storage tissues according to the requirements of the plant appeared to be decisive. The extent of the disproportion of the two factors was the original cause of the early morphological changes which, in their turn, impaired the natural circulation of substancs inside the organism, including the substances containing nitrogen.     

The relation between nitrogen deficiency and leaf senescence

Because the "mobilization" of nitrogen resulting from nutritional nitrogen deficiency is also prominent during leaf senescence, the characteristics of these two syndromes were compared. Oat plants ( Avena sativa L. cv. Victory) were raised on a nutrient solution, complete except for nitrogen supply (i.e., with only the seed protein as nitrogen source), and the senescence of their leaves was compared with that of controls grown on a full nutrient solution. The N-deficient plants flowered after forming only 4 leaves and each set a single seed. The nitrogen lack affected the content of chlorophyll somewhat more than the content of the amino acids or protein nitrogen. However, spraying the plants with kinetin solution was able to retain 20–30% of the chlorophyll and protein. During senescence, the chlorophyll appears to be less stable in the N-deficient leaves than in the controls, while the protein is somewhat more stable than in the controls. Also, when the detached leaves from N-deficient plants senesced in white light or in darkness, kinetin delayed their senescence almost as effectively as that of control leaves. Most strikingly, the stomata of N-deficient leaves after detachment and floating on water were largely closed in light, just as in senescence, but could be partially induced to open by kinetin treatment. Since stomatal closure has earlier been shown to cause senescence, the characteristic syndrome of foliar nitrogen deficiency is concluded to be partly that of senescence.     

The Remobilization of Nitrogen Related to Leaf Growth and Senescence in Rice Plants (Oryza sativa L.)

Rice plants (Oryzae sativa L.) grown in a nutrient solutionwere fed with (¹⁵NH₄)₂SO₄ during the 5 days of their young panicleformation. At the end of that time in the youngest leaf blade, which hadstarted to emerge during the labelling, absorbed-nitrogen accountedfor 37% of the increased nitrogen of the tissue; in the nextdeveloping leaf blade it accounted for 55%. Thus, remobilized-nitrogenoriginating from older patrs of the plant made up 63 and 45%,respectively, of their total nitrogen. The important contributionof the remobilized-nitrogen to the development of a leaf isevident. The remobilization of nitrogen in the 12th leaf blade on themain stem was examined in detail after labelling during itsdeveloping stage. The ¹⁵N level started to decrease soon afterthe end of the labelling period and continued to decrease untilfull senescence, although the total nitrogen in the same leafincreased until just after its complete expansion, suggestingthat even a young leaf plays a role as a supplier of remobilized-nitrogen. During the rapid decrease in the total nitrogen after its peakat full expansion of the leaf, the actual proportion of labelledabsorbed nitrogen remained nearly the same, indicating thatinflux of new nitrogen into a senescing leaf is very limited. (Received March 13, 1981; Accepted July 13, 1981)     

NADH- and Ferredoxin-Dependent Glutamate Synthase in the Life Span of the Second Leaf of Wheat Plant under Conditions of Senescence Induced by Nitrogen Deficiency and Natural Senescence

The aim of this paper was to study, in the second leaf of wheat plants with a long ontogenesis (47 d), the activity of the enzyme which catalyzes the synthesis of glutamic acid. The activity of the NADH-dependent glutamate synthase prevailed in young tissues of not yet fully expanded second leaf at the stage of incomplete autotrophy (at this stage, organic carbon and nitrogen substances are transferred into the leaf). This form was completely inhibited by azaserine (1 mmol1⁻¹). The activity of the ferredoxin-dependent GOGAT increased with increasing leaf blade area, with its peak occuring at the time of maximum expansion of the assimilation area. Thus fd-GOGAT activity was characteristic for the photosynthetic fully autotrophic phase of leaf development which is materialized in completely mature leaf tissues. In plants grown in full-strength Knop’s nutrient solution containing nitrogen, fd-GOGAT was active till the early and medium senescence, whereas only to the early senescence in plants grown in a solution lacking nitrogen. No fd-GOGAT could be detected at the stage of late leaf senescence.     

Effect of phosphorus deficiency on anthocyanin content in tomato plants

The effect of phosphorus deficiency on anthocyanin content in tomato plants was studied from the point of view of pathological anthocyanin formation. Phosphorus deficiency resulted in an evident increase of anthocyanin content in all experiments, independently of the tomato variety and of the cultivation conditions. The anthocyanin amount was five times higher on the average and the differences were statistically significant. The average growth inhibition of tomato plants under phosphorus deficiency was 18%. Accumulation of anthocyanins is limited by the temperature; anthocyanins are not synthesized at temperatures above 30°. The results of the experimental variant with enhanced phosphorus concentration in nutrient solution were not uniform. In some experiments a decrease of anthocyanins accompanied by slight growth stimulation was observed, in others an increase associated with growth inhibition. It seems that cultivation conditions, especially the light intensity, play an important role in these experimental variants.     

The reallocation of carbon in P deficient lupins affects biological nitrogen fixation

It is not known how phosphate (P) deficiency affects the allocation of carbon (C) to biological nitrogen fixation (BNF) in legumes. The alteration of the respiratory and photosynthetic C costs of BNF was investigated under P deficiency. Although BNF can impose considerable sink stimulation on host respiratory and photosynthetic C, it is not known how the change in the C and energy allocation during P deficiency may affect BNF. Nodulated Lupinus luteus plants were grown in sand culture, using a modified Long Ashton nutrient solution containing no nitrogen (N) for ca. four weeks, after which one set was exposed to a P-deficient nutrient medium, while the other set continued growing on a P-sufficient nutrient medium. Phosphorus stress was measured at 20 days after onset of P-starvation. During P stress the decline in nodular P levels was associated with lower BNF and nodule growth. There was also a shift in the balance of photosynthetic and respiratory C toward a loss of C during P stress. Below-ground respiration declined under limiting P conditions. However, during this decline there was also a shift in the proportion of respiratory energy from maintenance toward growth respiration. Under P stress, there was an increased allocation of C toward root growth, thereby decreasing the amount of C available for maintenance respiration. It is therefore possible that the decline in BNF under P deficiency may be due to this change in resource allocation away from respiration associated with direct nutrient uptake, but rather toward a long term nutrient acquisition strategy of increased root growth.     

Iron deficiency induces cluster (proteoid) root formation in Casuarina glauca

The effect of iron deficiency, phosphorus, NaHCO₃, chelator supply and nitrogen source on the formation of cluster (proteoid) roots was investigated in Casuarina glauca growing in water culture. The addition of iron-binding chelators (e.g. EDDHA, DTPA, EDTA) or increase in nutrient solution pH with NaHCO₃ resulted in the formation of cluster roots when plants were grown in solution lacking iron. Phosphorus supply even at a concentration of 500 µM did not inhibit cluster root formation if EDDHA was added to the iron-deficient medium. Cluster root formation was influenced significantly by nitrogen source and occurred only in nitrate-fed plants.C. glauca seemed to be very sensitive to iron deficiency as shown by plant chlorosis when grown on alkaline soil. The symptoms of chlorosis decreased as the chlorophyll content in shoots and the number of cluster roots increased, suggesting that the alleviation of iron deficiency in plant tissues was correlated with cluster root formation. It appears that iron deficiency is more important than phosphorus deficiency in inducing the formation of cluster roots in C. glauca.     

Nitrogen Effect on Water-Soluble Polysaccharide Accumulation in <Emphasis Type="Italic">Streblonema</Emphasis> sp. (Ectocarpales,Phaeophyceae)

The water-soluble polysaccharides of brown algae attract the increasing attention of researchers as an important class of polymeric materials of biotechnological interest. The sole source for production of these polysaccharides has been large brown seaweeds such as members of Laminariales and Fucales. A new source of water-soluble polysaccharides is suggested here: it is a filamentous brown alga Streblonema sp., which can be cultivated under controlled conditions in photobioreactors that allow obtaining algal biomass with reproducible content and quality of polysaccharides. The accumulation of water-soluble polysaccharides can be stimulated by macronutrient limitation. In response to nitrogen deficiency, Streblonema sp. accumulated water-soluble polysaccharides (WSPs) rich in laminaran. WSP accumulation started after 3–4 days following nitrate depletion and reached a plateau at around day 7. Polysaccharide accumulation was related to cellular nitrogen content. The critical internal N level that triggered the onset of polysaccharide accumulation was 2.3% dry weight (DW); at a cellular N concentration less than 1.4% DW, the polysaccharide synthesis stopped. Upon nitrate re-supply, mobilization of WSP occurred after 3 days. These results suggest that a two-stage cultivation process could be used to obtain large algal biomass with high water-soluble polysaccharide production: a first cultivation stage using nitrate-supplemented medium to accumulate algal biomass followed by a second cultivation stage in a nitrate-free medium for 3 to 7 days to enhance polysaccharide content in the alga.     

Rapid estimation of lipid content in an Antarctic ice alga (Chlamydomonas sp.) using the lipophilic fluorescent dye BODIPY505/515

Chlamydomonas sp. ICE-L, isolated from Antarctic coastal marine environments, was selected as a high lipid producer, which may be useful for biodiesel production. The lipophilic fluorescent dye BODIPY505/515 was used to determine the algal lipid content. Lipid bodies stained with BODIPY505/515 have a characteristic green fluorescence, and their volumes were determined using the sphere volume formula. In this study, lipid accumulation by Chlamydomonas ICE-L was analyzed under different cultivation conditions (nitrogen deficiency and UV-B radiation). The results demonstrated that nitrogen deficiency and UV-B radiation could significantly promote the accumulation of lipid content per cell. The highest yields of total lipid content (reaching 84?μL?L^?1) were obtained in full Provasoli medium after 12?days of cultivation, but not in the nitrogen-deficient medium. The inoculum used in this experiment was obtained from the late-exponential growth phase. The main reason was that the cell numbers in nitrogen-deficient medium had not increased and total lipid contents were offset by the lower growth rate. Considering the high lipid content in Chlamydomonas sp. ICE-L, this alga might be a promising alternative species for production of microalgal oil for the production of renewable biodiesel in the future.     

The effect of mineral nutrition on the growth and maintenance components of respiration during heterotrophic growth of barley seedlings

Spring barley seedling were grown in the dark for 21 d and respiration rates of the whole plant (including the seed), of the shoots, and of the roots were determined. A function describing the growth and maintenance components of respiration was interpolated through the experimental points and its parameters in plants under different mineral nutrition were compared. The plants grown in a complete nutrient solution showed the highest growth rate in the initial phase of development and thus reached the maximum respiration rate earlier than plants in the other variants. The highest proportion of substrate was respired in the shoot. Plants grown under deficiency of phosphorus and magnesium had a slower respiration rate than plants grown in the complete nutrient solution (NP), whereas the amount of respired substrate in plant parts was similar to that recorded in the NP plants. Plants grown in distilled water showed the lowest growth efficiency and respirated the highest proportion of substrate in the root.     

The dynamics of the accumulation of nitrogen,phosphorus and potassium in maize and peas in the first growth phases at constant mineral nutrition

The authors studied the growth intensity, the accumulation and distribution of nitrogen, phosphorus, and potassium in maize and pea plants under conditions of hydroponic culture. They found that RGR dropped by about 50% within 32 days of cultivation. The content (in mg/g dry weight) of nitrogen and potassium in maize, and of nitrogen and phosphorus in peas registered a substantial decrease, while the content of phosphorus in maize and that of potassium in peas exhibited a slight increase and a slight decrease towards the end of the experiments. The relative absorption rates of nitrogen and phosphorus in maize were maximum after 28 days of cultivation, while that of potassium reached a maximum immediately at the beginning; nitrogen and potassium absorption in peas reached maximum values after 28 to 30 days, whereas phosphorus was highest at the beginning. In the course of growth, the ratio of accumulated ions of N:P:K changed; maize accumulated relatively less potassium, and peas more nitrogen and potassium.     

Nutrient and productivity relations of the dune grasses Ammophila arenaria and Elymus mollis

Summary A comparative study of blade photosynthesis and nitrogen use efficiency was made on the dune grasses Ammophila arenaria and Elymus mollis. In the laboratory, an open system gas analysis apparatus was used to examine the gas exchange characteristics of blades as influenced by nitrogen supply. Plants were grown under near-ambient coastal conditions in a greenhouse near Bodega Bay, California, and given either high or low supplies of nitrogen in an otherwise complete nutrient solution. In the field, ¹⁴CO₂ uptake techniques were employed to measure the seasonal patterns of blade photosynthesis of plants growing in situ at Point Reyes National Seashore. Blades used in the lab and field studies were analyzed for total nitrogen content, thus allowing for calculations of photosynthetic nitrogen use efficiency (CO₂ fixed/unit of blade N.).Under laboratory conditions, the introduced Ammophila developed higher rates of light-saturated photosynthesis than the native Elymus, especially under the nitrogenlimited growth regime. Higher rates of photosynthesis and lower concentrations of blade N resulted in a significantly greater nitrogen use efficiency for Ammophila regardless of nutrient treatment. Low N availability induced qualitatively similar physiological responses in both species, including reductions in maximum net photosynthesis, mesophyll conductance, leaf conductance, dark respiration, and blade nitrogen content, and an increase in the CO₂ compensation point.Although the photosynthetic rates of Ammophila blades were higher in the lab, those of Elymus blades were consistently higher in the field. This could have resulted from differential effects of drought on the two species (i.e. Ammophila may have been more sensitive) or a higher photosynthetic capacity in Elymus that reflected the greater (1.2–1.5 X) nitrogen content of its blades. However, the nitrogen use efficiency of Ammophila blades was greater than that of Elymus throughout most of the sampling year, despite lower average rates of field photosynthesis.The results indicated that rates of photosynthesis perunit of blade area do not account for the greater aboveground productivity of Ammophila stands along the Pacific coast of North America. Instead, efficient nitrogen use in photosynthesis maycomplement other structural and physiological traits and thereby enhance long-term carbon gain in Ammophila relative to Elymus.     

Rhizosphere selection of highly motile phenotypic variants of Pseudomonas fluorescens with enhanced competitive colonization ability

Phenotypic variants of Pseudomonas fluorescens F113 showing a translucent and diffuse colony morphology show enhanced colonization of the alfalfa rhizosphere. We have previously shown that in the biocontrol agent P. fluorescens F113, phenotypic variation is mediated by the activity of two site-specific recombinases, Sss and XerD. By overexpressing the genes encoding either of the recombinases, we have now generated a large number of variants (mutants) after selection either by prolonged laboratory cultivation or by rhizosphere passage. All the isolated variants were more motile than the wild-type strain and appear to contain mutations in the gacA and/or gacS gene. By disrupting these genes and complementation analysis, we have observed that the Gac system regulates swimming motility by a repression pathway. Variants isolated after selection by prolonged cultivation formed a single population with a swimming motility that was equal to the motility of gac mutants, being 150% more motile than the wild type. The motility phenotype of these variants was complemented by the cloned gac genes. Variants isolated after rhizosphere selection belonged to two different populations: one identical to the population isolated after prolonged cultivation and the other comprising variants that besides a gac mutation harbored additional mutations conferring higher motility. Our results show that gac mutations are selected both in the stationary phase and during rhizosphere colonization. The enhanced motility phenotype is in turn selected during rhizosphere colonization. Several of these highly motile variants were more competitive than the wild-type strain, displacing it from the root tip within 2 weeks.     

The effect of exogenous phosphate deficiency on the activity of acid phosphatase of the root of two maize genotypes

In two maize genotypes, the effect of exogenous phosphate deficiency on acid phosphatase activity of the apical part of primary root was followed in dry and imbided grains. Higher acid phosphatase activity was found in the genotype LG 5. The enzyme activity increased after 18 h grain imbibition in the two genotypes. After 48 h germination no differences were found between the genotypes. After 24 h cultivation of root segments in a solution of 0.25 mM CaSO₄.2H₂O,0.1 mM MgSO₄.7H₂O, and further after 3,6 and 24 h cultivation in solutions with and without phosphate genotypic differences were found in acid phosphatase activity as well as in dry mass production. An increase in enzymatic activity due to exogenous phosphate deficiency was registered in the two genotypes only after 24 h cultivation.     

Sulfur deprivation and nitrogen metabolism in maize seedlings

The objective of this experiment was to elucidate the manner in which N metabolism is influenced by S nutrition. Maize (Zea mays L.) seedlings supplied with Hoagland solution minus SO₄²⁻ exhibited S deficiency symptoms 12 days after emergence. Prior to development of these symptoms, a decline in leaf blade nitrate reductase (NR, EC 1.6.6.1) activity was observed in S-deprived seedlings compared to normal seedlings. Twelve days after emergence, in vitro NR activity was diminished 50% compared to normal seedlings. Glutamine synthetase (EC 6.3.1.2) and NAD-glutamate dehydrogenase (EC 1.4.1.2) activities were less severely affected (19 and 13%, respectively, at day 12). NADP-glutamate dehydrogenase (EC 1.4.1.4) activity and leaf blade fresh weight were not altered by S deprivation. Concentrations of soluble protein and chlorophyll (a and b) in leaf blades were reduced 18 and 25%, respectively, at day 12. A significantly higher concentration of NO₃⁻-N was observed for leaf blade and stem (culms, leaf sheaths, and unfurled leaves) fractions (46 and 31%, respectively) in S-deprived plants. In contrast to the other parameters measured, NR activity in S-deprived seedlings could be readily restored to the normal level by addition of SO₄²⁻. The apparent preferential effect of S deprivation on NR activity could be causally related to the observed changes in NO₃⁻-N and soluble protein concentration.     

The relation between nitrogen deficiency and second leaf senescence in wheat plants

Life span of the second leaf of wheat(Triticum aestivum L., cv. Grana) plants was studied from day 8 to day 50 of plant age in a variant with nitrogen (+N) and in a variant in which plant senescence was induced by the omission of nitrogen from the nutrient solution (−N). Seed protein was the sole source of nitrogen for these plants. Specific leaf mass (SLM) in the −N variant, and specific leaf area (SLA), the mass of fresh leaf, soluble protein content and total nitrogen content in the +N variant peaked by day 22 of plant age (that is by day 19 of leaf age). Dry matter content, leaf length and leaf area, and SLM in the +N variant peaked by day 29 of plant age (that is by day 26 of leaf age). The ontogeny of the second leaf in the variant with enhanced senescence was shorter by at least 14 days. Plants from this variant showed typical symptoms of N deficiency, that is yellowing of leaves, tip burn, and lack of tillering. However, the growth and biochemical characters studied did not indicate an earlier onset of the senescence of the second leaf of −N plants. Both +N and −N variants reached their peaks (with the exception of an earlier peak by day 12 in case of total nitrogen content in the −N variant) on the same day of leaf age. Thus the first part of the leaf life span from leaf growth initiation to full expansion was of the same length in both the control and N-def icient plants. The stage of the proper senescence of the second leaf of −N plants was very short; the leaf completely died away within 7 days after senescence onset.     

Compensatory branching and changes in nitrogen content in the aquatic weed Salvinia molesta in response to disbudding

Summary Secondary side branching in Salvinia molesta plants grown in nutrient solution was dependent on the availability of nitrogen. The compensatory response of S. molesta to damage by complete manual disbudding was the production of extensive secondary side branching at nitrogen levels below those required for this type of branching in undamaged plants. After 28 days damaged plants had the same number of ramets as undamaged plants but the dry weight was considerably reduced.After 7 days there was no change in dry weight with partial or complete disbudding. However completely disbudded plants had no new ramets and plants with all terminal buds removed had numbers of ramets significantly reduced. The concentration of nitrogen in the tissue of new growth was higher in damaged than undamaged plants. The results are discussed in relation to the biological control of S. molesta by the bud-eating weevil, Cyrtobagous salviniae.