A comprehensive analysis of the proteomic and metabolomic changes occurring in sugar beet root tips under Fe deficiency and Fe resupply has been carried out. Root tip samples were taken from Fe-sufficient (+Fe), Fe-deficient (-Fe) and Fe-resupplied plants at 24 and 72 h (in the latter case in two different root zones). Proteome maps were obtained using two-dimensional IEF-SDS PAGE. More than 140 spots were detected in gels from root tips of Fe-deficient and control plants, and Fe deficiency induced significant changes in the intensity of a large number of these polypeptides, many of them related to carbohydrate catabolism. A protein not present in Fe-sufficient roots, DMRL synthase, was present in high amounts in root tips from Fe-deficient sugar beet plants and was also found to be transcriptionally regulated by Fe status. Seventy-seven metabolites were identified by GC-MS. Statistical analysis using univariate, breakdown one-way ANOVA, and multivariate, supervised partial least square was carried out. Score scatter plots using the first 2 components showed a good separation of the different treatments, with metabolites in the 72 h Fe-resupplied samples being close those obtained in Fe-sufficient conditions. An activation of TCA cycle components was observed in Fe-deficient root tips when compared to the controls. An increase in the amount of the raffinose series of oligosaccharides (RSOs), including raffinose, galactinol, lacto-bionic acid and myo-inositol was observed in root tips of Fe-deficient and 24 h Fe-resupplied plants when compared to the controls.
N fertiliser management is increasingly important in sugarcane crop as imperatives to reduce environmental impacts of N escalate. In this paper we report testing of a new concept for N management in sugarcane, the N Replacement system. This system aligns N applications with actual cane production, rather than potential production, by relying on soil N reserves to buffer differences in crop N needs and N fertiliser supply in individual crops. In 11 experiments that were conducted over an average of three crops, yields in the N Replacement treatment were similar to those achieved with the farmers’ conventional N management that had average N applications 18 to 157 kg/ha/crop greater than in the N Replacement treatments. The crop N surplus, an estimate of N potentially lost to the environment, was ~40% lower in the N replacement treatments compared with conventional N management. N concentrations and N uptake in cane for most crops were lower than those previously reported. These low N concentrations may be a response to the lower N application, and explain why yields were maintained in the N Replacement system at the lower N rates. The results show that the ecologically-based N Replacement system may deliver superior environmental outcomes without significantly reducing production. The results also show that predicting yield of the coming crop, a common basis for N management, is not necessary in sugarcane N management, provided N applications and production are matched in the longer term.
In northwest China the lack of knowledge on soil nutrient fertility and of appropriate nutrient management practices has restricted potato production. Field trials were conducted from 2002 to 2007 to determine the main limiting nutrients for potato (Solanum tuberosum L), and to evaluate the nutrient management practice (NMP) based on an Agro Services International (ASI) systematic approach. Results indicated that average potato yields in nutrient omission plots were in the order 0-N (22.2 t ha-1) ≈ 0-P (22.4 t ha-1) < 0-K (31.5 t ha-1). N deficiency is a general feature of irrigated potato in northwest region, but P and K supply are frequently additional limiting factors. The mean agronomic efficiencies (AE) of N, P and K were 34.4 kg tuber kg-1 N, 32.4 kg tuber kg-1 P2O5 and 41.3 kg tuber kg-1 K2O, respectively, and the mean partial factor productivities (PFP) of N, P and K were 220 kg tuber kg-1 N, 291 kg tuber kg-1 P2O5 and 306 kg tuber kg-1 K2O, respectively. There was a significant negative relationship between AE or PFP of N, P or K and the respective nutrient rate. The positive relationship between yield of nutrient omission plots and PFP and AE suggests nutrient use efficiency is affected by soil indigenous productivity. NMP based on an ASI systematic approach produced significant higher yields, nutrient use efficiencies and economic returns than farmer’s practice.
Based on the differences of lupin and corn in Si requirement and their capacity to release organic acids for P mobilisation both plant species were compared in respect to As mobilisation and plant As uptake and release which is closely linked to P and Si nutrition.
Plants were grown with and without P fertilization in an As contaminated floodplain soil in compartment systems which enabled temporally resolved sampling of soil solution with increasing distance from the root surface.
Although no direct increase of P or AsV concentration in soil solution could be detected, lupins showed higher P and As uptake but lower root to shoot translocation of As compared to corn plants. Higher root As concentrations in lupins corresponded to higher AsIII concentration in soil solution which increased with time and corresponded to the recently demonstrated diffusion driven efflux of As in the form of AsIII via aquaglycerol channels. It is well established that AsV, the form of As initially present in the floodplain soil, is taken up via P transporters. Hence the higher As uptake of lupin is in line with previous results showing higher P uptake capacity per unit root length for lupin compared to corn. A lower capacity for As efflux in lupin as it was expected due to lower Si requirement of lupin compared to corn could not be demonstrated.
Continuous air temperature measurements were made during 2006-2008 at 30 different locations within a topographically complex orchard containing 10 yr old ‘Sweetheart’ sweet cherry (Prunus avium L.) on Mazzard rootstock in southern British Columbia. Yield, trunk cross-sectional area, fruit quality, and leaf and fruit mineral concentrations were measured throughout the study on adjacent trees at each location. Granier sap flow probes were installed on 10 nearby ‘Sweetheart’ trees to monitor seasonal tree water use. Within-season average volume change of individual cherries showed similar annual patterns at all locations with a decreased growth rate immediately prior to harvest, especially in 2006, the warmest year, when the smallest cherries were harvested. Yield, TCSA and percent splits, with coefficients of variation frequently exceeding 50%, had highest within block variability. Yield was affected more by spring frost in 2007 than any nutritional consideration. TCSA was lower at warm locations which consistently accumulated higher growing degree days (5C) by harvest. Smaller trees had lower but apparently adequate leaf and soil K levels. Fruit splits and leaf K concentrations were positively correlated annually. Sap flow mirrored changes in atmometer-measured evapotranspiration, except during the periods of highest evaporative demand near to harvest when inadequate irrigation and water stressed trees occurred. The smaller trees growing on warmer locations within the block may reflect the historical consequences of greater cumulative water stress which would also reduced K uptake. Regional climate change scenarios predicting higher temperatures and increasing water demand may increase tree variability requiring improved irrigation strategies.
Effects of incorporating urea with wheat or corn straw at different soil moisture levels on ammonia volatilization were measured in a field experiment using a sponge-tripping method with KCl extraction. Over a 10-day period following incubation NH3 volatilization peaked on day 3 for urea alone, while highest emission rates were observed on day 2 for urea plus wheat or corn straw. Total NH3 losses decreased in the order: urea > urea + maize straw > urea + wheat straw. Emissions of NH3 were more sensitive to soil moisture after straw addition and correlation analysis showed that NH3 volatilization was also significantly affected by pH of the surface soil. To reduce ammonia losses at the farm level application of urea fertilizer should consider the straw type and soil properties.
Nitrogen (N) is a crucial plant nutrient that farmers tend to apply to their crops in excess in order to gain high yields. However, crop plants are generally inefficient at N uptake from the soil, much of the applied N fertilizers are lost to the plant through leaching, volatization and by microbial action. It is important to breed and/or design nitrogen use efficient (NUE) crop plants that can produce the same, or higher yields with less applied N fertilizer. Growth of NUE crops, coupled with implementation of best fertilizer management practices, would reduce the need for N fertilizer application, reducing both costs to the farmer and environmental pollution.
We have recently genetically engineered rice (Oryza sativa L.) by introducing a barley alanine aminotransferase (AlaAT) cDNA driven by a rice tissue specific promoter (Shrawat et. al., 2008). The transgenic rice showed significantly increased biomass and grain yield compared to control plants when grown at a fixed, high amount of ammonium. We also analysed the transcriptomic profile of these transgenic plants using Affymetrix Rice GeneChip microarrays (Beatty et al., 2009). In the current study, we compared various physiological and genetic data from alanine aminotransferase over-expressing transgenic plants to control plants grown at three different nitrogen levels and demonstrated significant changes between them. Our studies demonstrate that the manipulation of AlaAT can be affected by the level of available nitrogen. In addition, certain transcripts in the transgenic lines can be influenced by nitrogen levels as well.
We characterized the transport of cadmium (Cd) in soybean (Glycine max [L.] Merr.). A positron-emitting 107Cd (half-life: 6.5 hr) tracer and a gamma-emitting 109Cd (half-life: 453 d) tracer with non-radioactive Cd (final conc. 0.1 µM Cd) were fed as a mixture to the hydroponic culture. 107Cd distribution in the intact test plants was imaged non-invasively using the positron-emitting tracer imaging system (PETIS). The test plants were sampled and separated to roots, stems, petioles, leaves, pods and seeds at about 2, 3 and 5 days after Cd feeding. After the sufficient decay of 107Cd, 109Cd accumulation in each part was analyzed and quantified using autoradiography and well-type counter. The PETIS images showed that the Cd reached shoot base about a few hours after feeding and was transported to upper nodes through the stem. The autoradiographic images revealed that a part of Cd was transported to the pods and seeds without passing through leaves within 2 days after Cd feeding. And the results obtained from well-type counter showed that a part of Cd absorbed by the roots moved and accumulated into the seeds, pods, leaves and petioles gradually within 5 days.
The biological oxidation of ammonia (i.e. nitrification), results in the transformation of relatively immobile NH4+ into a highly mobile NO3-, which is vulnerable to losses through leaching and denitrification, resulting in low nitrogen-use efficiency in agricultural systems. The ability of certain plants to suppress soil nitrifier function by releasing inhibitors from roots is termed 'biological nitrification inhibition' (BNI). Using a recombinant luminescent Nitrosomonas europaea, we developed an assay to detect and quantify the inhibitory effects in plant soil systems termed, 'BNI activity', expressed in ATU (allylthiourea unit). Sorghum roots released (into water-based medium, hereafter referred to as root exudates) substantial amount of BNI activity. The BNI capacity (ATU g-1 root dry wt d-1) of roots changed with growth stage, from 60 ATU at 3 week old to 20 ATU at 45 day stage. In addition, sorghum roots released hydrophobic compounds, which can be recovered by washing with dichloromethane (hereafter referred to as DCM-root wash). One of the active constituents with BNI activity in root exudates, isolated by activity-guided HPLC fractionation, was a flavonoid, identified as sakuranetin. Using a similar approach, the major active constituent with BNI activity in DCM-root wash was isolated and identified as sorgoleone. Both sakuranetin and sorgoleone inhibited Nitrosomonas activity in a dose-response manner. Substantial genetic variability for sorgoleone production capacity was detected in sorghum. Some wild-sorghum species showed high-BNI capacity under field conditions. Potential implications of BNI in inhibiting nitrification and in reducing the nitrogen footprint from agricultural systems will be discussed.
Growing population pressure and increasing food demands are expected to multiply manifold in the coming years. Combined with a steady increase of rice consumption per capita and a looming shortage of rice on the world market, the use of inland valleys in the savannah zone of West Africa for rice production is imperative. However, the rice productivity in such inland valleys is likely to vary with the field position, the level of water control and the use of fertilizers. This study investigates the potential productivity of rice in an inland valley of the sudano-guinean savannah zone of Benin. We compared two valley positions (flood-prone center vs. drought-prone fringes), two levels of water control (open vs. bunded plots) and two rates of fertilizer amendment in a 3-year field experiment. Rice yields were significantly higher in the valley fringe (3.8 Mg ha-1) compared to the valley bottom center (2.5 Mg ha-1). Bunding increased grain yield on average by 0.7 Mg ha-1, probably as a result of a better water retention in the plots and an increased N availability. Fertilizer application showed no significant effect on yield but tended to alleviate the negative effects of iron toxicity in the valley bottom lands.
