Foliar Levels Research Articles

Influence of Spotted Lanternfly (Lycorma delicatula) on Multiple Maple (Acer spp.) Species Canopy Foliar Spectral and Chemical Profiles

Invasive species have historically disrupted environments by outcompeting, displacing, and extirpating native species, resulting in significant environmental and economic damage. Developing approaches to detect the presence of invasive species, favorable habitats for their establishment, and predicting their potential spread are underutilized management strategies to effectively protect the environment and the economy. Spotted lanternfly (SLF, Lycorma delicatula) is a phloem-feeding planthopper native to China that poses a severe threat to horticultural and forest products in the United States. Tools are being developed to contain the spread and damage caused by SLF; however, methods to rapidly detect novel infestations or low-density populations are lacking. Vegetation spectroscopy is an approach that can represent vegetation health through changes in the reflectance and absorption of radiation based on plant physiochemical status. Here, we hypothesize that SLF infestations change the spectral and chemical characteristics of tree canopies. To test this hypothesis, we used a full range spectroradiometer to sample canopy foliage of silver maple (Acer saccharinum) and red maple (Acer rubrum) trees in a common garden in Berks County, Pennsylvania that were exposed to varying levels of SLF infestation. Foliar spectral profiles separated between SLF infestation levels, and the magnitude of separation was greater for the zero-SLF control compared with higher infestation levels. We found the red-edge and portions of the NIR and SWIR regions were most strongly related to SLF infestation densities and that corresponding changes in vegetation indexes related to levels of chlorophyll were influenced by SLF infestations, although we found no change in foliar levels of chlorophyll. We found no influence of SLF densities on levels of primary metabolites (i.e., pigments, nonstructural carbohydrates, carbon, and nitrogen), but did find an increase in the phenolic compound ferulic acid in response to increasing SLF infestations; this response was only in red maple, suggesting a possible species-specific response related to SLF feeding. By identifying changes in spectral and chemical properties of canopy leaves in response to SLF infestation, we can link them together to potentially better understand how trees respond to SLF feeding pressure and more rapidly identify SLF infestations.

Application of rock dust for the management of Meloidogyne javanica in soybean

This study aimed to assess the effects of rock dust on Meloidogyne javanica in soybean grown in autoclaved and non-autoclaved soil and investigate the impacts on plant foliar nutrition. The nematode reproduction experiment was conducted in two periods (Trials 1 and 2) in a 5 × 2 factorial design (rock dust rates of 0, 1000, 2000, 3000, and 4000 kg ha−1 × autoclaved and non-autoclaved soil). Soybean were inoculated with 2000 eggs + second-stage juveniles (J2) of M. javanica, and nematode and vegetative variables were evaluated at 60 days after inoculation (DAI). The penetration experiment followed a 2 × 2 factorial design (rock dust rates of 0 and 2500 kg ha−1 × autoclaved and non-autoclaved soil). Soybean were inoculated with 2000 eggs + J2 of M. javanica and evaluated at 5, 10, 15, 20, and 25 DAI. The shoot dry biomass from the reproduction experiment (Trial 1) was analyzed for macro- and micronutrients. In Trial 1, nematode reproduction decreased proportionally to the increase in rock dust rate in non-autoclaved soil. In Trial 2, the lowest nematode numbers were predicted to be achieved with rates of 2213 to 2309 kg ha−1, and nematode numbers were lower in autoclaved than in non-autoclaved soil. Rock dust reduced J2 penetration at 10 and 15 DAI, and there was no formation of females in treated plants. Rock dust application increased foliar levels of Fe, B, and Cu. Rock dust reduced M. javanica reproduction, penetration, and development in soybean and promoted gains in Fe, Cu, and B foliar contents.

Effect of Co-Inoculation with Growth-Promoting Bacteria and Arbuscular Mycorrhizae on Growth of Persea americana Seedlings Infected with Phytophthora cinnamomi.

Avocado is one of the most in-demand fruits worldwide and the trend towards its sustainable production, regulated by international standards, is increasing. One of the most economically important diseases is root rot, caused by Phythopthora cinnamomi. Regarding this problem, antagonistic microorganism use is an interesting alternative due to their phytopathogen control efficiency. Therefore, the interaction of arbuscular mycorrhizal fungi of the phylum Glomeromycota, native to the Peruvian coast (GWI) and jungle (GFI), and avocado rhizospheric bacteria, Bacillus subtilis and Pseudomonas putida, was evaluated in terms of their biocontrol capacity against P. cinnamomi in the "Zutano" variety of avocado plants. The results showed that the GWI and Bacillus subtilis combination increased the root exploration surface by 466.36%. P. putida increased aerial biomass by 360.44% and B. subtilis increased root biomass by 433.85%. Likewise, P. putida rhizobacteria showed the highest nitrogen (24.60 mg ∙ g-1 DM) and sulfur (2.60 mg ∙ g-1 DM) concentrations at a foliar level. The combination of GWI and Bacillus subtilis was the treatment that presented the highest calcium (16.00 mg ∙ g-1 DM) and magnesium (8.80 mg ∙ g-1 DM) concentrations. The microorganisms' multifunctionality reduced disease severity by 85 to 90% due to the interaction between mycorrhizae and rhizobacteria. In conclusion, the use of growth promoting microorganisms that are antagonistic to P. cinnamomi represents a potential strategy for sustainable management of avocado cultivation.

Trichoplusia ni Transcriptomic Responses to the Phytosaponin Aglycone Hederagenin: Sex-Related Differences

Many plant species, particularly legumes, protect themselves with saponins. Previously, a correlation was observed between levels of oleanolic acid-derived saponins, such as hederagenin-derived compounds, in the legume Medicago truncatula and caterpillar deterrence. Using concentrations that reflect the foliar levels of hederagenin-type saponins, the sapogenin hederagenin was not toxic to 4th instar caterpillars of the cabbage looper Trichoplusia ni nor did it act as a feeding deterrent. Female caterpillars consumed more diet than males, presumably to obtain the additional nutrients required for oogenesis, and are, thus, exposed to higher hederagenin levels. When fed the hederagenin diet, male caterpillars expressed genes encoding trypsin-like proteins (LOC113500509, LOC113501951, LOC113501953, LOC113501966, LOC113501965, LOC113499659, LOC113501950, LOC113501948, LOC113501957, LOC113501962, LOC113497819, LOC113501946, LOC113503910) as well as stress-responsive (LOC113503484, LOC113505107) proteins and cytochrome P450 6B2-like (LOC113493761) at higher levels than females. In comparison, female caterpillars expressed higher levels of cytochrome P450 6B7-like (LOC113492289). Bioinformatic tools predict that cytochrome P450s could catalyze the oxygenation of hederagenin which would increase the hydrophilicity of the compound. Expression of a Major Facilitator Subfamily (MFS) transporter (LOC113492899) showed a hederagenin dose-dependent increase in gene expression suggesting that this transporter may be involved in sapogenin efflux. These sex-related differences in feeding and detoxification should be taken into consideration in insecticide evaluations to minimize pesticide resistance.

Co-application of biochar and plant growth regulators improves maize growth and decreases Cd accumulation in cadmium-contaminated soil

To ensure the sustainable cultivation of agronomic crops in agricultural soils polluted with cadmium (Cd), the integrated application of Cd-remediation strategies at edaphic and foliar levels has been examined. However, the integrated application of biochar (BC) and plant growth regulators (PGRs) for mitigating Cd stress, especially in maize, remains unexplored. Additionally, the expression patterns of PGRs and heavy metal transporters during Cd stress are unknown. To address these gaps, a pot experiment (having four replications) was performed to explore the potential effects of the integrated application of BC (B0 = no BC added; B1 = low BC at 2.5% w/w; and B2 = high BC at 5% w/w) and PGRs (H0 = control; WS = water spray; GA = gibberellin, and IAA = auxin) on maize growth, Cd remediation, and productivity. The study was conducted following a factorial completely randomized design. The pots were artificially spiked with Cd (30 ppm) by using Cd(NO3)2 as a source. The synergistic application of IAA/GA and BC, improved the morphological characteristics, photosynthetic activity, stomatal conductance, and catalase activity of maize under Cd stress while simultaneously decreasing electrolyte leakage and oxidant activity. The leaf area, shoot fresh biomass (SFB), and root fresh biomass (RFB), were increased by (13.4, 11.7%), (52.8, 39.3%), and (89.2, 74.3%) in the synergistic application of PGRs (i.e., IAA and GA) + BC (5% w/w) treatments, respectively, than control. Furthermore, a drastic reduction in Cd uptake was observed in maize leaves by (201.53, 179.24%) under the dual application of PGRs + BC (5% w/w) treatments, compared to control, which altered Cd bioconcentration in plant parts and modified Cd species in the soil. Decreased expression of heavy metal transporter PMPCB gene and YCF1 indicated reduced Cd uptake in 5% w/w BC based on RT-PCR quantification. The synergistic application of BC with PGRs can serve as an environmentally friendly remediation to mitigate the hazardous effects of Cd stress on cultivated maize. This was achieved by reducing the bio-concentration and metal transport coefficients of Cd in plants through BC's absorption properties. Overall, applying BC and foliar application of PGRs could be suggested as a sustainable approach for cultivating crops on Cd-contaminated soils while ensuring safety.

What happens to trees and soils during five decades of experimental nitrogen loading?

High deposition of nitrogen was postulated to drive losses of NO3- and nutrient base cations, causing soil acidification, nutrient deficiencies reducing tree growth and ultimately tree mortality. We tested these predictions in a uniquely long-term study involving three NH4NO3 addition treatments (N1-N3) in a boreal Pinus sylvestris forest. The lowest level (N1), 30 kg N ha−1 yr−1 was applied during 50 years. Twice this rate (N2) was added 38 years, followed by 12 years of recovery, while thrice this rate (N3) was added 20 years followed by 30 years of recovery. We compared tree growth, changes in foliar and soil chemistry among treatments including control plots without N additions. As predicted, the N treatments lowered soil pH and reduced soil base saturation by around 50 %. They also lowered foliar levels of Ca, Mg, K, P and B initially, but after 50 years only Ca and Mg remained lower than in the control. Lack of B motivated a single addition of 2.5 kg ha−1 after ten years of N treatment. Tree stem growth became and then remained higher in N1 than in the other treatments through the 50 years of treatments. In N2 and N3, foliar δ15N increased during the N-loading phase, but declined during the recovery phase, indicating a return of ectomycorrhizal fungi and their role in tightening the N cycle in N-limited forests. In the terminated, initially highest N treatments, N2 and N3, the trees even show signs of returning to N-limitation. In these treatments, the soil base saturation remains lower, while the pH was only lower at 0–10 depth in the mineral soil, but not in the 10–20 cm depth horizon or in the superficial organic mor-layer. Accurately documenting the effect of N additions on forest growth required a long-term approach, where reasonable rates of application could be compared with extreme rates. Such long-term experiments are necessary to support forest management in achieving goals for developing future forests as they shift in response to major, global-scale changes.

Micronutrient Fertiliser Reinforcement by Fulvate–Lignosulfonate Coating Improves Physiological Responses in Tomato

Micronutrients are essential to plants, and enhancing their availability is one of the agronomic challenges to improving crop quality and yield. This study, under controlled greenhouse conditions, compares tomato plants’ responses to two different micronutrient EDTA-chelated formulations, one of them including a newly developed fulvate–lignosulfonate coating. Growth, yield, and several physiological parameters, including photosynthetic gas exchange, water-use efficiency, leaf nutrient content, leaf greenness and the effective quantum yield of photosystem II, were measured to compare their efficiency. The results showed that the new coated formulation significantly improved growth and most of the determined physiological parameters. At the end of the experiment, higher foliar levels of Fe (2.4-fold) and Mn (2.9-fold) were measured, revealing increased availability of lignofulfonate-complexed micronutrients compared to the traditional fertiliser. Moreover, the photosynthesis rate and stomatal conductance were 9- and 20-fold higher, respectively, than when using the standard fertiliser. In conclusion, the new coated fulvate–lignosulfonated fertiliser provided a more suitable source of micronutrients for tomato plant fertilisation, allowing for higher yields, which correlated with a generally improved physiological response.

Technological Quality of Sugarcane Inoculated with Plant-Growth-Promoting Bacteria and Residual Effect of Phosphorus Rates.

Phosphate fertilization in highly weathered soils has been a major challenge for sugarcane production. The objective of this work was to evaluate the foliar levels of phosphorus (P) and nitrogen (N) and the technological quality and productivity of second ratoon cane as a function of inoculation with plant-growth-promoting bacteria (PGPBs) together with the residual effect of phosphate fertilization. The experiment was carried out at the research and extension farm of Ilha Solteira, state of São Paulo, Brazil. The experiment was designed in a randomized block with three replications in a 5 × 8 factorial scheme. The treatments consisted of five residual doses of phosphorus (0, 45, 90, 135 and 180 kg ha-1 of P2O5, 46% P) applied at planting from the source of triple superphosphate and eight inoculations from three species of PGPB (Azospirillum brasilense, Bacillus subtilis and Pseudomonas fluorescens), applied in single or co-inoculation at the base of stems of sugarcane variety RB92579. Inoculation with PGPBs influenced leaf N concentration, while inoculations with Pseudomonas fluorescens and combinations of bacteria together with the highest doses exerted a positive effect on leaf P concentration. Co-inoculation with A. brasilense + Pseudomonas fluorescens associated with a residual dose of 135 kg ha-1 of P2O5 increased stem productivity by 42%. Thus, it was concluded that inoculations with Pseudomonas fluorescens and their combinations are beneficial for the sugarcane crop, reducing phosphate fertilization and increasing productivity.

Effects of biostimulants on the morphological growth of cocoa seedlings at the nursery stage

Biostimulants help cocoa plants to improve vegetative development and nutrient uptake, therefore, the objective was to evaluate the effects of biostimulants on morphological growth in cocoa seedlings in nursery stage, through a completely randomized experimental design with four treatments (T1: control, T2: humic acids + fulvic acids, T3: silicon oxide + monosilicic acid; and T4: marine algae + humic and fulvic acids) and four replicates. The results showed no significant differences in variables such as plant height (T4: 29.63 cm), number of leaves (T2: 25.19) and root length (T2: 37.23 cm). Significant differences were found in stem diameter (T3: 7.08 cm) and root dry mass (T4: 8.67 g). The biostimulants showed positive results in nutritional elements at foliar level, improving the values of N, P, K, Zn, Mn, Mg, Ca and Fe. Likewise, there was a decrease in Cu and Na values. These results support the hypothesis that biostimulants help cocoa plants to improve vegetative development and nutrient uptake, reducing plant losses and improving plant nutrition at the nursery stage.

PRODUCTION OF AÇAÍ SEEDLINGS UNDER DIFFERENT SHADE LEVELS AND CONTROLLED RELEASE FERTILIZER

This study aimed to evaluate the production and quality of açaí seedlings regarding the presence and absence of controlled-release fertilization under different shading levels. The study was conducted at the experimental field of Embrapa - Acre, using a completely randomized design in a 4 x 4 factorial arrangement. The factors included four evaluation periods (60, 120, 180, and 240 days after transplanting) and four shading environments (20%, 30%, 50%, and 75%), along with the presence or absence of controlled-release fertilization. The following variables were analyzed: plant height, stem diameter, number of leaves, dry mass of leaves, stem, root, and total dry mass, as well as the seedling quality index and foliar levels of macro and micronutrients. The growth and development of açaí seedlings are influenced by the evaluation periods, shade environments, and the use of fertilization. Fertilization with controlled-release fertilizer and environments with30% and 50% shading improved the quality of açaí palm seedlings.

Selection of Prunus clonal rootstocks based on nutritional efficiency state

Rootstock contributes to increase the absorption and nutrients translocation efficiency. We aimed to select rootstocks according to the nutritional physiological state of the scion cultivar. The experiment was carried out during three periods of leaf collect on the 4-year old peach cv. BRS Libra budded onto 21 rootstocks cultivated in a high density orchard. The following traits were evaluated: xylem water potential, dry leaf mass and chemical leaf nutritional analysis. The collected data were submitted to analysis of variance by the F test and some genetic parameters were estimated. When significant, the means were compared using the Scott-Knott test, at 5% significance. The principal component analysis was performed to verify the interrelationships between the rootstocks and the evaluated traits. The deviation from optimum percentage index was used to select the most nutritional stable rootstock. We observed that rootstock affects the dynamic absorption nutrient parameters in interactions with the scion. The highest foliar levels of P were found in the BRS Libra cultivar when budded onto the rootstocks ʹSanta Rosaʹ, ʹBarrierʹ, ʹTsukuba-1ʹ and ʹRosaflorʹ. The leaf analysis revealed a high variation in the mineral nutritional status among the studied Prunus rootstocks. Most of the mineral macro-elements varied between medium and optimal levels. The rootstocks ʹRigitanoʹ and ʹNemaredʹ showed less nutritional limitation and is recommended for cultivations in high density orchards.

Evaluation of resistance to Fusarium wilt race 1 in new banana clones

In previous works, a method was developed for the differentiation at the foliar level of the response of banana plants to Fusarium race 1 wilt, which constitutes a useful tool to increase the efficiency of resistance selection in ex vitro conditions. The objective of this work was to evaluate resistance to this disease in new banana clones using the evaluation method mentioned. For this, six moments of evaluation were made; and ten plants of each selected line of the irradiated ‘Zanzíbar’ clone were used. The results showed that the plants of the evaluated lines of the irradiated ‘Zanzíbar’ clone indicate that they are promising materials for genetic improvement in the crop aimed at resistance to this disease. On the other hand, a response to selection was obtained in a short time (48 hours), as well as evaluating the lines selected from large populations of plants (60 plants) with the exclusion of other organisms; and the control of environmental conditions that could interfere with the results obtained. However, it is necessary to continue additional studies in the field to confirm the resistance in the evaluated lines.

Effect of the concentration of the nutrient solution on the nutrient content of chrysanthemum (Dendranthema grandiflorum (Ramat.)

Objective: Evaluate the nutrient concentration at the foliar level of chrysanthemums grown in tezontle sand using three concentrations of the Steiner Universal Nutrient Solution.
 Design/Methodology/Approach: A completely randomized design was used, each treatment represented a concentration of the nutrient solution and each concentration had 11 repetitions, the study variables were: foliar concentration of nutrients: N, P, K, Ca, Mg and S, plant height (AP), stem diameter (DT), number of leaves (NH), flower diameter (DF), fresh weight (PF) and dry weight (PS).
 Results: The results showed this order of extraction K>N>Ca>P>Mg>S, for all concentrations, the foliar N content was low in the three treatments (<3.35%), the P was found in high concentrations. (>0.63%), K was higher in the 100% concentration treatment, Mg (>0.44%) was in sufficient levels, in Ca the 100% concentration had greater absorption and finally the S content was only the adequate in the concentration of 100 %, in the morphological variables there were no significant differences.
 Limitations of the study/Implications: High temperatures helped the proliferation of pests; therefore, it would be good to have a better control of temperatures inside the greenhouse.
 Findings/Conclusions: Therefore, using different concentrations of the nutrient solution in chrysanthemums grown in tezontle sand affects the nutrient content at the foliar level but not necessarily its morphology.

Interspecific differences in microhabitat use expose insects to contrasting thermal mortality

AbstractEcotones linking open and forested habitats contain multiple microhabitats with varying vegetal structures and microclimatic regimes. Ecotones host many insect species whose development is intimately linked to the microclimatic conditions where they grow (e.g., the leaves of their host plants and the surrounding air). Yet microclimatic heterogeneity at these fine scales and its effects on insects remain poorly quantified for most species. Here we studied how interspecific differences in the use of microhabitats across ecotones lead to contrasting thermal exposure and survival costs between two closely‐related butterflies (Pieris napiandP. rapae). We first assessed whether butterflies selected different microhabitats to oviposit and quantified the thermal conditions at the microhabitat and foliar scales. We also assessed concurrent changes in the quality and availability of host plants. Finally, we quantified larval time of death under different experimental temperatures (thermal death time [TDT] curves) to predict their thermal mortality considering both the intensity and the duration of the microclimatic heat challenges in the field. We identified six processes determining larval thermal exposure at fine scales associated with butterfly oviposition behavior, canopy shading, and heat and water fluxes at the soil and foliar levels. Leaves in open microhabitats could reach temperatures 3–10°C warmer than the surrounding air while more closed microhabitats presented more buffered and homogeneous temperatures. Interspecific differences in microhabitat use matched the TDT curves and the thermal mortality in the field. Open microhabitats posed acute heat challenges that were better withstood by the thermotolerant butterfly,P. rapae, where the species mainly laid their eggs. Despite being more thermosensitive,P. napiwas predicted to present higher survivals thanP. rapaedue to the thermal buffering provided by their selected microhabitats. However, its offspring could be more vulnerable to host‐plant scarcity during summer drought periods. Overall, the different interaction of the butterflies with microclimatic and host‐plant variation emerging at fine scales and their different thermal sensitivity posed them contrasting heat and resource challenges. Our results contribute to setting a new framework that predicts insect vulnerability to climate change based on their thermal sensitivity and the intensity, duration, and accumulation of their heat exposure.

Use of calcium in bareroot pine nurseries

Bareroot nursery managers may apply dolomite, gypsum, or Ca-nitrate to increase Ca in nursery soils. Although a few managers follow S.A. Wilde’s recommendations and maintain soil at levels of 500 to 1,000 μg g-1 Ca, there is no need to keep Ca levels this high. In contrast, managers at sandy nurseries apply Ca when soil tests drop below 200 μg g-1 Ca. In fact, acceptable pine seedlings have been produced in irrigated soil with <100 μg g-1 available Ca. In plantations, asymptomatic wildlings grow when topsoil contains 17 μg g-1 Ca. In sandy soils, applying too much gypsum can result in a temporary Mg deficiency and too much lime will result in chlorotic needles.
 Managers apply Ca when foliar levels fall below a published “critical value.” The belief that the critical value for Ca varies by stock type is not valid. In fact, numerous “critical” values are invalid since they were not determined using growth response curves. Critical values determined for small seedlings using CaCl2 in sand are apparently not valid for use in bareroot nurseries. 
 At bareroot nurseries, the soil extractable Ca level can decline during a year by 30 μg g-1 or more. Harvesting 1.7 million pine seedlings may remove 20 kg ha-1 of Ca but irrigation can replace this amount or more. When water contains 5 mg l-1 Ca, 600 mm of irrigation will add 30 kg ha-1 Ca. In some areas, 1,000 mm of rainfall will supply 7 kg ha-1 Ca. Even when a Mehlich 1 test shows no exchangeable Ca in the topsoil, pine needles on tall trees may exceed 2,000 μg g-1 Ca due to root growth in subsoil.
 There are few documented cases of deficient pine needles (<300 μg g-1 Ca) in irrigated nurseries in Australia, New Zealand, Scotland and in the Americas. Even when soil fumigation delays the inoculation of ectomycorrhiza, bareroot pines have adequate levels of Ca. Typically, foliage samples from pine nurseries contain at least 1,000 μg g-1 Ca. Samples from 9-month-old seedlings range from 300 to 11,000 μg g-1 Ca. Although the “critical value” for Pinus echinata foliage is not known, 1-0 seedlings with 300 μg g-1 Ca were not stunted and apparently grew well after ouplanting.

Physiological response of adult Salix aurita in wetland vegetation affected by flooding with As-rich fine pyrite particles

An uncontrolled, natural episode of flooding with waters contaminated with As-rich pyrite (FeAsS) particles caused serious ecological damage leading to necrosis of plants growing in a fresh wet meadow located in an area characterized by unique geological structures rich in arsenopyrites. One of the few plant species capable of surviving this event was Salix aurita L., which grew in numbers in the analyzed area, but individual plants were affected differently by toxic flooding. No significant phenotypic changes (Group I), through partial leaf and/or stem necrosis (Group II) up to necrosis of the whole parental plant and root suckers (Group III), were observed for various willow clumps. These varied phenotypic responses of S. aurita to As-rich sediments were compared with the biochemical status of the foliage of willow trees, and with their rhizosphere physiological parameters.Our in situ study revealed that the biochemical status of leaves reflects the phenotypic damage incurred by adult willows growing in their natural environment and affected by the flooding. In leaves of willows with increasingly negative phenotypic changes (Groups I → II → III) as well as increasing levels of reactive oxygen species, malondialdehyde and decreased levels of glutathione and thiol groups were detected. Phytochelatins, commonly considered major As chelators, were not detected in S. aurita leaves. Despite a decrease in the size of leaves with the intensity of tree damage, all leaves expressed a normal level of leaf pigments.Phenotypic changes observed for particular willow clumps were only partly related to soil As levels. Moreover, As and S (but not Fe) foliar levels were related but did not correspond strictly with foliar biochemical features, or with soil As levels, soil pH or soil microbial activity, with the latter two drastically decreased in the rhizospheres of willows from Groups II and III.

INFLUENCE OF LEAF AND RADICULAR FERTILIZATION ON APPLE GROWTH AND FRUITING PROCESSES

Fertilization is a basic condition of agriculture, as a branch of sustainable development. It is often recommended to supplement mineral nutrition with organic product administration because, through their bio-stimulating effect, it potentiates mineral nutrition. Under these conditions, between 2020 and 2022, a bifactorial study was carried out on three apple cultivars (5-7 years after planting), grown at the Research Institute for Fruit Growing Pitesti-Maracineni, in a high-density orchard. The influence of five foliar and one soil fertilizers, on the background of standard mineral fertilization, over the mineral elements and chlorophyll content of the foliar apparatus for 'Red Braeburn', 'Jonagold Boerekamp', and 'Jonagold Novajo' cvs. was studied. Indicators of growth, fruiting processes, and fruit quality were also assessed. The foliar diagnosis results indicated that the level of mineral elements (N, P, Ca, Mg, Zn, Cu, and Fe) was within the limits of normality established for apple leaves, except for manganese, which accumulated in slightly excess (108.8, compared to 100.0 ppm). On average, during the experiment, the fertilization variants significantly increased the foliar level of mineral elements such as K, Cu, and Fe, compared to the control. Regarding the growth-fruiting processes, the mean of the tree trunk cross-sectional area annual growth was 6.6 cm2. Given that the percentage of fruit set fluctuated around 66.9%, a fruit yield of 66.8 t/ha was obtained. On average, the percentage of fruit set increased significantly by 16.9-19.5% when CropMax (0.2%), M1 (0.5%), and M2 (0.5%) products were applied, and fruit yield by 19.3-21.2% for Poly-Feed (1%) and Fertisol (2 kg/tree). The fruit weight ranged from 72.3 to 443.2 g, with an average of 166.5 g. The average values recorded for firmness, juice pH and total soluble content were 76.4 units HPE-II- FFF Bareiss, 3.6, and 12.7°Brix respectively. All fertilization treatments significantly increased the average weight of the fruit, by 6.2-9.2%, compared to the untreated variant. The results of the study certify the favorable effect of supplementing the fertilization plans with the studied products, containing biostimulators that enhance and harmonize the physiological processes of the apple in a high-density system.

Diplodia sapinea infection reprograms foliar traits of its pine (Pinus sylvestris L.) host to death.

Infection with the necrotrophic fungus Diplodia sapinea (Fr.) Fuckel is among the economically and ecologically most devastating diseases of conifers in the northern hemisphere and is accelerated by global climate change. This study aims to characterize the changes mediated by D. sapinea infection on its pine host (Pinus sylvestris L.) that lead to the death of its needles. For this purpose, we performed an indoor infection experiment and inoculated shoot tips of pine seedlings with virulent D. sapinea. The consequences for foliar traits, including the phytohormone profile, were characterized at both the metabolite and transcriptome level. Our results showed that D. sapinea infection strongly affected foliar levels of most phytohormones and impaired a multitude of other metabolic and structural foliar traits, such as reactive oxygen species scavenging. Transcriptome analysis revealed that these changes are partially mediated via modified gene expression by fungal exposure. Diplodia sapinea appears to overcome the defense reactions of its pine host by reprogramming gene expression and post-transcriptional controls that determine essential foliar metabolic traits such as the phytohormone profile, cell wall composition and antioxidative system.

Traffic patterns, more than adjacent land use, influence element content of roadside forbs for insect pollinators

Abstract Roadsides are targeted for restoration of pollinator‐friendly plants. Yet, roads are sources of macronutrient, micronutrient and heavy metal pollution that may contaminate roadside plants. Adjacent landscape features such as railroads and agriculture provide additional macronutrient and heavy metal pollution that may exacerbate traffic effects. However, we lack perspective on how roads combine with rural landscape features to influence nutrition of roadside plants, which could have implications for pollinator health. We surveyed roadsides across Minnesota, USA and measured foliar levels of dietary macronutrients (nitrogen, phosphorous and potassium), a micronutrient (sodium) and metals (iron, zinc, copper, chromium, nickel, lead, aluminium and cadmium) in six abundant roadside forb species used by insect pollinators: Asclepias syriaca, Dalea purpurea, Monarda fistulosa, Ratibida pinnata, Solidago spp. and Trifolium pratense. We aimed to determine (1) how road variables (traffic volume and distance from road) combine with adjacent land use (railroad and agriculture) to influence element content of roadside forbs and (2) whether some forb species show consistent differences in their accumulation of potentially toxic heavy metals, which could inform selection of species to plant along roadsides. We found that foliar concentrations of nine elements increased with greater traffic volume (nitrogen, phosphorous, iron, zinc, copper, chromium, nickel, lead and aluminium), and concentrations of six elements declined with distance from the road (nitrogen, phosphorous, potassium, iron, zinc and copper). Leaves collected adjacent to railroad had less phosphorous, potassium, iron, nickel and aluminium than leaves collected from sites not adjacent to railroad. Additionally, leaves collected from sites adjacent to agriculture had lower copper levels than leaves from sites without adjacent agriculture. We found no evidence that particular ford species along roadsides consistently rank higher than other species in their accumulation of heavy metals. Our results show that traffic alters more elements in roadside plants than does adjacent landscape context, alleviating concerns that landscape features exacerbate pollutant levels in roadside pollinator habitat. However, nutrient contamination of most roadside plants is unlikely to reach toxic levels for insect pollinators. This work is consistent with the positive conservation potential of low to moderate traffic roadsides for pollinators.

Lack of Tradeoff between Leaf Hydraulic Efficiency and Safety across Six Contrasting Water-Stress Tolerant Fruit Tree Species

Water deficits affect the capacity of leaves to transport water, a process that is related to the obstruction of air in the xylem (embolism). The tolerance to this process has been negatively associated with water-transport efficiency at the xylem level across species, suggesting a tradeoff between hydraulic efficiency and safety. But there is a lack of observation at higher integration levels, i.e., organs. This study aimed to evaluate this tradeoff across six fruit tree species with a wide range of water-stress tolerance: pomegranate, olive, fig tree, mandarin, avocado, and vine. Efficiency was represented by the maximum foliar hydraulic conductance (Kmax) and stomatal conductance, whereas hydraulic security by water potential in which the leaf loses 50% of its water-transport capacity (P50), and at the point of loss of leaf turgor (Ψtlp). Results suggest that the compensation is weak or null at the foliar level. We observed that species with higher hydraulic efficiency tend to be more tolerant to leaf dehydration (higher hydraulic safety), except mandarin, which had lower Kmax and relatively higher P50. Morphological traits associated with carbon investment dynamic (leaf mass per area and petiole density) were highly correlated to water-stress tolerance across fruit tree species.