Combined application of zinc and iron-lysine and its effects on morpho-physiological traits, antioxidant capacity and chromium uptake in rapeseed (Brassica napus L.)

Environmental contamination of chromium (Cr) has gained substantial consideration worldwide because of its high levels in the water and soil. A pot experiment using oil seed crop (rapeseed (Brassica napus L.)) grown under different levels of tannery wastewater (0, 33, 66 and 100%) in the soil using the foliar application of zinc (Zn) and iron (Fe)–lysine (lys) has been conducted. Results revealed that a considerable decline in the plant growth and biomass elevates with the addition of concentrations of tannery wastewater. Maximum decline in plant height, number of leaves, root length, fresh and dry biomass of root and leaves were recorded at the maximum level of tannery wastewater application (100%) compared to the plants grown without the addition of tannery wastewater (0%) in the soil. Similarly, contents of carotenoid and chlorophyll, gas exchange parameters and activities of various antioxidants (superoxidase dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX)) were also reduced significantly (P < 0.05) with the increasing concentration of tannery wastewater (33, 66 and 100%) in the soil. In addition, a combined application of Zn and Fe-lys reduced the accumulation and uptake of toxic Cr, while boosting the uptake of essential micronutrients such as Zn and Fe in different tissues of the plants. Results concluded that exogenous application of micronutrients chelated with amino acid successfully mitigate Cr stress in B. napus. Under field conditions, supplementation with these micronutrient-chelated amino acids may be an effective method for alleviating metal stress in other essential seed crops.

Kaolin Film Increases Gas Exchange Parameters of Coffee Seedlings During Transference From Nursery to Full Sunlight

Increases in water use efficiency (WUE) and the reduction of negative impacts of high temperatures associated with high solar radiation are being achieved with the application of fine particle film of calcined and purified kaolin (KF) on the leaves and fruits of various plant species. KF was applied on young Coffea arabica and Coffea canephora plants before their transition from nursery to full sunlight during autumn and summer. The effects of KF were evaluated through the responses of leaf temperature (Tleaf), net CO2 assimilation rate (A), stomatal conductance (gs), transpiration (E), WUE, crop water stress index (CWSI), index of relative stomatal conductance (Ig), initial fluorescence (F0), and photosynthetic index (PI) in the first 2–3 weeks after the plant transitions to the full sun. All measurements were performed at midday. In Coffea plants, KF decreased the Tleaf up to 6.7°C/5.6°C and reduced the CWSI. The plants that were not protected with KF showed lower A, gs, E, and Ig than those protected with KF. C. canephora plants protected with KF achieved higher WUE compared with those not protected by 11.23% in autumn and 95.58% in summer. In both Coffea sp., KF application reduced F0, indicating reduced physical dissociation of the PSII reaction centers from the light-harvesting system, which was supported with increased PI. The use of KF can be recommended as a management strategy in the transition of Coffea seedlings from the nursery shade to the full sunlight, to protect leaves against the excessive solar radiation and high temperatures, especially in C. canephora during the summer.

Application of phytohormones as attenuators of salt stress in Tropaeolum majus L. (Tropaeolaceae)

The salinity of the soil and irrigation water is one of the great challenges of agriculture. Salinity can have harmful effects on physiological processes and plant growth, including Tropaeolum majus L. (Tropaeolaceae). The application of phytohormones can be a strategy to mitigate these effects. The aim of this study was to evaluate the application of jasmonic acid, salicylic acid, cytokinin and polyamine as attenuators of salt stress in T. majus. Three levels of salt stress were used: 0 mM NaCl (no stress), 50 mM NaCl (moderate stress) and 100 mM NaCl (severe stress). Four phytohormones and a control treatment were used: control (deionized water), jasmonic acid (200 µM), salicylic acid (2 mM), cytokinin (6-benzylaminopurine – 10 µM) and polyamine (spermine – 1 mM). Growth and gas exchange parameters were evaluated. Applied in conditions of moderate salt stress, all the phytohormones were efficient in improving plant height and leaf area (except salicylic acid); cytokinin and polyamine improved the number of flowers as well as gs, A and iCE; jasmonic acid improved the stem dry mass and total dry mass. In relation to severe salt stress, applications of jasmonic acid and polyamine were efficient in improving plant height; cytokinin improved leaf dry mass as well as gs, A, E, WUE, iWUE and iCE. The application of cytokinin, polyamine and jasmonic acid can be used to mitigate moderate salt stress in T. majus.

Light Spectrum Variably Affects the Acclimatization of Grafted Watermelon Seedlings While Maintaining Fruit Quality

In many countries of Europe and Eastern Asia, watermelon production is mainly based on the use of grafted seedlings. Upon grafting, seedlings undergo a period of healing where artificial lighting is provided by light-emitting diodes in controlled chambers in order to accelerate and improve the healing process. The objective of our study was to test the effect of light quality on the final product (i.e., seedlings ready for transplanting) in the nursery, as well as to evaluate the possible implications on fruit quality after field cultivation. Narrow-band blue (B) and red (R) wavelengths, 64–36% R-B (36B), 76–24% R-B (24B), 88–12% R-B (12B), and 83–12% R-B plus 5% far-red (12B+FR) wavelengths were tested. 12B+FR enhanced the root dry weight, root architecture, and maximum photosynthetic rate, while RB combinations generally showed better root system development with increased blue portion. R light induced inferior root dry weight and quality indices (root/shoot and shoot–dry–weight/length ratios), lower gas exchange parameters, and chlorophyll content, but high shoot length and leaf area. B light led to inferior root architecture, lower stem diameter, leaf area, and maximum photosynthetic rate. Both R and B wavelengths showed decreased concentration of macronutrients and trace elements. After field cultivation, fruit quality (i.e., morphology and color), and valuable nutritive characteristics (i.e., phenolics, carotenoids, lycopene, antioxidants) maintained high quality irrespective of light treatments. Overall, 12B+FR performed well in almost all qualitative parameters including the morphology, the root development, and photosynthesis, while also maintaining high fruit quality.

Effect of drought on gas exchange and chlorophyll fluorescence of groundnut genotypes

Drought is one of the major threats to groundnut productivity, causing a greater loss than any other abiotic factor. Water stress conditions alter plant photosynthetic activity, impacting future growth and assimilating mobilization towards sink tissues. The purpose of this study was to investigate how drought impacts the photosynthesis of plants and its links to drought tolerance. The influence of reproductive stage drought on photosynthetic activity and chlorophyll fluorescence of groundnut is well studied. The experiment was conducted in Kharif 2019 (Jul-Sep), where recent series in groundnut genotypes (60 nos) sown under rainfed conditions and water stress was created by withholding irrigation for 20 days between 35-55 days after sowing in the field to simulate drought conditions. Imposition of water deficit stress reduced PS II efficiency, which significantly altered the photosynthetic rate in the leaf. Observation of gas exchange parameters viz., photosynthetic rate, stomatal conductance and transpiration rate after 20 days of stress imposition revealed that of all 60 genotypes, 20 genotypes (VG 17008, VG 17046VG 18005, VG 18102, VG 18077, VG 19572, VG 19709, VG 18111, VG19561, VG19576, VG 19620, VG 19681, VG 19688, etc.,) had better Photosynthetic rate, Stomatal conductance. Similarly, PS II efficiency analyzed through fluorescence meter revealed that among the 60 and all the genotypes given above recorded higher value in Fv/Fm. Results obtained from Cluster analysis and PCA confirmed that photosynthetic rate and Fv/Fm is useful parameter in screening adapted cultivars under drought stress. These findings lay the groundwork for a future study to decipher the molecular pathways underpinning groundnut drought resistance.

Ploidy level enhances the photosynthetic capacity of a tetraploid variety of Acer buergerianum Miq.

Background Polyploidy plays an important role in plant breeding and has widespread effects on photosynthetic capacity. To determine the photosynthetic capacity of the tetraploid variety Acer buergerianum Miq. ‘Xingwang’, we compared the gas exchange parameters, chloroplast structure, chlorophyll contents, and chlorophyll fluorescence parameters between the tetraploid Acer buergerianum ‘Xingwang’ and the diploid ‘S4’. To evaluate the effects of genome duplication on the photosynthetic capacity of Acer buergerianum ‘Xingwang’, the transcriptomes of the autotetraploid ‘Xingwang’ and the diploid ‘S4’ of A. buergerianum were compared. Methods The ploidy of Acer buergerianum ‘Xingwang’ was identified by flow cytometry and the chromosome counting method. An LI-6800 portable photosynthesis system analyzer was used to assess the gas exchange parameters of the tetraploid variety ‘Xingwang’ and diploid variety ‘S4’ of A. buergerianum. We used a BioMate 3S ultraviolet-visible spectrophotometer and portable modulated fluorometer to measure the chlorophyll contents and chlorophyll fluorescence parameters, respectively, of ‘Xingwang’ and ‘S4’. Illumina high-throughput sequencing technology was used to identify the differences in the genes involved in the photosynthetic differences and determine their expression characteristics. Results The single-cell DNA content and chromosome number of the tetraploid ‘Xingwang’ were twice those found in the normal diploid ‘S4’. In terms of gas exchange parameters, the change in stomatal conductance, change in intercellular CO2 concentration, transpiration rate and net photosynthetic rate of ‘Xingwang’ were higher than those of the diploid ‘S4’. The chlorophyll contents, the maximal photochemical efficiency of PSII and the potential photochemical efficiency of PSII in ‘Xingwang’ were higher than those of ‘S4’. The chloroplasts of ‘Xingwang’ contained thicker thylakoid lamellae. By the use of Illumina sequencing technology, a total of 51,807 unigenes were obtained; they had an average length of 1,487 nt, and the average N50 was 2,034 nt. The lengths of most of the unigenes obtained ranged from 200–300 bp, with an average value of 5,262, followed by those longer than 3,000 bp, with an average value of 4,791. The data revealed numerous differences in gene expression between the two transcriptomes. In total, 24,221 differentially expressed genes were screened, and the percentage of differentially expressed genes was as high as 46.75% (24,224/51,807), of which 10,474 genes were upregulated and 13,747 genes were downregulated. We analyzed the key genes in the photosynthesis pathway and the porphyrin and chlorophyll metabolism pathway; the upregulation of HemB may promote an increase in the chlorophyll contents of ‘Xingwang’, and the upregulation of related genes in PSII and PSI may enhance the light harvesting of ‘Xingwang’, increasing its light energy conversion efficiency.

Physiological and Morphometric Response of Forage Grass Species and Their Biomass Distribution Depending on the Term and Frequency of Water Deficiency

Periodic and repeated water scarcity has become an increasing concern on grasslands, causing not only to a reduction in productivity but also negative alterations in the carbon balance. The objective of this work was to comprehensively investigate some physiological performance traits of forage grasses, their roots morphometric features and distribution of biomass under simulated water deficit applied in different terms over a period of study. Plants were exposed to water shortage for 21 days, and then grown in optimal substrate moisture conditions. The gas exchange parameters and the main traits of root system architecture of three grass forage species and their cultivars were analyzed: Festulolium braunii (Richt.) A. Camus, cvs. Felopa and Sulino, Lolium perenne L., cvs. Bajka and Gagat and Festuca arundinacea Schreb. cvs. Odys and Rahela. Rapid decrease in the values of parameters related to the gas exchange process in grasses in the following days of water shortage was noticed. Water use efficiency (WUE) value was low in drought conditions due to increased transpiration of plants and was associated with a low C:N ratio in shoots. No obvious, positive effect of previously experienced drought stress on survival of tested grass species after another stress was observed. Cutting of plants after drought period most probably underlied the lack of memory and also additional factor weakened plant regrowth. When the drought was applied for the second time in spring during intensive plant growth, higher biomass allocation to the roots was observed. It was associated with the reduction of plant dry biomass, a decrease of carbon accumulation and the C:N ratio in the shoots. Due to the drought applied for the second time in summer, some biometric features of the roots were strongly and positively correlated with WUE, which is an important feature from the point of view of yield optimization and moisture use by plants.

Respiration monitoring in PACU using ventilation and gas exchange parameters

The importance of perioperative respiration monitoring is highlighted by high incidences of postoperative respiratory complications unrelated to the original disease. The objectives of this pilot study were to (1) simultaneously acquire respiration rate (RR), tidal volume (TV), minute ventilation (MV), SpO2 and PetCO2 from patients in post-anesthesia care unit (PACU) and (2) identify a practical continuous respiration monitoring method by analyzing the acquired data in terms of their ability and reliability in assessing a patient’s respiratory status. Thirteen non-intubated patients completed this observational study. A portable electrical impedance tomography (EIT) device was used to acquire RREIT, TV and MV, while PetCO2, RRCap and SpO2 were measured by a Capnostream35. Hypoventilation and respiratory events, e.g., apnea and hypopnea, could be detected reliably using RREIT, TV and MV. PetCO2 and SpO2 provided the gas exchange information, but were unable to detect hypoventilation in a timely fashion. Although SpO2 was stable, the sidestream capnography using the oronasal cannula was often unstable and produced fluctuating PetCO2 values. The coefficient of determination (R2) value between RREIT and RRCap was 0.65 with a percentage error of 52.5%. Based on our results, we identified RR, TV, MV and SpO2 as a set of respiratory parameters for robust continuous respiration monitoring of non-intubated patients. Such a respiration monitor with both ventilation and gas exchange parameters would be reliable and could be useful not only for respiration monitoring, but in making PACU discharge decisions and adjusting opioid dosage on general hospital floor. Future studies are needed to evaluate the potential clinical utility of such an integrated respiration monitor.

Defining Age-related OSA Features in Robin Sequence Using Polysomnographic-based Analyses of Respiratory Arousal Responses and Gas-exchange Parameters

Introduction Robin sequence (RS) is a leading cause of obstructive sleep apnea (OSA) in newborns. Most studies have focused on understanding anatomic factors leading to OSA and changes in apnea–hypopnea index (AHI) on polysomnography (PSG) beyond the neonatal period. This study aims to define age-related OSA features between patients with RS, without RS and healthy controls using PSG-based analyses of respiratory arousal responses and gas-exchange parameters. Design Retrospective comparison of PSG features in a total of 48 children encompassing three groups: (a) infants with RS (n = 24, <1-year old), (b) non-RS older children (1-2 years old) with severe OSA (obstructive AHI (OAHI) of ≥10 events; n = 12), and (c) control infants and children (0-2 years old) without sleep apnea (OAHI ≤1.5/h, n = 12). We examined OSA sleep-stage specific and position-specific indexes, and the relationship between OSA severity and respiratory arousal indexes (OAHI/respiratory arousal indexes). Results OSA sleep-stage specific indexes (rapid eye movement [REM] vs non-REM[NREM]) as well as position-specific indexes (supine vs nonsupine) were similar in individuals with and without RS. Relative to the non-RS groups, infants with RS have more sustained hypoxemia (time with SpO2 < 90%) and reduced arousal responses to OSA demonstrated by higher OAHI/respiratory arousal indexes. OAHI/respiratory arousal indexes significantly correlated with the severity of hypoxemia in infants with RS. Conclusion Infants with RS and OSA show reduced arousal responses to apneic events, which correlates with higher hypoxemia severity. OAHI/respiratory arousal indexes in RS may identify high-risk individuals with upper airway obstruction and reduced arousal protective responses.