Growth and nutrient concentrations of alfalfa and common bean as influenced by soil acidity

Growth and nutrient utilization of alfalfa (Medicago sativa L. cv. Arc) and common bean (Phaseolus vulgaris L. cv. Carioca) were studied in an acid soil adjusted to eight levels of soil acidity by lime addition. Application of lime significantly (P<0.05) increased shoot and root growth for both species. However, common bean was far less sensitive to soil acidity than alfalfa. Maximum alfalfa growth was obtained at a soil pH of 5.8 and maximum bean growth was achieved at pH 5.0. Root and shoot growth of both legumes was positively correlated (P<0.01) with soil pH, exchangeable Ca and exchangeable Mg and negatively correlated (P<0.01) with soil exchangeable Al. Common bean had a lower internal P requirement for maximum growth and was more efficient than alfalfa in taking up Ca and Mg. These characteristics would contribute to the favorable growth of common bean in acid-infertile soils.     

Growth and regenerability of long-term suspension cultures of the U.S. rice cultivar Mercury

Suspension cultures of the U.S. rice cultivar Mercury have been maintained in modified General Medium for more than 3 years. These suspensions have continued to have high and relatively stable regeneration rates. Two different explants, immature panicles and seeds, were compared during the development of these embryogenic suspensions. Initial formation of secondary embryogenic callus from immature panicles on induction medium was greater than that from seeds. Suspensions of these two cell lines, however, did not differ morphologically and maintained similar regeneration rates. After 5 months in culture the rates of regeneration began to decline. The suspensions were plated onto regeneration medium without growth regulators for 2 weeks and then embryogenic cells were manually selected and used to develop secondary suspensions. Through this simple rejuvenation procedure, the suspensions retained high and stable regeneration rates. Variability in suspension growth, however, was observed during the culture period. Slower growth occurred at weeks 13, 15, 27, and 29 and was associated with a decrease in regeneration rates. Reproductive fertility of regenerated plants remained high for 3.5 years but then declined.Abbreviations CH casein (acid hydrolysate) - 2,4-d 2,4-dichlorophenoxyacetic acid - MS Murashige & Skoog basal medium - SE standard error     

Ecological significance of root tip rotation for seedling establishment of Oryza sativa L

How plant seeds secure root penetration into soil to obtain good seedling establishment is one of the basic ecological problems. In this study, seminal root growth was investigated to clarify the cause of varietal difference of seedling establishment in direct seeding of rice in flooded paddy fields, with special reference to root tip rotation. In a field experiment, seedling establishment percentage had a weak correlation with seminal root elongation rate but was not correlated with apparent seedling weight in water, which has been reported to be the cause of floating seedlings resulting in poor seedling establishment. Root tip rotation was analyzed for indoor-grown seedlings using spectrum analysis: the maximum entropy method (MEM) was used. Maximum entropy method power spectrum analysis clarified that maximum MEM power density (practically corresponds to spiral angle) detected in the frequency range above 0.1 cycles mm^-1 was highly and positively correlated to seedling establishment percentage in the field experiment. Maximum MEM power density in high correlation with seedling establishment was mostly found around frequencies of 0.2 cycles mm^–1, which corresponded to 2.0–3.4 cycles of root tip rotation per day. From these results, root tip rotation (circumnutation) with a larger spiral angle was suggested to play an important role in the establishment of rice seedlings on flooded and very soft soil. A possible explanation for why a larger spiral angle was advantageous for seedling establishment is that if buoyancy and seedling weight are constant, a larger pushing force of the seminal root is available without causing floating of a seedling, due to the upward force being a reaction of the seminal root pushing force.     

Variation in nitrogen use efficiency among soft red winter wheat genotypes

Summary Nitrogen use efficiency (NUE), defined as grain dry weight or grain nitrogen as a function of N supply, was evaluated in 25 soft red winter wheat genotypes for two years at one location. Significant genotypic variation was observed for NUE, nitrogen harvest index, and grain yield. Genotype x environment interaction for these traits was not significant. Several variables including N uptake efficiency (total plant N as a function of N supply), grain harvest index, and N concentration at maturity were evaluated for their role in determining differences in NUE. Nitrogen uptake efficiency accounted for 54% of the genotypic variation in NUE for yield and 72% of the genotypic variation in NUE for protein. A path coefficient analysis revealed that the direct effect of uptake efficiency on NUE was high relative to indirect effects.The investigation reported in this paper (No. 85-3-122) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with approval of the Director     

QTLs and Candidate Genes for Rice Root Growth Under Flooding and Upland Conditions

To investigate the genetic factors underlying constitutive and adaptive root growth under different water-supply conditions, a double haploid (DH) population, derived from a cross between lowland rice variety IR64 and upland rice variety Azucena, with 284 molecular markers was used in cylindrical pot experiments. Several QTLs for seminal root length (SRL), adventitious root number (ARN) and total root dry weight (RW) respectively, under both flooding and upland conditions were detected. Two identical QTLs for SRL and RW were found under flooding and upland conditions. The relative parameters defined as the ratio of parameters under the two water-supply conditions were also used for QTL analysis. A comparative analysis among different genetic populations was performed for the QTLs for root traits and several consistent QTLs for root traits across genetic backgrounds were detected. Candidate genes for cell expansion and elongation were used for comparative mapping with the detected QTLs. Four cell wall-related expressed sequence tags (ESTs) for OsEXP2, OsEXP4, EXT and Xet were mapped on the intervals carrying the QTLs for root traits.     

Defining phosphorus efficiency in plants

The many different definitions for "nutrient efficiency" make the use of the term ambiguous. We evaluated nutrient efficiency using data from a study of response to phosphorus (P) supply in white clover (Trifolium repens L.) and lucerne (Medicago sativa L.). Application of various criteria identified in the literature as measures of nutrient efficiency did not clarify differences between purportedly P efficient and inefficient germplasm. Germplasm differed in maximum shoot and total dry mass and in solution P concentration ([P]_s) required to achieve 80% maximum yield, but not in P concentration of tissue ([P]_t), internal P utilization, or P uptake per unit of fine root dry mass. Differences in yield may have resulted from factors other than efficient use of P. To reduce the confounding effects that other factors have on nutrient efficiency, it is essential that equivalent yields of germplasm be demonstrated where nutrients are not limiting. Mechanisms that enable enhanced nutrient efficiency can be identified less ambiguously using this approach.Joint contribution of the Minn. Agric. Exp. Stn. and the USDA-ARS     

Glutathione reduces the inhibition of rice seedling root growth caused by cadmium

We investigated the effects of agents known to affect cellular glutathione (reduced form, GSH) levels on the growth of rice seedlings treated with Cd. CdCl₂ was more effective than CdSO₄ in inhibiting root growth. However, CdCl₂ had no effect on shoot growth. GSH, a substrate for phytochelatin synthesis, was effective in counteracting growth inhibition of roots by CdCl₂. Root growth in the CdCl₂ medium was found also to be enhanced by the addition of L-glutamic acid and L-cysteine, both of which are substrates for GSH formation. Buthionine sulfoximine, an inhibitor of GSH synthesis, rendered the roots susceptible to growth inhibition by Cd. Our results suggest that GSH level may play a role in regulating Cd-inhibited growth of rice roots.Abbreviations BSO buthionine sulfoximine - GSH reduced form glutathione     

Growth responses and N and P use efficiency of three Alnus species as affected by arbuscular-mycorrhizal colonisation

In this study it was determined how different species ofAlnus (A. cordata, A. incana and A. glutinosa) responded tocolonisation by arbuscular mycorrhizal (AM) fungi (Glomusmosseae or Glomus intraradices) with regard togrowth and their ability to acquire and utilise nitrogen and phosphorus.Non-mycorrhizal plants but with phosphorus added, were used as control. InA. glutinosa the application of 75 ppm P hadsimilar effect on growth and P acquisition as did AM. Nevertheless,A.cordata and A. incana grew poorly when suppliedwith 75 ppm of P and required AM symbiosis for optimum growth andNand P uptake. The percentage increases in shoot dry biomass in AM colonised ascompared with P-fertilised plants were 441 (A. cordata)and644 (A. incana) whilst AM-colonised A.glutinosa matched P-fertilised plants. Plant shoot N/P ratioincreased in response to AM-colonisation indicating that mycorrhizal effects onN uptake are greater than on P uptake. Information concerning the directinfluence of AM on N acquisition and nutrient use efficiency byAlnus species is important. AM-colonisation provides anexcellent biological mechanism by which Alnus plantsbecamemore efficient P-users. That Alnus sp. are highlymycorrhizal-dependent plants was apparent because AM-colonisation was criticalfor growth of A. incana and A.cordata. In this respect, for maximizing the efficient uptake anduseof N and P, under the growth conditions provided, Alnusplants need to be mycorrhizal. AM symbiosis seems decisive for the successfulestablishment of Alnus sp. in revegetation strategies. Thelow N and P availability in soils where Alnus species areuseful candidates in any recolonisation and reclamation process emphasises theneed to investigate systems by which N and P uptake byAlnus plants can be enhanced.     

A simple diffusion test for soil phosphorus availability

The availability of phosphorus to plants was estimated by a new method based on the diffusion of P from a thin layer of water-saturated stationary soil to a disc of iron oxide coated filter paper. Twenty-one acid Finnish soil samples were tested using four modifications of the method which differed in the duration of the diffusion time and in the thickness of the soil layer. The new diffusion tests were compared with other soil P testing methods and evaluated as indicators of the availability of P to pot-grown barley and oats. Close linear correlations were found between the initial (18 or 42 h) P diffusion rate and the water extractable P contents determined at the extraction ratios of 1:10 and 1:60, respectively (r=0.97–0.99). The amounts of P obtained by the new method were small when the diffusion time was short, but after prolonged diffusion (1 week) the test values were close to the amounts of P taken up by plants. The relationships of plant yield and P uptake with soil P test values were affected by soil acidity. Although the original soil P test values were significantly correlated, the accuracy of all methods drastically improved when the interfering effect of soil acidity was taken into account using a simple pH-correction model. The correlation coefficients (r) between the test values of diffusible P in soil and the uptake of P by plants increased up to 0.97.     

Response of irrigated dry-seeded rice to nitrogen and phosphorus in a semi-arid environment

Summary Under semi-arid conditions, three field experiments were conducted at Gezira Research Station to determine response of irrigated dry-seeded rice (Oryza sativa L. var IR 2053-206-1-3-6) to addition of nitrogen and phosphorus fertilizers. The experimental treatments included the factorial combinations of seven levels of nitrogen applied as urea and four levels of phosphorus applied as super phosphate. Plant growth and grain yield were significantly and progressively increased with the rise in the levels of added nitrogen and phosphorus. However, response to added phosphorus was restricted by the applied level of nitrogen. The responses of grain yield to nitrogen and phosphorus levels are given by quadratic regression equations. Without addition of nitrogen or phosphorus grain yield averaged 1.52 t/ha compared to 6.07 t/ha with addition of the optimal levels (160 kg N plus 35 kg P/ha). The high potential for rice production in semi-arid environment is evidently restricted by addition of relatively high rates of nitrogen and phosphorus.     

高产磷高效水稻磷素吸收利用特征

通过正常供磷的大田试验（2011年）,以产量和磷籽粒生产效率为指标,将27份中熟水稻亲本材料划分为4个类型,再通过正常和低磷处理的土培试验（2012年）,筛选出高产磷高效水稻材料,并探讨各种磷效率对产量的贡献率.结果表明： 结合两年的试验结果,供试材料的产量和磷利用效率均存在显著的基因型差异,筛选出GR泸17/矮TTP//泸17_2（QR20）为高产磷高效材料.在两个供磷水平下,QR20的产量和磷利用效率均显著高于低产磷低效材料玉香B,其产量分别是玉香B的1.96和1.92倍.大田和土培试验结果均表明,磷积累量对产量的贡献率均高于磷籽粒生产效率和磷收获指数.正常供磷条件下,磷积累量和磷籽粒生产效率对产量的贡献率差异不大,低磷条件下差异较大（66.5%和26.6%）,磷收获指数对产量的贡献率最低,最高仅为11.8%（土培）.土培试验中,正常供磷条件下,拔节-抽穗阶段的磷积累量对产量和磷收获指数的贡献率最高,分别为93.4%和85.7%,对磷籽粒生产效率的贡献率为41.8%;在低磷条件下,分蘖-拔节阶段的磷积累量对产量和磷籽粒生产效率的贡献率最高,分别为56.9%和20.1%,对磷收获指数的贡献率为16.0%.土培正常供磷条件下,水稻QR20的产量、磷积累量和磷收获指数相对于低磷处理分别增加了20.6%、18.1%和18.2%,差异显著.综上,磷效率对水稻产量的贡献率大小依次为磷吸收效率＞利用效率＞转运效率;正常供磷条件下,拔节-抽穗阶段的磷积累量对产量的贡献率最高,低磷胁迫下,分蘖-拔节阶段的磷积累量对产量的贡献率最高,这两个阶段可能是水稻高产磷高效协调统一的关键时期.
     

Improved isolated microspore culture efficiency in medium with maltose and optimized growth regulator combination in japonica rice (Oryza sativa)

The influence of maltose and growth regulators on microspore culture response was investigated in japonica rice. High frequency of callus induction of isolated microspores was obtained with liquid medium containing MS salts, 100 mg l^–1 myo-inositol, 1 mg l^–1 thiamine-HCl, 500 mg l^–1 glutamine, 60 g l^–1 maltose, and several growth regulators. The effect of maltose on promoting callus formation was associated with keeping a high proportion of swollen microspores after 5 day preculture and increasing the microspore division rate on the 3rd day after culture initiation. No significant effect of maltose in place of sucrose on plantlet regeneration was seen in regeneration medium. Among the growth regulators tested, the combination of auxin 2,4-dichlorophenoxyacetic acid (1 mg l^–1), naphthaleneacetic acid (1 mg l^–1), and cytokinin (6-benzyl-aminopurine 1 mg l^–1) in the medium proved to be much better for callus formation than in the other media, and the percentage of callusing microspores of that medium reached 0.86%. Indole-3-acetic acid (0.5 mg l^–1) and kinetin (2 mg l^–1) in regeneration medium were beneficial for green plantlet differentiation. The results also showed that the frequencies of microspores initial division, callus formation and green plant regeneration varied among genotypes no matter what kind of growth regulator and sugar were used. Xiushui 117 was the best variety for callusing followed by 02428 & Taipei 309. Taipei 309 showed a good ability for green plantlet regeneration.Abbreviations 2,4-d 2,4-dichlorophenoxyacetic acid - NAA naphthaleneacetic acid - 6-BA 6-benzylaminopurine - KT kinetin - IAA indole-3 acetic acid     

Root growth and water uptake in winter wheat under deficit irrigation

Root growth is critical for crops to use soil water under water-limited conditions. A field study was conducted to investigate the effect of available soil water on root and shoot growth, and root water uptake in winter wheat (Triticum aestivum L.) under deficit irrigation in a semi-arid environment. Treatments consisted of rainfed, deficit irrigation at different developmental stages, and adequate irrigation. The rainfed plots had the lowest shoot dry weight because available soil water decreased rapidly from booting to late grain filling. For the deficit-irrigation treatments, crops that received irrigation at jointing and booting had higher shoot dry weight than those that received irrigation at anthesis and middle grain filling. Rapid root growth occurred in both rainfed and irrigated crops from floral initiation to anthesis, and maximum rooting depth occurred by booting. Root length density and dry weight decreased after anthesis. From floral initiation to booting, root length density and growth rate were higher in rainfed than in irrigated crops. However, root length density and growth rate were lower in rainfed than in irrigated crops from booting to anthesis. As a result, the difference in root length density between rainfed and irrigated treatments was small during grain filling. The root growth and water use below 1.4 m were limited by a caliche (45% CaCO₃) layer at about 1.4 m profile. The mean water uptake rate decreased as available soil water decreased. During grain filling, root water uptake was higher from the irrigated crops than from the rainfed. Irrigation from jointing to anthesis increased seasonal evapotranspiration, grain yield, harvest index and water-use efficiency based on yield (WUE), but did not affect water-use efficiency based on aboveground biomass. There was no significant difference in WUE among irrigation treatments except one-irrigation at middle grain filling. Due to a relatively deep root system in rainfed crops, the higher grain yield and WUE in irrigated crops compared to rainfed crops was not a result of rooting depth or root length density, but increased harvest index, and higher water uptake rate during grain filling.     

Segregation for endosperm lysine in F2, F3 and F4 progeny from a cross of in vitro-selected and unselected cultivar of rice

Summary Lysine is a limiting amino acid for optimal nutritional quality in rice grain. In vitro selections using inhibitory levels of lysine plus threonine or s-aminoethylcysteine allow the predictable recovery of variants with elevated levels of lysine and protein. These methods may generate useful starting germplasm for plant breeders. This study was conducted to define the genetics of lysine mutants in progeny from crosses of mutants derived from cells cultured in vitro in the presence of inhibitory levels of lysine plus threonine and s-(2-aminoethyl)-cysteine. In vitro selections produce a wide range of mutants, including endosperm mutants with elevated lysine and protein levels as well as mutants for high and low seed weights. Mutants were analyzed for lysine content by the endosperm half-seed method in which the halves without the embryo were ground and acid hydrolyzed for amino acid determinations. The halves with the embryos were preserved for later germination. In two different F₂ populations derived from a cross of a selected mutant x M-101, a parental marker, there was an inverse relationship between seed weight and percent lysine in endosperm protein (R² 0.52 and 0.56). The F₂ segregation patterns show that elevated lysine is inherited as a recessive gene and that increased lysine is correlated with decreased seed size. F₃ and F₄ data provide evidence for the transmission of high lysine genes to advanced germplasm in rice. This work supports our earlier conclusions that high lysine phenotypes can be recovered predictably from in vitro selections. The elevated lysine phenotypes are frequently, but not exclusively, associated with opaque seed. Some segregants from crosses produced increased lysine in plants with near normal seed weight and good fertility.Research done under the auspices of the USDA, ARS, Plant Sciences Institute, Plant Molecular Biology Laboratory, Beltsville, MD 20705, USA     

Effects of Proline and Betaine on Heat Inactivation of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase in Crude Extracts of Rice Seedlings

Activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) in heated crude extracts from seedlings of the rice cultivars Hitomebore and IR28 was investigated in the presence of proline and betaine. Both solutes retarded the inactivation of the enzyme extracted from the leaves of both cultivars at temperature-stress from 35 to 45 °C. At 50 °C, however, betaine was effective in both cultivars. Stabilization of RuBPCO activity was independent of the added solute from 1 to 2 M concentration. This revised version was published online in June 2006 with corrections to the Cover Date.     

Nutrient uptake relationship to root characteristics of rice

Data on root parameters and distribution are important for an improved understanding of the factors influencing nutrient uptake by a crop. Therefore, a study was conducted on a Crowley silt loam at the Rice Research and Extension Center near Stuttgart, Arkansas to measure root growth and N, P and K uptake by three rice (Oryza sativa L.) cultivars at active tillering (36 days after emergence (DAE)), maximum tillering (41 DAE), 1.25 cm internode elongation (55 DAE), booting (77 DAE) and heading (88 DAE). Soil-root core samples were taken to a depth of 40 cm after plant samples were removed, sectioned into 5 cm intervals, roots were washed from soil and root lengths, dry weights and radii were measured. Root parameters were significantly affected by the soil depth × growth stage interaction. In addition, only root radius was affected by cultivar. At the 0- to 5-cm soil depth, root length density ranged from 38 to 93 cm cm^-3 throughout the growing season and decreased with depth to about 2 cm cm^-3 in the 35- to 40-cm depth increment. The increase in root length measured with each succeeding growth stage in each soil horizon also resulted in increased root surface area, hence providing more exposed area for nutrient uptake. About 90% of the total root length was found in the 0- to 20-cm soil depth throughout the season. Average root radius measured in the 0- to 5-cm and 35- to 40-cm depth increments ranged from 0.012 to 0.013 cm and 0.004 to 0.005 cm, respectively throughout the season. Total nutrient uptake by rice differed among cultivars only during vegetative growth. Differences in total nutrient uptake among the cultivars in the field appear to be related to absorption kinetics of the cultivars measured in a growth chamber study. Published with permission of the Arkansas Agricultural Experiment Station.     

Disturbed ammonium assimilation is associated with growth inhibition of roots in rice seedlings caused by NaCl

The effects of NaCl on changes in ammonium level and enzyme activities of ammonium assimilation in roots growth of rice (Oryza sativa L.) seedlings were investigated. NaCl was effective in inhibiting root growth and stimulated the accumulation of ammonium in roots. Accumulation of ammonium in roots preceded inhibition of root growth caused by NaCl. Both effects caused by NaCl are reversible. Exogenous ammonium chloride and methionine sulfoximine (MSO), which caused ammonium accumulation in roots, inhibited root growth of rice seedlings. NaCl decreased glutamine synthetase and glutamate synthase activities in roots, but increased glutamate dehydrogenase activity. The growth inhibition of roots by NaCl or MSO could be reversed by the addition of L-glutamic acid or L-glutamine. The current results suggest that disturbance of ammonium assimilation in roots may be involved in regulating root growth reduction caused by NaCl.Abbreviations GDH glutamate dehydrogenase - GOGAT glutamate synthase - GS glutamine synthetase - MSO methionine sulfoximine     

应用AFLP与RFLP标记研究水稻磷吸收与利用率的数量性状位点

从耐低磷胁迫水稻（Ｏｒｙｚａ ｓａｔｉｖａ Ｌ．）品种“ＩＲ２０”与低磷敏感品质ＩＲ５５１７８－３Ｂ－９－３杂交发展的重组自交系群体中选择的８４个系在液体培养条件下,测定了相对生物量,植株相对磷含量及相对磷利用率;在酸性土壤盆栽条件下测定了相对分蘖力与相对地上部生物量。用选择的８４个系构建了包括２６个ＲＦＬＰ标记与１５３个ＡＦＬＰ标记的分子标记图谱用于基因定位分析。溶液培养条件下在第１２,６,７三