Nitrate fertilizers are the most commonly used nitrogen sources for growing vegetables. The use of nitrate fertilizers in vegetable production may result in its accumulation in the plants if uptake exceeds assimilation. High nitrate concentrations in leafy vegetables represent a possible threat to human health. Leafy vegetables are the highest contributor to total food nitrate intake as a result of their high specific concentration and the large amount consumed. Consequently, European Union regulations were established for nitrate concentrations in leafy vegetables such as lettuce, spinach and rucola (Diplotaxis tenuifolia). Therefore, the need for a reliable, easy, fast and universal method to meet these demands is essential. We reassessed nitrate determination by comparing fresh and dry leaf material extracts of rucola. Our results indicate that the leaf nitrate concentration with both measurement methods is similar. Consequently, the use of the dry leaf extracts method is feasible and worth recommending to the European Union as an official method for determining nitrate concentrations in leafy vegetables.
Plant branching shoot number is strongly influenced by nitrogen (N) supply status. However, detailed descriptions of this phenomenon and the regulatory mechanism are lacking. In this study, we show that, in rice, in comparison to sufficient supply of ammonium sulfate or ammonium nitrate (2.5 or 5 mM N), low N (0.2 mM) or nitrate as the only N source limited shoot branching, i.e., tillering number. We observed that N deficiency did not affect the initiation, but suppressed the elongation of the tiller buds. We carried out in-situ hybridization of the tiller buds and showed that the expression of histone H4, a marker of S-phase in the cell cycle, could not be detected in the tiller buds that had stopped growing, indicating that cell division was suppressed in the tissues. Consistent with this finding, we further detected that the expression of other cell cycle marker genes was decreased in the N-deficient tiller buds in comparison to N-sufficient tiller buds. In addition, expression of the genes involved in the strigolactone pathway was induced in the tiller buds by N deficiency, in accordance with other reports. These results shed light on the importance of proper N application to control tiller bud outgrowth in grain production.
Desalinated water has become a legitimate alternative water resource for the irrigation of intensive crops in semiarid regions. The concentrations of calcium (Ca) and magnesium (Mg) in water (CCa and CMg, respectively) supplied from desalinated plants are much lower than the values typically found in irrigation water resources in semiarid regions. blossom-end rot (BER), a physiological disorder at the blossom-end part of the fruit resulting in tissue disintegration and dehydration, is considered a Ca-related disorder and therefore the optimization of CCa has to consider not only total fruit production but also the occurrence of BER. There is a lack of information regarding the optimal CCa and CMg and Ca/Mg ratio in low-salinity water under Mediterranean conditions for high-quality yield of tomato fruits.
The main objective of the research was to optimize CCa and CMg for the production of high tomato fruit yield with minimal occurrence of BER. A secondary objective was to determine critical levels of Ca, Mg and Ca/Mg ratio in leaves in relation to yield and the occurrence of BER.
Tomato plants were grown in an inert media and fed with a wide range of CCa and CMg. Fruit yield was shown to decrease significantly when CCa was at or below 0.40 mmol l–1. In moderate CMg (1.4 mmol l–1) treatment, BER was negatively correlated to Ca level up to and including 1.4 mmol l–1 and was not manifested above that level under the prevailing conditions. Elevating CMg above 0.25 mmol l–1 enhanced BER occurrence. Concentrations of Ca and Mg in tomato organs increased with the respective mineral concentration in irrigation solution, whereas each element was reduced in organs as a function of the increased solution concentration of the other. The Ca concentration in diagnostic leaves (the diagnostic leaf is the fully developed youngest leaf) for optimal fruit yield with minimum BER was found to be 1.6%. The optimum CCa for high fruit yield with minimal BER occurrence was found to be in the range of 1.5–2.5 mmol l–1 combined with CMg at 0.25 mmol l–1.
High-throughput phenotyping is a rapidly evolving field, with new technologies being developed that need to be tested under different experimental conditions. In this study, the PlantEye, a high-resolution three-dimensional (3D) laser scanner was used to phenotype wheat plants grown under control and salt stress in controlled environment conditions. The PlantEye scans plants from overhead, creating a data cloud from which the system computes traits such as 3D leaf area, plant height and leaf number. Moderately high correlations were observed between automatically calculated trait; 3D leaf area, and the manually measured traits leaf area, fresh biomass and dry biomass, although correlations were lower than those reported in previous studies in different crop species. As expected, salt stress caused significant reduction in plant growth, particularly leaf area and biomass production, which resulted in significantly reduced grain number and yield. The results here suggest that PlantEye was effective in phenotyping wheat, although improvements in the system setup, data processing and customer support would make this phenotyping tool suitable to be widely adopted for a range of plant species under diverse environmental conditions.
Polyhalite is a hydrated sulfate of potassium (K), calcium (Ca) and magnesium (Mg) with the formula: K2Ca2Mg(SO4)4·2H2O. The main objective of the present study was to investigate and compare the efficiency of polyhalite as a fertilizer supplying K, Ca, Mg and sulfur (S) relative to equivalent soluble salts. The specific objectives were to investigate: 1. The release and transport of Ca, Mg, K and S in soil; 2. Uptake of these minerals by wheat plants and 3. Biomass production of wheat plants. To meet these objectives, two pot experiments (20 l pots filled with dune sand) were conducted in which the effects of four doses of polyhalite (0, 500, 1,500 and 2,500 kg/ha) and one dose of Ca, Mg and K sulfate salts (equivalent to the 1500 kg/ha polyhalite dose) were investigated. In a third experiment, residual effects of the fertilizers were studied using the pots from the first experiment. Different leaching fractions were used in the experiments (30% in the first one and 7–10% in the second and third experiments), to investigate the effect of water management on mineral transportation in the soil and plant uptake. Polyhalite was found to be a more efficient fertilizer for supplying K, Ca, Mg and S relative to equivalent soluble salts. To meet the plant required ratios for Ca, Mg and K, the polyhalite dose should be applied accordingly to provide sufficient Ca and Mg, and additional fertilizers should be used as a source of K. Transport and leaching of Ca, Mg, K and S in soil following polyhalite application was lower than following the application of the equivalent sulfate salts. The residual effect of polyhalite fertilizer on the subsequently grown crop was higher than the effect from the equivalent sulfate salts, especially regarding Ca, Mg and S. Irrigation management, as determined by the leaching fraction, has a strong impact on the efficiency of polyhalite as a source of K, Ca, Mg and S for plant nutrition.
Eucalyptus silver dollar (Eucalyptus cinerea) is cultivated under intensive agronomic practices for production of cut foliage branches for the floriculture industry. A range of damage symptoms, suspected to be related to unoptimized mineral nutrition, routinely occur in the leaves at the production plantations and reduce yield quality. No information is available about the nutritional requirements of Eucalyptus silver dollar, or of any other Eucalyptus species under intense cultivation for cut foliage branches production. In this study we evaluated the hypotheses that: (1) leaf damage symptoms in the Eucalyptus silver dollar plantations might be related to the nutritional status of the leaves; and (2) they are affected by environmental and growing conditions, and will therefore differ between seasons and location of the plantations. To test these hypotheses we studied the seasonal and location variations in the ionomics of damaged and healthy leaves, physiological parameters, and postharvest attributes of cut foliage branches during vase life in four plantations of Eucalyptus silver dollar in Israel. The observed leaf symptoms were also characterized anatomically. The range of concentrations for individual macronutrients in the leaves was (in g kg–1): N (18–40); P (1.2–3.0); K (5.5–17.0); Ca (3.5–14.0); Mg (1.1–2.8); S (1.3–2.6). The concentrations range for micronutrients was (in mg kg–1): B (10–100); Fe (30–170); Zn (14–27); Mn (38–190); Cu (3.5–5.9). None of the identified leaf symptoms correlated with a consistent increase or decrease of the content of a specific mineral nutrient or heavy metal compared to the healthy leaves, suggesting that they were not caused by mineral deficiency or toxicity. The leaf ionomics was affected by season and varied between locations. The main damage symptoms observed in the four examined plantations during the four harvests were red and purple spots, and oil stains. Postharvest experiments showed that the quality of branches was reduced during 7–15 days of vase life following transport simulation to the local market. The degree of reduced quality during vase life was also dependent on the location of the plantation and the season of harvest. The oil stains appeared in the two most southern locations during summer, suggesting that this symptom might be derived from the summer conditions such as the high temperatures and high light intensities occurring in the southern part of Israel.
Semi-arid and arid regions are characterized by water scarcity and long dry summers. To ensure continued food supply and to combat desertification in these regions, marginal waters such as saline water and treated domestic sewage (effluent) are increasingly used for irrigation. These conditions may decrease plant growth and fruit yields of vegetables, which are relatively sensitive to environmental stress, and increase the accumulation in plant shoots of toxic elements which could enter the human food supply. In addition, the use of highly saline water for irrigation may increase the susceptibility of plants to soil and airborne pathogens. Experiments conducted in the field and in greenhouses show that grafting, a horticultural technique whereby tissues from one plant are inserted into those of another so that the two sets of vascular tissues may join, in general increases the tolerance of vegetable plants to salinity, high concentrations of toxic elements, and soilborne diseases. Moreover, the concentrations of toxic elements, such as B, Zn, Sr, Mn, Cu, Ti, Cr, Ni, Cd, and Na are lower in the tissues of grafted than in those of nongrafted plants. This difference is most likely a result of exclusion of toxic elements by the rootstock of the grafted plants. It is suggested that grafting could be a useful tool to increase the tolerance of vegetable plants to salt, toxic elements, and soilborne diseases, and to prevent the entry of contaminants and saline elements into the human food supply under arid and semi-arid conditions.
Phenomics is a relatively new approach by breeders, who use modern sensors for monitoring germplasm performance and as a selection tool. Plant physiologists can also make use of phenotyping in their studies, which usually focus on plant response to abiotic and biotic stresses. Simple active radiometer sensors such as RapidScan enable phenotyping within the framework of field experiments, and may open new horizons for breeders. The objectives of this study were to: (i) test the ability of vegetation indices (VIs) to distinguish between wheat cultivars during the entire growth period; and (ii) evaluate the accuracy of yield estimation based on only one or a few monitoring days. The following studies were conducted to test RapidScan as a tool for wheat phenotyping in the field: (i) response of 10 cultivars to water deficiency; (ii) response of 13 cultivars to late top N application. Plants were scanned weekly. The default VI parameters, NDVI and NDRE, could be used to show development during the growing season. However, due to low repeatability, it was almost impossible to use these indices for cultivar differentiation, unless there was wide variation in the cultivar phenotype. Nevertheless, combining the data from a few monitoring days improved cultivar classification and yield estimation. Although variation between fields and treatments affected the VI vs. crop parameter relationships more than the within-field variation, the results showed that the use of the proximal-sensing technique allows for rapid and quite accurate phenotyping. Thus, RapidScan can assist breeders during breeding programs for wide-scale in-field phenotyping.
The link of the Mediterranean Sea to the Indian and Pacific Oceans was artificially created with the opening of the first Suez Canal in 1897, and the second in 2015, allowing the direct passage of marine organisms into the Eastern Mediterranean Sea. About 307 macroalgae (seaweeds) exist in the Israeli Mediterranean shores. The current study lists marine macroalgae within the Levant basin described after the year 1900, with special focus on species from Israeli shores. We identified 86 species for the whole Levant area regarded as exotic, namely, introduced by artificial vectors derived from human activities, including arrivals via the Suez Canal (Lessepsian invasion). Of those 86 species, 42 are Rhodophyta, 23 are Chlorophyta and 21 are Ochrophyta. Further, about 68% are of Indo-Pacific origin, 20% of Atlantic origin, with 12% of the species of uncertain origin. With precaution, we suggest that about 16% of the marine flora in the Israeli Mediterranean shores are of exotic nature. This survey also indicates that about half of the exotic Ochrophyta are of Atlantic origin, while there are no reports of Chlorophyta of Atlantic origin in the Levant basin. Key aspects when evaluating the exotic nature of marine macroalgae are the trustworthiness of past taxonomic identification and long-term records and description of seaweed collections, both particularly troublesome for the Levant basin.
Allium palaestinum, a long-forgotten taxon of arid Israel and Jordan, is re-described here. The new description is based on Kolmann's work in 1971 and on living plants and fresh herbarium specimens. Independence of the species is confirmed not only by differing morphological and ecological features of the nearest related Allium species, but also by molecular methods. Hence, the species is no longer treated within Allium neapolitanum. Discussion on phylo-geography, distribution, conservation status and habitat is provided.