Full Sunlight Research Articles

Phenology, growth and productivity of rice (Oryza sativa l.) under reduced sunlight intensity and foliar nitrogen application

The field experiments related to the study were conducted at Punjab Agricultural University, Ludhiana and Krishi Vigyan Kendra, Bahowal. There were 20 treatment combinations comprising of four levels of sunlight intensity [control (full sunlight), 50% reduction in sunlight light intensity during 15-45(R15-45), 46-75(R46-75) and 76-105(R76-105) DAT] and five levels of foliar nitrogen application [control (only recommended nitrogen, no foliar spray), spray of 3% urea before (NB), midway(NM), afterwards(NA) and midway-afterwards(NMA) the reduction in sunlight intensity in addition to the recommended nitrogen application]. Radiation level of R15-45 significantly preponed (2-5 days) the occurrence of phenological stages from maximum tillering to physiological maturity. Similarly, R46-75 significantly preponed (3-9 days) the occurrences of flag leaf initiation to physiological maturity. The nitrogen level of NB, significantly delayed the occurrence of flag leaf initiation to physiological maturity stages (2-5 days), NM delayed flag leaf initiation to physiological maturity (2-4 days), NA delayed anthesis to physiological maturity (1-4 days) and NMA delayed panicle emergence to physiological maturity (2-5 days). Plant height of rice was significantly increased due to R15-45 (5.21-5.26%) and R46-75 (6.95-7.61%) and also with foliar nitrogen application levels of NB, NM, NA and NMA by 9.95-9.89, 9.65-10.06, 8.06-7.57 and 9.65-9.29 per cent, respectively. Number of tillers m-2 was significantly reduced (4.71-15.99%) under low light conditions and was increased (5.59-23.34%) with foliar nitrogen application. Yield attributes were affected by the reduced sunlight intensity and foliar nitrogen application. Grain yield was significantly reduced as a result of R15-45 (9.19-11.41%), R46-75 (14.29-16.35%) and R76-105 (8.15-10.67%) and foliar nitrogen application levels of NB, NM and NMA resulted in significant increase the grain yield by 9.32-10.19, 5.74-6.38 and 4.59-5.74 per cent respectively, as compared to control.

Influence of plant size and neighboring plants on the herbivory of the columnar cactus Pilosocereus leucocephalus

Background: Plant-plant facilitation provides benefits to the protected species since the host species reduces the intensity of stressful physical conditions. However, it has been hypothesized that the outcome of the interaction could be regulated by the characteristics of the interacting species and that herbivores could counteract the benefits of protective plants.
 Question: Can cactus size and identity of neighboring plants influence the herbivory of the columnar cactus P. leucocephalus?
 Studied species / Mathematical model: Pilosocereus leucocephalus (Poselg.) Byles & G.D. Rowley /One-way ANOVA, Repeated measures ANOVA, Analysis of covariance and linear regression.
 Study site and dates: San Ignacio, Veracruz, Mexico. April to May 2019.
 Methods: We randomly selected 60 P. leucocephalus plants growing underneath the canopy of seven species of shrubs and P. leucocephalus plants growing ≥ 3 m away from other species and exposed to full sunlight conditions. We obtained the size of the P. leucocephalus plants (size of main stem from ground to apex) and determined the intensity (number of bites on the stem) of vertebrate herbivory.
 Results: The number of bite scars by small vertebrate species was significantly higher on the stems of cacti established in open spaces than on those underneath the canopy of seven shrub species and increased significantly with the stem size of the protected species.
 Conclusions: We conclude that herbivory damage by rodents on a giant cactus in a dry tropical forest depends on cactus size and the identity, but not the shade, of the nearest neighbor.

Photosynthetic electron transport in a tropical moss Hyophila involuta

Despite their global distribution moss physiology is not well understood, particularly in tropical environments. Photosynthetic Electron Transport Rate (ETR) of Hyophila involuta was measured using PAM technology. The plants were growing in a heavily shaded habitat with irregular sunflecks of full sunlight. Two models were used for estimating photosynthetic electron transport (ETR), the Waiting-in-Line and Eilers-Peeters models. Both take photoinhibition into account and gave similar results. The population studied was growing on bricks and stonework and so periodically dried out. The same species is sometimes found in waterfall environments where it is semi-aquatic. ETRmax was low at dawn, increased to an early morning maxima and then decreased during the course of the day, partially reversed by rainstorms. Mid-morning (10:30 solar time): Eopt ≈ 521 ± 77 µmol photon m–2 s–1 which is higher than might be expected in a shaded sun-fleck environment, ETRmax ≈ 28.3 ± 2.5 µmol e- m–2 s–1 on a projected surface area basis or ≈ 57.7 ± 5.1 (µmol e- g–1 Chl a s–1), photosynthetic efficiency (Alpha, α0) ≈ 0.301 (e- photon–1 g–1 Chl a). Chl a content of Hyophila was ≈ 453 mg Chl a m–2 with Chl b/a ≈ 0.371. The O2 electrode-based respiration rate was R = 6.78 ± 0.698 µmol O2 g–1 Chl a s–1, the ETRmax is roughly equivalent to Gross photosynthesis (Pg) ≈ 14.4 ± 1.28 µmol O2 g–1 Chl a s–1 (4 e-/ O2), so the optimum Pg/R ratio is about 2.12 ± 0.289 and net photosynthesis (Pn) is ≈ 7.62 ± 1.46 µmol O2 g–1 Chl a s–1. Thus even under optimum irradiance net photosynthesis was actually rather low. pH experiments showed that Hyophila used both CO2 & HCO3- inorganic carbon sources, suggesting that a concentrating mechanism (CCM) is present. Hyophila is partially homiochlorophyllous, recovering well from desiccation after 2h of lighted rehydration and recovers more after 24h but lost ≈30% of its Chl a. The moss retained its chlorophyll content if desiccated in the dark. The moss lost ≈ 2/3 of its Chl a during the monsoonal dry season.

Tailoring Multifunctional Self‐Assembled Hole Transporting Molecules for Highly Efficient and Stable Inverted Perovskite Solar Cells

AbstractThe self‐assembled hole transporting molecules (SAHTMs) bearing anchoring groups have been established as the hole transporting layers (HTLs) for highly efficient p–i–n perovskite solar cells (PSCs), yet their stability and engineering at the molecular level remain challenging. A topological design of highly anisotropic aligned SAHTM‐based HTLs for operationally stable PSCs that exhibit exceptional solar‐to‐electric power conversion efficiencies (PCEs) is demonstrated. The judiciously designed multifunctional self‐assembled molecules comprise the donor–acceptor subunit for hole transporting and the phosphonic acid group for anchoring, realizing face‐on π‐stacking parallel to the transparent conductive oxide substrate. The high affinity of SAHTMs to the multi‐crystalline perovskite thin film benefits passivating the perovskite buried interface, strengthening interfacial contact while facilitating interfacial hole transfer. Consequently, highly efficient p–i–n PSC devices are obtained with a champion PCE of 23.24% and outstanding operational stability toward various environmental factors including long‐term full sunlight soaking at evaluated temperatures. Perovskite solar modules with a champion efficiency approaching 20% are also fabricated for an active device area above 17 cm2.

Alkaloids (emetine and cephalin) production – affected by full sunlight stress in Carapichea ipecacuanha

This study evaluated the responses of Carapichea ipecacuanha to sunlight stress-induced changes in the electron transport chain and its extended effects on alkaloid production (emetine and cephalin). The treatments consisted of: (i). 50, 70, and 90% shading (controls) and their respective exposure to full sunlight; besides, full sunlight (55 days of direct sun exposure). Photosynthetic pigments, chlorophyll a fluorescence transient, antioxidant enzymatic system, and quantification of cephalin and emetine were analyzed. Several changes in the Chl a fluorescence induction were observed, such as a decline in the quantum yield of the conversion of photochemical energy and photosynthetic performance and; an increase in emetine production of plants exposed to full sunlight. These results demonstrated that ipecac plants are extremely sensitive to full exposure to solar radiation, especially in periods with high temperatures, such as in summer, however with increment in emetine production.

Light Intensity Alters the Growth and Quality of Volatile Components from Hexane Extracts of Hyptis suaveolens (Family Lamiaceae): A Medicinal Plant

Aim: This study was carried out to investigate the impact of light intensity on plant growth and n-hexane extracts of the leaves of Hyptis suaveolens. Materials and Methods: Plants were subjected to full sunlight (FS, 58753 lux), medium light intensity (MLI, 35880 lux) and low light intensity (LLI, 1250 lux) and were grown in loamy soil for 16 weeks. The parameters investigated include leaf area, shoot and root weight, number of leaves, Net Assimilation Rate (NAR), Leaf Area Ratio (LAR), Relative Growth Rate (RGR), type and amount of volatile components from n-hexane extract present in the leaves, using GC-MS. Results: There were mostly slight differences in the growth parameters but consistently the plants subjected to FS showed highest growth rate followed by those subjected to MLI. The dry weight roots of LLI plants, were significantly lower than the other treatments at p = 0.05 and these plants did not flower. Though there were only slight differences between the growth parameters of plants subjected to different light intensities, type and quantity of volatile compounds varied markedly. Volatile compounds like Ar-Abietatriene and 1-Phenanthrenemethanol were present under the three varying light intensities. Furthermore, LLI induced the highest concentration of 1-Phenanthrenemethanol than the other treatments, while FS induced the highest concentration of Ar-Abietatriene. Though full sunlight improved the growth of plants, the number of volatile compounds increased with decreasing light intensity from 7 to 12 compounds in the n-hexane extracts. Conclusion: This report shows that low light intensity increases the volatile compounds of Hyptis suaveolens markedly and this could enhance its antimicrobial activity.

Responses of photosystem to long-term light stress in a typically shade-tolerant species Panax notoginseng.

Photosynthetic adaptive strategies vary with the growth irradiance. The potential photosynthetic adaptive strategies of shade-tolerant species Panax notoginseng (Burkill) F. H. Chen to long-term high light and low light remains unclear. Photosynthetic performance, photosynthesis-related pigments, leaves anatomical characteristics and antioxidant enzyme activities were comparatively determined in P. notoginseng grown under different light regimes. The thickness of the upper epidermis, palisade tissue, and lower epidermis were declined with increasing growth irradiance. Low-light-grown leaves were declined in transpiration rate (Tr) and stomatal conductance (Cond), but intercellular CO2 concentration (C i) and net photosynthesis rate (P n) had opposite trends. The maximum photo-oxidation (P m) was greatly reduced in 29.8% full sunlight (FL) plants; The maximum quantum yield of photosystem II (F v/F m) in 0.2% FL plants was significantly lowest. Electron transport, thermal dissipation, and the effective quantum yield of PSI [Y(I)] and PSII [Y(II)] were declined in low-light-grown plants compared with high-light-grown P. notoginseng. The minimum value of non-regulated energy dissipation of PSII [Y(NO)] was recorded in 0.2% FL P. notoginseng. OJIP kinetic curve showed that relative variable fluorescence at J-phase (V J) and the ratio of variable fluorescent F K occupying the F J-F O amplitude (W k) were significantly increased in 0.2% FL plants. However, the increase in W k was lower than the increase in V J. In conclusion, PSI photoinhibition is the underlying sensitivity of the typically shade-tolerant species P. notoginseng to high light, and the photodamage to PSII acceptor side might cause the typically shade-tolerant plants to be unsuitable for long-term low light stress.

Light effects on seedling growth in simulated forest canopy gaps vary across species from different successional stages

Tropical forests continue to suffer from various kinds of disturbances in the Anthropocene. An immediate impact of disturbances on forest ecosystems is the creation of numerous large and small canopy gaps, which dramatically affect forest structure and function. Yet, we know little about the effect of canopy gaps on forest successional trajectory. More specifically, the responses of seedlings from different successional stages to increased light intensity under large and small canopy gaps in understory remain unclear. In this study, dominant tree seedlings from early-, mid-, and late-successional stages were selected, respectively from a tropical montane forest in Hainan Island, China to study their growth rate, biomass and traits. Our results showed that the light condition under small canopy gaps (SG, 10–15% of full sunlight) and large canopy gaps (LG, 40–50% of full sunlight) induced greater increment of relative growth rates for seedlings from early- and mid-successional stages relative to that in late-successional stage. Both SG and LG also significantly increased photosynthesis rate, leaf area (LA), light saturation point (LSP), root mass ratio (RMR) and root: shoot ratio, but decreased specific leaf area (SLA) of seedlings across successional stages. Tree seedlings from the early-successional stage displayed the greatest decrease in leaf mass ratio, increase in LA, LSP, and RMR, in comparison to those from mid- and late- successional stages. Light condition and SLA were the most important factors for seedlings’ relative growth rate across successional stages. SLA connected the interaction between the light condition and successional stage on seedlings’ growth, thereby jointly explaining the 93% variation of seedlings’ growth, combining with area-based light saturated rate of CO2 assimilation. Our study highlights the distinct effect of disturbance-induced canopy gaps on seedling regeneration in the understory in tropical forest due to the variation of light intensity. We suspect that the seedlings from late-successional stage will recover relatively slow after disturbances causing canopy losses, which can have detrimental impacts on structure feature and successional trajectory in tropical forest, as well as forest-based ecosystem services.

Spatial Distribution of Citrus Pseudocercospora Leaf and Fruit Spot Disease and Shade Effect on Disease Intensity

Adapting agricultural systems to face persistent environmental hazards is at the center of global concerns. In line with this, understanding and highlighting the structural characteristics of agroforestry systems could strengthen their resilience in terms of disease management. This study was conducted to evaluate the effect of shade on the intensity of citrus leaf and fruit spot disease caused by Pseudocercospora (PLFSD). Investigations to assess the effects of shade components on the incidence of PLFSD were carried out on 15-year-old tangerine trees in a cocoa-based agroforestry plot (Bokito) during four fruits seasons. Tangerines under the shade of large forest trees were compared to others located under full sunlight. A complementary experiment was conducted on young grapefruit plants in an orchard with mango and avocado groves in Foumbot. Three shading conditions, i.e., under avocado trees, under mango trees, and without shade, were explored. Data on shade and PLFSD incidence were collected and analyzed. Our findings show that PLFSD incidence was null on tangerine leaves from trees under shade compared to those under full sunlight. The same trends were observed in fruits under shade and under full sunlight. Disease incidence on grapefruit leaves was lower on trees under shade compared to those under full sunlight. In short, shade trees appear to constitute potential physical barriers to disease progression. This study also highlights disease spatial distribution as beyond 12 m of distance between neighboring trees, no spatial dependence of disease spread was observed. Management actions based on the distance between citrus trees and regulating shade are envisaged.

Chicória da Amazônia: cultivo a pleno sol ou sombreado?

ABSTRACT Climatic factors can decisively influence the growth and productivity of agricultural crops. For unconventional vegetables, such as the Amazon chicory, the influence of sunlight on growing cycle is unknown. The aim of this study was to evaluate the influence of shading levels on the productive performance of Amazon chicory. The authors used a randomized block design, with four treatments and five replicates. The treatments were black polypropylene screens, 30, 50 and 70% shading, and cultivation at full sunlight. Vegetative development and production traits were evaluated. Correlation and principal components analysis (PCA) were performed with the aid of the computer program R. No significant difference between the shading levels for the evaluated traits was noticed. Nevertheless, the cultivation at full sunlight allowed an increase in production, compared to the 70% shading screen. A strong positive correlation between productivity, leaf fresh mass and amount of water in the shoot area was verified, with a coefficient equal to 1. Only the leaf area characteristic was poorly correlated with other traits (angle >90º). Therefore, we suggest growing the Amazon chicory both at full sunlight and under 70% shading.

Particle films improve photosynthesis of citrus trees under excess irradiance by reducing leaf temperature

High irradiance and increased air temperature during extreme weather conditions affect tree crops and impact the yield and quality of fruits. Moreover, flowering and fruit set of Citrus are likely impaired by UV radiation and/or reduced carbon assimilation, which increase reactive oxygen species production and damage the leaf photosynthetic apparatus. Particle coating films sprayed on leaves have been offered as a way to minimize crop losses due to the climate change scenario, even though the extent of leaf protection is not characterized. We evaluated the use of two protective films on the oxidative stress and leaf photosynthesis of sweet orange trees exposed to varying daylight levels. Trees were maintained under full sun light, sprayed or not (control) with kaolin or calcium carbonate, and under reduced irradiance using either aluminum shade cloth 50% or anti-UV transparent plastic. Kaolin or calcium carbonate reflected 20%-30% of the incident light on the leaf surface compared to leaves not sprayed and under full sunlight. Leaves with coating exhibited improved CO2 assimilation and photosystem II efficiency, and lower leaf temperatures over time. In addition, the coating protected leaves against excess irradiance due to dissipation of excess energy into the photosynthetic apparatus (NPQt). Nonenzymatic mechanisms for UV protection, such as carotenoids, were higher in full sun control plants than in leaf-coated plants. Comparable responses were observed on trees maintained covered either by the cloth or the plastic film. Finally, we conclude that the use of suspension particles mitigates the harmful effects of excess UV irradiance and temperature in sweet orange trees.

Effects of radiation and plant population on growth and yield attributes of wheat

Radiation plays a crucial role for growth and yield of wheat. A field experiment was conducted at the Field Laboratory of Agrotechnology Discipline of Khulna University in Bangladesh during November 2018 to March 2019 to study the effect of radiation levels and plant population on growth and yield attributes of wheat. The study was set out in the randomized complete block design with four radiation levels (full sunlight, 75% light, 55% light, 25% light) and three plant population densities (160 plant/m2, 200 plant/m2, 230 plant/m2) that replicated thrice. Growth and yield attributes of wheat were generally similar between two light levels (full sunlight, 75% light) and two plant densities (200 plant/m2, 230 plant/m2). However, the attributes were usually minimum at 25% light. The interaction effect of full sunlight or 75% light with optimal (200 plant/m2) or maximal (230 plant/m2) plant densities produced statistically similar plant height, leaf number, tiller number, total dry matter, grain yield, straw yield, and biological yield. Therefore, combination of 75% light with 230 plant/m2 is suggested for growing wheat in light limited areas and in agroforestry system with acceptable yield.

Efeito do desbaste das árvores de eucalipto sobre rendimento da soja em sistemas de integração lavoura-pecuária-floresta

ABSTRACT: The aim of the study was to evaluate the effects of integrated crop-livestock-forestry (ICLF) systems and the thinning of eucalyptus trees on the agronomical performance of soybean. Treatments consisted of cultivation under: crops under full sunlight (CFS) conditions; ICLF with triple-row tree configuration (ICLFT) in which trees were submitted to selective thinning in the fifth year after planting through removal of 50% of trees while maintaining triple-row bands; and ICLF with single-row tree band configuration (ICLFS) in which the lateral rows of the triple-row tree bands were subjected to systematic thinning at the fourth year after planting. The physiological and agronomical variables of the soybean crop were evaluated at the R5 and R8 reproductive stages during the eighth harvesting season (2018/2019). Soybean sampling was carried out at five random positions in the CFS and in four transects at distances of 3, 6, 10 and 15 m from the tree bands in both the north and south faces of the ICLF systems. There were no differences between soybean grown under the ICLF and CFS systems with respect to specific leaf area, plant density, lodging index and mass of a thousand grains. However, the ICLF increased dry leaf mass and leaf area index and reduced soybean plant heights. Soybean productivity was reduced by 26% in ICLF-T and 14% in ICLF-S, that is, a 12% reduction in the productivity loss with systematic thinning. It is concluded that ICLF reduces soybean productivity in the effective grain production area of the system, regardless of the degree of thinning, although systematic thinning by removing the lateral tree lines to conversion of triple-rows into single-rows minimizes the loss of soybean grain yield.

Differential responses of yield and shoot traits of five tropical grasses to nitrogen and distance to trees in silvopastoral systems

Context Light intensity and nitrogen availability are important factors influencing the growth of C4 forage species. Trade-offs may occur in the adaptive responses of species to shading and nitrogen inputs, and functional shoot traits can help to explain the consequences of these responses for species performance. Aims Our objective was to gain understanding of the mechanisms involving shoot traits of grasses that determine above-ground dry matter yield (DMY) when resources, light and nitrogen all vary. Methods Five C4 perennial forage grasses were grown in six shading conditions (full sunlight vs five positions between Eucalyptus dunnii rows) with two nitrogen levels (0 vs 300 kg N ha−1 year−1) and clipped when the canopy reached 95% light interception. Path analysis was used to explore the relationship between DMY, shading levels, nitrogen nutrition index and shoot traits. Key results Yield increased between 126 and 569 g dry matter m−2 with nitrogen fertilisation. Plant nitrogen concentration was the most important predictor of DMY. Increased shading reduced DMY by 6.94–12.5 g dry matter m−2 for each 1% increase in shading. DMY was also modulated by shoot traits such as specific leaf area, sheath length and leaf area index (via leaf area and tiller density), but with different responses according to species. Conclusions The five species compared adopted different mechanisms involving shoot traits, revealing different strategies to cope with changes in light and nitrogen availability. Implications Agroforestry practitioners may want to choose forages that are more likely to maintain biomass yield as trees grow.

Secondary sexual dimorphism in biomass production of Ilex paraguariensis progenies associated with their provenances and morphotypes

Summary Secondary sexual dimorphism (SSD) in flowering plants is expressed as differences in sexual characteristics that are not directly related to gamete production, involving a wide variety of morphological and physiological traits. Yerba mate (Ilex paraguariensis) is an evergreen dioecious tree native to South America. It was hypothesized that: (1) in early years, the two yerba-mate genders would segregate with lower frequency in biomass production than during later years; (2) in the case of SSD, higher biomass production would be seen for female plants when compared to male plants at a more advanced age; (3) higher SSD would appear in morphotypes that represent leaf adaptations to full sunlight cultivation; and (4) progenies originated from provenances from higher altitudes will show greater SSD in biomass production. One experiment with 135 progenies originated from six provenances with different altitudes was established in 1997 in a monoculture (under full sunlight conditions). Biomass production (leaves and thin twigs) per plant was evaluated during four harvests (1999, 2001, 2003, and 2015). The frequency of SSD in biomass production did not change throughout the plant’s life. Males were more productive than females in 1999, 2001, and 2003, while the increased frequency of more productive female plants was observed during the most recent harvest (2015), resulting in an equal frequency of female and male progenies. Sexual segregation was observed in dully green, sassafras, and gray morphotypes that are characterized by their waxy leaf structures, an adaptation to elevated irradiance and UV. As a result of adaptative responses to stressful conditions and elevated interplant variability, the relationship between SSD and biomass production of progenies originated from the highest altitudes segregated with higher frequency when compared to the lowest altitudes.

Construction of Ultrasonic Fruit Fly Repellent Device in Orange Orchard

Ultrasonic waves are stated to be able to repel several types of pests. This study aimed to design a device to repel fruit fly in orange orchard using ultrasonic waves with a frequency range of 20-80 KHz. The device employed a microcontroller and real time clock (RTC) to control the ultrasonic wave transmitter automatically, in which the electrical energy is obtained from solar panel. The objective of using the solar panels is to directly powered device without installing the cable to the main power source (PLN) because the device should be placed in the middle of the orchard, which is located far from the main power source. Based on the design analysis, the solar panel should be placed facing the southern part of the orchard with the angle of around 5ºC since the orchard in the Karo regency, Sumatera Utara, Indonesia. The current was measured for each frequency, and based on that measurement the electrical power was calculated to be 142.56 Watt, so by using the battery of 1200 Watt, the device could work properly for 8 hours even without full sunlight. The resulted frequency was measured using oscillator; the results show that the average accuracy is 0.24%, which shows that the ultrasonic wave transmitters generate the ultrasonic wave accurately. Based on these results, it can be concluded that the ultrasonic fruit fly repellent device designed in this study is successfully constructed and works properly to generate the ultrasonic wave with the range frequency satisfied the condition to repel the fruit fly.

UV-Visible-Near-Infrared-Driven Photoelectrocatalytic Urea Oxidation and Photocatalytic Urea Fuel Cells Based on Ruddlensden–Popper-Type Perovskite Oxide La2NiO4

Photocatalysis and photoelectrocatalysis, as green and low-cost pollutant treatment technologies, have been widely used to simultaneously degrade pollutants and produce clean energy to solve the problems of environmental pollution and energy crisis. However, the disadvantages of photocatalysts in a narrow absorption range and low utilization rate of solar energy still hinder the practical application. Here we fabricate two-dimensional porous Ruddlensden–Popper type nickel-based perovskite oxide La2NiO4 as a noble metal-free photoanode for photoelectrocatalytic urea oxidation under full spectrum sunlight irradiation. The transient photocurrent density under near infrared (NIR) light (λ > 800 nm) can reach 50 μA cm−2. Urea wastewater was used as the fuel to obtain low-energy hydrogen production, and round-the-clock hydrogen production was achieved with the optimal yield of 22.76 μmol cm−2 h−1. Moreover, a photocatalytic urea fuel cell (PUFC) was constructed with La2NiO4 as the photoanode. The power density under UV-vis-NIR was 0.575 μW cm−2. Surprisingly, the filling factor (FF) under NIR light was 0.477, which was much higher than those under UV-vis-NIR and visible light. The results demonstrated that PUFCs constructed from low-cost nickel-based perovskite oxides have potential applications for low-energy hydrogen production and efficient utilization of sunlight.

Changes in Growth, Ionic Status, Metabolites Content and Antioxidant Activity of Two Ferns Exposed to Shade, Full Sunlight, and Salinity

The interactions between ferns and the environment have been frequently researched. However, detailed data on how ferns respond to specific stresses and a combination of stress factors during cultivation are lacking. This study assessed the effects of salinity and full sunlight and the combination of both stresses on the growth and selected metabolic parameters of two hardy ferns (Athyrium nipponicum cv. Red Beauty and Dryopteris erythrosora) under production conditions. Hardy ferns are highly interesting ornamental plants that can serve as a potential source of antioxidants for the pharmaceutical, cosmetic, and food industries. The results showed that in both ferns, salinity and salinity combined with full sunlight lowered the dry weight of the aerial part and potassium/sodium and calcium/potassium ratio compared with control plants. Salinity, full sunlight, and multi-stress did not affect the total polyphenol content in both ferns but increased the total free amino acids and flavonoids in D. erythrosora. In A. nipponicum cv. Red Beauty, all stressors decreased the total free amino acids content and the antioxidant activities determined by ABTS, DPPH, FRAP, and reducing power assays. By contrast, plants of D. erythrosora grown under full sunlight are characterized by higher antioxidant activities determined by DPPH, FRAP, and reducing power assays. Overall, a greater adaptive potential to abiotic stresses was found in D. erythrosora than in A. nipponicum cv. Red Beauty. Our findings shed some light on the physiological mechanisms responsible for sensitivity/tolerance to salinity, full sunlight, and combined stresses in hardy ferns.

Active and passive chlorophyll fluorescence measurements at canopy level on potato crops. Evidence of similitude of diurnal cycles of apparent fluorescence yields

We performed active and passive measurements of diurnal cycles of chlorophyll fluorescence on potato crops at canopy level in outdoors conditions for 26 days. Active measurements of the stationary fluorescence yield (Fs) were performed using Ledflex, a fluorescence micro-LIDAR described in Moya et al. (Photosynth Res 142:1–15, 2019), capable of remote measurements of chlorophyll fluorescence under full sun-light in the wavelength range from 650 to 800 nm. Passive measurements of solar-induced fluorescence (SIF) fluxes were performed with Spectroflex, an instrument based on the method of filling-in in the O2A and O2B absorption bands at 760 nm (F760) and 687 nm (F687), respectively.Diurnal cycles of Fs showed significant variations throughout the day, directly attributed to changes in photosystem II yield. Contrasting patterns were observed according to illumination conditions. Under cloudy sky, Fs varied in parallel with photosynthetically active radiation (PAR). By contrast, during clear sky days, the diurnal cycle of Fs showed a “M” shape pattern with a minimum around noon.F687 and F760 showed different patterns, according to illumination conditions. Under low irradiance associated with cloudy conditions, F687 and F760 followed similar diurnal patterns, in parallel with PAR. Under high irradiance associated with clear sky we observed an increase of the F760/F687 ratio, which we attributed to the contributions in the 760 nm emission of photosystem I fluorescence from deeper layers of the leaves, on one end, and by the decrease of 687 nm emission as a result of red fluorescence re-absorption, on the other end.We defined an approach to derive a proxy of fluorescence yield (FYSIF) from SIF measurements as a linear combination of F687 and F760 normalized by vegetation radiance, where the coefficients of the linear combination were derived from the spectral transmittance of Ledflex. We demonstrated a close relationship between diurnal cycles of FYSIF and Fs, which outperformed other approaches based on normalization by incident light.

DRY MATTER ALLOCATION AND GRAIN YIELD OF WHEAT AS INFLUENCED BY SOLAR RADIATION LEVEL AND PLANT DENSITY

An experiment was conducted from November 2018 to March 2019 to identify the effect of radiation levels and plant population on dry matter allocation and yield of wheat with the variety ‘BARI Gom 25’. The study was set out in the Randomized Complete Block Design with four radiation levels (full sunlight, 75% light, 55% light and 25% light) and three plant densities (160 plants m-2, 200 plants m-2, 230 plants m-2) that replicated thrice. Full sunlight or 75% light in combination with optimal plant density (200 plants m-2) resulted maximum culm dry weight, leaf dry weight, spike dry weight and total dry matter weight plant-1. The numbers of filled grain and unfilled grain plant-1 and yields of grain and straw m-2 were the highest from the above-mentioned combination. The lowest dry weights for culm, leaf, spike, and total dry matter and minimum grain yield and straw yield were obtained from 25% light either alone or in combination with any plant densities indicating the profound influence of light on dry matter production and grain yield of wheat. Therefore, reduced light (up to 25%) and optimal plant density can ensure wheat production without significant yield loss. This finding suggests possibility of wheat cultivation in agroforestry system and light limiting areas in Bangladesh and other parts of the world.