Kinetically Consistent Data Assimilation for Plant PET Sparse Time Activity Curve Signals.

Time activity curve (TAC) signal processing in plant positron emission tomography (PET) is a frontier nuclear science technique to bring out the quantitative fluid dynamic (FD) flow parameters of the plant vascular system and generate knowledge on crops and their sustainable management, facing the accelerating global climate change. The sparse space-time sampling of the TAC signal impairs the extraction of the FD variables, which can be determined only as averaged values with existing techniques. A data-driven approach based on a reliable FD model has never been formulated. A novel sparse data assimilation digital signal processing method is proposed, with the unique capability of a direct computation of the dynamic evolution of noise correlations between estimated and measured variables, by taking into explicit account the numerical diffusion due to the sparse sampling. The sequential time-stepping procedure estimates the spatial profile of the velocity, the diffusion coefficient and the compartmental exchange rates along the plant stem from the TAC signals. To illustrate the performance of the method, we report an example of the measurement of transport mechanisms in zucchini sprouts.

Factors Involved on Tiger-Stripe Foliar Symptom Expression of Esca of Grapevine.

Esca of grapevine causes yield losses correlated with incidence and severity symptom expression. Factors associated with leaf symptom mechanisms are yet to be fully clarified. Therefore, in 2019 and 2020, macro and microelement analyses and leaf reflectance measurements were carried out on leaves at different growth stages in a vineyard located in Abruzzo, central Italy. Surveys were carried out on leaves of both never leaf-symptomatic vines and different categories of diseased vine shoots. Never leaf-symptomatic and diseased vines were also treated with a fertilizer mixture that proved to be able to limit the symptom expression. Results showed that untreated asymptomatic diseased vines had high calcium contents for most of the vegetative season. On the contrary, treated asymptomatic diseased vines showed higher contents of calcium, magnesium, and sodium, at berries pea-sized, before the onset of symptoms. These vines had better physiological efficiency showing higher water index (WI), normalized difference vegetation index (NDVI), and green normalized difference vegetation index (GNDVI) values, compared to untreated asymptomatic vines, at fruit set. Results confirmed the strong response of the plant to symptom expression development and the possibility of limiting this response with calcium and magnesium applications carried out before the symptom onset.

Design Study of a Novel Positron Emission Tomography System for Plant Imaging.

Positron Emission Tomography is a non-disruptive and high-sensitive digital imaging technique which allows to measure in-vivo and non invasively the changes of metabolic and transport mechanisms in plants. When it comes to the early assessment of stress-induced alterations of plant functions, plant PET has the potential of a major breakthrough. The development of dedicated plant PET systems faces a series of technological and experimental difficulties, which make conventional clinical and preclinical PET systems not fully suitable to agronomy. First, the functional and metabolic mechanisms of plants depend on environmental conditions, which can be controlled during the experiment if the scanner is transported into the growing chamber. Second, plants need to be imaged vertically, thus requiring a proper Field Of View. Third, the transverse Field of View needs to adapt to the different plant shapes, according to the species and the experimental protocols. In this paper, we perform a simulation study, proposing a novel design of dedicated plant PET scanners specifically conceived to address these agronomic issues. We estimate their expected sensitivity, count rate performance and spatial resolution, and we identify these specific features, which need to be investigated when realizing a plant PET scanner. Finally, we propose a novel approach to the measurement and verification of the performance of plant PET systems, including the design of dedicated plant phantoms, in order to provide a standard evaluation procedure for this emerging digital imaging agronomic technology.

Past and Future of Plant Stress Detection: An Overview From Remote Sensing to Positron Emission Tomography.

Plant stress detection is considered one of the most critical areas for the improvement of crop yield in the compelling worldwide scenario, dictated by both the climate change and the geopolitical consequences of the Covid-19 epidemics. A complicated interconnection of biotic and abiotic stressors affect plant growth, including water, salt, temperature, light exposure, nutrients availability, agrochemicals, air and soil pollutants, pests and diseases. In facing this extended panorama, the technology choice is manifold. On the one hand, quantitative methods, such as metabolomics, provide very sensitive indicators of most of the stressors, with the drawback of a disruptive approach, which prevents follow up and dynamical studies. On the other hand qualitative methods, such as fluorescence, thermography and VIS/NIR reflectance, provide a non-disruptive view of the action of the stressors in plants, even across large fields, with the drawback of a poor accuracy. When looking at the spatial scale, the effect of stress may imply modifications from DNA level (nanometers) up to cell (micrometers), full plant (millimeters to meters), and entire field (kilometers). While quantitative techniques are sensitive to the smallest scales, only qualitative approaches can be used for the larger ones. Emerging technologies from nuclear and medical physics, such as computed tomography, magnetic resonance imaging and positron emission tomography, are expected to bridge the gap of quantitative non-disruptive morphologic and functional measurements at larger scale. In this review we analyze the landscape of the different technologies nowadays available, showing the benefits of each approach in plant stress detection, with a particular focus on the gaps, which will be filled in the nearby future by the emerging nuclear physics approaches to agriculture.

Proteomics of Durum Wheat Grain during Transition to Conservation Agriculture.

Nitrogen management in combination with sustainable agronomic techniques can have a great impact on the wheat grain proteome influencing its technological quality. In this study, proteomic analyses were used to document changes in the proportion of prolamins in mature grains of the newly released Italian durum wheat cv Achille. Such an approach was applied to wheat fertilized with urea (UREA) and calcium nitrate (NITRATE), during the transition to no-till Conservation Agriculture (CA) practice in a Mediterranean environment. Results obtained in a two-years field experiment study suggest low molecular weight glutenins (LMW-GS) as the fraction particularly inducible regardless of the N-form. Quantitative analyses of LMW-GS by 2D-GE followed by protein identification by LC-ESI-MS/MS showed that the stable increase was principally due to C-type LMW-GS. The highest accumulation resulted from a physiologically healthier state of plants treated with UREA and NITRATE. Proteomic analysis on the total protein fraction during the active phase of grain filling was also performed. For both N treatments, but at different extent, an up-regulation of different classes of proteins was observed: i) enzymes involved in glycolysis and citric acid cycles which contribute to an enhanced source of energy and carbohydrates, ii) stress proteins like heat shock proteins (HSPs) and antioxidant enzymes, such as peroxidases and superoxide dismutase which protect the grain from abiotic stress during starch and storage protein synthesis. In conclusion N inputs, which combined rate with N form gave high yield and improved quality traits in the selected durum wheat cultivar. The specific up-regulation of some HSPs, antioxidant enzymes and defense proteins in the early stages of grain development and physiological indicators related to fitness traits, could be useful bio-indicators, for wheat genotype screening under more sustainable agronomic conditions, like transition phase to no-till CA in Mediterranean environments.

Influence of phosphorus management on melon (Cucumis melo L.) fruit quality.

BACKGROUND: At harvest time, melon quality is related to internal and external parameters, which are very important for consumer attractiveness and marketable yield. Several agronomic factors can affect the quality of melon fruits and among them mineral availability may play a significant role. Therefore the aim of the work was to investigate the effect of phosphorus fertigation on melon fruit (Cucumis melo L.) qualitative characteristics, such as fruit size and yield, pulp colour and firmness, aroma and taste, as well as the accumulation of bioactive antioxidant compounds, namely phenols and carotenoids, and their antiradical properties. RESULTS: Results allowed us to extrapolate the optimal P doses to be used for melon fertigation, to achieve high yield and fruit quality characteristics. Modelling the optimal P dose allowed us to maximize yield and resulted in around 257 kg P2 O5 ha(-1) , even if the quality indices relating to carotenoid content, texture and colour of the melon flesh were not significantly different between samples fertigated with the two highest levels tested. CONCLUSION: It can be assumed that the level of 200 kg P2 O5 ha(-1) would be a good compromise between optimization of agronomic performance and melon fruit quality. © 2015 Society of Chemical Industry.

Phenolic compounds in grains, sprouts and wheatgrass of hulled and non-hulled wheat species.

BACKGROUND: The use of sprouts and young plantlets in human nutrition is increasing because they often contain phytochemicals and other high value nutrients. This is also the case for wheat, although there is no literature for hulled wheat species. Thus we determined total polyphenols, phenolic acids (PAs), fibre and minerals in grains, 5-day-old sprouts and 12-day-old wheatgrass of einkorn (cv. Monlis), emmer (cvs Augeo, Rosso Rubino, Zefiro), spelt (cvs Pietro, Giuseppe), durum wheat (cv. Creso) and soft wheat (cv. Orso). RESULTS: Grains of einkorn and emmer contained twice bound PAs as compared to soft and durum wheat and spelt, with p-coumaric acid accounting for about 50% of total bound PAs. In wheatgrass, differences between species for bound PAs decreased due to a decrease in einkorn and emmer and an increase in soft and durum wheat. In all species, total phenols and free PAs increased passing from grains to sprouts and wheatgrass. Neutral and acid detergent fibre content increased with sprouting only in einkorn and emmer. CONCLUSION: Our evidence suggests that the grains of einkorn and emmer and the sprouts and wheatgrass of all Triticum species might potentially be valuable for the development of functional foods.

Long-term impact of farm management and crops on soil microorganisms assessed by combined DGGE and PLFA analyses.

In the present study, long-term organic and conventional managements were compared at the experimental field of Monsampolo del Tronto (Marche region, Italy) with the aim of investigating soil chemical fertility and microbial community structure. A polyphasic approach, combining soil fertility indicators with microbiological analyses (plate counts, PCR-denaturing gradient gel electrophoresis [DGGE] and phospholipid fatty acid analysis [PLFA]) was applied. Organic matter, N as well as some important macro and micronutrients (K, P, Mg, Mn, Cu, and Zn) for crop growth, were more available under organic management. Bacterial counts were higher in organic management. A significant influence of management system and management x crop interaction was observed for total mesophilic bacteria, nitrogen fixing bacteria and actinobacteria. Interestingly, cultivable fungi were not detected in all analyzed samples. PLFA biomass was higher in the organic and Gram positive bacteria dominated the microbial community in both systems. Even if fungal biomass was higher in organic management, fungal PCR-DGGE fingerprinting revealed that the two systems were very similar in terms of fungal species suggesting that 10 years were not enough to establish a new dynamic equilibrium among ecosystem components. A better knowledge of soil biota and in particular of fungal community structure will be useful for the development of sustainable management strategies.

Application of photo-selective films to manipulate wavelength of transmitted radiation and photosynthate composition in red beet (Beta vulgaris var. conditiva Alef.).

BACKGROUND: Interest is increasing around both the use of plants as functional foods and the agronomic techniques which can increase nutrients and phytochemicals. Nevertheless, little research has focused on the effects of light on accumulation of active compounds in root storage organs. Red beet was treated with RED (red/far red ratio: 1.29; transmitted photosynthetically active radiation: 66.9%) and GREEN (red/far red ratio: 0.43; transmitted photosynthetically active radiation: 25.8%) photo-selective films and changes in nutrients and biomass accumulation were measured. RESULTS: Plants subjected to GREEN treatment had less dry weight accumulation both in storage roots (68%) and leaves (42%); moreover, soluble and structural carbohydrate concentration in roots was increased, as were the K, Mg and Zn concentrations (40.08, 2.95 and 0.023 mg g⁻¹ fresh weight, respectively). Conversely, GREEN lowered total phenolic concentration (0.33 vs. 0.47 mg g⁻¹ fresh weight) and antioxidant activity (0.65 vs. 0.94 µm Trolox equivalents g⁻¹ fresh weight) compared to CONTROL. Total pigment concentration was reduced by 20% and 48% with RED and GREEN treatments, respectively. CONCLUSION: Red beet showed a strong plasticity in its adaptation to light availability. Some macronutrients (fiber, sugars, minerals) can be concentrated in roots by modifying the amount and quality of the light, principally with GREEN photo-selective films.

Cadmium concentration in durum wheat grain (Triticum turgidum) as influenced by nitrogen rate, seeding date and soil type.

BACKGROUND: Cadmium (Cd) is a trace element that has been associated with various human health problems. Cd enters plants, either by direct absorption through leaves or by uptake from soils, allowing Cd into the food chain. Nitrogen (N) fertilizer management is important in optimizing crop yield and protein content of durum wheat, but may influence Cd availability and hence Cd concentration in crops, with the effects being strongly influenced by environmental conditions and crop cultivar. RESULTS: In field studies, Cd and protein concentration in durum wheat grain differed between cultivars and were strongly affected by N application, with only minor effects of N occurring on concentration and uptake of P and Zn. Protein content increased significantly with N application in five of six site-years, with the response being generally independent of cultivar and seeding data. Cd concentration also increased with N application in five of six seeding dates, with the response being greater in AC Melita than Arcola in three of the six site-years. There were large differences in Cd concentration from year to year and with seeding date, indicating a strong environmental influence. CONCLUSIONS: This study shows that different cultivars accumulate different levels of Cd in the grain and that seeding date and nitrogen fertilizer management can influence grain Cd concentration, with the magnitude of effects varying with environmental factors. In the future we may be able to manipulate management practices to optimize protein concentration and minimize Cd concentration in durum wheat, which could help to address the health and safety concerns of consumers.