Different Levels Of Nitrogen Supply Research Articles

Effects of Different Levels of Nitrogen Supply on Key Enzyme Activities of Nitrogen Metabolism and Growth Stimulation of Endive (Cichorium endivia L.)

In recent decades, people have blindly pursued increased yield; the excessive use of fertilizer not only causes the widespread waste of resources but also puts great pressure on environmental protection. In this study, to find out the optimum nitrogen application to endive crops under hydroponic conditions, this experiment was conducted to investigate the changes in nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), and glutamate dehydrogenase (GDH) activities under different nitrogen supply levels, and to fit the equations between nitrogen supply levels and aboveground dry matter accumulation, the aboveground nitrogen accumulation, and the yield of endive crops. The results showed that the activities of the key enzymes of nitrogen metabolism were higher at nitrogen supply concentrations of 8 and 11 mmol·L−1. The dry matter and nitrogen accumulation of endive at different nitrogen supply levels were analyzed with the logistic model; the theoretical yield was found to be the highest at 9.935~11.448 mmol·L−1 of nitrogen application in the two different fertility trials by function fitting.

Role of bundle sheath conductance in sustaining photosynthesis competence in sugarcane plants under nitrogen deficiency.

The role of bundle sheath conductance (gbs) in sustaining sugarcane photosynthesis under nitrogen deficiency was investigated. Sugarcane was grown under different levels of nitrogen supply and gbs was estimated using simultaneous measurements of leaf gas exchange and chlorophyll fluorescence at 21% or 2% [O2] and varying air [CO2] and light intensity. Maximum rates of PEPC carboxylation, Rubisco carboxylation, and ATP production increased with an increase in leaf nitrogen concentration (LNC) from 1 to 3gm-2. Low nitrogen supply reduced Rubisco and PEPC abundancies, the quantum efficiency of CO2 assimilation and gbs. Because of reduced gbs, low photosynthetic rates were not associated with increased leakiness under nitrogen deficiency. In fact, low nitrogen supply increased bundle sheath cell wall thickness, probably accounting for low gbs and increased estimates of [CO2] at Rubisco sites. Effects of nitrogen on expression of ShPIP2;1 and ShPIP1;2 aquaporins did not explain changes in gbs. Our data revealed that reduced Rubisco carboxylation was the main factor causing low sugarcane photosynthesis at low nitrogen supply, in contrast to the previous report on the importance of an impaired CO2 concentration mechanism under N deficiency. Our findings suggest higher investment of nitrogen into Rubisco protein would favour photosynthesis and plant performance under low nitrogen availability.

Nitrogen Levels Regulate Sugar Metabolism and Transport in the Shoot Tips of Crabapple Plants.

To comprehensively understand the responses of carbohydrate metabolism and transport to different levels of nitrogen supply in growing shoot tips of crabapple (Malus hupehensis Rehd), enzyme activities and related genes involved in the sugar metabolism pathway were investigated. The nitrogen and chlorophyll content of plants increased with increasing nitrogen supply. High nitrogen application increased the net photosynthesis rate and the growth rate of shoot tips but decreased the synthesis capability of sucrose and sorbitol in mature leaves. However, the shoot tips of plants under high-nitrogen treatment had higher contents of sucrose and sorbitol than did those under low-nitrogen treatment, while the activity of sucrose phosphate synthase and aldose-6-phosphate was increased and the transporters MdSOT and MdSUT were up-regulated. Moreover, the activities of enzymes involved in sucrose and hexose metabolism (including sucrose synthase, fructokinase, and hexokinase) were enhanced in the shoot tips of plants under high-nitrogen conditions, and the expression levels of MdSUSY3 and MdHK1 were significantly up-regulated. These findings indicate that a high nitrogen supply increases the metabolic capacity of assimilatory substances in shoot tips, accelerates the efficiency of sugar utilization and eventually leads to a rapid increase in the growth of shoot tips. Our results highlight that high nitrogen increases the capacity of sugar unloading and metabolic utilization in growing shoot tissues.

Inoculation of diazotrophic bacteria modifies the growth rate and grain yield of maize at different levels of nitrogen supply

ABSTRACT This work intended to evaluate the contribution of single inoculation of diazotrophic bacteria Herbaspirillum seropedicae or Azospirillum brasilense on growth and yield of maize crop at different levels of N fertilization. Two field experiments were carried out in the summer and winter seasons. Factorial design combined four fertilization levels (0, 50, 100 and 150 kg N ha−1) and three seed inoculations (non-inoculation, strains Hs-ZAE94 or Ab-Sp245), with four replications. Shoot dry matter, leaf area index, and N accumulation were evaluated in weekly samplings, and grain yield measured at maturity. Most expressive responses of inoculation were observed in the summer crop, with minor effects in the winter crop when growth and yield were lower. In the summer, inoculation increased shoot dry matter and leaf area of maize plants, enhancing crop growth rate, and increased N accumulated by shoots, particularly at low levels of N supply. In the summer, Hs-ZAE94 increased grain yield at the levels of 0, 50 and 100 kg N ha−1, and Ab-Sp245 at 100 kg N ha−1, as compared to non-inoculation. Inoculation with Hs-ZAE94 associated with 50 kg N ha−1 provided similar grain yield than the non-inoculation with 150 kg N ha−1, improving N use efficiency.

Effects of N-fertilization and rootstocks on the performance of ‘Red Delicious’ Spur apple trees

In a field trial with the Spur variety Super Chief® Sandidge, three different levels of nitrogen supply (50, 100, 150 kg ha(-1)) in combination with 3 rootstocks (M9 at 8333 trees ha(-1), M26 at 5555 trees ha(-1) and Pi80 at 4166 trees ha(-1)) were compared with respect to soil nitrogen dynamics, leaf nutrient levels, tree vigour and yield. The experimental orchard was planted in 2007 and the trial lasted until 2014. The data collected in this period revealed no significant effect of nitrogen levels above 50 kg ha(-1) year-1 on tree vigour and fruit yield, whereas clear differences emerge with respect to the different planting systems (rootstock/planting density). The observed soil nitrogen dynamics indicate that a considerable amount of mineral nitrogen may be lost by leaching from the very permeable soil at the site of the experiment, in particular in the case of high fertilizer applications and humid climatic conditions. Leaf nitrogen contents were not significantly affected by fertilizer rates.

Português

This work aimed to study the association of four nitrogen use efficiency (NUE) methods and the genetic parameters of grain weight in two groups of maize genotypes, under different levels of nitrogen supply, in the season 2012/13. 16 field experiments were carried out in the city of Gurupi, Tocantins, Brazil. Each genotype group was evaluated in different seeding date, and each one was tested with different levels of nitrogen supply. In all experiments the experimental design was completely randomized blocks with three repetitions. The following trait was evaluated after stage R6: grain yield (GY), and after, four indices of efficiency/stress to nitrogen were estimated. The Pearson correlation coefficients, estimated among the indices, were all significant (P < 0.01). Among the seeding dates, the average heritability of GY was 54.4% and among the levels of nitrogen supply, the following values were observed: 60.4% (low N); 50.9% (medium N); 51.2% (high N). There is the possibility of the use of environments with lower nitrogen supply in the search for superior and more efficient genotypes for the GY, and based on our results, the Low N index is more adequate.

Nitrogen fertilization affects silicon concentration, cell wall composition and biofuel potential of wheat straw

Nitrogen is an essential input factor required for plant growth and biomass production. However, very limited information is available on how nitrogen fertilization affects the quality of crop residues to be used as lignocellulosic feedstock. In the present study, straw of winter wheat plants grown at six different levels of nitrogen supply ranging from 48 to 288 kg nitrogen ha−1 was analyzed for major cell wall components and mineral elements. Enzymatic digestion of the straw was carried out to evaluate the saccharification efficiency. The nitrogen concentration in the straw dry matter increased linearly from 0.32% to 0.71% over the range of nitrogen treatments. Cellulose and hemicellulose were not affected by the nitrogen supply while lignin peaked at medium rates of nitrogen application. The nitrogen treatments had a distinct influence on the silicon concentration, which decreased from 2.5% to 1.5% of the straw dry matter when the nitrogen supply increased from 48 to 192 kg ha−1. No further decline in Si occurred at higher rates of nitrogen application. The most abundant metals in the straw were potassium and calcium and their concentrations almost doubled over the range of nitrogen supplies. The enzymatic saccharification efficiency was negatively correlated with the rate of nitrogen supply. We conclude that the level of nitrogen supply to wheat plants alters the composition of cell wall components in the straw and that this may result in reduced saccharification efficiency.

Biomass accumulation in mombasa guineagrass plants under different levels of nitrogen supply and plant densities

The objective of this study was to evaluate the effect of different levels of nitrogen supply and plants densities in the productivity of mombasa guineagrass (Panicum maximum) in the period of establishment. The design was of completely randomized blocks, with 12 treatments and three repetitions, with four nitrogen supplies (absence of application, 80, 160 and 320 kg/ha.year) and three plant densities (9, 25 and 49 plants/m²). The plot was cut at 30 cm from the ground when the sward high intercepted 95% of light. The following items were evaluated: sward height at 95% light interception, interval and number of cuts, dry mass production, total dry mass of leaves, stems and dead material and the morphologic composition. Nitrogen increased the dry mass production and the dry mass of stem in winter and summer, and decreased in the fall. The total dry mass of leaf presented decrease of 19% in the summer between the smallest and biggest densities in the 320 kg/ha. The dry mass of dead material had negative effect of the density in the fall. The leaf percentage increased 88% between the smallest and largest nitrogen level at the plant density of 49 plants/m2. Only density influenced the sward height in the condition of 95% of light interception. The number of cuts increased with nitrogen levels in the fall, spring and summer, while the interval of cuts decreased with fertilization in the spring and summer. Nitrogen increases the production of mombasa guineagrass in each cycle.

Nitrogen efficiency of Brussels sprouts under different organic N fertilization rates

The identification of nitrogen efficient varieties is important to improve yielding abilities in organic farming systems which are usually N-limited. This holds true particularly for crops with a long growing period and high nitrogen demand such as Brussels sprouts. Two field experiments with two different fertilizer levels were conducted on a hapludalf soil under the conditions of organic farming. Ten Brussels sprouts varieties with different growing periods were evaluated. For N accumulation efficiency differences between cultivars were not consistent over both experimental years, but similar under different levels of nitrogen supply. An allometric relationship between bud dry matter and total plant nitrogen accumulation comprising all varieties in both years and both fertilizer levels explained 56% of the total variation. Additionally, nitrogen utilization efficiency (NUE) was influenced by bud nitrogen content and harvest index. We found different relationships between bud dry matter and bud nitrogen with contrasting bud nitrogen percentage between years. However, relating bud nitrogen to total aboveground N again gave a linear relationship unifying all factors. Harvest index was linearly related to NUE indicating that dry matter partitioning is a major determinant of NUE. Varietal differences in NUE differed between years. Within years, yields of individual cultivars grown under different nitrogen levels were linearly related. We conclude that nitrogen accumulation in buds is environmentally stable, whereas dry matter partitioning into the same organs is more variable. Apparently, varieties performing well under high nitrogen supply yield also high under limited nitrogen. Further investigations are needed since the large genotypic variation between years is not fully understood.

Quantifying the effects of nitrogen on fruit growth and yield of cucumber crop in greenhouses

Nitrogen supply can improve crop growth and yield. An over-use of nitrogen fertilizer in greenhouse crop productions, however, causes many environmental problems. The aim of this study was to quantify the effects of nitrogen on fruit growth and yield so as to facilitate the optimization of nitrogen management for cucumber ( Cucumis sativus) crop in greenhouses. Four experiments with different levels of nitrogen treatments, substrates and planting dates on cucumber (cv. Deltastar) were conducted in greenhouses located at Shanghai during 2005 and 2007. Using data of one experiment, seasonal time courses of leaf nitrogen content ( N L), leaf area per plant ( LA), and the number of fruits growing per plant ( n FG), as well as time course of the length of individual fruit growing on the plant ( L F( i)) under different levels of nitrogen supply conditions were, respectively, determined as functions of a photo-thermal index ( PTI). The impact of N L on LA was determined by curve fitting to the experimental data. The source/sink ratio ( LA/ n FG), an indicative of the source size per fruit, was then derived from the seasonal time courses of LA and n FG. The impact of N L on L F( i) was indirectly quantified by the relationship between source/sink ratio ( LA/ n FG) and the elongation rate of individual fruit ( R FL( i)). Both the harvest date and fresh weight ( W F( i)) of individual fruit growing at different node, and number of harvested fruits ( n FH) were then calculated as functions of the fruit length. These quantitative relationships were assembled to form a model for predicting the effects of nitrogen on fruit growth and yield (fruit fresh weight per plant). Independent data from other experiments were used to validate the model. Our model gives satisfactory predictions of cucumber fruit growth and yield under different levels of nitrogen supply and growing season conditions. The coefficient of determination ( r 2) and the relative root mean squared error ( rRMSE) between the predicted and measured values are, respectively, 0.92 and 0.22 ( r 2, rRMSE) for leaf area per plant, 0.90 and 0.24 for the number of fruits growing on the plant, 0.91 and 0.22, 0.90 and 0.23, and 0.92 and 0.21, respectively, for the length, harvest date and fresh weight of individual fruit growing on the plant, 0.94 and 0.20 for yield. The model may be used for the optimization of nitrogen management for cucumber production in greenhouses. Further model calibration and test would be needed when applying this model to a wider range of conditions.

Image analysis method in application of digital image on diagnosing wheat nitrogen status

简便、快速、经济地诊断作物氮素营养状况是实施氮肥用量调控的关键。利用数码相机对作物冠层进行拍照, 通过图像处理软件获得作物色彩参数, 根据色彩参数与作物氮素营养状况的关系可以对其氮素丰缺进行诊断。针对作物数字图像色彩参数的获取方法, 结合小麦多水平氮肥试验, 采用遥感软件PCI Geomatics的非监督分类功能, 将小麦图像分为土壤、反光叶面和不反光叶面, 与Adobe Photoshop 软件普通图像处理方法对照, 比较分析了小麦图像不同类别叶片的8 种色彩参数与SPAD 值及植株全氮的相关性。结果表明, 返青期小麦反光叶面的G/R 与R/(R+G+B)色彩参数能较好地反映小麦的氮素营养状况; 拔节期不反光叶面和反光叶面的R/(R+G+B)色彩参数与植株全氮相关性较好。利用普通图像处理软件获得色彩参数的方法有待改进, 图像分类后能够提高其色彩参数对作物氮素营养诊断的准确性。

Effects of Low Nitrogen Supply on Tomato (Solanum lycopersicum) Fruit Yield and Quality with Special Emphasis on Sugars, Acids, Ascorbate, Carotenoids, and Phenolic Compounds

The objective of this study was to determine the impact of lowering nitrogen supply from 12 to 6 or 4 mM NO(3)(-) on tomato fruit yield and quality during the growing season. Lowering nitrogen supply had a low impact on fruit commercial yield (-7.5%), but it reduced plant vegetative growth and increased fruit dry matter content, improving consequently fruit quality. Fruit quality was improved due to lower acid (10-16%) and increased soluble sugar content (5-17%). The content of some phenolic compounds (rutin, a caffeic acid glycoside, and a caffeic acid derivate) and total ascorbic acid tended to be higher in fruit with the lowest nitrogen supply, but differences were significant in only a few cases (trusses). With regard to carotenoids, data did not show significant and univocal differences related to different levels of nitrogen supply. Thus, reducing nitrogen fertilization limited environmental pollution, on the one hand, and may improve, on the other hand, both growers' profits, by limiting nitrogen inputs, and fruit quality for consumers, by increasing tomato sugars content. It was concluded that primary and secondary metabolites could be affected as a result of a specific response to low nitrogen, combined with a lower degree of vegetative development, increasing fruit irradiance, and therefore modifying fruit composition.

Plant-endophyte-herbivore interactions

A recent paper by Rasmussen et al. (New Phytol 2007; 173:787-97) describes the interactions between Lolium perenne cultivars with contrasting carbohydrate content and the symbiotic fungal endophyte Neotyphodium lolii at different levels of nitrogen supply. In a subsequent study undertaken by Rasmussen et al. (Plant Physiol 2008; 146:1440-53) 66 metabolic variables were analysed in the same material, revealing widespread effects of endophyte infection, N supply, and cultivar carbohydrate content on both primary and secondary metabolites. Here, we link insect numerical responses to these metabolic responses using multiple regression analysis.Addendum to: Rasmussen S, Parsons AJ, Bassett S, Christensen MJ, Hume DE, Johnson LJ, Johnson RD, Simpson WR, Stacke C, Voisey CR, Xue H, Newman JA. High nitrogen supply and carbohydrate content reduce fungal endophyte and alkaloid concentration in Lolium perenne. New Phytol 2007; 173:787-97.andRasmussen S, Parsons AJ, Fraser K, Xue H, Newman JA. Metabolic profiles of Lolium perenne are differentially affected by nitrogen supply, carbohydrate content, and fungal endophyte infection. Plant Physiol 2008; 146:1440-53.

Respostas morfogênicas e estruturais de Panicum maximum cv. Mombaça sob diferentes níveis de adubação nitrogenada e alturas de corte

As características morfogênicas e estruturais da gramínea Panicum maximum cv. Mombaça foram estudadas em função de diferentes níveis de suprimento de nitrogênio e alturas de corte. O estudo foi conduzido em casa de vegetação, sendo avaliadas quatro doses de nitrogênio (0, 50, 100 e 200 mg/dm³) e três alturas de corte (5, 10 e 20 cm). As avaliações morfogênicas englobaram as taxas de aparecimento e alongamento de folhas, filocrono e duração de vida da folha. As estruturais avaliaram o número de folhas, o número de perfilhos e o comprimento final da lâmina foliar. Foi bastante expressiva a resposta da gramínea quanto às suas características morfogênicas em relação ao suprimento de nitrogênio na rebrotação, caracterizando o importante papel do nitrogênio como ferramenta para manipular a estrutura da planta. Todas as variáveis no estudo responderam positivamente ao suprimento de nitrogênio, com exceção do filocrono, que foi reduzido pelo efeito nutricional. As diferenças nas alturas de corte foram significativas para caracterização da duração de vida da folha, assim como para o comprimento de folhas e número de folhas verdes por perfilho. As taxas de alongamento e aparecimento de folhas foram incrementadas em até 133 e 104%, respectivamente, pelo aumento na disponibilidade de nitrogênio. A relação entre ambas as variáveis foi determinante na caracterização das principais mudanças vegetativas observadas. A grande resposta nas características morfogênicas do cultivar estudado constitui eficiente meio para manipular a estrutura do dossel, possibilitando melhor alocação dos recursos produtivos no processo de crescimento e desenvolvimento da planta.

Effects of Water and Nitrogen Supply on Water Use Efficiency and Carbon Isotope Discrimination in Edible Canna (Canna edulis Ker‐Gawler)

Abstract: Transpirational water use efficiency (WUE) is affected by nutrient and water supply, but relatively little is known about the response of Andean root and tuber crops, such as edible canna (Canna edulis Ker‐Gawler). Two Canna edulis genotypes were studied in semi‐controlled greenhouse experiments at the International Potato Centre (CIP) near Quito, Ecuador. Under conditions of low water supply, shoot dry matter (DM), leaf area and specific leaf nitrogen (SLN) all decreased, while WUE was higher and carbon isotope discrimination (Δ) decreased. The large water‐storing hypodermal cells characteristic of this plant's leaf morphology shrank, concertina‐like, the leaves became thinner, and the specific leaf area increased significantly (from 26 m‐2 kg‐1 to 43 m‐2 kg‐1). In a second experiment, plants were grown with three different levels of nitrogen supply: from low to high N supply, shoot DM increased significantly (from 16 to 37 g), along with leaf area and SLN. At the lowest level of nitrogen supply (N0), WUE was significantly lower and Δ increased. As expected, the linear correlation between Δ and WUE was negative, but variation in Δ could only explain 49 % of the variation in WUE. If, in addition to Δ, measured root fraction (RF) and estimated values of leaf‐to‐air vapour pressure deficit (Δe) and respiratory and unproductive carbon loss were used to calculate WUE, the correlation between measured and calculated WUE was substantially improved, except for the water stress treatment. It is considered that, for root and tuber crops, RF and Δe are the major variables when Δ of single leaves is to be used for up‐scaling to plant WUE.

Influence of elevated ozone and limited nitrogen availability on conifer seedlings in an open‐air fumigation system: effects on growth, nutrient content, mycorrhiza, needle ultrastructure, starch and secondary compounds

SummaryScots pine (Pinus sylvestris L.) and Norway spruce (Picea abies Karst.) seedlings were exposed to realistically elevated O3 levels in open‐air experiments over three growing seasons. The total O3 exposure doses were 1.2 × (1991), 1.5 × (1992) and 1.7 × (1993) ambient levels. During the 1992 and 1993 growing seasons pine and spruce seedlings received two different levels of nitrogen supply. Effects on growth, mycorrhiza formation, needle ultrastructure, primary and secondary compounds were studied. Ozone exposure had only slight effects on biomass production, growth height and nutrient content of studied conifers. Higher nitrogen availability improved growth of the seedlings and resulted in higher concentration of nitrogen in needles. In Scots pine O3 exposure did not have effects on quantity of total mycorrhizas and short roots, while higher nitrogen availability decreased quantity of mycorrhizas and short roots. In both tree species O3 exposure induced O3‐related ultrastructural symptoms, e.g. granulation and dark staining of the chloroplast stroma in the needle mesophyll cells, at both nitrogen availability levels. Ozone exposure and nitrogen availability did not have significant effects on starch concentrations in either tree species. Concentrations of some individual terpenes were higher in O3‐exposed needles, while concentrations of individual and total resin acids, total phenolics and catechins were not affected by O3 exposure. Nitrogen availability did not have substantial effects on concentrations of monoterpenes. By contrast, concentrations of some individual and total resin acids were lower in pine needles and higher in spruce needles with higher nitrogen availability, while phenolic concentration in spruce needles decreased at higher nitrogen availability. The results suggest that realistically elevated levels of O3 in the field can have some negative effects on the mesophyll ultrastructure of conifer needles, but carbon allocation to root and shoot growth and secondary metabolites are not affected substantially.

Regulation of shoot/root ratio by cytokinins from roots inUrtica dioica: Opinion

According to current knowledge, cytokinins are predominantly root-born phytohormones which are transported into the shoot by the transpiration stream. In the “hormone message concept” they are considered the root signals, which mediate the flux of the photosynthates to the various sinks of the plant. In this review, experiments are assessed, in which changes of the shoot to root ratio of biomass, caused by different levels of nitrogen supply to a model plant,Urtica dioica, could be traced to the natural cytokinin relations of the plant. Disturbance of the internal cytokinin balance of the plant resulted in a disproportionate distribution of the assimilates in favour of the cytokinin-enriched shoot. Inspite of some shortcomings of the “hormone message concept”, the presented work corroborates the significance of root-sourced cytokinins in the regulation of biomass partitioning between shoot and root.

Influence of nitrogen supply on the response of clones of birch (Betula pendula Roth.) to ozone

summaryClonal birch (Betula pendula Roth.) seedlings were exposed to slightly higher than ambient levels of ozone and different levels of nitrogen supply under open‐field conditions in three experiments: (1) three 2‐year‐old clones exposed to ozone and 74/150 kg N ha−1 y−1 for two growing seasons, (2) three 2‐year‐old clones under a corresponding exposure regime for one growing season and (3) one 2‐year‐old clone exposed to ozone and 37/74/150 kg N ha−1 y−1 for one growing season. The cumulative ozone exposures were 1–5 x (1992) and 1–7 x (1993) higher than ambient levels. In these experiments no significant differences between the clones were found in their response to each treatment. Ozone exposure reduced the mean leaf size and the leaf area, accelerated autumn yellowing and loss of leaves, and increased the palisade layer thickness. High nitrogen availability increased the height growth, the mean leaf size, the leaf area, the shoot/root ratio, the leaf water content and the stem dry weight, but decreased the number of leaves and the leaf dry mass per area, and retarded autumn senescence of leaves. It also reduced the leaf and palisade layer thickness and increased the intercellular space of the palisade layer. Significant interactions between ozone and nitrogen supply were found as an increase in leaf biomass production, root dry weight and spongy intercellular space, and as a decrease in leaf loss, yellowing of leaves and palisade layer thickness. The results suggest that sufficient nitrogen supply can confer the birch with greater resistance to ozone.

Variation of Relative Growth Rate and Survival in Ecologically Contrasting Populations of Agrostis stolonifera

Abstract Significant differentiation in relative growth rate (RGR) was found among three ecologically contrasting populations of Agrostis stolonifera. Under low nitrogen conditions the sand dune population had the highest mean RGR. The plastic response in RGR to different levels of nitrogen supply was significantly higher in the inland meadow population than in the polder and sand dune populations. The (colonizing) polder population tended to have the highest variation for RGR. Variation in RGR within populations was mainly environmentally determined, although in the polder population significant effects of genotype and of genotype × nitrogen level were found. The repeatability for RGR in this population proved to be different from zero under both nitrogen conditions. Root/shoot ratios of the three populations were not different from each other, independent of the level of nitrogen supply. Correlations between RGR and survival of genotypes within the populations were not significant, which points at the influence of genotype × environment interactions or the possibility that genotypic differences in RGR do not necessarily indicate an adaptation to any habitat, not even the home site.

Endosperm protein accumulation in wild and cultivated barley and their cross grown in spike culture

The high protein wild relatives of cultivated cereals have proven difficult to utilize in plant breeding by direct selection for high grain protein percentage, and hence alternative selection criteria are needed. In this study, a spike culture method was used to measure differences in protein accumulation between wild and cultivated barley, and their cross, at different levels of nitrogen supply. Three genotypes, barley cultivar Hordeum vulgare L. cv. Clipper, a wild barley accession H. spontaneum Koch line 363, and a high protein F5 line (38.4) derived from their cross, were grown from 8 to 27 days after flowering in in vitro spike culture. Nitrogen supply in the culture medium was either 0.4 g/l or 2.0 g/l of N supplied as NH4NO3. Spikes were harvested at approximately 3 day intervals during grain development, and salt soluble and hordein protein fractions were measured. Lines 363 and 38.4 differed from ‘Clipper’ in having extremely high initial rates of protein accumulation, even at 0.4 g/l N. In high nitrogen conditions all three genotypes reached similar salt soluble plus hordein protein levels. Hordein-1 and hordein-2 fractions were measured separately; the percent of hordein-1 was higher in lines 363 and 38.4 than in ‘Clipper’ at 0.4 g/l N. For all parameters measured, pot-grown spikes of matching age were harvested and were shown to be similar to the 0.4 g/l N treatment. The possible utilization of spike culture for identification of critical protein accumulation parameters is discussed, in relation to their possible utilization in breeding.