Biofortification with selenium and lithium improves nutraceutical properties of major winery grapes in the Midwestern United States

Enriching the micronutrients, selenium (Se) and lithium (Li), in grapes to improve their nutraceutical properties were implemented by foliar application of organic fertiliser rich in Se and Li onto five grape cultivars. The effects of this biofortification on vine vigour, fruit quality, overall micronutrients and phenolic compounds also were investigated. Agronomic biofortification was found greatly increased the Se and Li content in the whole grape by multiple times, meanwhile it did not significantly affect the vine vigour and fruit quality of grapes. However, the biofortification did impact the Ionome (including all the mineral nutrients and trace elements) and phenolic compounds in grapes and this varied among cultivars. This study demonstrated foliar spray of organic Se/Li fertiliser was a very effective strategy to biofortify these micronutrients in grape berries, particularly in the skin, and therefore might be a promising strategy to increase the consumption and awareness of these grapes.     

Spectral sensing of foliar water conditions in two co-occurring conifer species: Pinus edulis and Juniperus monosperma

Many fundamental ecosystem properties and dynamics are determined by plant water stress, particularly in dryland ecosystems where water is usually limiting. Indeed, under severe drought, plant water stress and associated insect infestations can produce landscape-scale mortality. Despite the fundamental importance of plant water stress in determining properties and dynamics at ecosystem and landscape scales, approaches for remotely sensing plant water stress are largely lacking, particularly for conifers. We evaluated the remotely sensed detection of foliar drought stress in two conifer species, Pinus edulis and Juniperus monosperma, which are co-dominants of extensive-juniper woodlands in North America, the first of which experienced extensive mortality in association with a recent drought. Needle spectra were made on these species in the field using an integrating sphere and portable spectrometer. Two indices of foliar water condition, plant water content (% of dry mass) and plant water potential, were compared to five spectral analyses: continuum removal of the 970 and 1200 nm water absorption features, the Normalized Difference Water Index (NDWI), the Normalized Difference Vegetation Index (NDVI), and the red edge wavelength position. For P. edulis, plant water content was significantly correlated with four of the five indices: NDVI (R²=0.71) and NDWI (R²=0.68) which exhibited stronger relationships than 970 nm continuum removal (R²=0.57) or red edge position (R²=0.45). All five indices were significantly correlated with P. edulis water content when trees undergoing mortality were included in analyses (R²=0.60-0.93). Although the correlations were weaker than for plant water content, plant water potential was significantly correlated with NDWI (R²=0.49), 970 nm (R²=0.44), NDVI (R²=0.35), and red edge (R²=0.34); again all five indices had significant relationships when trees undergoing mortality were included (R²=0.51-0.86). The relationships were weaker for J. monosperma: water content was significantly related to 970 nm (R²=0.50) and 1200 nm (R²=0.37) continuums and NDVI (R²=0.33), while water potential was related only to 1200 nm (R²=0.40). Our results demonstrate a critical link between plant physiological characteristics tied to water stress and associated spectral signatures for two extensive co-occurring conifer species.     

Effect of foliar application of selenium on its uptake and speciation in carrot

Carrot (Daucus carota) shoots were enriched by selenium using foliar application. Solutions of sodium selenite or sodium selenate at 10 and 100 μg Se ml⁻¹, were sprayed on the carrot leaves and the selenium content and uptake rate of selenium were estimated by ICP–MS analysis. Anion and cation exchange HPLC were tailored to and applied for the separation of selenium species in proteolytic extracts of the biological tissues using detection by ICP–MS or ESI–MS/MS. Foliar application of solutions of selenite or selenate at 100 μg Se ml⁻¹ resulted in a selenium concentration of up to 2 μg Se g⁻¹ (dry mass) in the carrot root whereas the selenium concentration in the controls was below the limit of detection at 0.045 μg Se g⁻¹ (dry mass). Selenate-enriched carrot leaves accumulated as much as 80 μg Se g⁻¹ (dry mass), while the selenite-enriched leaves contained approximately 50 μg Se g⁻¹ (dry mass). The speciation analyses showed that inorganic selenium was present in both roots and leaves. The predominant metabolised organic forms of selenium in the roots were selenomethionine and γ-glutamyl-selenomethyl-selenocysteine, regardless of which of the inorganic species were used for foliar application. Only selenomethionine was detected in the carrot leaves. The identity of selenomethionine contained in carrot roots and leaves was successfully confirmed by HPLC–ESI–MS/MS.     

Enhanced selenium content in buckwheat (<Emphasis Type="Italic">Fagopyrum esculentum</Emphasis> Moench) and pumpkin (<Emphasis Type="Italic">Cucurbita pepo</Emphasis> L.) seeds by foliar fertilisation

The fruit and thin-husked seeds of the pumpkin (Cucurbita pepo L.) and buckwheat grain (Fagopyrum esculentum Moench), both grown in Slovenia, were analysed for selenium (Se) content following foliar application of Se(VI) solution during the period of blooming. Samples were digested by a H₂SO₄-HNO₃-H₂O₂-V₂O₅ mixture and Se determined, based on hydride generation atomic fluorescence spectrometry. The whole procedure from weighing to measuring was carried out in the same Teflon vessel. The detection limit of the method was 0.14 ng g^–1 solution. Buckwheat seeds from untreated plants contained 47 ng g^–1 of Se and 394 ng g^–1 from plants after foliar fertilisation with Se. Pumpkin seeds from untreated plants contained 108 ng g^–1 of Se, and 381 ng g^–1 of Se from Se-treated plants, all per lyophilised sample. Se content in lyophilised pumpkin fruit was 15 ng g^–1 in untreated plants and 20 ng g^–1 in Se-treated pumpkin plants. It is thus feasible to enhance Se content in buckwheat and pumpkin seeds by foliar fertilisation, making them a rich source of dietary Se and useful as a raw material for enriched food products.     

Sucrose fatty acid esters enhance efficiency of foliar-applied urea-nitrogen to soybeans

A greenhouse study is described showing the effect of sucrose fatty acid esters (SFE) applied to soybeans (Glycine max (L.) Merrill cv Fukuyutaka) during the flowering and/or pod-filling periods on the efficiency of foliar-applied urea-nitrogen. SFE applied in combination with urea delayed senescence and when applied during both the flowering and pod-filling periods increased seed yields by 103% and nitrogen accumulation by 132% as compared to urea alone. Average total recovery of¹⁵N-urea in the above ground portions of the plant was 20.6%. SFE combined with urea increased the average recovery to 34.8%. Recovered¹⁵N-urea was only a small portion of the total nitrogen content of the plant. The yield increase resulting from a foliar application of urea may have been due to the leaves continuing to export photosynthates to the nodules hence maintaining the nodules' nitrogen fixing activity for a longer period of time. The addition of SFE to the urea solution increased the retention and/or absorption of urea and increased translocation of urea-nitrogen to the seeds.     

Iron concentration,bioavailability, and nutritional quality of polished rice affected by different forms of foliar iron fertilizer

The present study compared the effects of four different forms of foliar iron (Fe) fertilizers on Fe concentration, bioavailability and nutritional quality of polished rice. The results showed that foliar fertilisation at the anthesis stage was an effective way to promote Fe concentration and bioavailability of polished rice, especially in case of DTPA-Fe. Compared to the control, foliar application of DTPA-Fe increased sulphur concentration and the nutrition promoter cysteine content, whereas decreased phosphorus concentration and the antinutrient phytic acid content of polished rice, as a result increased 67.2% ferrtin formation in Caco-2 cell. Moreover, foliar DTPA-Fe application could maintain amylase, protein and minerals quality of polished rice. According to the current study, DTPA-Fe is recommended as an excellent foliar Fe form for Fe biofortification program.     

Response of Sesame (Sesamum indicum L.) Plants to Foliar Spray with Different Concentrations of Boron

Sesame plants were sprayed with different concentrations of boron solution at 20, 30 and 40 ppm at different stages of plant growth (1, 2 and 3 months). Comparing the treated plants with untreated controls, the obtained results showed that spraying sesame plants with boron (B) solutions improves their growth and yields. Treating plants with boron solution at 20 ppm gave the highest results in growth criteria as compared with corresponding control or plants treated with higher boron solutions (30 and 40 ppm). Moisture and oil percentages were nonsignificantly changed by the different boron concentrations. The highest oil viscosity was recorded at a boron concentration of 30 ppm. Fatty acids were decreased by the effect of boron spray. A remarkable increase in the amino acid content of the plants was observed as a result of treatments with boron solutions, especially in the plants treated at 40 ppm. Spraying sesame plants with boron decreased the Fe, K, Mg and P contents, whereas the lowest concentration of boron (20 ppm) increased Ca and the highest concentration (40 ppm) increased Cl and Na.     

Interactive Influence of Leaf Age,Light Intensity,and Girdling on Green Ash Foliar Chemistry and Emerald Ash Borer Development

Biotic and abiotic environmental factors affect plant nutritional quality and defensive compounds that confer plant resistance to herbivory. Influence of leaf age, light availability, and girdling on foliar nutrition and defense of green ash (Fraxinus pennsylvanica Marsh) was examined in this study. Longevity of the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), adults reared on green ash foliage subjected to these factors was assayed. Mature leaves generally were more nutritious with greater amino acids and a greater ratio of protein to non-structural carbohydrate (P:C) than young leaves, in particular when trees were grown in shade. On the other hand, mature leaves had lower amounts of trypsin and chymotrypsin inhibitors, and total phenolics compared to young leaves. Lower defense of mature leaves alone, or along with higher nutritional quality may lead to increased survival and longevity of emerald ash borer feeding on mature leaves. Sunlight reduced amino acids and P:C ratio, irrespective of leaf age and girdling, and elevated total protein of young foliage, but not protein of mature leaves. Sunlight also dramatically increased all investigated defensive compounds of young, but not mature leaves. Girdling reduced green ash foliar nutrition, especially, of young leaves grown in shade and of mature leaves grown in sun. However emerald ash borer performance did not differ when fed leaves from trees grown in sun or shade, or from girdled or control trees. One explanation is that emerald ash borer reared on lower nutritional quality food may compensate for nutrient deficiency by increasing its consumption rate. The strong interactions among leaf age, light intensity, and girdling on nutrition and defense highlight the need for caution when interpreting data without considering possible interactions.     

Integrating imaging spectroscopy and neural networks to map grass quality in the Kruger National Park, South Africa

A new integrated approach, involving continuum-removed absorption features, the red edge position and neural networks, is developed and applied to map grass nitrogen concentration in an African savanna rangeland. Nitrogen, which largely determines the nutritional quality of grasslands, is commonly the most limiting nutrient for grazers. Therefore, the remote sensing of foliar nitrogen concentration in savanna rangelands is important for an improved understanding of the distribution and feeding patterns of wildlife. Continuum removal was applied on two absorption features located in the visible (R_550-757) and the SWIR (R_2015-2199) from an atmospherically corrected HYMAP MKI image. A feature selection algorithm was used to select wavelength variables from the absorption features. Selected band depths from the absorption features as well as the red edge position (REP) were input into a backpropagation neural network. The best-trained neural network was used to map nitrogen concentration over the whole study area. Results indicate that the new integrated approach could explain 60% of the variation in savanna grass nitrogen concentration on an independent test data set, with a root mean square error (rmse) of 0.13 (±8.30% of the mean observed nitrogen concentration). This result is better compared to the result obtained using multiple linear regression, which yielded an R² of 38%, with a RMSE of 0.16 (±10.30% of the mean observed nitrogen concentration) on an independent test data set. The study demonstrates the potential of airborne hyperspectral data and neural networks to estimate and ultimately to map nitrogen concentration in the mixed species environments of Southern Africa.     

Response to fertilization and nutrient deficiency diagnostics in peach palm in Central Amazonia

Peach palm (Bactris gasipaes Kunth) is increasingly grown in the tropics for its heart-of-palm and fruit. Determining fertilization response and diagnosing nutrient status in peach palm may require methods that consider the particularities in nutrient acquisition and recycling of perennial crops. Responses to nutrient additions, and the diagnostic value of soil and foliar analyses were examined in three field experiments with three-year old peach palm stands on Oxisols in Central Amazonia. To diagnose P-deficiency levels in soils, samples from 0–5 cm and 5–20 cm depth were analyzed for available P by different methods (Mehlich-1, Mehlich-3 and Modified Olsen). The second and fifth leaves were analyzed to assess N, P and K deficiencies. Field experiments involved several combinations of N (from 0 to 225 kg ha^–1 yr^–1), K (from 0 to 225 kg ha^–1 yr^–1) and P (from 0 to 59 kg ha^–1 yr^–1). Palms on control plots (unfertilized) and those receiving 225 kg ha^–1 yr^–1 N and 2 Mg ha^–1 of lime yielded between 4 and 19% of the maximum growth which was obtained with N, P and K applications. In one of the experiments, yield of heart-of-palm was positively related to N additions at the lowest levels of P (8.6 kg ha^–1 yr^–1) and K (60 kg ha^–1 yr^–1) additions. In one experiment, critical leaf N level was 2.5% for the second leaf and 2.2% for the fifth leaf. Some growth responses to P additions at constant N and K levels were observed (e.g., 797 kg ha^–1 yr^–1 of heart-of-palm with 39.3 kg ha^–1 yr^–1 of applied P, and 632 kg ha^–1 yr^–1 of heart-of-palm with 10.9 kg ha^–1 yr^–1 of applied P in one experiment, and 2334 kg ha^–1 yr^–1 of heart-of-palm with 39.3 kg ha^–1 yr^–1 of P and 1257 kg ha^–1 yr^–1 of heart-of-palm with 19.7 kg ha^–1 yr^–1 of P in another trial). In the experiment for fruit production from peach palm, total plant height did not respond to P additions between 19.7 and 59 kg ha^–1 yr^–1 and K additions between 75 and 225 kg ha^–1 yr^–1. Leaf P levels were found to be above the proposed critical levels of 0.23% for the third leaf and 0.16% for the fifth leaf. Plants in this experiment, however, showed evident symptoms of Mg deficiency, which was associated with a steep gradient of increasing Mg concentration from the fifth leaf to the second leaf. Standard leaf diagnostic methods in most cases proved less useful to show plant N and P status and growth responses to N and P additions. Soil P determined by common extractions was in general too variable for prediction of growth.