Duration Of Shading Research Articles

Minimal light requirements and performance under reduced photosynthetic photon flux of GA2ox‐transformed and conventional Kentucky bluegrass

AbstractShade stress is a common problem encountered in turfgrass management situations worldwide. Shade reduces photosynthetic photon flux (PPF), alters light quality, reduces air movement, and may introduce tree root competition. As a species, Kentucky bluegrass (Poa pratensis L.) possesses relatively poor shade tolerance, which limits its use in reduced light environments. However, genetic alteration of the gibberellic acid enzyme pathway has shown promise in some plant species for improving growth in shade. The objective of this 2‐year field study was to determine the comparative performance under reduced PPF and determine minimal daily light integral (DLIm) requirements for acceptable quality of a conventional (CONV) Kentucky bluegrass (KBG) blend and gibberellic acid 2‐oxidase (GA2ox) transformed “ProVista” (PV) KBG. A 2‐year field study was conducted under neutral density shade treatments producing monthly daily light integrals averaging from ∼5.8 (90% shade) to 48 mol m−2 day−1 (full sun) for mid‐June through October study periods. Based on nonlinear regression of mean monthly DLI during the study period versus turfgrass quality (TQ) at the end of each study period, DLIm was found to range from 7.5 to 10 mol m−2 day−1 for PV and from 22.5 to 26.2 mol m−2 day−1 for CONV KBG. Improved TQ of PV under low light intensities may be associated with reduced rates of leaf elongation, greater stand density, higher chlorophyll concentrations, and darker green color compared to CONV KBG. Although shade duration did not exceed 4 months, the results suggest that GA2ox‐transformed PV KBG possesses improved tolerance to reduced PPF compared to CONV KBG.

Influence of Shading and Anatomical Structure of the Stem Cutting on Rooting Performance of Fig (Ficus Sp.)

Fig (Ficus sp.) belongs to tropical and subtropical climates which have great potential for the commercial cultivation. Cutting is the most common and effective method of propagation for figs which is influenced by different exogenous and endogenous factors. In this light, a study was conducted to observe the responses of stem cutting of fig (Ficus sp.) of one exotic and two indigenous varieties (Teen- Ficus carica; wild fig- Ficus hispida and joggo fig- Ficus racemosa) in respect of duration of shade and anatomical status of stem. The study was laid in Completely Randomized Design (CRD) with two factors (duration of shade and cultivars) and three replications of the treatments. The four different treatments of shade duration were as T1= open or control, T2=3 days of shading, T3= 6 days of shading and T4= 9 days of shading. Data were collected on root and sprout growth of the cuttings at weekly interval from two weeks of planting the cuttings in sand filled plastic cups. When the duration of shading increased, the teen (Ficus carica) showed the longest sprout (1.59 mm) and root (2 mm) as well as maximum number of root (5.67) and sprout (2.33). Better rooting performance was found in teen and it was very low in wild fig. A relationship between rooting performance and anatomical structure was clearly observed in this study. Long period of shading has positive effect on number and length of sprout in teen and wild fig. On the other hand, short period of shading minimized the days required for sprouting in teen Presence of thin cuticle, thin trichome and the absence of druses crystal in ground tissue and medulla also enhanced the performance of stem cutting of teen.

Quantifying the cumulative cooling effects of 3D building and tree shade with high resolution thermal imagery in a hot arid urban climate

Shading is an effective heat-mitigation strategy, with tree and building shade naturally cooling heated surfaces in hot-arid climates. However, increasing shade through tree planting and building arrangement has associated costs, such as tree maintenance and loss of solar access. To make strategic decisions, quantifying shade’s cooling effectiveness is crucial. This study examines the extent to which shade reduces land surface temperature (LST) in a hot-arid residential environment by considering shade’s areal coverage, overall duration, and time of day. Using fine-resolution 3D city models (1 m/pixel), land cover classification (1 m/pixel), and high-resolution thermal imagery (6 m/pixel) for Tempe, Arizona, USA, hourly shade calculations are conducted from 7:30 to 13:30 on July 12, 2011. The relationships among the observed LST at 13:30, land cover types, and shade characteristics are analyzed using linear and spatial regressions. The results reveal that shade’s cooling effect is cumulative, rather than instantaneous, as surface cooling by earlier shade persists to later times to some degree. Areas shaded for longer hours are cooler than those shaded only temporarily. The results further indicate that tree-shaded areas are significantly cooler than those shaded by other features, including buildings, with the difference increasing with shade duration. Shifting a 6 × 6 m area from 0% to 100% shade in the early morning generates a 2.3℃ LST reduction at 13:30. The same shift in shade for the whole morning and the entire period (7:30–13:30) would lower LST by 8.3℃ and 11.3℃, respectively. The importance of temporal shade planning and policy recommendation for urban heat mitigation is discussed.

Planning the installation of building-integrated photovoltaic shading devices: A GIS-based spatiotemporal analysis and optimization approach

Building-integrated photovoltaics (BIPV) can produce power while occupying little urban space. Photovoltaic-integrated shading devices (PVSDs) are a key component of BIPV that can generate electricity while blocking excess daylight. However, previous studies have lacked a systematic design of PVSDs that accurately estimates the trade-offs between indoor sunshade duration and electricity generation. This study proposes a multi-objective optimization framework for maximizing PV potential, minimizing PV area, and enabling proper sunshade duration in complex urban surfaces. A GIS-based spatiotemporal analysis and optimization approach was applied to three PVSD planning scenarios: (i) parallel to the horizontal land surface, (ii) inclined at an angle equal to the local latitude, and (iii) rotated in real-time to keep the PV surface perpendicular to the solar radiation. Different PV widths are determined under different scenarios considering power generation and solar shading duration. In the real-time rotating scenario, the optimized 0.7-m-wide PVSDs can generate 0.861 GWh of electricity annually, with a competitive average power generation efficiency of 0.811 kWh/m2/day and a solar shading duration of 6.61 h/day. Flexible installation scenarios are suggested to account for shading from other upper PVSDs and surrounding buildings. This study can facilitate solar farming in global cities and contribute to renewable energy penetration.

Crop Load Management in Nashi Pear—A Review

Most nashi cultivars require heavy thinning, and this has traditionally been performed by the time and labour-intensive practice of hand thinning. Crop load management is a key cost driver for nashi production, but there are limited cost-effective options available for nashi growers compared to other pome fruit, especially apples and, to a lesser extent, European pears. There is, however, potential to adapt some of the thinning tools and techniques used in apples and European pears to reduce the labour requirements and high cost of thinning in nashi, thus improving industry profitability. Several chemical thinning agents have potential for nashi, and an understanding of the optimal application rates, times and weather conditions for each chemical, as well as the conditions/factors that impact the tree carbon balance, will improve the predictability of chemical thinning. However, it is difficult to target specific flowers/fruitlets within a cluster with chemicals, and the flowers that produce the preferred fruit shape and size are in the middle of the flower cluster. Mechanical thinning during the flowering period with either Darwin or BAUM-style string thinners has potential, particularly as these devices can be used as early as flower emergence. As for chemical thinning, the issue of non-selectivity needs to be addressed; however, the development of mechatronic systems should overcome most problems that occur with the currently available mechanical thinners. Shading at critical times is an avenue that could be explored further to ascertain the critical stage when developing fruit are susceptible to enable the determination of the optimal timing and duration of shading. Targeted pruning and bud thinning during the dormant winter period to reduce the floral bud numbers is a valuable option for the precise placement of fruit in optimal positions and to set up the required number of clusters. This review highlighted several tools/techniques that, with further work, can be incorporated into a systematic approach to crop load management in nashi while reducing the risk and cost.

Optimizing the Quality and Commercial Value of Gyokuro-Styled Green Tea Grown in Australia

Gyokuro is a style of Japanese green tea produced by employing agricultural shading in the weeks before harvest. This method results in a tea product with different organoleptic and chemical properties than common Japanese green tea. In an effort to yield the highest quality and commercially valuable green tea product, the present study explores the influence of shading treatments and the duration of shading on the natural biochemistry of the green tea plant. This study applied shading treatments at light intensity conditions of 40%, 16%, 10% and 1% of available ambient light and the application of a red-colored shade cloth of 60% opacity. The Quality Index Tool was used to measure the quality and commercial value of the green tea, using individual target constituents (theanine, caffeine and the catechins) quantified from HPLC analysis. This study shows that very high levels of total visible spectrum light shading (~99%) is required to achieve improvements in quality and commercial value. Specifically, this improvement is a direct result of changes in the mood- modifying bioactive metabolites theanine and caffeine. This study concludes that in green tea growing regions with more hours of sunlight per year, such as on the Central Coast of Australia, more intense shading will achieve products with improved quality and commercial value, which has more potential to be marketed as a functional ingredient.

The Critical Period of Production of the Secondary Metabolite Indican in (Indigofera tinctoria L.) on Light Intensity

Background: Indigofera tinctoria plays the role of a natural dye source that produces indigo color and contains the secondary metabolite indican which is highly responsive to light intensity. This study aims to examine the critical period for the formation of the secondary metabolite indican on light intensity. Methods: The method used was a completely randomized block design with a split-plot design. The study consisted of 2 treatment factors, namely: length of shade (main plot) and light intensity (subplot). The length of shade included 5 levels, namely early growth phase (up to 1 month after planting), mid-growth phase (up to 2 months after planting), maximum growth phase (up to 3 months after planting), 1 month before harvest and 2 months before harvest. Light intensity had 3 levels, namely 50% light intensity (38,464.3 lux), 25% (19,232.15 lux) and 10% (7,692.86 lux). Result: The combination of duration of shade and light intensity affected the growth, yield and content of secondary metabolites (indican) in Indigofera tinctoria. The highest number of leaves, plant fresh weight and biomass was found in the combination of shade in the early growth phase (up to 1 month after planting) with 50% light intensity. The highest indican production was found in the mid-growth shading (up to 2 months after planting) with 10% light intensity, which was 843.33 ppm. The critical period of shade to increase indican production along with the number of leaves was the mid-growth phase (up to 2 months after planting).

Shading under drought stress during grain filling attenuates photosynthesis, grain yield and quality of winter wheat in the Loess Plateau of China

AbstractIn the Loess Plateau region of China, winter wheat often undergoes prolonged cloudy days without rain which may affect the grain yield and quality. This study examined the impacts of shading and drought conditions during the grain‐filling period of winter wheat (Triticum aestivum L.) on photosynthesis, grain yield and quality traits in a greenhouse experiment. The imposed shading and irrigation‐deficit treatments were corresponded with naturally cloudy weather in the rainfed area. Five shading treatments, 15 days shading (SD15); 12 days shading (SD12); 9 days shading (SD9); 6 days shading (SD6); and 3 days shading (SD3), and four irrigation treatments: full irrigation (I100); 75% of full irrigation (I75); 50% of full irrigation (I50); and 25% of full irrigation (I25), were applied after completion of flowering. The results showed that shading during grain filling decreased the grain yield and individual grain weight irrespective of the dry or wet conditions of the soil. Plant height increased with a decrease in shading duration to favour the efficient capturing of light. The reduction in the rate of photosynthesis was noted with an increase in the drought intensity. Shading significantly reduced the grain protein contents and increased the grain starch contents. In conclusion, shading for a long duration (SD15, SD12 and SD9) and drought stress (I25) during the grain‐filling stage significantly decreased the yield and grain quality of winter wheat. The shading of few days without drought (I100: SD3, SD6 and SD9) improved the plant height, photosynthetic activity and increased the distribution of dry matter from vegetative organs to grains.

Tall fescue is a superturfgrass: Tolerance to shade conditions under deficit irrigation

To evaluate the morpho-physiological characteristics of some cool-season turfgrass species under shade stress, an experiment was conducted outdoor in two subsequent years. Then, tall fescue, as the best-recognized turf from the former test, was exposed to combined drought and shade stress, aiming to measure to what extent shade can decrease turfgrasses water consumption and alleviate drought effects. The first test included 35 treatments at 7 different levels of continuous and temporal shade conditions in the morning and afternoon (60% and 80%) and full sunlight, and 5 cool-season turfgrass species, i.e., tall fescue ( Festuca arundinacea Schreb.), red fescue ( Festuca rubra L.), perennial ryegrass ( Lolium perenne L.), Kentucky bluegrass ( Poa pratensis L.) and sheep fescue ( Festuca ovina L.)]. The second test was consisted of 9 treatment, including 3 different irrigation intervals (i. e. 3, 6, and 9 days), 3 shade stress (i.e. full sunlight, 60% and 80% permanent shade), and 3 replications. Seeds of different cool-season turfgrass species were sown in April 2015 and 2016 in a loamy soil. Treated turfgrasses were evaluated for morpho-physiological and biochemical characteristics. Results showed that in the first test tall fescue has the highest quality in terms of morpho-physiological characteristics at a high level of shade stress (80% continuous shade). Perennial ryegrass and Kentucky bluegrass showed weak tolerance to shade stress conditions. The 80% constant shade had the greatest influence on turfgrass qualitative and quantitative traits, but in some cases did not show a significant difference between temporal shades. Turfgrasses quality decreased by increasing the intensity and duration of shade; however tall fescue was an excellent turfgrass species under shade stress conditions. Although visual quality, tiller density, and total chlorophyll content of tall fescue were significantly reduced by less frequent irrigation, they were improved by shade treatment compared with control plants. In addition, tall fescue has the highest amount of proline, catalase activity, starch, and reducing sugars under 9 days of drought and 60% shade stress. This is the first report of the interaction of shade and drought stress on the biochemical and morpho-physiological responses of tall fescue plants.

Cautious clams? Energetic state modifies risk assessment in giant clams

AbstractA fundamental trade‐off exists between the essential activities of acquiring energy and avoiding predators, thus animals are expected to make decisions that optimize foraging and avoid predation. These assessments are often state‐dependent with hungrier animals taking greater risks when foraging. Previous studies have explored state‐dependent risk assessment in a variety of taxa, yet no studies have focused on giant clams, genus Tridacna. These organisms provide a unique system to test foraging‐risk trade‐offs because they have two main energy sources: photosynthesizing symbiotic algae and siphoning nutrients from the water column. These activities can only occur when the clams’ shells are open and the mantle is vulnerable to predation. Here, we tested whether risk assessment in giant clams was state‐dependent. We designed three experiments of different shading durations (within‐day and multiday) to block photosynthesis while allowing limited water flow for siphoning. We measured the latency of the clams to reopen after a simulated predator touch to determine whether different duration of shading modified their antipredator response. Our single‐day experiment did not show a change in the hiding times across the three treatments. However, clams increased their hiding time as the treatments increased food deprivation (no restrictions on flow or photosynthesis, restriction on flow, restriction on flow and photosynthesis) when exposed to treatments for multiple days. Overall, we found that clams that were more energy‐deprived had a longer hiding time. This contrasts with findings from previous state‐dependent risk assessment literature and suggests that clams are more cautious when energy deprived, a result that may be generalizable to other sessile invertebrates.

Photosynthetic base of reduced grain yield by shading stress during the early reproductive stage of two wheat cultivars

The young microspore (YM) stage is the most sensitive period for wheat grain formation to abiotic stress. Shading stress during YM stage reduces grain yield mainly due to grain number decrease. However, the photosynthetic base for grain number decrease is still unclear. In this study, 100% (control), 40% (S1), and 10% (S2) of natural light were applied for 1, 3, 5, and 7 days (D1, D3, D5 and D7) during YM stage of two wheat cultivars (Henong825, Kenong9204). The results showed that grain number in Henong825 and Kenong9204 was reduced by − 3.6 to 33.3% and 14.2–72.7%, respectively. The leaf photosynthetic rate (Pn) in Henong825 and Kenong9204 was deducted by 4.5–93.9% and 26.4–99.0%. Under S1–D1, the leaf Pn of Henong825 reducing was mainly due to the reduction of light intensity. With shading intensity and duration increasing, the reasons for leaf Pn decrease were the low light intensity, the low Gs (stomatal conductance) and chlorophyll content, the damage of ultrastructure of chloroplast and photosynthetic system. Under S2–D7, the chlorophyll content, Fv/Fm (maximal photochemical efficiency of photosystem II) and Jmax (maximum electron transport) were reduced by 19.6%, 5.2% and 28.8% in Henong825, and by 29.9%, 7.8% and 33.1% in Kenong9204. After shading removal, the leaf Pn of Kenong9204 under D5 and D7 could not reach to the level of CK. This study indicated that the reduction of leaf Pn was mainly due to the low light intensity under short shading duration (shorter than 3 days), and due to low light intensity and damage of the leaf photosynthetic system under longer shading duration (longer than 5 days), especially for Kenong9204 (shade-sensitive cultivar).

Container Size and Shade Duration Affect Growth of Flowering Dogwood

Flowering dogwood (Cornus florida) is a valuable nursery product typically produced as a field-grown crop. Container-grown flowering dogwood can grow much faster than field-grown plants, thus shortening the production cycle, yet unacceptable crop loss and reduced quality continue to be major issues with container-grown plants. The objective of this research was to evaluate the effects of container size and shade duration on growth of flowering dogwood cultivars Cherokee Brave™ and Cherokee Princess from bare-root liners. In 2015, bare-root liners were transplanted to 23-L (no. 7) containers and placed under shade for 0 months (full sun), 2 months (sun4/shade2), 4 months (sun2/shade4), or 6 months (full shade) during the growing season. In 2016, one-half of the plants remained in no. 7 containers and the other half were transplanted to 50-L (no. 15) containers and assigned to the same four shade treatments. In 2015, plant height was greatest with full shade for both cultivars, whereas stem diameter and shoot dry weight (SDW) were greatest in full shade for Cherokee Brave™. In 2016, both cultivars in no. 15 containers had greater plant height, stem diameter, root dry weight (RDW), and SDW. Full shade resulted in the greatest height, stem diameter, RDW, and SDW for Cherokee Brave™, and improved overall growth for ‘Cherokee Princess’. However, vigorous growth due to container size and shade exposure increased the severity of powdery mildew (Erysiphe pulchra) in both years. Substrate leachate nutrient concentration (nitrate nitrogen and phosphate) was greater in no. 15 containers but shade duration had no effect.

Sustainable co-production of food and solar power to relax land-use constraints

Renewable energy could often be land constrained by the diffuse nature of renewable resources. To relax land constraints, we propose the concept of ‘aglectric’ farming, where agricultural land will be sustainably shared for food and energy co-production. While wind turbines on agricultural land are already put into practice, solar power production on agricultural land is still under research. Here, we propose photovoltaic systems that are suitable for installation on agricultural land. Adjusting the intensity, spectral distribution and duration of shading allows innovative photovoltaic systems to achieve significant power generation without potentially diminishing agricultural output. The feasibility of solar aglectric farms has been proven through shadow modelling. The proposed solar aglectric farms—used alone or in combination with regular solar parks or wind plants—could be a solution for a sustainable renewable economy that supports the ‘full Earth’ of over 10 billion people. Diffusion of renewable energy technologies can be constrained by alternative land uses. Here the authors propose the idea of ‘aglectric’ farming and show with modelling how to use agricultural land sustainably for food and energy co-production.

Light intensity controls rhizosphere respiration rate and rhizosphere priming effect of soybean and sunflower

Rhizosphere respiration (Rroot) and rhizosphere priming effect (RPE) are crucial for regulating soil carbon dynamics. However, their responses to light intensity are not fully resolved. We investigated Rroot and RPE of soybean and sunflower using a continuous isotope-labeling technique. The two species were subjected to five levels of light intensity in a growth chamber. Plants were maintained at full light from seeding for 45 or 59 days, and switched to shading treatments for four days. Soil respiration was partitioned into root- and soil-derived CO2 during the last five days (day0, full light; day1–4, shading). Both soybean and sunflower Rroot showed significant positive relationships with light intensity, particularly after one day of shading. Moreover, both plants showed positive RPE (44–98%) at full light, but with increasing duration and intensity of shading, the RPE declined and even became negative (up to –20%). Indeed, a positive relationship between light intensity and RPE was observed in both species. Overall, our results showed that shading, by influencing light intensity and presumably photosynthesis rate and belowground carbon allocation, exerts a significant control of rhizosphere respiration rate and priming effect of the two species.

Photosynthetic duration, carboxylation efficiency and stomatal limitation of sun and shade leaves of different ages in field-grown grapevine ( Vitis vinifera L.)

The relationship of photosynthesis (A) of grapevine ( Vitis vinifera L.) sun and shade leaves of primary and secondary (lateral) shoots to insertion level was investigated over two seasons in the field. The leaf plastochron index (LPI) was used to denote leaf position on the shoot. Additionally, laboratory and field measurements of the response of A to CO 2 were conducted. An empirical model was developed to estimate carboxylation efficiency (CE) and stomatal limitations (1) of A. In sun leaves, the relationship of A to LPI changed little until the end of the season (October), whereas stomatal conductance (g) and the intercellular partial pressure of CO 2 (c i ) increased. Leaves acclimated to low light and leaves older than LPI 5 had 30 % lower A and were operating at a slightly higher ci as sun leaves. During September and October, lateral leaves had highest rates of CO 2 assimilation and CE. In mid-October, A and g decreased rapidly and simultaneously for all leaf types, leaf positions and both treatments (sun and shade). Photosynthesis responded similar to individual leaf age as to leaf position. A was linearly related to c i up to non-limiting conductances for sun and shade leaves, for all ages and at all times during the season. The CE and 1 were highest at the beginning of the season and strongly dependent on leaf position. Stomatal limitation declined continuously from about 55 % at the beginning to about 23 and 18 % for sun and shade leaves, respectively, at the end of the season.

Partial shading of lateral branches affects growth, and foliage nitrogen- and water-use efficiencies in the conifer Cunninghamia lanceolata growing in a warm monsoon climate.

The degree to which branches are autonomous in their acclimation responses to alteration in light environment is still poorly understood. We investigated the effects of shading of the sapling crown of Cunninghamia lanceolata (Lamb.) Hook on the whole-tree and mid-crown branch growth and current-year foliage structure and physiology. Four treatments providing 0, 50, 75 and 90% shading compared with full daylight (denoted as Treatment(0), Treatment(50%), Treatment(75%) and Treatment(90%), and Shaded(0), Shaded(50%), Shaded(75%) and Shaded(90%) for the shaded branches and Sunlit(0), Sunlit(50%), Sunlit(75%) and Sunlit(90%) for the opposite sunlit branches under natural light conditions, respectively), were applied over two consecutive growing seasons. Shading treatments decreased the growth of basal stem diameter, leaf dry mass per unit leaf area, stomatal conductance, transpiration rate, the ratio of water-soluble to structural leaf nitrogen content, photosynthetic nitrogen-use efficiency and instantaneous and long-term (estimated from carbon isotope composition) water-use efficiency in shaded branches. Differences between shaded and sunlit branches increased with increasing severity and duration of shading. A non-autonomous, partly compensatory behavior of non-shaded branches was observed for most traits, thus reflecting the dependence between the traits of sunlit branches and the severity of shading of the opposite crown half. The results collectively indicated that tree growth and branch and leaf acclimation responses of C. lanceolata are not only affected by the local light environment, but also by relative within-crown light conditions. We argue that such a non-autonomous branch response to changes in light conditions can improve whole-tree resource optimization. These results contribute to better understanding of tree growth and utilization of water and nitrogen under heterogeneous light conditions within tree canopies.

Duration and intensity of shade differentially affects mycorrhizal growth- and phosphorus uptake responses of Medicago truncatula.

Plant and fungal partners in arbuscular mycorrhizal symbiosis trade mineral nutrients for carbon, with the outcome of this relationship for plant growth and nutrition being highly context-dependent and changing with the availability of resources as well as with the specific requirements of the different partners. Here we studied how the model legume Medicago truncatula, inoculated or not with a mycorrhizal fungus Rhizophagus irregularis, responded to a gradient of light intensities applied over different periods of time, in terms of growth, phosphorus nutrition and the levels of root colonization by the mycorrhizal fungus. Short-term (6 d) shading, depending on its intensity, resulted in a rapid decline of phosphorus uptake to the shoots of mycorrhizal plants and simultaneous accumulation of phosphorus in the roots (most likely in the fungal tissues), as compared to the non-mycorrhizal controls. There was, however, no significant change in the levels of mycorrhizal colonization of roots due to short-term shading. Long-term (38 d) shading, depending on its intensity, provoked a multitude of plant compensatory mechanisms, which were further boosted by the mycorrhizal symbiosis. Mycorrhizal growth- and phosphorus uptake benefits, however, vanished at 10% of the full light intensity applied over a long-term. Levels of root colonization by the mycorrhizal fungus were significantly reduced by long-term shading. Our results indicate that even short periods of shade could have important consequences for the functioning of mycorrhizal symbiosis in terms of phosphorus transfer between the fungus and the plants, without any apparent changes in root colonization parameters or mycorrhizal growth response, and call for more focused research on temporal dynamics of mycorrhizal functioning under changing environmental conditions.

Trajectory correction of the Spektr-R spacecraft motion

The results of refining the parameters of the Spektr-R spacecraft (RadioAstron project) motion after it was launched into the orbit of the Earth’s artificial satellite in July 2011 showed that, at the beginning of 2013, the condition of staying in the Earth’s shadow was violated. The duration of shading of the spacecraft exceeds the acceptable value (about 2 h). At the end of 2013 to the beginning of 2014, the ballistic lifetime of the spacecraft completed. Therefore, the question arose of how to correct the trajectory of the motion of the Spektr-R satellite using its onboard propulsion system. In this paper, the ballistic parameters that define the operation of onboard propulsion system when implementing the correction, and the ballistic characteristics of the orbital spacecraft motion before and after correction are presented.

Effects of Shading on Grain-Filling Properties and Yield of Maize at Different Growth Stages

The objective of this study was to explore the effect of shading at different growth stages on grain filling properties and yield of maize(Zea mays L.). The Field experiments were carried out using maize cultivars(Jingke 968, Zhengdan 958) with shading of 50% at the 13 th leaf fully expanded(T1), the silking(T2) and the15 th day after silking(T3) for seven days in 2012–2013. The natural light condition without shading was used as the control. The Logistic equation was used to analyze the grain filling process. The results showed that grains per ear, 1000-kernel weight and yield were all decreased to a different degree under shading conditions at different growth stages, and the decrease rate of grain yield was increased with lasting shading duration. The yield was significantly different under different shading treatments. The duration of the maximum grain filling and active grain-filling period(P) were shortened, the maximum and mean grain-filling rate(Gmax) decreased and the final grain weight(A) reduced under shading conditions. The relation among grain weight, grain number per ear and grain yield was determined by characteristics of maize cultivar. The grain weight of the same cultivar was significantly positively correlated with grain weight with the maximum grain-filling rate(Wmax), and the grain weight of different maize cultivars was determined by active grain-filling period(P). The grain number per ear of the same maize cultivar was significantly positively correlated with Gmax, and the grain number per ear of different maize cultivars was determined by Wmax. It is an important way to keep a high or stable yield by selecting the suitable cultivar, improving Wmax and Gmax and prolonging active grain-filling period(P) under weak light stress.

Lindera melissifolia responses to flood durations and light regimes suggest strategies for recovery and conservation

Passive management to preserve endangered plant species involves measures to avoid anthropogenic disturbance of natural populations, but this approach may not sustain plants that require disturbance-maintained habitats. Active management is often necessary to maintain existing habitats or provide new habitats for endangered species recovery. Our objective was to examine the effects of two disturbances in floodplain forests, soil flooding and light availability, on survival, stem length, stem diameter and ramet production of endangered Lindera melissifolia (Walt.) Blume. We used a water impoundment facility to control the timing and duration of flooding (0, 45 or 90 days) and shade houses to vary light availability (70, 63 or 5 % ambient light). Hydroperiod had little direct effect on steckling survival, stem length growth and stem diameter growth, supporting indications that soil flooding may be important for reduction of interspecific competition in L. melissifolia habitat. Greater ramet production by stecklings receiving no soil flooding likely resulted from longer periods of favorable soil conditions during each growing season. Positive stem length growth and stem diameter growth under all light levels demonstrates the plasticity of this species to acclimate to a range of light environments, though, greatest survival and stem length growth occurred when L. melissifolia received 37 % light, and stem diameter growth was greatest beneath 70 % light. Further, female clones produced more ramets as light availability increased. These results indicate that passive management absent natural disturbance could jeopardize sustainability of extant L. melissifolia populations, and this species would respond favorably to active management practices that create canopy openings to increase understory light availability.