Blue Light Improves Photosynthetic Performance during Healing and Acclimatization of Grafted Watermelon Seedlings.

To investigate the importance of light on healing and acclimatization, in the present study, grafted watermelon seedlings were exposed to darkness (D) or light, provided by blue (B), red (R), a mixture of R (68%) and B (RB), or white (W; 35% B, 49% intermediate spectra, 16% R) LEDs for 12 days. Survival ratio, root and shoot growth, soluble carbohydrate content, photosynthetic pigments content, and photosynthetic performance were evaluated. Seedling survival was not only strongly limited in D but the survived seedlings had an inferior shoot and root development, reduced chlorophyll content, and attenuated photosynthetic efficiency. RB-exposed seedlings had a less-developed root system. R-exposed seedlings showed leaf epinasty, and had the smallest leaf area, reduced chlorophyll content, and suppressed photosynthetic apparatus performance. The R-exposed seedlings contained the highest amount of soluble carbohydrate and together with D-exposed seedlings the lowest amount of chlorophyll in their scions. B-exposed seedlings showed the highest chlorophyll content and improved overall PSII photosynthetic functioning. W-exposed seedling had the largest leaf area, and closely resembled the photosynthetic properties of RB-exposed seedlings. We assume that, during healing of grafted seedlings monochromatic R light should be avoided. Instead, W and monochromatic B light may be willingly adopted due to their promoting effect on shoot, pigments content, and photosynthetic efficiency.

Xylogenesis in zinnia (Zinnia elegans) cell cultures: unravelling the regulatory steps in a complex developmental programmed cell death event.

MAIN CONCLUSION: Physiological and molecular studies support the view that xylogenesis can largely be determined as a specific form of vacuolar programmed cell death (PCD). The studies in xylogenic zinnia cell culture have led to many breakthroughs in xylogenesis research and provided a background for investigations in other experimental models in vitro and in planta . This review discusses the most essential earlier and recent findings on the regulation of xylem elements differentiation and PCD in zinnia and other xylogenic systems. Xylogenesis (the formation of water conducting vascular tissue) is a paradigm of plant developmental PCD. The xylem vessels are composed of fused tracheary elements (TEs)-dead, hollow cells with patterned lignified secondary cell walls. They result from the differentiation of the procambium and cambium cells and undergo cell death to become functional post-mortem. The TE differentiation proceeds through a well-coordinated sequence of events in which differentiation and the programmed cellular demise are intimately connected. For years a classical experimental model for studies on xylogenesis was the xylogenic zinnia (Zinnia elegans) cell culture derived from leaf mesophyll cells that, upon induction by cytokinin and auxin, transdifferentiate into TEs. This cell system has been proven very efficient for investigations on the regulatory components of xylem differentiation which has led to many discoveries on the mechanisms of xylogenesis. The knowledge gained from this system has potentiated studies in other xylogenic cultures in vitro and in planta. The present review summarises the previous and latest findings on the hormonal and biochemical signalling, metabolic pathways and molecular and gene determinants underlying the regulation of xylem vessels differentiation in zinnia cell culture. Highlighted are breakthroughs achieved through the use of xylogenic systems from other species and newly introduced tools and analytical approaches to study the processes. The mutual dependence between PCD signalling and the differentiation cascade in the program of TE development is discussed.

Post-harvest proteomics and food security.

To guarantee sufficient food supply for a growing world population, efforts towards improving crop yield and plant resistance should be complemented with efforts to reduce post-harvest losses. Post-harvest losses are substantial and occur at different stages of the food chain in developed and developing countries. In recent years, a substantially increasing interest can be seen in the application of proteomics to understand post-harvest events. In the near future post-harvest proteomics will be poised to move from fundamental research to aiding the reduction of food losses. Proteomics research can help in reducing food losses through (i) identification and validation of gene products associated to specific quality traits supporting marker-assisted crop improvement programmes, (ii) delivering markers of initial quality that allow optimisation of distribution conditions and prediction of remaining shelf-life for decision support systems and (iii) delivering early detection tools of physiological or pathogen-related post-harvest problems. In this manuscript, recent proteomics studies on post-harvest and stress physiology are reviewed and discussed. Perspectives on future directions of post-harvest proteomics studies aiming to reduce food losses are presented.

Mastoparan-induced programmed cell death in the unicellular alga Chlamydomonas reinhardtii.

BACKGROUND AND AIMS: Under stress-promoting conditions unicellular algae can undergo programmed cell death (PCD) but the mechanisms of algal cellular suicide are still poorly understood. In this work, the involvement of caspase-like proteases, DNA cleavage and the morphological occurrence of cell death in wasp venom mastoparan (MP)-treated Chlamydomonas reinhardtii were studied. METHODS: Algal cells were exposed to MP and cell death was analysed over time. Specific caspase inhibitors were employed to elucidate the possible role of caspase-like proteases. YVADase activity (presumably a vacuolar processing enzyme) was assayed by using a fluorogenic caspase-1 substrate. DNA breakdown was evaluated by DNA laddering and Comet analysis. Cellular morphology was examined by confocal laser scanning microscopy. KEY RESULTS: MP-treated C. reinhardtii cells expressed several features of necrosis (protoplast shrinkage) and vacuolar cell death (lytic vesicles, vacuolization, empty cell-walled corpse-containing remains of digested protoplast) sometimes within one single cell and in different individual cells. Nucleus compaction and DNA fragmentation were detected. YVADase activity was rapidly stimulated in response to MP but the early cell death was not inhibited by caspase inhibitors. At later time points, however, the caspase inhibitors were effective in cell-death suppression. Conditioned medium from MP-treated cells offered protection against MP-induced cell death. CONCLUSIONS: In C. reinhardtii MP triggered PCD of atypical phenotype comprising features of vacuolar and necrotic cell deaths, reminiscent of the modality of hypersensitive response. It was assumed that depending on the physiological state and sensitivity of the cells to MP, the early cell-death phase might be not mediated by caspase-like enzymes, whereas later cell death may involve caspase-like-dependent proteolysis. The findings substantiate the hypothesis that, depending on the mode of induction and sensitivity of the cells, algal PCD may take different forms and proceed through different pathways.

The impact of wounding and postharvest storage conditions on retention of soluble protein in sugar beet leaves.

Sugar beet leaves can be a viable and economically interesting source of high-quality protein for the food industry. We investigated how storage conditions and leaf wounding at harvest affect the content and quality of the soluble protein. After collection, leaves were either stored intact or shredded to mimic wounding induced by commercial leaf harvesters. Leaf material was stored in small volumes at different temperatures to assess leaf physiology or in larger volumes to assess temperature development at different locations in the bins. Protein degradation was more pronounced at higher storage temperatures. Wounding accelerated the degradation of soluble protein at all temperatures. Both wounding and storage at higher temperatures greatly stimulated respiration activity and heat production. At temperatures below 5°C, ribulose-1,5-biphosphate carboxylase oxygenase (RuBisCO) in intact leaves was preserved for up to 3 weeks. At temperatures of 30-40°C, RuBisCO degradation occurred within 48 h. Degradation was more pronounced in shredded leaves. In 0.8-m3 storage bins at ambient temperature, core temperatures rapidly increased, up to 25°C in intact leaves and up to 45°C in shredded leaves within 2-3 days. Immediate storage at 5°C greatly suppressed the temperature increase in intact but not in shredded leaves. The indirect effect of excessive wounding, that is, heat production, is discussed as the pivotal factor responsible for increased degradation of protein. For optimal retention of soluble protein levels and quality in harvested sugar beet leaves, it is advised to minimize wounding and to store the material at temperatures around -5°C. PRACTICAL APPLICATION: To preserve the soluble protein content and quality for at least 3 weeks, sugar beet leaves should be harvested with minimal wounding and stored at temperatures between 1 and 5°C. When aiming to store minimally wounded leaves in larger volumes, it must be ensured that the product temperature in the core of the biomass meets the temperature criterium or the cooling strategy must be adjusted. The principles of minimal wounding and low temperature storage are transferable to other leafy crops that are harvested for food protein.

High CO2 Reduces Spoilage Caused by Botrytis cinerea in Strawberry Without Impairing Fruit Quality.

High CO2 (> 20 kPa) conditions are beneficial for suppressing spoilage caused by Botrytis cinerea in strawberry fruit; however, these conditions are often accompanied by discoloration, off-flavors, and faster softening. Stepwise increments of CO2 concentrations have been proposed to alleviate injuries in fruits caused by high CO2. In this study, we investigated whether stepwise increments of CO2, up to 30 kPa and under a reduced O2 concentration, are beneficial for reducing fungal spoilage without inducing CO2 injury symptoms in strawberry fruit. Based on recommended settings (5-10 kPa O2 with 15-20 kPa CO2), we first selected optimal O2 and CO2 concentrations that best-reduced spoilage caused by B. cinerea in red ripe "Sonsation" strawberry fruit. We found that higher O2 (10 kPa) and CO2 (20 kPa) concentrations were most beneficial for prolonging strawberry fruit shelf life. Subsequently, we studied the performance of red ripe "Arabella" strawberry fruit stored at 5°C under different controlled atmosphere (CA) conditions (10 kPa O2 with either 0, 20, or 30 kPa CO2). The CO2 concentrations were achieved either within 8 h or in a stepwise manner within the first 4 days of storage. As a control, 21 kPa O2 and 0 kPa CO2 were used. Following storage for up to 11 days, the spoilage incidence was assessed at 12°C for 5 days. The application of high CO2 (20 and 30 kPa) combined with 10 kPa O2 greatly suppressed fruit spoilage during storage and subsequent shelf life. High CO2 suppressed respiration as well as maintained a higher pH and firmness in treated fruit. The level of total sugars did not change, but during storage, a substantial part of sucrose was converted into glucose and fructose, especially under high CO2 conditions. High CO2 did not affect ascorbic acid and anthocyanin levels. The stepwise increments of CO2 did not result in beneficial effects compared to the static application of high CO2. Our results show that "Arabella" strawberry fruit are highly tolerant to elevated CO2 and can be stored under 30 kPa CO2 to prolong the shelf life.

High light intensity at End-Of-Production improves the nutritional value of basil but does not affect postharvest chilling tolerance.

Basil suffers from chilling injury (CI) when stored at temperatures below 10-12 °C which seems related to the imbalance between reactive oxygen species (ROS) and antioxidants. We hypothesized that increased light intensity applied shortly before harvest (EOP, End-Of-Production) increases nutritional value i.e. carbohydrates and antioxidants and could improve the chilling tolerance. Two basil cultivars were grown in a vertical farming set-up at a light intensity of 150 µmol m-2 s-1. During the last 5 days of growth, EOP light treatments ranging from 50 to 600 µmol m-2 s-1 were applied. After harvest the leaves were stored at 4 or 12 °C in darkness. Higher EOP light intensity increased the antioxidant (total ascorbic acid, rosmarinic acid) and carbohydrate contents at harvest. During storage antioxidants decreased more rapidly at 4 than at 12 °C. However, increased EOP light intensity did not alleviate chilling symptoms suggesting a minor role of antioxidants studied against chilling stress.

Lack of Blue Light Regulation of Antioxidants and Chilling Tolerance in Basil.

Blue light, measuring from 400 to 500 nm, is generally assumed to increase the content of antioxidants in plants independent of the species. Blue light stimulates the biosynthesis of phenolic compounds such as flavonoids and their subclass anthocyanins from the phenylpropanoid pathway. Flavonoids, anthocyanins, and phenolic acids are strong reactive oxygen species (ROS) scavengers and may lessen the symptoms of abiotic stresses such as chilling. We tested the hypothesis that a high percentage of blue light induces the accumulation of antioxidants and that this effect depends on the photosynthetic photon flux density (PPFD, 400-700 nm). The effect may be more pronounced at a lower PPFD. We investigated the changes in primary and secondary metabolites of basil in response to the percentage of blue light (9, 33, 65, and 100%) applied either as a 5-day End-Of-Production (EOP) treatment or continuous throughout the growth cycle in the green cv. Dolly. We also studied if the response to the percentage of blue light (9 or 90%) was dependent on the total PPFD (100 or 300 µmol m-2 s-1 PPFD) when applied as a 5-day EOP treatment in the green cv. Dolly and the purple cv. Rosie. For both green and purple basil, it was found that the percentage of blue light had little effect on the levels of antioxidants (rosmarinic acid, total ascorbic acid, total flavonoids, and total anthocyanins) at harvest and no interactive effect with PPFD was found. Antioxidants generally decreased during postharvest storage, wherein the decrease was more pronounced at 4 than at 12°C. Chilling injury, as judged from a decrease in F v /F m values and from the occurrence of black necrotic areas, was not affected by the percentage of blue light. Particularly, chilling tolerance in the purple cultivar was increased in plants grown under higher PPFD. This may be related to the increased levels of soluble sugar and starch in leaves from high PPFD treated plants.

Additional Blue LED during Cultivation Induces Cold Tolerance in Tomato Fruit but Only to an Optimum.

Tomato is a chilling-sensitive fruit. The aim of this study is to examine the role of preharvest blue LED lighting (BL) to induce cold tolerance in 'Foundation' tomatoes. Blue and red supplemental LED light was applied to achieve either 0, 12 or 24% additional BL (0B, 12B and 24B). Mature green (MG) or red (R) tomatoes were harvested and cold stored at 4 °C for 0, 5, 10, 15 and 20 d, and then stored for 20 d at 20 °C (shelf life). Chilling injury (CI) indices, color and firmness, hydrogen peroxide, malondialdehyde, ascorbic acid and catalase activity were characterized. At harvest, R tomatoes cultivated at 12B were firmer and showed less coloration compared to fruit of other treatments. These fruits also showed higher loss of red color during cold storage and lower CI symptoms during shelf-life. MG tomatoes cultivated at 12B showed delayed coloring (non-chilled) and decreased weight loss (long cold stored) during shelf life compared to fruit in the other treatments. No effects of light treatments, both for MG and R tomatoes, were observed for the selected antioxidant capacity indicators. Improved cold tolerance for R tomatoes cultivated at 12B points to lycopene having higher scavenging activity at lower concentrations to mitigate chilling injury.

The association between the susceptibility to Botrytis cinerea and the levels of volatile and non-volatile metabolites in red ripe strawberry genotypes.

The relations between physical and chemical characteristics (e.g., color, firmness, volatile and non-volatile metabolites) of red ripe strawberry fruit and the natural spoilage caused by Botrytis cinerea were investigated. The spoilage rates differed between genotypes, and this was highly correlated over two successive years. Among seventeen genotypes, a more intense red coloration of the fruit skin was associated with a lower spoilage rate (r = -0.63). Additionally, weakly negative correlations were found between the levels of anthocyanins, ascorbic acid, malic acid and spoilage rates. No clear correlations were found between spoilage rates and soluble sugars, most volatiles, firmness and dry weight percentage. High levels of two volatile compounds, ethyl butanoate (r = 0.55) and 1-hexanol (r = 0.61), were correlated to high spoilage rates. These characteristics may assist strawberry breeders in selecting for genotypes with reduced susceptibility to B. cinerea.

Identifying key wavenumbers that improve prediction of amylose in rice samples utilizing advanced wavenumber selection techniques.

This study utilizes advanced wavenumber selection techniques to improve the prediction of amylose content in grounded rice samples with near-infrared spectroscopy. Four different wavenumber selection techniques, i.e. covariate selection (CovSel), variable combination population analysis (VCPA), bootstrapping soft shrinkage (BOSS) and variable combination population analysis-iteratively retains informative variables (VCPA-IRIV), were used for model optimization and key wavenumbers selection. The results of the several wavenumber selection techniques were compared with the predictions reported previously on the same data set. All the four wavenumber selection techniques improved the predictive performance of amylose in rice samples. The best performance was obtained with VCPA, where, with only 11 wavenumbers-based model, the prediction error was reduced by 19% compared to what reported previously on the same data set. The selected wavenumbers can help in development of low-cost multi-spectral sensors for amylose prediction in rice samples.

Handling batch-to-batch variability in portable spectroscopy of fresh fruit with minimal parameter adjustment.

Near-infrared (NIR) spectroscopy models for fresh fruit quality prediction often fail when used on a new batch or scenario having new variability which was absent in the primary calibration. To handle the new variability often model updating is required. In this study, to solve the challenge of updating NIR models related to fresh fruit quality properties, the use of a semi-supervised parameter-free calibration enhancement (PFCE) approach was proposed. Model updating with PFCE was shown in two ways: first where the model on the primary batch was updated individually for each new fruit batch, and second where the model was sequentially updated for the next batches. Furthermore, for the first time, a case of updating an instrument transferred model was also presented. The PFCE approach was shown in two real cases related to moisture and total soluble solids prediction in pear and kiwi fruit. In the case of pear, the model was later updated for 3 new measurement batches, while, for kiwi, a commercial model was updated to incorporate the variability of a new experiment carried out with a new instrument in the laboratory environment. For each modelling demonstration, the performance was benchmarked with the partial least-square (PLS) regression analysis on the primary batch. The results showed that the models updated with a semi-supervised approach kept a high predictive performance on new measurement batches, without any extra parameter optimization. An instrument transferred model was also updated to maintain its performance on different batches. Further, the sequential updating approach was found to be performing better than the update for individual batches, as the models were able to learn from multiple batches. Model updating with a semi-supervised approach can allow the NIR spectroscopy of fresh fruit to be scalable, where models can be shared between scientific or application community.

High Light Intensity Applied Shortly Before Harvest Improves Lettuce Nutritional Quality and Extends the Shelf Life.

The effect of light intensity applied shortly before harvest on the nutritional quality, postharvest performance, and shelf life of loose-leaf lettuce (Lactuca sativa L. cv. Expertise RZ Salanova®) was investigated. Lettuce was grown either in a greenhouse with supplemental high-pressure sodium light (Experiment 1, EXP 1) or in a climate room under white LED light (Experiment 2, EXP 2). In both experiments full grown plants were transferred to a climate room for the End of Production (EoP) light treatments during the last week of cultivation. During EoP lighting plants were exposed to different intensities (0, 110, and 270 µmol m-2 s-1 in EXP 1; 50, 210, and 470 µmol m-2 s-1 in EXP 2) from white-red LEDs for 6 (EXP 2) or 7 days (EXP 1). Mature leaves were then harvested and stored in darkness at 10°C to study the postharvest performance. Changes in dry matter content, total ascorbic acid, and carbohydrates (including glucose, fructose sucrose, and starch) levels were determined during EoP lighting and during the subsequent shelf life as indicators of lettuce nutritional quality. Quality aspects (appearance, texture, and odor) were accessed during the shelf life as indicators of postharvest performance. In both experiments, high light intensities applied in EoP lighting increased dry matter percentage and contents of ascorbic acid (AsA) and carbohydrates at harvest and these increased levels were maintained during the shelf life. Increased light intensity in EoP treatment also extended the shelf life. The levels of AsA and carbohydrates at harvest correlated positively with the subsequent shelf life, indicating that the prolonged shelf life relies on the improved energy and antioxidant status of the crop at harvest.

Low Oxygen Storage Improves Tomato Postharvest Cold Tolerance, Especially for Tomatoes Cultivated with Far-Red LED Light.

We investigated the effects of low oxygen storage on chilling injury development, colour development, respiration and H2O2 levels of 'Merlice' tomatoes cultivated with and without far red (FR) LED lighting during 20 days of shelf-life. Mature green (MG) and red (R) tomatoes were stored at 2 °C in combination with 0.5, 2.5, 5 and 21 kPa O2 for 15 days (experiment 1). MG tomatoes cultivated under either white LED or white LED light with FR LED light were stored at 2 °C in combination with 1, 5 and 21 O2 kPa for 14 days (experiment 2). Chilled MG and R tomatoes from experiment 1 showed decay, firmness loss and higher weight loss during shelf-life which were reduced under low oxygen conditions. FR during cultivation improved chilling tolerance of MG tomatoes. Fastest colour development and lowest respiration rate during shelf-life were observed for MG fruit cultivated with FR lighting prior to storage at 1 kPa O2/0 kPa CO2. H2O2 levels during the shelf-life were not affected during cold storage. The improved cold tolerance of MG tomatoes cultivated with FR lighting is likely due to lower oxygen uptake that led to both higher lycopene synthesis and less softening.

Predicting sensitivity of recently harvested tomatoes and tomato sepals to future fungal infections.

Tomato is an important commercial product which is perishable by nature and highly susceptible to fungal incidence once it is harvested. Not all tomatoes are equally vulnerable to pathogenic fungi, and an early detection of the vulnerable ones can help in taking timely preventive actions, ranging from isolating tomato batches to adjusting storage conditions, but also in making right business decisions like dynamic pricing based on quality or better shelf life estimate. More importantly, early detection of vulnerable produce can help in taking timely actions to minimize potential post-harvest losses. This paper investigates Near-infrared (NIR) hyperspectral imaging (1000-1700 nm) and machine learning to build models to automatically predict the susceptibility of sepals of recently harvested tomatoes to future fungal infections. Hyperspectral images of newly harvested tomatoes (cultivar Brioso) from 5 different growers were acquired before the onset of any visible fungal infection. After imaging, the tomatoes were placed under controlled conditions suited for fungal germination and growth for a 4-day period, and then imaged using normal color cameras. All sepals in the color images were ranked for fungal severity using crowdsourcing, and the final severity of each sepal was fused using principal component analysis. A novel hyperspectral data processing pipeline is presented which was used to automatically segment the tomato sepals from spectral images with multiple tomatoes connected via a truss. The key modelling question addressed in this research is whether there is a correlation between the hyperspectral data captured at harvest and the fungal infection observed 4 days later. Using 10-fold and group k-fold cross-validation, XG-Boost and Random Forest based regression models were trained on the features derived from the hyperspectral data corresponding to each sepal in the training set and tested on hold out test set. The best model found a Pearson correlation of 0.837, showing that there is strong linear correlation between the NIR spectra and the future fungal severity of the sepal. The sepal specific predictions were aggregated to predict the susceptibility of individual tomatoes, and a correlation of 0.92 was found. Besides modelling, focus is also on model interpretation, particularly to understand which spectral features are most relevant to model prediction. Two approaches to model interpretation were explored, feature importance and SHAP (SHapley Additive exPlanations), resulting in similar conclusions that the NIR range between 1390-1420 nm contributes most to the model's final decision.

Monochromatic red light during plant growth decreases the size and improves the functionality of stomata in chrysanthemum.

Light emitting diodes (LEDs) now enable precise light quality control. Prior to commercialisation however, the plant response to the resultant light quality regime ought to be addressed. The response was examined here in chrysanthemum by evaluating growth, chlorophyll fluorescence (before and following water deficit), as well as stomatal anatomy (density, size, pore dimensions and aperture heterogeneity) and closing ability. Plants were grown under blue (B), red (R), a mixture of R (70%) and B (RB), or white (W; 41% B, 39% intermediate spectrum, 20% R) light LEDs. Although R light promoted growth, it also caused leaf deformation (epinasty) and disturbed the photosynthetic electron transport system. The largest stomatal size was noted following growth under B light, whereas the smallest under R light. The largest stomatal density was observed under W light. Monochromatic R light stimulated both the rate and the degree of stomatal closure in response to desiccation compared with the other light regimes. We conclude that stomatal size is mainly controlled by the B spectrum, whereas a broader spectral range is important for determining stomatal density. Monochromatic R light enhanced stomatal ability to regulate water loss upon desiccation.

Sequential fusion of information from two portable spectrometers for improved prediction of moisture and soluble solids content in pear fruit.

Near infrared (NIR) spectroscopy allows rapid estimation of quality traits in fresh fruit. Several portable spectrometers are available in the market as a low-cost solution to perform NIR spectroscopy. However, portable spectrometers, being lower in cost than a benchtop counterpart, do not cover the complete near infrared (NIR) spectral range. Often portable sensors either use silicon-based visible and NIR detector to cover 400-1000 nm, or InGaAs-based short wave infrared (SWIR) detector covering the 900-1700 nm. However, these two spectral regions carry complementary information, since the 400-1000 nm interval captures the color and 3rd overtones of most functional group vibrations, while the 1st and the 2nd overtones of the same transitions fall in the 1000-1700 nm range. To exploit such complementarity, sequential data fusion strategies were used to fuse the data from two portable spectrometers, i.e., Felix F750 (~400-1000 nm) and the DLP NIR Scan Nano (~900-1700 nm). In particular, two different sequential fusion approaches were used, namely sequential orthogonalized partial-least squares (SO-PLS) regression and sequential orthogonalized covariate selection (SO-CovSel). SO-PLS improved the prediction of moisture content (MC) and soluble solids content (SSC) in pear fruit, leading to an accuracy which was not obtainable with models built on any of the two spectral data set individually. Instead, SO-CovSel was used to select the key wavelengths from both the spectral ranges mostly correlated to quality parameters of pear fruit. Sequential fusion of the data from the two portable spectrometers led to an improved model prediction (higher R2 and lower RMSEP) of MC and SSC in pear fruit: compared to the models built with the DLP NIR Scan Nano (the worst individual block) where SO-PLS showed an increase in R2p up to 56% and a corresponding 47% decrease in RMSEP. Differences were less pronounced to the use of Felix data alone, but still the R2p was increased by 2.5% and the RMSEP was reduced by 6.5%. Sequential data fusion is not limited to NIR data but it can be considered as a general tool for integrating information from multiple sensors.

Caspase inhibitors affect the kinetics and dimensions of tracheary elements in xylogenic Zinnia (Zinnia elegans) cell cultures.

BACKGROUND: The xylem vascular system is composed of fused dead, hollow cells called tracheary elements (TEs) that originate through trans-differentiation of root and shoot cambium cells. TEs undergo autolysis as they differentiate and mature. The final stage of the formation of TEs in plants is the death of the involved cells, a process showing some similarities to programmed cell death (PCD) in animal systems. Plant proteases with functional similarity to proteases involved in mammalian apoptotic cell death (caspases) are suggested as an integral part of the core mechanism of most PCD responses in plants, but participation of plant caspase-like proteases in TE PCD has not yet been documented. RESULTS: Confocal microscopic images revealed the consecutive stages of TE formation in Zinnia cells during trans-differentiation. Application of the caspase inhibitors Z-Asp-CH2-DCB, Ac-YVAD-CMK and Ac-DEVD-CHO affected the kinetics of formation and the dimensions of the TEs resulting in a significant delay of TE formation, production of larger TEs and in elimination of the 'two-wave' pattern of TE production. DNA breakdown and appearance of TUNEL-positive nuclei was observed in xylogenic cultures and this was suppressed in the presence of caspase inhibitors. CONCLUSIONS: To the best of our knowledge this is the first report showing that caspase inhibitors can modulate the process of trans-differentiation in Zinnia xylogenic cell cultures. As caspase inhibitors are closely associated with cell death inhibition in a variety of plant systems, this suggests that the altered TE formation results from suppression of PCD. The findings presented here are a first step towards the use of appropriate PCD signalling modulators or related molecular genetic strategies to improve the hydraulic properties of xylem vessels in favour of the quality and shelf life of plants or plant parts.

Involvement of ethylene and nitric oxide in cell death in mastoparan-treated unicellular alga Chlamydomonas reinhardtii.

This work demonstrates a contribution of ethylene and NO (nitric oxide) in MP (mastoparan)-induced cell death in the green algae Chlamydomonas reinhardtii. Following MP treatment, C. reinhardtii showed massive cell death, expressing morphological features of PCD (programmed cell death). A pharmacological approach involving combined treatments with MP and ethylene- and NO-interacting compounds indicated the requirement of trace amounts of both ethylene and NO in MP-induced cell death. By employing a carbon dioxide laser-based photoacoustic detector to measure ethylene and a QCL (quantum cascade laser)-based spectrometer for NO detection, simultaneous increases in the production of both ethylene and NO were observed following MP application. Our results show a tight regulation of the levels of both signalling molecules in which ethylene stimulates NO production and NO stimulates ethylene production. This suggests that, in conjunction with the elicitor, NO and ethylene cooperate and act synchronously in the mediation of MP-induced PCD in C. reinhardtii. To the best of our knowledge, this is the first report on the functional significance of ethylene and NO in MP-induced cell death.

Postharvest Spectral Light Composition Affects Chilling Injury in Anthurium Cut Flowers.

The effect of the lighting environment during postharvest storage of ornamentals has largely been neglected in previous research. Anthurium is a cold-sensitive species originating from tropical climates and is widely cultivated all around the world for its colorful spathes. To investigate the effects of light spectrum on the performance of Anthurium cut flowers under cold storage, two cultivars [Calore (red spathe) and Angel (withe spathe)] were placed at low temperature (4°C), either in darkness (D) or under different light spectra [red (R), blue (B), 70:30% red:blue (RB), and white (W)] at an intensity of 125 µmol.m-2.s-1. In both cultivars, the longest and shortest vase lives were observed in spathes exposed to the R and B spectra, respectively. In both cultivars, electrolyte leakage (EL) of spathe was highest under the B and W spectra and lowest under the R spectrum. The highest rate of flower water loss from the spathes was observed under the B-containing light spectra, whereas the lowest rate of water loss was observed in D and under the R spectrum. Negative correlations were observed between EL and vase life and between anthocyanin concentration and EL for both Anthurium cultivars. A positive correlation was found between anthocyanin concentration and vase life. For both Anthurium cultivars, spectral light composition with higher percentage of B resulted in higher EL and as a result shorter vase life in cut flowers under cold storage condition. The negative effect of the B light spectrum on vase life of Anthurium can be explained through its effect on water loss and on oxidative stress and membrane integrity. The quality of Anthurium cut flowers should benefit from environments with restricted B light spectrum during postharvest handling.