Radiation Interception Research Articles

Radiation interception and leaf area index from foliage cover in diploid potato

AbstractThe leaf area index (LAI) is defined as the proportion of leaf area per unit of land area. It is also considered as an essential factor in the crop's ability to capture solar energy. Direct methods of LAI estimation involve significant areas of cultivation and individually measuring the total leaf area, which is not an accurate method to assess the LAI in diploid potato (Solanum phureja Juz. et Buk.) cultivars. The objective of this study was to evaluate a practical method for determining the fractional radiation interception and the LAI based on the fractional foliage cover in diploid potato cultivars found using digital photographs and applying open‐source software. Then, we compared the results of this method with the results obtained using a canopy analyzer. The results obtained allow us to estimate foliage and obtain the fractional radiation interception properly, and with these two variables, it is possible to make reasonable estimates of the LAI. It is common to model the LAI, and from this value estimate, the fractional radiation interception. We propose to model the architecture of the plant to know how the diploid potato plant covers the soil in a given space and how much radiation it intercepts, then estimate LAI. This method of estimation would be the closest to the cultivation conditions. Foliage cover depends on the architecture, and the crop simulation model would approximate the plant architecture and not just biomass production and yield.

Defoliation frequency affects litter responses and nitrogen excretion by heifers in palisadegrass–forage peanut pastures

AbstractLegumes can contribute significantly to nitrogen (N) input in grazing systems. Grazing management is a critical factor affecting N cycling in mixed pastures, altering the legume N input as a result. This study assessed how defoliation frequency affects N cycling in rotationally stocked palisadegrass (Brachiaria brizantha) and forage peanut (Arachis pintoi) pastures. Treatments included four grazing management strategies, defined by the rest period interruption when the canopy reached 90 (90LI), 95 (95LI), and 100% (100LI) of photosynthetically active radiation interception (LI), and a fixed rest period of 42 d (42D). A 2‐yr experimental period was adopted. Existing litter was greater at 100LI (2208 vs. 1964 kg ha−1; average of 42D, 90LI, and 95LI, respectively). Greater defoliation frequency (42D and 90LI) resulted in increase of litter legume proportion, resulting in greater decomposition rate, lower litter half‐life (p < .001, and p = .015, respectively), and greater N cycling (91 vs. 64 kg ha−1 season−1). Less frequent defoliation (100LI) resulted in reduced total forage intake, proportion of legume intake, and lower N intake compared with other treatments (p = .007, p = .081, and p < .001, respectively). Greater defoliation frequency increased N cycling via litter, but did not affect excretion due to compensation with stocking rate. Defoliation frequency between 90 and 95% LI optimizes N cycling in palisadegrass‐forage peanut mixed pastures.

Grain productive efficiency of soybean plants under lactofen application

Adverse factors cause a decrease in the productive potential of crops. For soybean [(Glycine max (L.) Merrill], the excessive growth is a factor that results in plants with low effective efficiency. Thus, plants with an architecture that favours greater interception of solar radiation and deposition of pesticides tend to be more productive. The objective of this study is to evaluate the different application of lactofen, which is used as a growth inhibitor, improve the productive efficiency of soybeans by increasing the biological activity of the leaves. The study was conducted in the field with soybean cultivars NA 5909 RG and BMX Potência RR. The experiment followed a randomized complete block design with four treatments and five replicates: T1: control; T2: application of 140 g a.i ha-1 of lactofen in phenological stage V3; T3: application of 140 g a.i ha-1 of lactofen in phenological stage V6; and T4: application of 70 g a.i ha-1 of lactofen in phenological stage V3 + 70 g a.i ha-1 of lactofen in phenological stage V6. The interception of photosynthetically active radiation in the lower layer increased in all treatments. Lactofen application increased the percent area covered and the number of phytosanitary products spray droplets per cm² in the middle and lower layers of the plants. The lower third of the plants experienced the greatest effect of the treatments with regard to the number of pods, grains and grain weight, with treatment T2 presenting significant increases. The use of lactofen as a growth inhibitor at the beginning of pod development in soybean caused changes to plant architecture and root development, consequently enhanced the productive efficiency of the plant, primarily due to increased grain production in the lower layer. Future research using lactofen in different phenological stages and cultivars may provide more insights in to the performance of this growth inhibitor in soybean.

Acclimation of Growth and Photosynthesis in Petunia Seedlings Exposed to High-intensity Blue Radiation

Indoor production of bedding plant seedlings using sole-source radiation may present value in increasing uniformity and consistency compared with greenhouse production. However, information on physiological acclimation related to growth and photosynthesis in seedlings exposed to high-intensity blue radiation and elevated CO2 is limited. Seedlings of petunia (Petunia ×hybrida) ‘Dreams Midnight’ were exposed to red (peak = 660 nm):blue (peak = 451 nm) radiation ratios of 50:50 (R50:B50) or 90:10 (R90:B10) and radiation intensities of 150 or 300 µmol·m−2·s–1 under two CO2 regimes of 450 or 900 µmol·mol–1. Shoot dry mass (SDM), leaf area index (LAI), internode length, and whole-plant photosynthesis and light-use efficiency (LUE) responses to increasing radiation intensity were measured. In addition, leaf photosynthetic rate (A) was measured at ambient and supra-optimal CO2 concentrations for plants grown under 450 µmol·mol–1 CO2. Our results indicated growth (based on SDM, LAI, and internode length) was lowered for seedlings produced under R50:B50 compared with R90:B10. However, we observed an increase in whole-plant light-saturated photosynthesis (Ag,max) and whole-plant light saturation point (LSP) under R50:B50 compared with R90:B10. In addition, we observed lower LUE below and higher LUE above a radiation intensity of 500 µmol·m−2·s–1 in seedlings grown under R50:B50 compared with R90:B10. Based on our results, seedling growth was lowered under a high proportion of blue radiation mainly due to lower radiation interception (due to lower LAI and shorter internode length) and LUE of intercepted radiation at the intensities used. Higher Ag,max and LSP in R50:B50 compared with R90:B10 under higher radiation intensities was likely in part due to higher LUE. Further investigation revealed A was higher at both optimal and supra-optimal CO2 concentrations under R50:B50 compared with R90:B10, indicating a lack of stomatal effects of a higher proportion of blue radiation on carboxylation and LUE. We hypothesize that higher LUE in R50:B50 compared with R90:B10 under higher radiation intensities is due to improved photochemical quenching from increased biosynthesis of carotenoids and anthocyanins. The results from our study generated fundamental information on growth and photosynthetic responses to excess blue radiation, data that can be further used in optimizing plant production in controlled environments.

Application of seed and foliar priming strategies to improve the growth and productivity of late sown wheat (Triticum aestivum L.)

Under north Indian conditions, wheat is sown late in the season due to delayed harvesting of basmati rice and cotton, which limit the productivity of the crop. Various priming strategies might help in improving the growth and productivity of the late sown wheat crop. To test the seed and foliar priming response on the emergence, growth and yield of late sown wheat, two field experiments were conducted at the research farm of the Punjab Agricultural University, Ludhiana, during 2015–2016 and 2016–2017. Both experiments were conducted in completely randomized block design with 3 treatments in the first (November 5, November 20 and December 5) and 9 treatments in the second experiment [control, water spray, seed priming (SP), salicylic acid foliar priming (SA: 50, 75 and 100 ppm), combination of SP and SA]. Lower germination was observed in December 5 as compared to November 5 sowing. Seed priming significantly improved the emergence and growth of the late sown wheat. Seed priming increased tiller density, dry matter accumulation, leaf area index, normalized difference vegetative index (NDVI) and photosynthetically active radiation interception, number of effective tillers, grain and biomass yield and harvest index as compared to control. Foliar priming recorded significantly higher NDVI, proline content, grains ear−1, 1000-grain weight, grain yield and harvest index. Combined priming recorded the highest grain yield and harvest index as compared to seed and foliar priming alone. Wheat can be successfully grown under late sown condition with seed and foliar priming for less yield penalty.

Assessing Yield, Growth and Climate Traits in Agroforestry Systems in Southern Brazil

ABSTRACT The relationship between growth, yield and climate variables using multivariate analysis on agroforestry system has not been documented yet. Considering the potential of agroforestry systems as strategy to improve the balance of crop production and environmental health, the aims of this study were (i) to analyze the canonical correlations among groups of tree growth and climatic variables during four seasons of the year; and (ii) to characterize the relationships between sugarcane growth, yield, and quality variables in two agroforestry arrangements and sugarcane monocropping system. A field experiment was conducted from September 2011 to June 2016. The information generated in this study is relevant, as it provides information to farmers and can assist in the planning of new agroforestry systems due to the better knowledge of tree–crop interactions and climate effects in Southern Brazil. In this study, we demonstrated that crops and trees interact dynamically as a result of variations in the interception of solar radiation by trees in time due to the effect of tree age and arrangement, and we concluded that larger tree arrangements are suggested to benefit sugarcane growth and yield in agroforestry systems in Southern Brazil.

Biomass and potential energy yield of perennial woody energy crops under reduced planting spacing

Woody biomass can be used for supplying energy as a strategy to mitigate climate change and increase energy security by reducing the dependency on fossil fuels. The aims of this study were: (i) to evaluate the biomass production for energy generation; and (ii) to determine the leaf area index, solar radiation interception and mean annual increment of three perennial woody crops Eucalyptus grandis, Mimosa scabrella and Ateleia glazioviana, grown under four planting spacings in Southern Brazil. A field experiment was conducted from September 2008 to September 2018 in Frederico Westphalen, Brazil. The above-belowground woody biomass was determined by the destructive method. Also, the solar radiation interception, leaf area index, potential energy yield, biomass yield and partitioning were evaluated. Findings have shown that the highest biomass yield and potential energy yield were obtained in the planting spacing (2.0 × 1.5 m) for the Eucalyptus grandis. Among the woody species studied, the Eucalyptus grandis was the one that presented the largest potential to produce biomass for energy, followed by Mimosa scabrella and Ateleia glazioviana. Therefore, reduced planting spacings should be recommended for woody energy crops plantations, changing the planting spacing pattern (3.0 × 1.5 m) used by the majority of the forest producers.

High-Throughput Prediction of Whole Season Green Area Index in Winter Wheat With an Airborne Multispectral Sensor.

IntroductionIn recent decades, the interest has grown to quantify the green area index as one of the key characteristics of crop canopies (e.g. for modelling transpiration, light interception, growth). The approach of estimating green area index based on multispectral reflection data from unmanned airborne vehicles with lightweight sensors might have the potential to deliver data with sufficient accuracy and high throughput during the whole season.Materials and MethodsWe therefore examined the applicability of a recently launched drone-based multispectral system (Sequoia, Parrot) for the prediction of whole season green area index in winter wheat, with data from field trials in Northern Germany (2017, 2018 and 2019). The explanatory power of different modeling approaches to predict green area index based on multispectral data was tested: linear and non-linear regression models, multivariate techniques, and machine learning algorithms. Further, different predictors were implemented in these models: multispectral data as raw bands and as ratios. Additionally, a new approach for the evaluation of green area index predictions during senescence is introduced. It is shown that a robust calibration during growth phase is applicable during senescence as well.Results and DiscussionA linear model which includes all four wavebands provided by the sensor in three ratios (VIQUO) and a Support Vector Machine (SVM) algorithm allow a reliable and sufficiently accurate whole season prediction. The VIQUO-model is recommended as the best model, as it is precise but still relatively simple, thus easier to communicate and to apply than the SVM. The integrated values of predicted green area indices in an independent trial are highly correlated with their final biomass (R2: VIQUO = 0.84, SVM = 0.85) which represents the process of radiation interception, one of the determining factors of growths. This is an indicator for both, a robust model calibration and a high potential of the tested multispectral system for agricultural research and crop management.

Higher Radiation Use Efficiency Produces Greater Biomass Before Heading and Grain Yield in Super Hybrid Rice

To reveal the physiological mechanism underlying the yield advantage of super hybrid rice compared with inbred super rice, a super hybrid rice cultivar Yliangyou 3218 (YLY) and an inbred super rice cultivar Zhendao 11 (ZD) were field grown under five nitrogen (N) fertilizer rates in 2016 and 2017. The average grain yield of YLY across nitrogen fertilizer rates was 10.1 t ha−1 in 2016 and 9.7 t ha−1 in 2017, 29.6% and 21.3% higher than that of ZD in 2016 and 2017, respectively. YLY showed higher above-ground biomass accumulation, especially growth before heading, which was mainly due to its faster green leaf area index (GLAI) formation and greater maximum GLAI (GLAImax). The daily radiation interception (RIdaily) was 15.0% higher in YLY than ZD, but the accumulated radiation interception (RIacc) before heading showed little difference between them because ZD had a longer growth duration. The radiation use efficiency (RUE) of YLY before heading was 54.7% higher than that of ZD (YLY, 2.12 g MJ−1; ZD, 1.37 g MJ−1). Our result demonstrated that the yield advantage of YLY was due to its higher above-ground biomass before heading, which was mainly achieved by its improvement in RUE rather than radiation interception.

Soybean (Glycine max (L.) Merr.) Yield Reduction due to Late Sowing as a Function of Radiation Interception and Use in a Cool Region of Northern Japan

Yields decrease when soybean is sown later than recommended in the cool climate of the Tohoku region of Japan. However, the factors responsible for this decrease are not fully understood. We investigated the effects of late sowing on growth, phenological development, yield, yield components, and radiation interception of three soybean cultivars in two consecutive years and analyzed the relationships of those variables with temperature and soil volumetric moisture content (SMC). Averaged across years and cultivars, yields decreased significantly when plants were sown approximately three weeks late. Yield reductions were partially due to reductions in node number per plant, dry matter production, and capture of cumulative irradiance, resulting from slowed canopy development during vegetative and early reproductive stages. The number of seeds per pod was one of the major determinants of the variation in yield. Owing to the delay in sowing date, the reduction in seeds per pod was likely due to low temperatures during the 20 days after seed filling began. Occasional lower SMC during reproductive stages did not affect yield, yield components, and growth parameters. However, these results were obtained from the two years’ experiments. Therefore, further investigations of the relationship of yield with temperature and SMC under different years and sites are needed.

Effect of artificial shading on soybean growth and yield

Soybean (Glycine max) stands out in the agricultural scene, being one of the main sources of protein and oil for human and animal nutrition. The aim of this study was to evaluate the growth, radiation use efficiency, and the yield of soybean, cultivated under four levels of artificial shading to simulate the environment provided by an agroforestry system. A field experiment was conducted in Frederico Westphalen, Rio Grande do Sul, Brazil, from December 2015 to April 2016. The experimental design was completely randomized with four levels of shading (0, 30, 50, and 70%) as treatment, and eight collections of plants at specific growth stages. The growth and yield traits of the soybean crop are influenced differently as a function of shade levels. Thus, the simulation of an agroforestry system from artificial shading allowed the recommendation of soybean cultivation for intercropping systems, provided that the interception of solar radiation by the tree component is less than 30%, in order to enable soybean cultivation.

The Use of Reflective Mulch in Soybean-Oil Palm Intercropping System

Demand for soybean is increasing nowadays as it provides a high nutrition food at affordable price. To fulfill the demand, an intercropping system of soybean-oil palm may increase the production of soybean. However, shading by the oil palm canopy would reduce the amount of radiation reaching the soil surface. Theoritically, application of reflective mulches may increase the amount of solar radiation intercepted by the shaded plants, hence it gives a positive effect for plant growth. The study aimed to analyze the effect of an increased radiation transmission with reflective mulch on the growth and development of soybean under an intercropping system with 4-year olds oil palm. The experiments were carried out on PT. Perkebunan Nusantara VIII located in Cimarga District, Lebak Regency, from March to June 2018. There were three treatments based on mulch application, namely soil without mulch (R0), soil with black silver plastic mulch (R1), and soil with dry palm oil leaf mulch (R2). The results showed that a canopy of 4-year-olds oil palm transmitted around 42% of an incoming radiation. The use of mulch as radiation reflector has a positive effect on an increased interception of solar radiation and potential productivity. Under R1 and R2 treatments, intercepted radiation was 25% and 15% larger than that of R0. In addition, mulch increased radiation use efficiency (RUE) by 2.3 times under R1 (1.6 g/MJ) and 1.7 times under R2 (1.2 g/MJ). The potency of productivity also increased (1.48 and 1.42 times higher under R1 and R2, respectively). The finding confirmed that mulch application did not affect the plant development in any treatment. Furthermore, we suggest that an intercropping system of soybean and 4-year-olds oil palm may be applied to increase the soybean production in Indonesia.

Modeling leaf area development in soybean (Glycine max L.) based on the branch growth and leaf elongation

ABSTRACT Several models have been proposed to simulate the leaf area index (LAI) in soybean (Glycine max L.); however, these models do not directly account for the effect of branch growth. Because the increases in branches and branch node vary with plant density, the evaluation of branch growth is necessary for the application of the LAI model at various plant densities. In this study, we developed an LAI model for soybean, considering the branch growth and leaf elongation at each node. To simplify this model, we estimated the rate of branch and branch node increase based on the rate of main stem node increase. Branch growth was assumed to be restricted when the fraction of canopy radiation interception was increased. Moreover, we calculated the leaf area growth at each node based on leaf elongation at each leaflet. This LAI model was validated using the data of different years and plant densities for model calibration, and it estimated the LAI with a root mean square error of 0.76, which accounted for 92% of the variation in the data. Although further evaluation is needed, the LAI model proposed in this study reveals a high potential for accurate estimation of LAI at various plant densities.

Intercepted radiation and radiation-use efficiency in sunflower crops grown at conventional and wide inter-row spacings: Measurements and modeled estimates of intercepted radiation

The underlying eco-physiological principle behind row spacing choice in many field crops is that early and complete ground cover will maximize yield via greater crop photosynthesis during the critical period for grain number determination in environments with no major water limitations. Recently this principle has been put in doubt: wide row-spacing (1.40 m instead of 0.7 m) did not reduce oil or biomass yield in sunflower at plant densities of between 2 and 7 pl m−2, in spite of incomplete ground cover at the wider row spacing. Here, we report the effect of two row spacings (0.7 and 1.4 m), in sunflower crops of equal plant density, on interception of radiation, radiation use efficiency (RUE), crop biomass and oil yields in three experiments. Two approaches were used to estimate interception of radiation by the crops: i) periodic diurnal measurements during the crop cycle of interception in the inter-row space and on the sides of the hedgerows; and ii) the use of a olive hedgerow model, adapted to sunflower, to estimate radiation intercepted by the two crop arrays. Biomass at anthesis, at physiological maturity, and oil yield in crops grown in the two row-spacings did not differ. The results show that the increased RUE of the 1.4-m spaced crops in pre-anthesis phase was able to compensate for the delay of these crops in achieving close to full interception of irradiance. The daily patterns of irradiance incident on the hedgerow faces, especially the sunlit face, in the pre-anthesis phase and in the early and late hours of the day, were strongly affected by row-spacing. A more favorable irradiance in these periods of the day in the mid- and upper portions of the sunlit face of the 1.4-m spaced hedgerows may have contributed to the greater RUE values of these crops in the pre anthesis phase.The hedgerow model provided descriptions of the seasonal dynamics of intercepted radiation that were fully consistent with measured values for both row spacings.

Water and radiation use efficiencies in maize: Breeding effects on single-cross Argentine hybrids released between 1980 and 2012

Water deficit has been signaled as an important determinant of grain yield (GY) gaps between potential and actual GYs. Breeding for improved water as well as solar radiation productivities is a sustainable means to reduce this gap. The aim of this study was to evaluate breeding effects on GY and its physiological determinants, including water (WUE) and radiation (RUE) use efficiencies, of temperate maize hybrids grown under a wide range of environmental conditions in Argentina. We hypothesized that breeding focused on GY performance and broad adaptation produced an increase in crop biomass linked to an increased tolerance to adverse growing conditions, a trend associated with an increase in WUE and/or RUE. For this purpose, hybrids were grown under three stand densities and eight environmental conditions in the main target environment for the production of temperate hybrids in Argentina. Analyzed traits were GY, total shoot biomass (BT) production, harvest index (HI = GY/BT), crop evapotranspiration (ETC), crop radiation interception (IPARC: cumulative amount of intercepted incident photosynthetically active radiation), radiation use efficiency (RUE = BT/IPARC), water use efficiency (WUE) for biomass production (WUEB,ETc= BT/ETC) and WUE for GY production (WUEGY,ETc= GY/ETC). No breeding effect was registered on ETC and IPARC, whereas significant breeding effects (P < 0.05) were detected on GY (0.5 % YOR−1 from 1980 onwards). The latter were due to the improvement of BT (from 1993 onwards) as well as of HI (between 1980 and 1993), with gains of 0.5 % YOR−1 in both cases. Mentioned trends were associated with a significant increase in RUE (0.7 % YOR−1 from 1993 onwards) and consequently in WUEB,ETc (0.6 % YOR−1 from 1993 onwards) and WUEGY,ETc (0.5 % YOR−1 from 1980 onwards). Results demonstrated that breeding efforts, which have been driven almost exclusively by GY improvement, had no evident effect on the crop water use but had clear effects on crop biomass production and its partitioning. These unintended positive effects of breeding on RUE and WUEs are welcome on a global scale, considering that predicted trends of increasing human demand for water will require increased water productivity rather than increased water use by crops.

Efeito da carga de gemas da videira ‘Cabernet Franc’ na interceptação da radiação solar e na fertilidade de gemas

Devido a uma carência de informações técnico-cientificas sobre o efeito da carga de gemas em relação a interceptação da radiação solar, e o seu efeito na fertilidade de gemas, tem-se como objetivo desse trabalho avaliar o efeito do aumento da carga de gemas da videira ‘Cabernet Franc’ em relação a interceptação da radiação fotossinteticamente ativa e o seu efeito na fertilidade de gemas em região de elevada altitude de Santa Catarina. Este experimento foi conduzido durante safra 2016/2017, em um vinhedo comercial, localizado no munícipio de São Joaquim. Utilizaram-se plantas de ‘Cabernet Franc’ enxertadas sobre o porta-enxerto ‘Paulsen 1103’. Os tratamentos consistiram em quatro diferentes níveis de cargas de gemas: 15, 30, 50 e 75 gemas planta-1. O delineamento experimental utilizado foi o de blocos ao acaso, com quatro blocos e cinco plantas por parcela. Os dados foram submetidos à análise de variância (ANOVA) e comparados pelo Teste Tukey a 5% de probabilidade de erro. Os resultados desse estudo evidenciam a importância da interceptação da radiação fotossinteticamente ativa na fertilidade de gemas, observando-se redução da fertilidade de gemas em situações de redução da interceptação da radiação fotossinteticamente ativa, nesse caso, causado pelo aumento da carga de gemas, que resulta em um maior número de ramos, proporcionando um dossel mais denso, reduzindo a interceptação da radiação fotossinteticamente ativa que alcança as gemas da videira, sendo esse efeito, mais pronunciado nas gemas localizada na posição basal do ramo.

The Contribution of Functional Traits to the Breeding Progress of Central-European Winter Wheat Under Differing Crop Management Intensities.

Wheat yields in many of the main producing European countries stagnate since about 20 years. Hence, it is of high interest, to analyze breeding progress in terms of yield and how associated traits changed. Therefore, a set of 42 cultivars (released between 1966 and 2012) was selected and yield as well as functional traits defined by the Monteith and Moss equation were evaluated under three levels of management intensity. The Monteith Moss equation thereby calculates grain yield as the product of incident photosynthetically active radiation, fraction of intercepted radiation, radiation use efficiency, and harvest index. The field trial was performed in a high yielding environment in Northern Germany in two seasons (2016–2017 and 2017–2018) with very contrasting rainfall rates. The three differing managements were: intensive (high N + pesticides), semi-intensive (high N − pesticides), and extensive (low N − pesticides). The results indicate that the stagnation of wheat yields in Central-Europe is not caused by a diminishing effect of breeding on yield potential. This equally applies to suboptimal growing conditions like extensified crop management and restricted water supply. Nearly all functional sub-traits showed a parallel progress but coefficients of determination of relationships between traits and year of variety release are decreasing along the hierarchy of yield formation. One exception is radiation interception which did not show a stable linear increase during breeding history. In recent years, biomass is getting more important in comparison to harvest index. Values of harvest index are slowly approaching theoretical maxima and correlations with grain yield are decreasing.

Local adaptation along a sharp rainfall gradient occurs in a native Patagonian grass, Festuca pallescens, regardless of extensive gene flow

Increasing global aridity combined with changing environmental conditions might cause irreparable alterations in arid and semiarid ecosystems. Knowledge of within-species genetic diversity and adaptive responses, especially along climatic gradients, becomes critical to inform management, conservation and restoration efforts. We combine the analysis of neutral (microsatellites) and adaptive divergence (morphological traits in common garden experiments) between populations along a sharp precipitation gradient in the native Patagonian grass Festuca pallescens, to disentangle patterns of local adaptation and genetic diversity. The identification of genetically based traits under divergent selection denoted the existence of local adaptation in spite of extensive gene flow. Two plant growth patterns were detected associated with two ecological regions. In arid environments, a trade-off between not resigning foliage production, and reducing the exposure to drying agents resulted in a compacted plant architecture; while in dry subhumid environments, populations exhibited a wide architecture to cope with rainfall and radiation interception. Increasing aridity and grazing might favor a compact plant architecture, and fragmentation might reduce genetic diversity across these environments. Being a widely distributed species, F. pallescens is an excellent model species to study adaptive responses across environmental gradients facing climate change predictions, especially in dryland rangelands that maintain multiple ecosystem functions.

Sensor radiation interception risk control in target tracking

This paper is mainly on the problem of radiation interception risk control in sensor network for target tracking. Firstly, the sensor radiation interception risk is defined as the product of the interception probability and the cost caused by the interception. Secondly, the radiation interception probability model and cost model are established, based on which the calculation method of interception risk can be obtained. Thirdly, a sensor scheduling model of radiation risk control is established, taking the minimum interception risk as the objective function. Then the Hungarian algorithm is proposed to obtain sensor scheduling scheme. Finally, simulation experiments are mad to prove the effectiveness of the methods proposed in this paper, which shows that compared with the sensor radiation interception probability control method, the interception risk control method can keep the sensor scheduling scheme in low risk as well as protect sensors of importance in the sensor network.

Light energy utilization and distribution characteristics of flag leaf 13C assimilate in different spike-type wheat varieties and their responses to supplementary irrigation

To clarify the differences in light energy utilization and distribution characteristics of flag leaf 13C assimilate in different spike-type wheat varieties and their responses to supplementary irrigation, we set three water treatments in a field experiment, including no irrigation during growth duration of wheat (W0), water-saving irrigation (W1, irrigating at jointing and anthesis of wheat to keep the relative moisture of 0-40 cm soil to 65% and 70%), full irrigation (W2, irrigating at jointing and anthesis of wheat to keep the relative moisture of 0-40 cm soil to 85% and 90%) with the medium-spike wheat cultivars Jimai 22 and Qingnong 2, large-spike wheat cultivars Shannong 23 and Shannong 30 as test materials. The effects of different water treatments on canopy light energy utilization and 13C assimilate distribution characteristics of two spike-type wheat varieties were examined. The results showed that leaf area index, canopy light interception rate, and light energy utilization rate of the two varieties at 2, 11, 20 and 31 days after anthesis were significantly higher than W0 treatment, but there was no significant change in each index when the irrigation increased to W2 treatment. The distribution of flag leaf 13C assimilates of Jimai 22 and Shannong 23 of W1 in grain was 159.34 and 171.1 g·hm-2 higher than W0, respectively, and the distribution ratio was 6.5% and 6.5%, with no significant difference compared with W2. The grain yields of both varieties under W1 were significantly higher than that under W0, but with no significant difference with W2. Under water-saving irrigation, the medium-spike cultivars had higher canopy photosynthetically active radiation interception and utilization ability at 2 and 11 days after anthesis and large-spike cultivars at 20 and 31 days after anthesis. The distribution amount and ratio of 13C assimilates in the grain of medium-spike variety Jimai 22 flag leaf were 6.8% and 2.7% lower than that of the large-spike variety Shannong 23.