Decreased Plant Growth Research Articles

Chloroplasts require glutathione reductase to balance reactive oxygen species and maintain efficient photosynthesis.

Thiol-based redox-regulation is vital for coordinating chloroplast functions depending on illumination and has been throroughly investigated for thioredoxin-dependent processes. In parallel, glutathione reductase (GR) maintains a highly reduced glutathione pool, enabling glutathione-mediated redox buffering. Yet, how the redox cascades of the thioredoxin and glutathione redox machineries integrate metabolic regulation and detoxification of reactive oxygen species remains largely unresolved because null mutants of plastid/mitochondrial GR are embryo-lethal in Arabidopsis thaliana. To investigate whether maintaining a highly reducing stromal glutathione redox potential (EGSH ) via GR is necessary for functional photosynthesis and plant growth, we created knockout lines of the homologous enzyme in the model moss Physcomitrella patens. In these viable mutant lines, we found decreasing photosynthetic performance and plant growth with increasing light intensities, whereas ascorbate and zeaxanthin/antheraxanthin levels were elevated. By in vivo monitoring stromal EGSH dynamics, we show that stromal EGSH is highly reducing in wild-type and clearly responsive to light, whereas an absence of GR leads to a partial glutathione oxidation, which is not rescued by light. By metabolic labelling, we reveal changing protein abundances in the GR knockout plants, pinpointing the adjustment of chloroplast proteostasis and the induction of plastid protein repair and degradation machineries. Our results indicate that the plastid thioredoxin system is not a functional backup for the plastid glutathione redox systems, whereas GR plays a critical role in maintaining efficient photosynthesis.

Plant performance and survival across transplant experiments depend upon temperature and precipitation change along elevation

Abstract Understanding how plant individuals perform in non‐local sites is key in the context of contemporary range shifts along elevation. Transplant experiments conducted in mountain ecosystems are rising as key tools to measure the intraspecific response of individuals transplanted across contrasting elevations. However, a synthesis quantifying patterns of plant performance in response to changes in abiotic factors across different species and mountain ranges is still lacking. We conducted a meta‐analysis to quantitatively summarize patterns of plant species' performance variation in response to changes in temperature and precipitation within their elevation range across multiple transplant experiment studies. We compiled a dataset obtained from 38 studies and 49 vascular plant species in total addressing intraspecific performance variation in terms of survival, germination, biomass, height, number of vegetative organs, number of reproductive units, SLA and leaf size. We both compared pairs of transplanted individuals to those growing at their site of origin (‘away vs. home’) and to the local individuals found at the site of transplant (‘foreign vs. local’). Overall, individuals transplanted downward showed larger biomass and height compared to their site of origin but failed to adjust these traits and survival to that of local individuals. Individuals transplanted upward adjusted their traits by decreasing plant growth and number of reproductive units to that of local individuals but showed lower survival. Importantly, changes in survival, biomass, height, leaf size, number of vegetative organs and reproductive units increased linearly with the difference in mean annual temperature between site of transplant and site of origin in the ‘away vs. home’ comparison. Conversely, changes in biomass, leaf size, number of vegetative organs and reproductive units increased with mean annual precipitation difference between sites in the ‘foreign vs. local’ comparison. Synthesis. We detected common trends in survival and intraspecific trait variation across different species and transplant experiments conducted along elevational gradients. Because plasticity and adaptation play a crucial role in plant shift, establishment and persistence under non‐local environmental conditions, our meta‐analysis contributes to better understand how rapid plant shifts are constrained by climatic conditions within species' elevational range.

Remediation of Cr(VI)-Contaminated Soil by Nano-Zero-Valent Iron in Combination with Biochar or Humic Acid and the Consequences for Plant Performance.

Nano-scale zero-valent iron (nZVI) is among the most common nanoparticles widely used for the treatment of various environmental contaminants. However, little is known about the combined effects of nano-zero-valent iron (nZVI) and other soil amendments on soil remediation and plant performance. For the first time, we studied the remediation of Cr(VI)-contaminated soil using bare nZVI (B-nZVI) and starch-supported nZVI (S-nZVI) in combination with either biochar (BC) or humic acid (HA), and the consequent effects on plant growth and Cr accumulation. Both S-nZVI and B-nZVI decreased the contents of Cr(VI) and available Cr in soil, but increased available Fe content, with S-nZVI generally showing more pronounced effects at a higher dose (1000 mg/kg). B-nZVI exerted no inhibition and even stimulation on plant growth, but 1000 mg/kg S-nZVI produced significant phytotoxicity, resulting in decreased plant growth, low chlorophyll content in leaves, and excessive accumulation of Fe in roots. Each nZVI decreased shoot and root Cr concentrations. BC and HA produced synergistic effects with nZVI on Cr(VI) removal from soil, but HA decreased soil pH and increased the availability of Cr and Fe, implying a potential environmental risk. Addition of BC or HA did not alter the effects of either nZVI on plant growth. In conclusion, combined application of 100 mg/kg nZVI and BC could be an ideal strategy for the remediation of soil contaminated with Cr(VI), whereas high-dose S-nZVI and HA are not recommended in the remediation of agricultural soils for crop production or in the phytostabilization of Cr(VI).

Changes of plant biomass partitioning, tissue nutrients and carbohydrates status in magnesium-deficient banana seedlings and remedy potential by foliar application of magnesium

Magnesium (Mg) is involved in many biochemical and physiological processes affecting plant growth and development. Although Mg deficiency is a widespread problem in banana production, detailed study of physiological responses to Mg deficiency in banana crops is lacking. Here, we characterized plant biomass partitioning, tissue nutrient distribution and carbohydrates status of banana seedlings grown under sufficient and deficient Mg supply. We also studied the potential of remedying Mg deficiency by foliar application of Mg. Mg deficiency severely decreased plant growth, especially biomass partitioning from rhizome to root and led to a reduction of root/shoot dry weight ratio. Under Mg deficiency, plant Mg status was reduced but the concentrations of N, P and K were increased in most tissues. Mg deficiency caused an overall reduction in tissue glucose and fructose contents, and accumulation of sucrose, amylose and amylopectin in leaves. Sucrose, amylose and amylopectin contents were however reduced in pseudostem, rhizome and root of plants with Mg deficiency. Foliar application of Mg to Mg-deficient plants completely recovered banana plant growth, nutrients and carbohydrates status.

Copper Uptake and Accumulation, Ultra-Structural Alteration, and Bast Fibre Yield and Quality of Fibrous Jute (Corchorus capsularis L.) Plants Grown Under Two Different Soils of China.

Copper (Cu) is an essential heavy metal for plants, but high Cu concentration in the soil causes phytotoxicity. Some plants, however, possess a system that can overcome Cu toxicity, such as Cu localization, and an active antioxidant defence system to reduce oxidative damage induced by high Cu concentration. The present study was conducted to explore the phytoremediation potential, morpho-physiological traits, antioxidant capacity, and fibre quality of jute (Corchorus capsularis) grown in a mixture of Cu-contaminated soil and natural soil at ratios of 0:1 (control), 1:0, 1:1, 1:2 and 1:4. Our results showed that high Cu concentration in the soil decreased plant growth, plant biomass, chlorophyll content, gaseous exchange, and fibre yield while increasing reactive oxygen species (ROS), which indicated oxidative stress induced by high Cu concentration in the soil. Antioxidant enzymes, such as superoxidase dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) scavenge ROS in plant cells/tissues. Furthermore, high Cu concentration did not significantly worsen the fibre quality of C. capsularis, and this plant was able to accumulate a large amount of Cu, with higher Cu accumulation in its shoots than in its roots. Transmission electron microscopy (TEM) revealed that Cu toxicity affected different organelles of C. capsularis, with the chloroplast as the most affected organelle. On the basis of these results, we concluded that high Cu concentration was toxic to C. capsularis, reducing crop yield and plant productivity, but showing little effect on plant fibre yield. Hence, C. capsularis, as a fibrous crop, can accumulate a high concentration of Cu when grown in Cu-contaminated sites.

Assessment of the Possible Reuse of Extractive Waste Coming from Abandoned Mine Sites: Case Study in Gorno, Italy

Supply of resources, a growing population, and environmental pollution are some of the main challenges facing the contemporary world. The rapid development of mining activities has produced huge amounts of waste. This waste, found in abandoned mine sites, provides the potential opportunity of extracting raw material. The current study, therefore, focuses on testing the validation of a shared methodology to recover extractive waste from abandoned mines, and applies this methodology to a case study in Gorno, northwest Italy. The methods focused on: (1) analyzing the impact of tailings and fine fraction of waste rock (<2 mm) on plants (Cress - Lepidium Sativum) to assess usability of both as soil additive, and (2) recovering raw materials from tailings and coarse fraction (>2 mm) of waste rock, by means of dressing methods like wet shaking table and froth flotation. The results indicated that the fine fraction of waste rock and tailings did not have detrimental effects on seed germination; however, there was marked decrease in plant growth. As for the recovery of raw materials, the coarse waste rock samples, crushed to <0.5 mm, produced a recovery of Cd, Ga, and Zn—as much as 66%, 56%, and 64%, respectively—using the wet shaking table. The same samples when crushed to 0.063–0.16 mm and used for froth flotation produced a recovery of Cd, Ga, and Zn of up to 61%, 72%, and 47%, respectively. The flotation experiment on tailings showed a recovery of Cd, Ga and Zn at pH 7 of 33%, 6% and 29% respectively. The present investigation highlights the methodologies used for extracting raw materials from extractive waste.

Foliar application of lead and arsenic solutions to Spinacia oleracea: biophysiochemical analysis and risk assessment.

Atmospheric contamination by heavy metal(loid)s is a widespread global issue. Recent studies have shown foliar pathway of heavy metal(loid) uptake by plants, thus menacing plant productivity and threatening health risks. In contrast to root uptake of heavy metal(loid)s, there is scarce data available on heavy metal(loid) foliar uptake, accumulation in different plant parts, changes in growth and other biophysiochemical processes/reactions, detoxification mechanisms and associated health risks due to the consumption of contaminated vegetables. This study evaluated the effect of foliar application of two potentially toxic metal(loid)s (arsenic (As) and lead (Pb)) on their uptake by Spinacia oleracea, plant growth, pigment contents, physiological changes, and activation of antioxidative enzymes. Results revealed that S. oleracea seedlings can accumulate both the metal(loid)s in their leaves via foliar pathway. Arsenic was transferred from the leaves towards the roots, while Pb was mainly sequestered in S. oleracea leaves. Both the metal(loid)s significantly decreased plant growth and pigment contents, As being more toxic than Pb. Foliar application of As and Pb did not cause lipid peroxidation and overproduction of reactive oxygen species (ROS). However, both the metal(loid)s enhanced the activities of antioxidative enzymes. We also calculated possible health risks (both non-carcinogenic and carcinogenic) due to As and Pb accumulation in the edible parts for both the adults and children. It was observed that As can induce non-carcinogenic effects (HQ > 1) in children only, while both As and Pb can cause carcinogenic hazards in both adults and children under their all applied foliar levels. Therefore, it is proposed that As and Pb contents in the atmosphere must be monitored continuously for their possible foliar uptake and accumulation in edible plant parts to avoid cancer risks. Moreover, multivariate analysis traced weak-strong correlations between metal(loid) treatments and plant response variables.

Effect of single and combined Cu, NaCl and water stresses on three Atriplex species with phytostabilization potential

Phytostabilization of metal enriched substrates in arid and semiarid areas depends on the use of metal-tolerant or metallophyte plants in order to decrease metal mobilization and dispersion. However, the co-occurrence of other abiotic restrictions on plant growth, such as drought and salinity calls for a new perspective for plant selection. Since components of salt and drought tolerance traits of halophytes are also present in metal stress, Atriplex species, typical of dry and salty soils, emerge as good candidates for phytostabilization. But in order to confirm this potential, it is necessary to explore specific responses to increasing copper, salt and water stress.In this study, we compared the effect of single and combined copper, NaCl and PEG- induced water stresses on growth parameters of the Chilean Atriplex atacamensis, European A. halimus and Australian A. nummularia under controlled hydroponic assays. Results showed that increasing copper had severe effects on root development of all three species, with subsequent effects on their shoot biomass. Salt stress effects were mostly osmotic, with a decrease in shoot fresh weight and water content, and PEG- induced water stress had no clear effect on growth of roots and shoots. Combination of copper with NaCl and PEG further decreased plant growth, but this effect varied among Atriplex species. This shows that growth of Atriplex species responds differently to each individual stress and that stressor combination causes an overall negative effects in their growth parameters.

Mutualistic Outcomes Across Plant Populations, Microbes, and Environments in the Duckweed Lemna minor.

The picture emerging from the rapidly growing literature on host-associated microbiota is that host traits and fitness often depend on interactive effects of host genotype, microbiota, and abiotic environment. However, testing interactive effects typically requires large, multi-factorial experiments and thus remains challenging in many systems. Furthermore, most studies of plant microbiomes focus on terrestrial hosts and microbes. Aquatic habitats may confer unique properties to microbiomes. We grew different populations of duckweed (Lemna minor), a floating aquatic plant, in three microbial treatments (adding no, "home", or "away" microbes) at two levels of zinc, a common water contaminant in urban areas, and measured both plant and microbial performance. Thus, we simultaneously manipulated plant source population, microbial community, and abiotic environment. We found strong effects of plant source, microbial treatment, and zinc on duckweed and microbial growth, with significant variation among duckweed genotypes and microbial communities. However, we found little evidence of interactive effects: zinc did not alter effects of host genotype or microbial community, and host genotype did not alter effects of microbial communities. Despite strong positive correlations between duckweed and microbe growth, zinc consistently decreased plant growth, but increased microbial growth. Furthermore, as in recent studies of terrestrial plants, microbial interactions altered a duckweed phenotype (frond aggregation). Our results suggest that duckweed source population, associated microbiome, and contaminant environment should all be considered for duckweed applications, such as phytoremediation. Lastly, we propose that duckweed microbes offer a robust experimental system for study of host-microbiota interactions under a range of environmental stresses.

Alternate partial root-zone drip irrigation with nitrogen fertigation promoted tomato growth, water and fertilizer-nitrogen use efficiency

Irrigation and fertilization play key roles in crop production. Scarcity of available water resources and low nutrient use efficiency calls for a need to improve water and nitrogen (N) use efficiency. This study aimed to investigate the effects of different irrigation and nitrogen treatments on the growth, yield, irrigation water-use efficiency (IWUE) and fertilizer-N utilization of tomato plants by using pre-buried soil columns (100 cm in depth) in a field. The irrigation treatments included conventional drip irrigation (CDI) and alternate partial root-zone drip irrigation (ADI) with sufficient or deficient water supply. Nitrogen fertilizer was set as high and low N input (8.30 g or 4.15 g 15N-labeled urea per plant) supplied as drip fertigation. Compared with the CDI treatment at the same nitrogen drip fertigation level, ADI promoted tomato root growth, induced more 15N accumulation in the 0−100 cm soil profile, facilitated the absorption of fertilizer-15N as well as soil N by plants, thus increasing plant growth and yield as well as IWUE and fertilizer-N use efficiency, while decreased 15N loss. Low nitrogen supply decreased plant growth, yield, 15N absorption, 15N accumulation in soil profile and IWUE, but increased both the 15N-use efficiency and 15N loss percentage. Thus, ADI coupled with nitrogen fertigation has a potential to save irrigation water, increase use efficiencies of both water and nitrogen fertilizers with reduced loss of N to the environment.

Morphological and Physiological Responses of Cornus alba to Salt and Drought Stresses under Greenhouse Conditions

Tatarian dogwood (Cornus alba) is an ornamental shrub with white fruits, creamy-white flowers, and red stems in fall through late winter and is widely used in residential landscape, public parks, and botanical gardens. Two greenhouse experiments were conducted to characterize the survival, morphological, aesthetic, and physiological responses of tatarian dogwood seedlings to salinity and drought stresses. In Expt. 1, tatarian dogwood seedlings grown in three soilless growing substrates (Metro-Mix 360, 560, and 902) were irrigated with a nutrient solution at an electrical conductivity (EC) of 1.2 dS·m−1 (control) or saline solution (by adding calculated amount of sodium chloride and calcium chloride) at an EC of 5.0 or 10.0 dS·m−1 once per week for 8 weeks. Results showed that substrate did not influence the growth of tatarian dogwood seedling. All plants irrigated with saline solutions at an EC of 10.0 dS·m−1 died, whereas those irrigated with saline solutions at an EC of 5.0 dS·m−1 exhibited severe foliar salt damage with an average visual score of 1.0 (on a scale of 0 to 5, with 0 = dead and 5 = excellent without foliar salt damage). Compared with the control, saline solutions at an EC of 5.0 dS·m−1 reduced plant height and shoot dry weight (DW) by 50.8% and 55.2%, respectively. Relative chlorophyll content [soil plant analysis development (SPAD) reading], chlorophyll fluorescence (Fv/Fm), and net photosynthesis rate (Pn) also decreased when plants were irrigated with saline solutions at an EC of 5.0 and 10.0 dS·m−1. Leaf sodium (Na+) concentration of tatarian dogwood seedlings irrigated with saline solutions at an EC of 5.0 and 10.0 dS·m−1 increased 11 and 40 times, respectively, compared with the control, whereas chloride (Cl-) concentration increased 25 and 33 times, respectively. In Expt. 2, tatarian dogwood seedlings were irrigated at a substrate volumetric water contents (volume of water/volume of substrate, VWC) of 15%, 20%, 25%, 30%, 35%, 40%, or 45% using a sensor-based automated irrigation system for 60 days. Results showed that drought stress decreased plant growth of tatarian dogwood seedlings with a reduction of 71%, 85%, and 87% in plant height, leaf area, and shoot DW, respectively, when VWC decreased from 45% to 15%, but all plants survived at all VWC treatments. Significant reductions of photosynthesis (Pn), stomatal conductance (gS), transpiration rate (E), and water potential were also found in plants at a VWC of 15%, compared with other VWCs. However, SPAD readings and Fv/Fm of tatarian dogwood seedlings were similar among the VWCs. In conclusion, tatarian dogwood seedlings were sensitive to the salinity levels tested in this study but could survive at all tested substrate volumetric water contents and exhibited resistance to drought conditions.

Sweet Basil Growth, Physiological and Ultrastructural Modification, and Oxidative Defense System Under Water Deficit and Silicon Forms Treatment

The current investigation aimed to evaluate the role of silicon forms on sweet basil (Ocimum basilicum L.) biomass and essential oil (EO) production, as well as some physiological and ultrastructural modification under different irrigation regimes. Drought significantly decreased plant growth, photosynthetic pigment, ion, relative water content, catalase activity, and EO yield, meanwhile, increased organic and antioxidant solute concentration, EO percentage, peroxidase activity, and oxidative impairment criteria (hydrogen peroxide, lipid peroxidation, and membrane permeability percentage). Concerning EO constituents, linalool and methyl chavicol were the major components that decreased under drought relative to well-watered plants. Exogenous application of silicon forms under well-watered or drought condition may fully or partially compensate to some extent to sweet basil plant development and biochemical attributes (photosynthetic pigment, ion percentage, antioxidant solutes, and organic osmolytes). The maximum EO yield was obtained by 250 mg L−1 sodium metasilicate (Si) under mild drought. Cell organelles exhibited a different degree of malformation and lyse under severe drought; conversely, application of Si forms nullify the abovementioned injuries caused by drought. In conclusion, application of 250 mg L−1 Si improved drought tolerance in sweet basil herb and EO yield by accelerating their antioxidant system, osmoregulation, and maintaining organelles ultrastructure that induced herb growth and EO yield.

Optimizing the Electrical Conductivity of a Nutrient Solution for Plant Growth and Bioactive Compounds of Agastache rugosa in a Plant Factory

The objective of this study was to determine the proper electrical conductivity (EC) of a nutrient solution (NS) for accumulating bioactive compounds of Agastache rugosa without decreasing plant growth. Six-week-old seedlings were transplanted in a deep flow technique system with Hoagland NS with a 2.0 dS·m−1 EC for the initial week. From eight days after transplanting, the plants were treated with six EC treatments of 0.5, 1.0, 2.0, 4.0, 6.0, and 8.0 dS·m−1 for three weeks. Plant growth parameters, leaf gas exchange parameters, the relative chlorophyll value, and the ratio of variable to maximum fluorescence (Fv/Fm) were measured, and the rosmarinic acid (RA), tilianin, and acacetin concentrations were analyzed at 28 days after transplanting. The results showed that almost all plant growth parameters were maximized at 2.0 and 4.0 dS·m−1 and minimized at 8.0 dS·m−1 compared with the other EC treatments. The relative chlorophyll and Fv/Fm values were maximized at 2.0 and 4.0 dS·m−1. Similarly, leaf gas exchange parameters were increased at 2.0 and 4.0 dS·m−1. The RA content exhibited significantly higher values at 0.5, 1.0, 2.0, and 4.0 dS·m−1 compared with other treatments. The tilianin and acacetin contents exhibited the significantly highest values at 4.0 and 0.5 dS·m−1, respectively. These results suggest optimal EC treatment at 4.0 dS·m−1 for increasing bioactive compounds in A. rugosa plants without decreasing plant growth. Excessively high or low EC induced salinity stress or nutrient deficiency, respectively. Furthermore, among the plant organs, the roots of A. rugosa contained the highest RA concentration and the flowers contained the highest tilianin and acacetin concentrations, which revealed a higher utilization potential of the roots and flowers for bioactive compounds.

The effect of electromagnetic eretreatment on lemon balm (<em>Melissa officinalis</em> L.) seeds subjected to static magnetic fields

The effects of magnetic waves as natural environmental factors on the growth and development of plants is not well known. The present study evaluated the effects of a static magnetic field (SMF) (4 and 6mT for 30 and 120 min) on the growth, contents of proline and total soluble sugar, phenolic compounds, accumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA) of pretreated seeds. The activity of antioxidant enzymes and the essential oil composition of lemon balm seedlings subjected to SMF treatment (4 and 6mT for 30 and 120 min for 7 days) were also examined. The SMF treatments decreased plant growth by reducing the contents of photosynthetic pigments and inducing oxidative stress; however, pretreated plants had greater contents of pigments, proline, soluble sugars, total phenol and flavonoids than non-pretreated plants. The contents of MDA and H2O2 were decreased in pretreated plants compared to non-pretreated plants; this result was associated with the reduction in antioxidant enzyme activity. The exposure of seeds to SMF also increased the yield and altered the chemical composition of essential oils compared to both non-pretreated and control plants. These results indicate that pretreatment of lemon balm seeds with SMF can be effectively used as a pre-sowing treatment to increase essential oil yield for medical purposes.

Arbuscular Mycorrhizal Fungi Can Compensate for the Loss of Indigenous Microbial Communities to Support the Growth of Liquorice (Glycyrrhiza uralensis Fisch.).

Soil microorganisms play important roles in nutrient mobilization and uptake of mineral nutrition in plants. Agricultural management, such as soil sterilization, can have adverse effects on plant growth because of the elimination of indigenous microorganisms. Arbuscular mycorrhizal (AM) fungi are one of the most important beneficial soil microorganisms for plant growth. However, whether AM fungi can compensate for the loss of indigenous microbial communities to support plant growth and metabolism is largely unknown. In this study, a pot experiment was conducted to investigate the effects of AM fungi on plant growth and secondary metabolism in sterilized and unsterilized soil. We used liquorice (Glycyrrhiza uralensis Fisch.), an important medicinal plant as the host, which was inoculated with the AM fungus Rhizophagus irregularis or not and grown in unsterilized or sterilized soil. Plant photosynthesis traits, plant growth and nutrition level, concentrations of the secondary metabolites, and expression levels of biosynthesis genes were determined. The results showed that soil sterilization decreased plant growth, photosynthesis, and glycyrrhizin and liquiritin accumulation, and moreover, downregulated the expression of related biosynthesis genes. Inoculation with R. irregularis in sterilized soil offset the loss of indigenous microbial communities, resulting in plant growth and glycyrrhizin and liquiritin concentrations similar to those of plants grown in unsterilized soil. Thus, AM fungi could compensate for the loss of indigenous microbial communities by soil sterilization to support plant growth and secondary metabolism.

Growth, physiological, anatomical and nutritional responses of two phenotypically distinct passion fruit species (Passiflora L.) and their hybrid under saline conditions

Passion fruit is one of the main crops produced in the irrigated areas of Northeastern Brazil. However, soil salinization in this region has limited its productivity. This work aimed to compare the effects of saline stress on three populations of passion fruit (Passiflora edulis Sims, P. mucronata Lam. and the interspecific hybrid P. edulis x P. mucronata) using physiological, anatomical, nutritional, agronomic traits and application of near-infrared spectroscopy (NIRS). Plants were grown on sterile washed sand and irrigated with a nutrient solution with or without NaCl (0 or 150 mM) in a completely randomized design with eight replicates. Most of the physiological traits, such as transpiration, stomatal conductance, net photosynthetic rate, chlorophyll content and leaf osmotic potential, were negatively affected by the saline stress. There was also a negative effect for the majority of anatomical traits evaluated in the presence of NaCl, except the stomatal density and upper epidermal thickness. The NaCl also induced changes in uptake of macro- and micronutrients and decreased plant growth, fresh shoot and root weights, and dry shoot weight. Based on the principal component analysis (PCA), 18 informative traits were identified for the discrimination of the passion fruit population for saline stress. P. mucronata exhibited better salt tolerance in comparison with the other populations, especially with higher values for root traits, a lower accumulation of sodium in the leaves, and maintenance of photosynthesis, conductance and stomatal functionality. Near-infrared spectrophotometry (NIRS) allowed the separation of the parental Passiflora populations submitted to the saline treatment, opening the possibility of validating its use for screening passion fruit genotypes for tolerance of salinity. Breeding for salt tolerance in passion fruit is feasible using wild species such as P. mucronata.

Molybdate toxicity in Chinese cabbage is not the direct consequence of changes in sulphur metabolism.

In polluted areas, plants may be exposed to supra‐optimal levels of the micronutrient molybdenum. The physiological basis of molybdenum phytotoxicity is poorly understood. Plants take up molybdenum as molybdate, which is a structural analogue of sulphate. Therefore, it is presumed that elevated molybdate concentrations may hamper the uptake and subsequent metabolism of sulphate, which may induce sulphur deficiency.In the current research, Chinese cabbage (Brassica pekinensis) seedlings were exposed to 50, 100, 150 and 200 μm Na2MoO4 for 9 days.Leaf chlorosis and a decreased plant growth occurred at concentrations ≥100 μm. Root growth was more affected than shoot growth. At ≥100 μm Na2MoO4, the sulphate uptake rate and capacity were increased, although only when expressed on a root fresh weight basis. When expressed on a whole plant fresh weight basis, which corrects for the impact of molybdate on the shoot‐to‐root ratio, the sulphate uptake rate and capacity remained unaffected. Molybdate concentrations ≥100 μm altered the mineral nutrient composition of plant tissues, although the levels of sulphur metabolites (sulphate, water‐soluble non‐protein thiols and total sulphur) were not altered. Moreover, the levels of nitrogen metabolites (nitrate, amino acids, proteins and total nitrogen), which are generally strongly affected by sulphate deprivation, were not affected. The root water‐soluble non‐protein thiol content was increased, and the tissue nitrate levels decreased, only at 200 μm Na2MoO4.Evidently, molybdenum toxicity in Chinese cabbage was not due to the direct interference of molybdate with the uptake and subsequent metabolism of sulphate.

Effects of Brassinosteroids on Photosynthetic Performance and Nitrogen Metabolism in Pepper Seedlings under Chilling Stress

To investigate the effects of brassinosteroids on plant growth and nitrogen metabolism in pepper seedlings under chilling stress, pepper seedlings with three true leaves were foliar pretreated with 0.1 μM exogenous 24-epibrassinolide (EBR) before carrying out chilling stress for 7 days. The results showed that perapplication of EBR mitigated the chill-induced decrease in plant growth via maintenance of a high net photosynthetic rate (Anet), maximum quantum efficiency (Fv/Fm), and photochemical quenching coefficient (qP). Exogenous EBR markedly increased the levels of partial free amino acids (proline, arginine, aspartic acid, and glycine) and promoted nitrogen metabolism through increasing the activities of nitrate reductase (NR), glutamine synthase (GS), glutamate synthase (GOGAT), and glutamate dehydrogenase (GDH) in the leaves of pepper seedlings under chilling stress. The effect of exogenous EBR on the content of reactive oxygen species was also investigated. Pretreatment with EBR reduced the accumulation of hydrogen peroxide (H2O2) and superoxide anion (O2−·), and concomitantly alleviated membrane lipid peroxidation of pepper leaves under chilling stress. These results suggest that foliar pretreatment of EBR has a positive effect on improving the chilling tolerance of pepper seedlings via maintaining a high photosynthetic capability and enhancing the nitrogen metabolism.

Lead (Pb) toxicity effect on physio-anatomy of bead-tree, jatropha, castor bean and Philippine-tung grown in water culture

Abstract. Hamim, Hanifatunisa, Hadisunarso, Setyaningsih L, Saprudin D. 2019. Lead (Pb) toxicity effect on physio-anatomy of bead-tree, jatropha, castor bean and Philippine-tung grown in water culture. Biodiversitas 20: 3690-3697. Heavy metal contamination in both land and water has been intensively studied because of their broad impact for the environment. Bead-tree (Melia azedarach), Jatropha (Jatropha curcas), castor bean (Ricinus communis) and Philippine tung (Reutealis trisperma) are kinds of non-edible oil-producing species, that are able to grow well on degraded lands and may have potential use for phytoremediation of heavy metals contaminated areas. This study aimed to analyze the response of bead-tree (Melia azedarach), jatropha (Jatropha curcas), castor bean (Ricinus communis) and Philippine-tung (Reutealis trisperma) to lead (Pb) contaminant in water culture experiment based on morphological, physiological and anatomical parameters. Two months old plants were transferred to the media containing Hoagland solution. After three weeks of planting, Pb (NO3)2 treatments with five concentrations, i.e. control (0 mM), 0.5 mM, 1 mM, 2 mM, and 3 mM were added together with Hoagland replacement and the plants were treated for three weeks. The growth, anatomical and physiological parameters were observed during the treatment until three weeks. The results showed that Pb treatment, especially with higher concentration, dramatically decreased plant growth, such as plant height, number of leaves, as well as shoot and root dry weight of all the species. Lead treatment triggered the emergence of free radicals and oxidative stress as indicated by a significant increase of malondialdehyde (MDA) content, while it decreased chlorophyll content of all the species. The higher concentration of Pb (NO3)2 caused the thickness of upper epidermis, lower epidermis, and spongy mesophyll tissue to decrease significantly which contributed to the decrease of leaves thickness. Among the species, Philippine-tung was the most tolerant of Pb toxicity. This species is potential to be used in phytoremediation program of lead-contaminated land such as gold mine area as well as heavy industrial areas.

Effect of Plant Residues-Treated Urea on Growth and N-Uptake of Wheat (Triticum aestivum L.)

A pot experiment was carried out to study the effect of the urea fertilizer treated with corn or conocarpus residues on growth and N uptake of wheat plant. Three kilograms of dry soil (Silt clay loam) were placed in a plastic pots and four levels of nitrogen (0, 60, 120 and 180 kg N ha -1) were added as urea. Urea was treated with one of the following methods : mix with the conocarpus leaves powder at rate of 4% of dry soil weight, mix with the conocarpus roots powder at rate of 4% of dry soil weight dissolved in, aqueous extract of the corn root at rate of 1/4 of the field capacity ,or coated with dried aqueos extract of corn root at ratio of 10% of urea weight. Treatment included urea treated with the standard chemical inhibitor (PMA) was used. shoot dry weight, N conc., N-uptake and N recovery were obtained. The results showed that treatment of urea fertilizer with water extract or coated with corn root extract resulted in improved growth parameters as compared with a PMA and control treatments .However ,treating urea with leaves or root powders decreased plant growth parameters .Urea coated with 10 % dried extract of corn roots gave the highest dry matter of 3.06 g pot-1 and nitrogen uptake of 69.90 mg pot-1 resulting in saving of 60 kg N ha-1 to give the same results for control and PMA treatments.