Effect of macronutrient fertilization on olive oil composition and quality under irrigated, intensive cultivation management.

BACKGROUND: Intensive olive (Olea europaea L.) orchards are fertilized, mostly with the macronutrients nitrogen (N), phosphorus (P) and potassium (K). The effects of different application levels of these nutrients on olive oil composition and quality were studied over 6 years in a commercial intensively cultivated 'Barnea' olive orchard in Israel. RESULTS: Oil quality and composition were affected by N, but not P or K availability. Elevated N levels increased free fatty acid content and reduced polyphenol level in the oil. Peroxide value was not affected by N, P or K levels. The relative concentrations of palmitoleic, linoleic and linolenic fatty acids increased with increasing levels of N application, whereas that of oleic acid, monounsaturated-to-polyunsaturated fatty acid ratio and oleic-to-linoleic ratio decreased. CONCLUSION: These results indicate that intensive olive orchard fertilization should be carried out carefully, especially where N application is concerned, to avoid a decrease in oil quality due to over-fertilization. Informed application of macronutrients requires leaf and fruit analyses to establish good agricultural practices, especially in view of the expansion of olive cultivation to new agricultural regions and soils. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Phosphorus fertilization induces nectar secretion for honeybee visitation and cross-pollination of almond trees.

Precise phosphorus (P) application requires a mechanistic understanding of mineral effects on crop biology and physiology. Photosynthate assimilation, metabolism, and transport require phosphorylation, and we postulated that P is critical for the bloom and fruit-set of almond trees that rely on stored carbohydrate reserves. Hence, we studied the growth, physiology and carbohydrate dynamics in 2-year-old almond trees irrigated with P concentrations between 1 mg l-1 and 20 mg l-1. Almond trees attained maximal photosynthesis, transpiration, and growth by 6 mg P l-1 irrigation. Nevertheless, almond trees continued to extract P in 10 mg P l-1 and 15 mg P l-1 irrigations, which corresponded to larger yields. We attributed the augmented productivity to increased fruit-set (59% between 6 mg P l-1 and 15 mg P l-1), caused by more frequent (29%) honeybee visits. High P improved pollinator visitation by enabling almond trees to utilize more of their starch reserves for nectar secretion (which increased by ~140% between 6 mg P l-1 and 15 mg P l-1). This work elucidates the benefits of P fertilization to plant-pollinator mutualism, critical to almond productivity, and reveals novel indices for optimal P application in almond orchards.

Productivity versus drought adaptation in olive leaves: Comparison of water relations in a modern versus a traditional cultivar.

The physiological traits that set the tradeoff between productivity and drought adaptation in plants are still under debate. To reveal these traits, we compared the water relations of two olive (Olea europaea) cultivars: "Barnea"-a highly productive modern cultivar; and "Souri"-a drought-adapted traditional cultivar. We hypothesized that Souri has lower hydraulic conductivity and lower hydraulic vulnerability. The hypothesis was tested at the leaf level. The soil volumetric water content (θ), stem water potential (ΨS ), and gas exchange were measured in both cultivars while they dried until a significant reduction in their maximal photochemical potential (Fv /Fm  < 0.6) was obtained. Additionally, pressure-volume relations, leaf hydraulic vulnerability, and the petiole xylem architecture were evaluated. To our surprise, Souri's leaf hydraulic conductivity was more vulnerable to low ΨS , approaching zero at -8 MPa compared with <-10 MPa in "Barnea." At the same time, Souri's higher osmotic content and cell rigidity enabled it to sustain 1.4 MPa lower ΨS , while maintaining near optimal (Fv /Fm ). However, both cultivars significantly reduced their Fv /Fm (<0.6) at the same θ, suggesting that the capability to sustain a low θ is not the issue. Instead, Souri's lower transpiration enabled it to withstand a longer drought while avoiding low θ. Barnea's larger xylem vessels and hydraulic conductivity supported higher stomatal conductance (gs ) and assimilation rate, which nurtured its higher productivity but resulted in quick depletion of θ. These results suggest that hydraulic resistance or the ability to sustain low θ do not set the tradeoff between productivity and drought adaptation in olive leaves.

Anti-Herpes Simplex 1 Activity of Simmondsia chinensis (Jojoba) Wax.

Jojoba (Simmondsia chinensis (Link) Schneider) wax is used for various dermatological and pharmaceutical applications. Several reports have previously shown beneficial properties of Jojoba wax and extracts, including antimicrobial activity. The current research aimed to elucidate the impact of Jojoba wax on skin residential bacterial (Staphylococcus aureus and Staphylococcus epidermidis), fungal (Malassezia furfur), and virus infection (herpes simplex 1; HSV-1). First, the capacity of four commercial wax preparations to attenuate their growth was evaluated. The results suggest that the growth of Staphylococcus aureus, Staphylococcus epidermidis, and Malassezia furfur was unaffected by Jojoba in pharmacologically relevant concentrations. However, the wax significantly attenuated HSV-1 plaque formation. Next, a complete dose-response analysis of four different Jojoba varieties (Benzioni, Shiloah, Hatzerim, and Sheva) revealed a similar anti-viral effect with high potency (EC50 of 0.96 ± 0.4 µg/mL) that blocked HSV-1 plaque formation. The antiviral activity of the wax was also confirmed by real-time PCR, as well as viral protein expression by immunohistochemical staining. Chemical characterization of the fatty acid and fatty alcohol composition was performed, showing high similarity between the wax of the investigated varieties. Lastly, our results demonstrate that the observed effects are independent of simmondsin, repeatedly associated with the medicinal impact of Jojoba wax, and that Jojoba wax presence is required to gain protection against HSV-1 infection. Collectively, our results support the use of Jojoba wax against HSV-1 skin infections.

Rangeland sharing by cattle and bees: moderate grazing does not impair bee communities and resource availability.

Rangelands are a dominant anthropogenic land use and a main driver of natural habitat loss worldwide. Land sharing, the integration of agricultural production and biodiversity conservation, may provide a platform for managing rangelands to fulfill multiple ecosystem services. However, livestock grazing can greatly affect biodiversity and little is known about its effects on providers of focal ecosystem services, such as pollinators. We investigated the effect of cattle grazing on bee communities and their foraging and nesting resources in Mediterranean rangelands. Specifically, we explored the effect of moderate cattle grazing on flowering plant abundance, species richness and composition, the diversity of nesting substrates, and consequently, the possible effects on wild bee and honey bee foraging activity, species diversity, and community composition. We conducted field research in the Mediterranean rangelands of Israel during the main bee activity season, in the spring of 2012 and 2013, comparing paired cattle-grazed and ungrazed areas. The availability of floral and nesting resources for bees was unaffected or positively affected by grazing. Similarly, wild bee abundance, species richness, and composition were not affected by grazing, but were instead shaped by spatiotemporal factors. Nor was honey bee activity level impaired by grazing. The foraging preferences of bees, as well as flower species composition and peak bloom differed between grazed and ungrazed areas. Therefore, in our studied rangelands, grazing had its main effect on the foraging choices of honey bees and wild bees, rather than on their abundance and diversity. Moreover, our results indicate the potentially important role of ungrazed patches in increasing nectar and pollen diversity and availability in rangelands for both honey bees and wild bees in the spring. Hence, maintaining a mosaic of moderately grazed and ungrazed patches is expected to provide the greatest benefits for wild bee conservation and honey bee activity in Mediterranean rangelands. Our findings support the notion of rangeland sharing by cattle and bees in Mediterranean ecosystems under moderate grazing intensities, mimicking the coexistence of honey bees, wild bees, and cattle in Mediterranean ecosystems on an evolutionary timescale.

Effects of nitrogen fertilization on pomegranate fruit, aril and juice quality.

BACKGROUND: Nitrogen (N) fertilization influences plant growth and yield, and may also affect fruit quality. For two consecutive seasons, we examined the effects of various N fertilization levels - 5 to 200 mg L-1  - on pomegranate fruit, aril and juice quality. Evaluations included fruit and aril weight, size and color, appearance of peel blemishes, internal black rot and nutritional composition of extracted juices. RESULTS: Nitrogen fertilization affected pomegranate fruit, aril and juice quality. The most pronounced effects were observed in trees grown under the lowest N fertilization level, which bore smaller fruit and arils, the latter with lighter color; the fruit suffered from sunburn, and the juice had lower total soluble solid, acidity and anthocyanin contents. The proportion of edible aril weight per total fruit weight gradually increased with an increase in N fertilization concentration. In contrast, N fertilization did not affect peel color, roughness or cracking incidence. Black rot incidence increased with increasing N concentration. CONCLUSIONS: Nitrogen fertilization affected pomegranate fruit, aril and juice quality, and the total number of marketable fruits per tree. The optimal N fertilization levels, which were most beneficial for achieving high-quality marketable fruit, were between 40 and 100 mg L-1 . © 2019 Society of Chemical Industry.

Natural Variation in Flower Color and Scent in Populations of Eruca sativa (Brassicaceae) Affects Pollination Behavior of Honey Bees.

Plants of Eruca sativa Mill. (Brassicaceae) from desert and Mediterranean populations in Israel differ in flower color and size. In the desert habitat, the population has higher abundance of flowers with cream color and longer petals, whereas in the Mediterranean habitat, the population has higher abundance of flowers with yellow and shorter petals. Choice experiments with honey bee foragers (Apis mellifera Linn., Apidae, Hymenoptera), the main pollinator in the natural habitat in Israel, confirmed that they are more attracted to the yellow flower morph than to the cream one. A proboscis extension response test indicated that honey bees are able to discriminate between flower scents of the desert and Mediterranean populations. Considering the advantage of plants of the yellow morph in attracting pollinators, we further tested in a common garden experiment whether these possess higher fitness than plants of the desert population. Indeed, a significant association was found between flower color and fruit set, and seed mass. In general, our results provide evidence for ecotypic differentiation between populations imposed by pollinators. The advantage of the yellow color morph in attracting pollinators may explain its dominance among plants of the Mediterranean population. We discuss why the cream color morph may be dominant in the desert habitat, considering the possibility of different pollinators, tradeoffs between traits, or pleiotropy.

Irrigation-induced salinity affects olive oil quality and health-promoting properties.

BACKGROUND: Olive oil, a functional food, is increasingly produced from trees irrigated with water containing high concentrations of salts. We studied the effects of irrigation-induced salinity on quality and health-related compounds in olive oil. Trees (cv Barnea) were grown in lysimeters with continuous control and monitoring of root-zone salinity. Salinity in the root zone was altered by changing irrigation solution salinity or by changing the extent of leaching. Extracted oil was analyzed for quality parameters including free fatty acid content, polyphenol, tocopherol, sterol and carotenoid levels, fatty acid (FA) profile, and antioxidative capacity. RESULTS: While not all parameters changed, fruit water percentage and fruit oil content significantly decreased with increasing exposure to salt. As salinity increased, there was a desirable rise in measured polyphenol and tocopherol levels and a contrasting undesirable reduction in a number of important compounds, including 16:1 and 18:3 FA. CONCLUSION: The possible negative effects on olive oil quality due to FA-related parameters should concern producers dependent on, or considering, irrigation with high-salinity water sources. A number of important quality parameters were differentially influenced by the method of inducing the root zone salinity, suggesting that additional environmental variables leading to oxidative responses were affected by the treatments. © 2018 Society of Chemical Industry.

Effects of reclaimed wastewater irrigation and fertigation level on olive oil composition and quality.

BACKGROUND: Irrigation of olives increases fruit and oil yields. Due to scarcity of freshwater, low-quality water including recycled wastewater (RWW) is utilized in orchards. Here, effects of irrigation with RWW and of fertilization on the composition and quality of olive oil were studied. RESULTS: Long-term RWW irrigation of 'Barnea' and 'Leccino' olive had no significant negative effects on either oil composition or quality parameters, including free fatty acids (FFAs), peroxide value (PV), total phenolics content (TPC), fatty acid profiles and organoleptic characteristics. The average FFA contents for both cultivars were less than 0.8% during most of the experimental period, except the seasons 2009 and 2012-2013 for Barnea where the values were raised up to 1.4%. The measured PV levels were less than 9 and 5 mmol O2 kg-1 oil for Barnea and Leccino, respectively. In the last season of the experiment for each cultivar, higher TPC were observed in oils obtained from RWW irrigation with reduced fertilization (Re-) as compared to the treatments with the recommended fertilization [freshwater irrigation (Fr) and RWW irrigation (Re+) with standard dose of fertilizers], where the TPC increment exceeded 70% in Barnea and 25% in Leccino. The treatments had only minor effects on the fatty acid profile, reflected in slightly altered levels of C18:2 and C18:3 fatty acids. CONCLUSION: The use of RWW, combined with the consideration of nutrients arriving with such water to provide appropriate fertilization, was found suitable for olive irrigation to ensure optimal yields while preserving oil quality. © 2019 Society of Chemical Industry.

Omega-3 deficiency impairs honey bee learning.

Deficiency in essential omega-3 polyunsaturated fatty acids (PUFAs), particularly the long-chain form of docosahexaenoic acid (DHA), has been linked to health problems in mammals, including many mental disorders and reduced cognitive performance. Insects have very low long-chain PUFA concentrations, and the effect of omega-3 deficiency on cognition in insects has not been studied. We show a low omega-6:3 ratio of pollen collected by honey bee colonies in heterogenous landscapes and in many hand-collected pollens that we analyzed. We identified Eucalyptus as an important bee-forage plant particularly poor in omega-3 and high in the omega-6:3 ratio. We tested the effect of dietary omega-3 deficiency on olfactory and tactile associative learning of the economically highly valued honey bee. Bees fed either of two omega-3-poor diets, or Eucalyptus pollen, showed greatly reduced learning abilities in conditioned proboscis-extension assays compared with those fed omega-3-rich diets, or omega-3-rich pollen mixture. The effect on performance was not due to reduced sucrose sensitivity. Omega-3 deficiency also led to smaller hypopharyngeal glands. Bee brains contained high omega-3 concentrations, which were only slightly affected by diet, suggesting additional peripheral effects on learning. The shift from a low to high omega-6:3 ratio in the Western human diet is deemed a primary cause of many diseases and reduced mental health. A similar shift seems to be occurring in bee forage, possibly an important factor in colony declines. Our study shows the detrimental effect on cognitive performance of omega-3 deficiency in a nonmammal.

Testing the potential significance of different scion/rootstock genotype combinations on the ecology of old cultivated olive trees in the southeast Mediterranean area.

BACKGROUND: A previous multi-locus lineage (MLL) analysis of SSR-microsatellite data of old olive trees in the southeast Mediterranean area had shown the predominance of the Souri cultivar (MLL1) among grafted trees. The MLL analysis had also identified an MLL (MLL7) that was more common among rootstocks than other MLLs. We here present a comparison of the MLL combinations MLL1 (scion)/MLL7 (rootstock) and MLL1/MLL1 in order to investigate the possible influence of rootstock on scion phenotype. RESULTS: A linear regression analysis demonstrated that the abundance of MLL1/MLL7 trees decreases and of MLL1/MLL1 trees increases along a gradient of increasing aridity. Hypothesizing that grafting on MLL7 provides an advantage under certain conditions, Akaike information criterion (AIC) model selection procedure was used to assess the influence of different environmental conditions on phenotypic characteristics of the fruits and oil of the two MLL combinations. The most parsimonious models indicated differential influences of environmental conditions on parameters of olive oil quality in trees belonging to the MLL1/MLL7 and MLL1/MLL1 combinations, but a similar influence on fruit characteristics and oil content. These results suggest that in certain environments grafting of the local Souri cultivar on MLL7 rootstocks and the MLL1/MLL1 combination result in improved oil quality. The decreasing number of MLL1/MLL7 trees along an aridity gradient suggests that use of this genotype combination in arid sites was not favoured because of sensitivity of MLL7 to drought. CONCLUSIONS: Our results thus suggest that MLL1/MLL7 and MLL1/MLL1 combinations were selected by growers in traditional rain-fed cultivation under Mediterranean climate conditions in the southeast Mediterranean area.

Genetic variation of naturally growing olive trees in Israel: from abandoned groves to feral and wild?

BACKGROUND: Naturally growing populations of olive trees are found in the Mediterranean garrigue and maquis in Israel. Here, we used the Simple Sequence Repeat (SSR) genetic marker technique to investigate whether these represent wild var. sylvestris. Leaf samples were collected from a total of 205 trees at six sites of naturally growing olive populations in Israel. The genetic analysis included a multi-locus lineage (MLL) analysis, Rousset's genetic distances, Fst values, private alleles, other diversity values and a Structure analysis. The analyses also included scions and suckers of old cultivated olive trees, for which the dominance of one clone in scions (MLL1) and a second in suckers (MLL7) had been shown earlier. RESULTS: The majority of trees from a Judean Mts. population and from one population from the Galilee showed close genetic similarity to scions of old cultivated trees. Different from that, site-specific and a high number of single occurrence MLLs were found in four olive populations from the Galilee and Carmel which also were genetically more distant from old cultivated trees, had relatively high genetic diversity values and higher numbers of private alleles. Whereas in two of these populations MLL7 (and partly MLL1) were found in low frequency, the two other populations did not contain these MLLs and were very similar in their genetic structure to suckers of old cultivated olive trees that originated from sexual reproduction. CONCLUSIONS: The genetic distinctness from old cultivated olive trees, particularly of one population from Galilee and one from Carmel, suggests that trees at these sites might represent wild var. sylvestris. The similarity in genetic structure of these two populations with the suckers of old cultivated trees implies that wild trees were used as rootstocks. Alternatively, trees at these two sites may be remnants of old cultivated trees in which the scion-derived trunk died and was replaced by suckers. However, considering landscape and topographic environment at the two sites this second interpretation is less likely.

The effect of water stress on super-high- density 'Koroneiki' olive oil quality.

BACKGROUND: Over the last two decades, the area of cultivated super-high-density olive orchards has increased rapidly. Water stress is an important tool in super-high-density orchards to reduce tree growth and promote suitability for overhead mechanical harvesters. Little is known regarding the effect of water stress in super-high-density orchards on oil quality parameters. In this study the effect of irrigation rate on oil quality parameters was evaluated in a six-year-old super-high-density 'Koreneiki' olive orchard for five consecutive seasons. Five water status levels, determined by irrigating in order to maintain various midday stem water potential threshold values (-1.5, -2, -2.5, -3 and -4 MPa), were applied during the oil accumulation stage. RESULTS: The MUFA/PUFA ratio and free fatty acid content generally decreased as a function of increasing tree water stress. In most seasons a reduction in polyphenols was found with decreasing irrigation level. Peroxide value was not affected by the water stress level. CONCLUSION: The present study demonstrates that limiting irrigation and exposure of olive trees to water stress in a super-high-density orchard lowers free fatty acid content and therefore benefits oil quality. However, the decreased MUFA/PUFA ratio and the reduction in polyphenol content that were also found under increased water stress negatively influence oil quality.

A comparative analysis of genetic variation in rootstocks and scions of old olive trees - a window into the history of olive cultivation practices and past genetic variation.

BACKGROUND: Past clonal propagation of olive trees is intimately linked to grafting. However, evidence on grafting in ancient trees is scarce, and not much is known about the source of plant material used for rootstocks. Here, the Simple Sequence Repeat (SSR) marker technique was used to study genetic diversity of rootstocks and scions in ancient olive trees from the Levant and its implications for past cultivation of olives. Leaf samples were collected from tree canopies (scions) and shoots growing from the trunk base (suckers). A total of 310 trees were sampled in 32 groves and analyzed with 14 SSR markers. RESULTS: In 82.7% of the trees in which both scion and suckers could be genotyped, these were genetically different, and thus suckers were interpreted to represent the rootstock of grafted trees. Genetic diversity values were much higher among suckers than among scions, and 194 and 87 multi-locus genotypes (MLGs) were found in the two sample groups, respectively. Only five private alleles were found among scions, but 125 among suckers. A frequency analysis revealed a bimodal distribution of genetic distance among MLGs, indicating the presence of somatic mutations within clones. When assuming that MLGs differing by one mutation are identical, scion and sucker MLGs were grouped in 20 and 147 multi-locus lineages (MLLs). The majority of scions (90.0%) belonged to a single common MLL, whereas 50.5% of the suckers were single-sample MLLs. However, one MLL was specific to suckers and found in 63 (22.6%) of the samples. CONCLUSIONS: Our results provide strong evidence that the majority of olive trees in the study are grafted, that the large majority of scions belong to a single ancient cultivar containing somatic mutations, and that the widespread occurrence of one sucker genotype may imply rootstock selection. For the majority of grafted trees it seems likely that saplings were used as rootstocks; their genetic diversity probably is best explained as the result of a long history of sexual reproduction involving cultivated, feral and wild genotypes.

Topical application of jojoba (Simmondsia chinensis L.) wax enhances the synthesis of pro-collagen III and hyaluronic acid and reduces inflammation in the ex-vivo human skin organ culture model.

Jojoba (Simmondsia chinensis L.) wax was previously reported to increase cutaneous wound healing, ameliorate acne and psoriasis manifestations, and reduce oxidative stress and inflammation. However, its potential cosmetic properties have not been fully investigated. Thus, the current study aimed to evaluate the anti-inflammatory activities of jojoba wax and its impact on the synthesis of extracellular components following topical application. The fatty acid and fatty alcohol profiles of two industrial and two lab-scale cold-press jojoba waxes were analyzed along with total tocopherol and phytosterol content. The dermo-cosmetic effect of all jojoba wax preparations was evaluated ex-vivo, using the human skin organ culture model, which emulates key features of intact tissue. The ability of jojoba wax to reduce secreted levels of key pro-inflammatory cytokines and the safety of the applications in the ex-vivo model were evaluated. In addition, the impact on the synthesis of pro-collagen and hyaluronic acid levels upon treatment was investigated. The results demonstrate that topically applied jojoba wax can reduce LPS-induced secretion of IL-6, IL-8, and TNFα by approx. 30% compared to untreated skin. This effect was enhanced when treatment was combined with low non-toxic levels of Triton X-100, and its efficacy was similar to the anti-inflammatory activity of dexamethasone used as a positive control. In addition, mRNA and protein levels of collagen III and synthesis of hyaluronic acid were markedly increased upon topical application of jojoba. Moreover, the enhanced content of extracellular matrix (ECM) components correlated with the enhanced expression of TGFß1. Collectively, our results further demonstrate that jojoba can reduce local skin inflammation, and this effect may be increased by emulsifier which increases its bioavailability. In addition, the finding that topical application of jojoba wax enhances the synthesis of pro-collagen and hyaluronic acid and may be beneficial in the treatment of age-related manifestations.

The history of olive cultivation in the southern Levant.

The olive tree (Olea europaea L. subsp. europaea var. europaea) is one of the most important crops across the Mediterranean, particularly the southern Levant. Its regional economic importance dates at least to the Early Bronze Age (~3600 BCE) and its cultivation contributed significantly to the culture and heritage of ancient civilizations in the region. In the southern Levant, pollen, pits and wood remains of wild olives (O. europaea subsp. europaea var. sylvestris) has been found in Middle Pleistocene sediments dating to approximately 780 kya, and are present in numerous palynological sequences throughout the Pleistocene and into the Holocene. Archeological evidence indicates the olive oil production from at least the Pottery Neolithic to Chalcolithic transition (~7600-7000 BP), and clear evidence for cultivation by, 7000 BP. It is hypothesized that olive cultivation began through the selection of local genotypes of the wild var. sylvestris. Local populations of naturally growing trees today have thus been considered wild relatives of the olive. However, millennia of cultivation raises questions about whether genuine populations of var. sylvestris remain in the region. Ancient olive landraces might thus represent an ancient genetic stock closer to the ancestor gene pool. This review summarizes the evidence supporting the theory that olives were first cultivated in the southern Levant and reviews our genetic work characterizing local ancient cultivars. The significance and importance of old cultivars and wild populations are discussed, given the immediate need to adapt agricultural practices and crops to environmental degradation and global climate change.

Elevated fruit nitrogen impairs oil biosynthesis in olive (Olea europaea L.).

Oil in fruits and seeds is an important source of calories and essential fatty acids for humans. This specifically holds true for olive oil, which is appreciated for its superior nutritional value. Most olive orchards are cultivated to produce oil, which are the outcome of fruit yield and oil content. Little information is available on the effect of nitrogen (N) on olive fruit oil content. The response of olive trees to different rates of N was therefore studied in soilless culture (3 years) and commercial field (6 years) experiments. In both experiments, fruit N level and oil biosynthesis were negatively associated. Fruit N increased in response to N fertilization level and was inversely related to fruit load. The negative correlation between fruit N and oil content was more pronounced under high fruit load, indicating sink limitation for carbon. These results agree with those reported for oilseed crops for which a trade-off between oil and protein was proposed as the governing mechanism for the negative response to elevated N levels. Our results suggest that the protein/oil trade-off paradigm cannot explain the noticeable decrease in oil biosynthesis in olives, indicating that additional mechanisms are involved in N-induced inhibition of oil production. This inhibition was not related to the soluble carbohydrate levels in the fruit, which were comparable regardless of N level. These results emphasize the importance of balanced N nutrition in oil-olive cultivation to optimize production with oil content.

Optimizing Nitrogen Application for Jojoba under Intensive Cultivation.

Although jojoba (Simmondsia chinensis) has been cultivated for years, information on its N requirements is limited. A 6-year study of mature jojoba plants grown under field conditions with an intensive management regime evaluated the effect of N application rate on plant nutrient status, growth, and productivity, and nitrate accumulation in the soil. Five levels of N application were tested: 50, 150, 250, 370, and 500 kg N ha-1. Fertilizers were provided throughout the growing season via a subsurface drip irrigation system. Leaf N concentration, in both spring and summer, reflected the level of N applied. A diagnostic leaf (youngest leaf that has reached full size) concentration of 1.3% N was identified as the threshold for N deficiency. Increasing rates of N application resulted in higher P levels in young leaves. Plant K status, as reflected in the leaf analysis, was not affected by N treatment but was strongly affected by fruit load. Vegetative growth was inhibited when only 50 kg N ha-1 was applied. Soil analysis at the end of the fertilization season showed substantial accumulation of nitrate for the two highest application rates. Considering productivity, N costs, and environmental risk, 150 kg N ha-1 is the recommended dosage for intensively grown jojoba. N deficiencies can be identified using leaf analysis, and excess N can be detected via soil sampling toward the end of the growing season. These results and tools will facilitate precise N fertilization in intensive jojoba plantations.

Canopy-cooling systems applied on avocado trees to mitigate heatwaves damages.

With climate change, spring heatwaves have become frequent in the Mediterranean region. High temperatures combined with wind and low humidity are problematic for subtropical crops adapted to high humidity and mild climate. Avocado is a valuable crop-nutritionally and economically-and many new orchards are planted in Mediterranean areas. Spring heatwaves increase avocado fruitlets dropping, severely decreasing yields. Addressing and solving the problem are necessary to maintain the crop's profitability. This study presents a sprinkler-based canopy cooling method that uses the existing pressurized irrigation system. The study aimed to test the system's performance during spring heatwaves, after the flowering season, in avocado orchards cultivated in a semi-arid region. The experiments examined the effect of various sprinkler types with varying flow rates and installation methods: sprayers, sprinklers and pulsing sprinklers, on foliage temperature, stem water potential, salt accumulation in the leaf, fruitlet survival and yield. The system reduced leaf temperatures by approximately 10 °C, significantly decreasing the trees' drought stress and increasing yields by 8-12%. Using low-quality water is possible, but requires adjustments to avoid salt damage to the leaves. The system can mitigate heat stress, and provides a relatively simple solution for handling spring heatwaves. The evaporative cooling system is modeled for semi-desert and desert conditions; the dry, windy climate contributes to the method's effectiveness.

Determining Reproductive Parameters, which Contribute to Variation in Yield of Olive Trees from Different Cultivars, Irrigation Regimes, Age and Location.

Olive (Olea europaea L.) trees can reach a very old age and still bear fruit. Although traditional groves are planted at low density and are rainfed, many newer groves are planted at higher densities and irrigated. As expected, initial yields per area are larger in high density plantations, yet some farmers claim they experience a reduction in productivity with grove age, even in well maintained trees. In order to test the accuracy of this claim and its underlying cause, we measured several productivity parameters in selected branches of trees in seven sites differing in cultivar ('Barnea' or 'Souri'), location and irrigation regime (rainfed or irrigated) for two consecutive years. For each site (cultivar/location/regime), we compared neighboring groves of different ages, altogether 14 groves. There was no consistent reduction in productivity in older groves. Differences in productivity between irrigated cultivars were mostly due to variation in the percentage of inflorescences that formed fruit. Several parameters were higher in irrigated, compared to rainfed 'Souri'. Differences in productivity between years within the same grove was mostly due to variation in the percentage of nodes forming inflorescences. We studied the expression of OeFT2 encoding a FLOWERING LOCUS T protein involved in olive flower induction in leaves of trees of different ages, including juvenile seedlings. Expression increased during winter in mature trees and correlated with the percentage of inflorescences formed. The leaves of juvenile seedlings expressed higher levels of two genes encoding APETALA2-like proteins, potential inhibitors of OeFT2 expression. The buds of juvenile seedlings expressed higher levels of OeTFL1, encoding a TERMINAL FLOWER 1 protein, a potential inhibitor of OeFT2 function in the meristem. Our results suggest that olives, once past the juvenile phase, can retain a similar level of productivity even in densely planted well maintained groves.