Plant Senescence Research Articles

Stand Delineation of Pinus sylvestris L. Plantations Suffering Decline Processes Based on Biophysical Tree Crown Variables: A Necessary Tool for Adaptive Silviculture

Many planted Pinus forests are severely affected by defoliation and mortality processes caused by pests and droughts. The mapping of forest tree crown variables (e.g., leaf area index and pigments) is particularly useful in stand delineation for the management of declining forests. This work explores the potential of integrating multispectral WorldView-2 (WV-2) and Airborne Laser Scanning (ALS) data for stand delineation based on selected tree crown variables in Pinus sylvestris plantations in southern Spain. Needle pigments (chlorophyll and carotenes) and leaf area index (LAI) were quantified. Eight vegetation indices and ALS-derived metrics were produced, and seven predictors were selected to estimate and map tree crown variables using a Random Forest method and Gini index. Chlorophylls a and b (Chla and Chlb) were significantly higher in the non-defoliated and moderately defoliated trees than in severely defoliated trees (F = 14.02, p < 0.001 for Chla; F = 13.09, p < 0.001 for Chlb). A similar response was observed for carotenoids (Car) (F = 14.13, p < 0.001). The LAI also showed significant differences among the defoliation levels (F = 26.5, p < 0.001). The model for the chlorophyll a pigment used two vegetation indices, Plant Senescence Reflectance Index (PSRI) and Carotenoid Reflectance Index (CRI); three WV-2 band metrics, and three ALS metrics. The model built to describe the tree Chlb content used similar variables. The defoliation classification model was established with a single vegetation index, Green Normalized Difference Vegetation Index (GNDVI); two metrics of the blue band, and two ALS metrics. The pigment contents models provided R2 values of 0.87 (Chla, RMSE = 12.98%), 0.74 (Chlb, RMSE = 10.39%), and 0.88 (Car, RMSE = 10.05%). The cross-validated confusion matrix achieved a high overall classification accuracy (84.05%) and Kappa index (0.76). Defoliation and Chla showed the validation values for segmentations and, therefore, in the generation of the stand delineation. A total of 104 stands were delineated, ranging from 6.96 to 54.62 ha (average stand area = 16.26 ha). The distribution map of the predicted severity values in the P. sylvestris plantations showed a mosaic of severity patterns at the stand and individual tree scales. Overall, the findings of this work underscore the potential of WV-2 and ALS data integration for the assessment of stand delineation based on tree health status. The derived cartography is a relevant tool for developing adaptive silvicultural practices to reduce Pinus sylvestris mortality in planted forests at risk due to climate change.

Arabidopsis TCX8 functions as a senescence modulator by regulating LOX2 expression.

TCX8 localizes to nucleus and has transcriptional repression activity. TCX8 binds to the promoter region of LOX2 encoding lipoxygenase, causing JA biosynthesis suppression, and thereby delays plant senescence. Conserved CXC domain-containing proteins are found in most eukaryotes. Eight TCX proteins, which are homologs of animal CXC-Hinge-CXC (CHC) proteins, were identified in Arabidopsis, and three of them, TSO1, TCX2/SOL2 and TCX3/SOL1, have been reported to affect cell-cycle control. TCX8, one of the TCX family proteins, was believed to be a TF but its precise function has not been reported. Yeast two-hybrid screening revealed TCP20, a TF that binds to the promoter of LOX2 encoding lipoxygenase, as a strong candidate for interaction with TCX8. We confirmed that TCX8 directly interacts with TCP20 using in vitro pull-down assay and in vivo BiFC and observed that TCX8, as a TF, localizes to nucleus. Using EMSA and by analyzing phenotypes of TCX8-overexpression lines, we demonstrated that TCX8 regulates the expression of LOX2 by binding to either cis-element of LOX2 promoter to which TCP20 or TCP4 binds, affecting JA biosynthesis, and thereby delaying plant senescence. Our study provides new information about the role of TCX8 in modulating plant senescence through regulating LOX2 expression.

ACCELERATED CELL DEATH 6 Acts on Natural Leaf Senescence and Nitrogen Fluxes in Arabidopsis.

As the last step of leaf development, senescence is a molecular process involving cell death mechanism. Leaf senescence is trigged by both internal age-dependent factors and environmental stresses. It must be tightly regulated for the plant to adopt a proper response to environmental variation and to allow the plant to recycle nutrients stored in senescing organs. However, little is known about factors that regulate both nutrients fluxes and plant senescence. Taking advantage of variation for natural leaf senescence between Arabidopsis thaliana accessions, Col-0 and Ct-1, we did a fine mapping of a quantitative trait loci for leaf senescence and identified ACCELERATED CELL DEATH 6 (ACD6) as the causal gene. Using two near-isogeneic lines, differing solely around the ACD6 locus, we showed that ACD6 regulates rosette growth, leaf chlorophyll content, as well as leaf nitrogen and carbon percentages. To unravel the role of ACD6 in N remobilization, the two isogenic lines and acd6 mutant were grown and labeled with 15N at the vegetative stage in order to determine 15N partitioning between plant organs at harvest. Results showed that N remobilization efficiency was significantly lower in all the genotypes with lower ACD6 activity irrespective of plant growth and productivity. Measurement of N uptake at vegetative and reproductive stages revealed that ACD6 did not modify N uptake efficiency but enhanced nitrogen translocation from root to silique. In this study, we have evidenced a new role of ACD6 in regulating both sequential and monocarpic senescences and disrupting the balance between N remobilization and N uptake that is required for a good seed filling.

Luxury zinc supply acts as antiaging agent and enhances reproductive fitness in Arabidopsis thaliana

Developmental senescence in plants is an age dependent process affected by phytohormones, nutrient status, and environmental factors, while the antiaging effects of zinc are recognized in humans. This study explores the possible influence of a high, non-toxic Zn-supply (12 μM) on senescence and reproductive fitness in A. thaliana. Auxin-resistance mutant, axr1–12, and auxin overexpressing YUCCA6 mutant, yuc6−1D, and their corresponding background genotypes were grown until complete rosette senescence to quantify the fruit biomass and seed number. Gene expression of different antioxidant, auxin and senescence-associated markers were analyzed after the onset of senescence. All mutants showed delayed developmental senescence. Luxury Zn delayed senescence in wild type, but not in the mutant genotypes. Excluding axr1−12 mutants, which showed very low expression of the auxin gene marker INDOLE-3-ACETIC ACID INDUCIBLE 2 (IAA2), enhanced expression of the senescence markers SENESCENCE-ASSOCIATED GENE 12 (SAG12) and AUXIN RESPONSE FACTOR 2 (ARF2) coincided with decreased expression of IAA2. Delayed senescence and total number of seeds per plant were related to higher expression of the peroxisomal antioxidant enzymes Cu/Zn superoxide dismutase (SOD3) and catalase (CAT2). These results evidence that high Zn-induced delayed senescence and improved reproductive fitness in Arabidopsis are related to an auxin-independent mechanism that retains antioxidant activity.

Melatonin: A Potential Agent in Delaying Leaf Senescence

Delaying early leaf senescence is important for improving photosynthetic efficiency and crop productivity. Melatonin, a multitasking bio-stimulator, participates widely in plant development and stress responses. In recent years, the cumulative researches show that melatonin has the ability to delay senescence in plants. This review covers the most recent advances on the mechanisms of melatonin-mediated leaf senescence. Melatonin biosynthesis in senescing leaves employs an alternative pathway and is significantly regulated by light. Melatonin increases the thickness of leaf cuticle, wax accumulation and the ratio of palisade/spongy of senescing leaves to maintain intact leaf structure. Melatonin eliminates free radicals through a scavenging cascade reaction and induces antioxidants and antioxidant enzymes; and provides better protection against lipid peroxidation via arranging parallel to the bilayers at high concentration. Meanwhile, melatonin’s ability to ensure high photosynthetic efficiency is predominantly attributed to the reduction of chlorophylls and chloroplast proteins degradation, and the acceleration of chlorophyll de novo synthesis. The dual role of melatonin-regulated autophagy is beneficial for maintaining cellular homeostasis. NACs, WRKYs and DREBs play essential roles in melatonin-controlled transcriptional reprogramming of senescing leaves. Additionally, melatonin improves the activity of cytokinin and auxin; and inhibits the action of abscisic acid, ethylene and jasmonic acid to impact indirectly leaf senescence. Epigenetic modification may be part of mechanisms of melatonin-mediated alterations in gene expression. Moreover, selection of germplasms rich in melatonin and application of genetic modification in agriculture are extensively discussed. Further studies are needed to detail the mechanisms of melatonin-mediated signaling transduction in leaf senescence.

Аналіз характеристик та обґрунтування індексів рослинності

In this article there has been given the analyzing of non-fiction sources in order to find out the popular indexes of the vegetable control parameters. There are such parameters as chlorophyll presence, water containing, the efficiency of a light use, nitrogen and carbon presence, foliage pigmentation.  The chlorophyll presence control is conducted by such indexes as the difference vegetation index, the global environmental monitoring index, the infrared percentage vegetation index, the modified simple ratio, the modified Soil adjusted vegetation index 2, the non-linear index, the normalized difference vegetation index, the optimized soil adjusted vegetation index, the renormalized difference vegetation index, the soil adjusted vegetation index, the simple ratio etc. The control of water content can be based on the moisture stress index, the normalized difference infrared index, the normalized difference water index, the normalized multi-band drought index, the water band index. There is the photochemical reflectance index, the structure insensitive pigment index, the red green ratio index for the efficiency control of the light use. The nitrogen presence is controlled by the normalized differential nitrogen index. The carbon presence can be detected by the implementing of cellulose absorption index, the lignin cellulose absorption index, the normalized difference lignin index, the plant senescence reflectance index. The foliage pigmentations can be controlled by the means of the anthocyanin reflectance index 1, the anthocyanin reflectance index 2, the carotenoid reflectance index 1, and the carotenoid reflectance index 2. The specificity of the presented indexes is described; the calculation formulas and its main straits are proposed.

Climate change and primary production: Forty years in a bunchgrass prairie.

Over the past 109 years, a Montana intermountain bunchgrass prairie annually became warmer (0.7°C) and drier (27%). The temperature and precipitation trends continued since 1978, as we studied nitrogen availability, annual aboveground primary production (ANPP), plant phenology and species composition. Given the annual increase in temperature and decrease in precipitation, ANPP might be expected to decline; however, it increased by 110%, as the period of greatest production (late-May–June) became wetter and cooler, counter to the annual pattern, and this was strongest at lower elevations. Grass production increased by 251%, while dicot production declined by 65%, which increased grass relative abundance by 54%. Summer temperatures increased 12.5% which increased plant senescence by 119% and decreased fall plant regrowth by 68%. More intense summer senescence changed plant species composition in favor of more drought tolerant species. The greater ANPP and summer senescence may increase susceptibility for fire, but fire tolerance of the plant species composition did not change. Invasive plant species increased 108% over the study with annual grasses accounting for >50% of this increase, which further increased summer plant senescence. Therefore, seasonal climate changes at a smaller geographical scale (local), rather than average annual climate changes over a larger geographical scale (regional), may better reflect plant community responses, and this makes ecological forecasting of climate change more difficult.

The neglected season: Warmer autumns counteract harsher winters and promote population growth in Arctic reindeer.

Arctic ungulates are experiencing the most rapid climate warming on Earth. While concerns have been raised that more frequent icing events may cause die-offs, and earlier springs may generate a trophic mismatch in phenology, the effects of warming autumns have been largely neglected. We used 25years of individual-based data from a growing population of wild Svalbard reindeer, to test how warmer autumns enhance population growth. Delayed plant senescence had no effect, but a six-week delay in snow-onset (the observed data range) was estimated to increase late winter body mass by 10%. Because average late winter body mass explains 90% of the variation in population growth rates, such a delay in winter-onset would enable a population growth of r=0.20, sufficient to counteract all but the most extreme icing events. This study provides novel mechanistic insights into the consequences of climate change for Arctic herbivores, highlighting the positive impact of warming autumns on population viability, offsetting the impacts of harsher winters. Thus, the future for Arctic herbivores facing climate change may be brighter than the prevailing view.

Feedstock Contract Considerations for a Piedmont Biorefinery

A biorefinery purchasing feedstock (perennial grass) must offer contracts that provide the same opportunity to earn a profit for a feedstock contractor located 50 or 5 km from the biorefinery. The business plan presented here specifies that the biomass is purchased in satellite storage locations (SSLs), and the load-out and hauling costs are paid by the biorefinery. Contracts can be offered for harvest in September, October, and November, a three-month harvest window, or the harvest window can be extended to December, January, and February, a six-month harvest window. Required total storage capacity is 75% of annual consumption for the three-month window and 50% for the six-month window, a significant difference in total storage capacity (cost). The storage cost difference paid by the biorefinery is 5.27 and 3.52 USD/Mg for the three-month and six-month, respectively. Several issues must be addressed in the feedstock contracts: (1) earlier harvest, before plant senescence, means less nutrients are translocated back into the soil and more are removed at harvest; (2) harvest losses are higher for all harvests after the September harvest; and (3) storage losses increase with storage time in the SSL. Time of removal from the SSL is dictated by the biorefinery; thus, the feedstock contractor must be compensated. The contracts paid by the biorefinery, averaged across the entire annual consumption, were about the same for the three-month window, and six-month window. This result was obtained because fertilizer cost decreases and harvest losses increase as the harvest date increases; thus, the two factors tend to offset. Using a 77 USD/Mg base cost, representative feedstock payment at the SSL (no storage losses included) for contractors with various month contracts are September (84.30), October (85.54), November (86.72), December 88.63), January (89.98), and February (90.58). Subsequent compensation for storage losses depends on the amount of time the particular unit of biomass is in storage before shipment.

Proper Glyphosate Application at Post-anthesis Lowers Grain Moisture Content at Harvest and Reallocates Non-structural Carbohydrates in Maize.

Glyphosate (GP)-based herbicides have been widely applied to crops for weed control and pre-harvest desiccation. The objective of this research was to evaluate the effects of pre-harvest GP application on maize or how it physiologically alters this crop. Here, we applied four GP treatment (Control, GP150, GP200, and GP250) on maize lines of Z58 and PH6WC belonging to different maturity groups at grain-filling stages form DAP30 to DAP45. GP application significantly decreased the grain moisture content at harvest by 22–35% for Z58 and by 15–41% for PH6WC. However, the responses of grain weight to glyphosate vary with inbred lines and application time. A high concentration of glyphosate (GP250) reduced the grain weight of Z58 and low concentrations (GP150 and GP200) did not affect, while the grain weight of PH6WC significantly decreased under glyphosate treatment. In summary, our results revealed that timely and appropriate GP application lowers grain moisture content without causing seed yield and quality loss. GP application adversely affected photosynthesis by promoting maturation and leaf senescence. Meanwhile, it also enhanced non-structural carbohydrate (soluble sugars and starch) remobilization from the vegetative organs to the grains. Hence, GP treatment coordinates plant senescence and assimilate remobilization. RNA sequencing revealed that glyphosate regulated the transcript levels of sugar signaling-related genes and induced assimilate repartitioning in grains. This work indicates the practical significance of GP application for maize seed production and harvest, which highlights the contributions of source-sink communication to maize yield in response to external stress or pre-harvest desiccant application.

Programmed Cell Death in Stigmatic Papilla Cells Is Associated With Senescence-Induced Self-Incompatibility Breakdown in Chinese Cabbage and Radish.

Self-incompatibility (SI) is a genetic mechanism flowering plants adopted to reject self-pollen and promote outcrossing. In the Brassicaceae family plants, the stigma tissue plays a key role in self-pollen recognition and rejection. We reported earlier in Chinese cabbage (Brassica rapa) that stigma tissue showed upregulated ethylene responses and programmed cell death (PCD) upon compatible pollination, but not in SI responses. Here, we show that SI is significantly compromised or completely lost in senescent flowers and young flowers of senescent plants. Senescence upregulates senescence-associated genes in B. rapa. Suppressing their expression in young stigmas by antisense oligodeoxyribonucleotide abolishes compatible pollination-triggered PCD and inhibits the growth of compatible pollen tubes. Furthermore, ethylene biosynthesis genes and response genes are upregulated in senescent stigmas, and increasing the level of ethylene or inhibiting its response increases or decreases the expression of senescence-associated genes, respectively. Our results show that senescence causes PCD in stigmatic papilla cells and is associated with the breakdown of SI in Chinese cabbage and in radish.

Interfering Peptides Targeting Protein-Protein Interactions in the Ethylene Plant Hormone Signaling Pathway as Tools to Delay Plant Senescence.

Interfering peptides (iPs) have been recognized as valuable substances to specifically target protein-protein interactions (PPIs) in senescence and disease. Although the concept of iPs has been validated for several PPIs in medical and pharmaceutical research, little attention so far has been paid to the enormous potential iPs that may provide to target and control plant growth and developmental processes or plant environmental responses. However, recent research on PPIs in the ethylene signaling pathway has identified the synthetic peptide NOP-1 derived from the nuclear localization signal of ethylene regulator EIN2 as an efficient inhibitor of typical ethylene responses such as ripening, aging, and senescence. Biophysical and biochemical studies on purified recombinant proteins of the ethylene receptor family from various plant species demonstrate that the synthetic peptide binds in the nM-μM range at the plant target. Here, we describe methods to evaluate and quantify the effect of the NOP-1 peptide on flower senescence as a typical ethylene response in the intact plant system. This approach will help to systematically advance our technological capability to delay plant ethylene responses and to expand shelf-life or vase life of fruits and flowers.

Bringing New Methods to the Seed Proteomics Platform: Challenges and Perspectives.

For centuries, crop plants have represented the basis of the daily human diet. Among them, cereals and legumes, accumulating oils, proteins, and carbohydrates in their seeds, distinctly dominate modern agriculture, thus play an essential role in food industry and fuel production. Therefore, seeds of crop plants are intensively studied by food chemists, biologists, biochemists, and nutritional physiologists. Accordingly, seed development and germination as well as age- and stress-related alterations in seed vigor, longevity, nutritional value, and safety can be addressed by a broad panel of analytical, biochemical, and physiological methods. Currently, functional genomics is one of the most powerful tools, giving direct access to characteristic metabolic changes accompanying plant development, senescence, and response to biotic or abiotic stress. Among individual post-genomic methodological platforms, proteomics represents one of the most effective ones, giving access to cellular metabolism at the level of proteins. During the recent decades, multiple methodological advances were introduced in different branches of life science, although only some of them were established in seed proteomics so far. Therefore, here we discuss main methodological approaches already employed in seed proteomics, as well as those still waiting for implementation in this field of plant research, with a special emphasis on sample preparation, data acquisition, processing, and post-processing. Thereby, the overall goal of this review is to bring new methodologies emerging in different areas of proteomics research (clinical, food, ecological, microbial, and plant proteomics) to the broad society of seed biologists.

Evaluating annual spruce budworm defoliation using change detection of vegetation indices calculated from satellite hyperspectral imagery

During spruce budworm (SBW; Choristoneura fumiferana (Clem.)) outbreaks, defoliation causes severe tree damage and mortality to spruce-balsam fir (Picea spp.-Abies balsamea (L.) Mill.) forests. Annual defoliation thematic maps provide vital information for forest protection planning against outbreaks, but such data are challenging to accurately collect over large areas during a short (2–3 week) period when damaged foliage peaks. Current operational methods for estimating annual defoliation are aerial surveys, through visual observations by professionals from small aircraft, defining broad defoliation classes which are subjective and spatially can be inaccurate. Remote sensing studies estimating annual defoliation are limited due to lack of ground verification data and difficulty of capturing spectral changes specific to the short detection period. Only one study has used satellite hyperspectral imagery to detect annual SBW defoliation, classifying just two classes of defoliation and using inaccurate aerial survey results for training and validation. In this paper, we introduce a new method to estimate annual SBW defoliation in three classes (light ≤ 30%, moderate 30–70%, and severe ≥ 70%), using change detection of vegetation indices (VIs) derived from satellite (EO-1 Hyperion) hyperspectral imagery acquired before and after annual defoliation. Random Forest and Support Vector Machine classifiers were used to classify defoliation, and intensive field measurements of branch-level defoliation per plot were used for accuracy assessment. Field plots, with spatially correlated defoliation within stands, were used to derive an additional 624 plots to obtain sufficient and independent datasets for training and validating the detection results. The top four VIs for detecting annual defoliation, based on Random Forest Total Variable Importance Score and Spearman's rank correlations, were Plant Senescence Reflectance Index, Normalized Difference Water Index, Moisture Stress Index, and Enhanced Vegetation Index. The spectral regions of VIs used to classify defoliation included visible, near-infrared, red-edge, and shortwave infrared. Accuracies of the light, moderate, and severe defoliation classes using our method ranged from 55–85%, 40–76%, and 40–80%, respectively, which were significantly higher than the 32% accuracy of aerial survey defoliation data for the plots.

Involvement of NAC transcription factor NaNAC29 in Alternaria alternata resistance and leaf senescence in Nicotiana attenuata

NAC-LIKE, ACTIVATED BY AP3/PI (NAP) is a NAC transcription factor regulating leaf senescence in Arabidopsis thaliana. In wild tobacco Nicotiana attenuata, a nuclear localized NAC transcription factor NaNAC29 was identified to be highly elicited after inoculation of Alternaria alternata, a notorious necrotic fungus on tobacco species. The NaNAC29 possesses similar tertiary structure to NAP with 60% amino acid identity. However, it remains unknown the role of NaNAC29 in plant defense responses to A. alternata and leaf senescence in N. attenuata. In this paper, Defensin-like protein 1 (NaDLP1) was highly induced in N. attenuata after A. alternata inoculation and bigger lesions were developed in NaDLP1-silenced plants. Interestingly, A. alternata-induced NaDLP1 was reduced by 76% in VIGS NaNAC29 plants and by 61% in JA deficient irAOC plants at 3 days post inoculation. The regulation of NaDLP1 expression by NaNAC29 was clearly independent on JA pathway, since exogenous methyl jasmonate treatment could not complement the induction levels of NaDLP1 in NaNAC29-silenced plants to the levels in WT plants. Otherwise, the expression of NaNAC29 was low expressed in young leaves but highly in senescent leaves and dark-treated leaves. NaNAC29-silenced plants, which were generated by virus-induced gene silencing (VIGS NaNAC29), showed delayed senescence phenotype. In addition, constitutive over-expression of NaNAC29 in A. thaliana could rescue the delayed-senescence phenotype of nap and caused precocious leaf senescence of wild-type Col-0 plants. All the data above demonstrate that NaNAC29 is a NAP homolog in N. attenuata participating in the defense responses to A. alternata by regulation of a defensin protein NaDLP1 and promoting leaf senescence.

Heterologous Overexpression of Arabidopsis cel1 Enhances Grain Yield, Biomass and Early Maturity in Setaria viridis.

Heterologous overexpression of Arabidopsis cellulase 1 (Atcel1) results in enhanced yield, early maturity, and increased biomass in dicotyledonous species like poplar and eucalyptus but has not been demonstrated in monocots. We produced transgenic Setaria viridis accession A10.1 plants overexpressing a monocotyledonous codon optimized (MCO) Atcel1. Agronomic characterization of the transgenic events showed that heterologous overexpression of MCOAtcel1 caused enhanced grain yield, shoot biomass, and accelerated maturation rate in the model grass species S. viridis under growth chamber conditions. The agronomic trait differences observed were consistent with previous reports in dicots but are here described in a monocot species and associated with increased seed yield. Overexpression of Atcel1 in S. viridis was shown to increase the number of panicles and seeds by 24–30%, enhance overall grain yield by up to 26%, and lead to a shoot dry biomass increase of 16–19%. Overexpression also reduced time to plant maturation and senescence by 12.5%. Our findings in S. viridis suggest that manipulation of Atcel1 has potential for developing early-maturing and higher-yielding monocotyledonous biomass crops suitable for climate-smart agriculture.

VEGETATION INDEX BASED IN UNMANNED AERIAL VEHICLE (UAV) TO IMPROVE THE MANAGEMENT OF INVASIVE PLANTS IN PROTECTED AREAS, SOUTHERN BRAZIL

Abstract. The biological invasion is considered the second largest global threat to the maintenance and conservation of natural ecosystems biodiversity. Strategies and actions that guide the control and monitoring of invasive species in protected areas are still a challenge on the management of these areas. Remote sensing is potential tool to detect and monitoring these species, gaining a timeline scale and allowing the adoption of more effective control methods. In this study, search to evaluate the vegetation index potential by using multispectral images acquired by UAV as a support on detection and monitoring of invasive plants in Quarta Colônia State Park located on the Brazil’s southern region. A sampling area with a density of invasive plants above 80% was evaluated, with predominance of Psidium guajava and Ligustrum lucidum, generating a large data set from the extracted indexes. Among the evaluated index, the ones that showed the most potential in this study were Green Normalized Difference Vegetation Index (GNDVI), Plant Senescence Reflectance Index (PSRI) and Red Green Ratio Index (RGRI). Believe us that the use of UAVs platforms will be an important tool for the management of invasive species in protected areas.

Using Amaranth as a Model Plant for Evaluating Imperfect Storages: Assessment of Solar-refrigerated and Evaporatively-cooled Structures in India

Some storages have limited control over their internal environment and undergo daily and seasonal fluctuations in both temperature and humidity, which cause variation in the metabolic activity of stored products. As a result, it is difficult to assess and compare the performance of these imperfect storages using measures of environmental control. We propose using measures of plant senescence as a proxy for estimating storage performance of these “imperfect” storages based on the premise that physiological processes integrate changes of temperature and/or humidity in a predictable, mathematically describable manner. We evaluated amaranth (Amaranthus tricolor L.) as a model plant for evaluating imperfect storages using a red-leaf cultivar Pusa lal chaulai and a green-leaf cultivar Pusa kiran. Amaranth is a leafy vegetable grown worldwide and is a highly nutritious and versatile food. Cumulative respiration, a measure of integrated metabolic activity, was regressed against leaf abscission, chlorophyll loss, and leaf yellowing of amaranth stems for four storages having different, variable, temperature profiles. Storages included 1) an evaporatively cooled (EC) structure; 2) a solar-refrigerated and evaporatively cooled (SREC) structure; 3) an uncooled laboratory (UL); and 4) a household refrigerator (REF). We found that the rate of abscission, chlorophyll loss, and leaf yellowing differed markedly for the four storages; however, these measures of senescence were linearly related to estimates of cumulative respiration. The ease of measuring leaf abscission, chlorophyll loss, and leaf yellowing permits data collection even with minimal resources. We propose that amaranth would make an effective model plant for comparing the performance of storages differing dramatically in temperature control. A 10% leaf abscission in amaranth is proposed as a target for comparing storages.

Genotype and Sowing Time Effects on Soybean Yield and Quality

The successful production of soybeans is largely dependent on the sowing time, because every sowing outside the optimal time contributes significantly to yield losses. This field study aimed to evaluate the effects of sowing time (optimal—April 5; late—April 27) on the quantitative and quality traits of three soybean genotypes (Galina—0 maturity group; Sava—I maturity group; and Rubin—II maturity group) under dryland conditions in Vojvodina Province (Serbia) during 2017 and 2018. The genotype Sava had higher yield in climatic-unfavorable 2017, while Rubin had a higher yield in climatic-favorable 2018. The yields significantly decreased when the soybeans were sown in late April due to reductions in the number of pods per plant, seed weight per plant, and 1000-seed weight. The reduction in yield components was likely due to the accelerated senescence of plants and the negative effect of high temperature and low precipitation during the seed filling stage. Accordingly, the various sowing times and properly chosen genotypes provide a better utilization of soil and water resources. A proper genotype selection and sowing time can contribute to a high yield. At the same time, the protein and oil contents can be altered by the sowing time, especially under water stress during the reproductive stage.

Identification of Cotton Root Rot by Multifeature Selection from Sentinel-2 Images Using Random Forest

Cotton root rot is a destructive cotton disease and significantly affects cotton quality and yield, and accurate identification of its distribution within fields is critical for cotton growers to control the disease effectively. In this study, Sentinel-2 images were used to explore the feasibility of creating classification maps and prescription maps for site-specific fungicide application. Eight cotton fields with different levels of root rot were selected and random forest (RF) was used to identify the optimal spectral indices and texture features of the Sentinel-2 images. Five optimal spectral indices (plant senescence reflectance index (PSRI), normalized difference vegetation index (NDVI), normalized difference water index (NDWI1), moisture stressed index (MSI), and renormalized difference vegetation index (RDVI)) and seven optimal texture features (Contrast 1, Dissimilarity 1, Entory 2, Mean 1, Variance 1, Homogeneity 1, and Second moment 2) were identified. Three binary logistic regression (BLR) models, including a spectral model, a texture model, and a spectral-texture model, were constructed for cotton root rot classification and prescription map creation. The results were compared with classification maps and prescription maps based on airborne imagery. Accuracy assessment showed that the accuracies of the classification maps for the spectral, texture, and spectral-texture models were 92.95%, 84.81%, and 91.87%, respectively, and the accuracies of the prescription maps for the three respective models were 90.83%, 87.14%, and 91.40%. These results confirmed that it was feasible to identify cotton root rot and create prescription maps using different features of Sentinel-2 imagery. The addition of texture features had little effect on the overall accuracy, but it could improve the ability to identify root rot areas. The producer’s accuracy (PA) for infested cotton in the classification maps for the texture model and the spectral-texture model was 2.82% and 1.07% higher, respectively, than that of the spectral model, and the PA for treatment zones in the prescription maps for the two respective models was 8.6% and 8.22% higher than that of the spectral model. Results based on the eight cotton fields showed that the spectral model was appropriate for the cotton fields with relatively severe infestation and the spectral-texture model was more appropriate for the cotton fields with low or moderate infestation.