Decreased Plant Dry Weight Research Articles

Melatonin improves drought stress tolerance of pepper (Capsicum annuum) plants via upregulating nitrogen metabolism.

While ameliorating effects of melatonin (MT) on abiotic stress tolerance in plants are widely reported, the mechanism that underlies this process remains elusive. This work investigated mechanisms by which MT improved drought tolerance in pepper (Capsicum annuum ) plants. A foliar spray of 0.1mM MT treatment was applied to plants grown at 80% and 40% of full field capacity for 3days. Drought stress caused a significant decrease in plant dry weight, relative water content, leaf water potential, PSII efficiency (F v /F m ratio), chlorophyll, soluble protein, leaf and root nitrogen content. Drought increased hydrogen peroxide, malondialdehyde (MDA), nitrate, ammonium, free amino acids, soluble sugars, proline and glycine betaine. Drought also increased peroxidase (POD), glutathione S-transferase (GST) and catalase (CAT) activities, electrolyte leakage (EL) and methylglyoxal (MG). MT pre-treatment reduced oxidative stress and improved nitrogen metabolism by activating various enzymes such as nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthetase (GOGAT) and glutamine dehydrogenase (GDH) activities. It also activated enzymes related to the glyoxalase system (Gly I and Gly II) and decreased NO3 - , NH4 + and free amino acid content. Our study suggests a cost-effective and sustainable solution to improve crop productivity in water-limited conditions, by enhancing plant growth, photosynthesis and nitrogen content.

Dual RNA and 16S ribosomal DNA sequencing reveal arbuscular mycorrhizal fungi-mediated mitigation of selenate stress in Zea mays L. and reshaping of soil microbiota

Excessively high concentrations of selenium (Se) in soil are toxic to crop plants, and inoculation with arbuscular mycorrhizal fungi (AMF) can reverse Se stress in maize (Zea mays L.). To investigate the underlying mechanisms, maize seedlings were treated with sodium selenate (5 mg Se[VI] kg-1) and/or AMF (Funneliformis mosseae and Claroideoglomus etunicatum). Dual RNA sequencing in mycorrhiza and 16 S ribosomal DNA sequencing in soil were performed. The results showed that Se(VI) application alone decreased plant dry weight, but increased plant Se concentration, total Se content (mainly selenocysteine), and root superoxide content. Inoculation with either F. mosseae or C. etunicatum increased plant dry weight, decreased Se accumulation and selenocysteine proportion, enhanced root peroxidase activity, and alleviated oxidative stress in Se(VI)-treated plants. Inoculation also downregulated the expression of genes encoding Se transporters, assimilation enzymes, and cysteine-rich receptor-like kinases in Se(VI)-stressed plants, similar to plant–pathogen interaction and glutathione metabolism related genes. Conversely, genes encoding selenium-binding proteins and those related to phenylpropanoid biosynthesis were upregulated in inoculated plants under Se(VI) stress. Compared with Se(VI)-free plants, Se tolerance index, symbiotic feedback percentage on plant dry weight, and root colonization rate were all increased in inoculated plants under Se(VI) stress, corresponding to upregulated expression of ‘key genes’ in symbiosis. AMF inoculation increased bacterial diversity, decreased the relative abundances of selenobacteria related to plant Se absorption (e.g., Proteobacteria and Firmicutes), and improved bacterial network complexity in Se(VI)-stressed soils. We suggest that stress-mediated enhancement of mycorrhizal symbiosis contributed to plant Se(VI) tolerance, whereas AMF-mediated reshaping of soil bacterial community structure prevented excessive Se accumulation in maize.

The potential of Central Java local black rice and red rice as drought tolerant cultivars

Black and red rice contain nutritional values not found in white rice. They contain anthocyanins which are beneficial to health. Drought stress can potentially reduce rice yield. So, it is necessary to develop local black and red rice into tolerant cultivars. This study used a completely randomized design (CRD) with cultivar factor (V) and drought stress level (K). Drought stress treatment was carried out when the plants were 35-95 DAP (days after planting) using the modified gravimetric method. Plant destruction was conducted at 7 and 21 DAT (days after treatment) to measure the growth analysis component. The observation of the growth analyses was plant dry weight, leaf area (LA), specific leaf area (SLA), relative growth rate (RGR), and net assimilation rate (NAR). Agronomic characters by observing shoot-root ratio and flowering age. The results showed drought stress decreased plant dry weight, leaf area, and relative growth rate on Sragen black rice. Jelitheng Karanganyar showed high RGR and NAR under drought stress and the fastest flowering age response. Wonogiri black rice gave the growth response by reducing specific leaf area. The highest shoot-root ratio was shown on Wonogiri black rice.

Exogenous nitric oxide alleviates manganese toxicity in bean plants by modulating photosynthesis in relation to leaf lipid composition.

Nitric oxide (NO) is a signaling molecule controlling several steps of plant development and defense process under stress conditions. NO-induced alleviation of manganese (Mn) toxicity was investigated on bean plants submitted for 28days to 500µM MnCl2. Manganese excess decreased plant dry weight and elongation and increased levels of reactive oxygen species and lipid peroxidation leading to up-regulation of superoxide dismutase, catalase, and ascorbate peroxidase activities. The inhibitory effects of Mn on plant growth were associated to reduction of light-saturated carbon assimilation (Amax), stomatal conductance (gs), and transpiration (E). By contrast, Mn induced significant increase in the apparent quantum yield (ɸ) and light compensation point (LCP). Interestingly, intracellular CO2 (Ci) remains stable under Mn stress. Concomitantly, leaf membrane lipids have drastically reduced under high Mn concentration. After Mn exposition, leaf fatty acids exhibited a significant loss of linolenic acid, accompanied by an accumulation of palmitoleic, stearic, and linoleic acids leading to alteration of lipid desaturation. NO supply reversed Mn toxicity as evidenced by enhancement of growth biomass and recovery of Amax, E, ɸ, and LCP. Similarly, NO addition has positive effects on leaf lipid content and composition leading to restoration of lipid unsaturation. The modulation of fatty acid composition can be a way to reduce leaf membrane damages and maintain optimal photosynthesis and plant growth. Despite the absence of enough evidences in how NO is involved in lipid and photosynthesis recovery under Mn stress conditions, it is assumed that NO beneficial effects are attributable to NO/Mn cross-talk.

Physiological role of osmoregulators proline and glycinebetaine in increasing salinity tolerance of chickpea

A pot experiment was performed at greenhouse, National Research Centre, Egypt, during winter seasons 2019/2020 and 2020/2021 to investigate the physiological role of two osmoregulators proline (5 mM and 10 mM) and glycinebetaine (10 mM and 20 mM) in alleviating the deleterious effect of salinity (3000 mg/l NaCl) on quality and quantity of chickpea plant (Sakha 4 cultivar). Salinity stress significantly decreased plant dry weight at vegetative stage, all components of photosynthetic pigments, seed yield accompanied by significant increases in osmo-protectant (proline and soluble carbohydrates) in dry leaves as well as phenolic content and antioxidant activity in the yielded seeds. Regarding proline and glycinebetaine effects, results indicated that all applied treatments caused significant increases in most of the investigated parameters of chickpea plants irrigated with either tap water or saline solution relative to corresponding control. It is worthy to mention that proline treatments were more effective than glycinebetaine treatments in increasing salinity tolerance of chickpea plants that reflected in its quality and quantity. Moreover, proline treatment at 5mM was the most pronounced treatment in alleviating the deleterious effect of salinity on chickpea plants.

Moderate Mn accumulation enhances growth and alters leaf hormone contents in the hyperaccumulator Celosia argentea Linn.

To better understand the unique concentration–response relationship in hyperaccumulators, the effects of manganese (Mn) accumulation on the growth of Celosia argentea Linn., a Mn hyperaccumulator, were investigated using hydroponic experiments. Manganese accumulation (8860–14200 mg/kg in leaves) is toxic to most plants but beneficial to the growth of C. argentea. The C. argentea root length and root surface area at Mn supply concentrations of 20 and 40 mg/L were significantly higher than those at 0.5 mg/L (control treatment). Leaf number and leaf area were 24 % and 66 % greater, respectively, at 20 mg Mn/L than at the control concentration. Moderate Mn accumulation (8860–14200 mg/kg) significantly increased plant dry weight (p < 0.05). However, high Mn accumulation (26,500 mg/kg) decreased plant dry weight. The chlorophyll content expressed a similar trend. The physiological responses of C. argentea to Mn may be regulated by endogenous hormones. Moderate Mn accumulation increased auxin, zeatin, gibberellin, and 6-benzylaminopurine contents, and decreased the abscisic acid content in the leaves (p < 0.05), thereby enhancing plant growth. However, high Mn accumulation significantly increased leaf jasmonic acid and abscisic acid contents (p < 0.05), which inhibited plant growth and stimulated stress tolerance. These findings suggested that the alterations in hormone homeostasis induced by Mn accumulation promoted growth and Mn tolerance in C. argentea.

Mann+Hummel, Germany

To better understand the unique concentration–response relationship in hyperaccumulators, the effects of manganese (Mn) accumulation on the growth of Celosia argentea Linn., a Mn hyperaccumulator, were investigated using hydroponic experiments. Manganese accumulation (8860–14200 mg/kg in leaves) is toxic to most plants but beneficial to the growth of C. argentea. The C. argentea root length and root surface area at Mn supply concentrations of 20 and 40 mg/L were significantly higher than those at 0.5 mg/L (control treatment). Leaf number and leaf area were 24 % and 66 % greater, respectively, at 20 mg Mn/L than at the control concentration. Moderate Mn accumulation (8860–14200 mg/kg) significantly increased plant dry weight (p < 0.05). However, high Mn accumulation (26,500 mg/kg) decreased plant dry weight. The chlorophyll content expressed a similar trend. The physiological responses of C. argentea to Mn may be regulated by endogenous hormones. Moderate Mn accumulation increased auxin, zeatin, gibberellin, and 6-benzylaminopurine contents, and decreased the abscisic acid content in the leaves (p < 0.05), thereby enhancing plant growth. However, high Mn accumulation significantly increased leaf jasmonic acid and abscisic acid contents (p < 0.05), which inhibited plant growth and stimulated stress tolerance. These findings suggested that the alterations in hormone homeostasis induced by Mn accumulation promoted growth and Mn tolerance in C. argentea.

Combined use of zinc nanoparticles and co-composted biochar enhanced wheat growth and decreased Cd concentration in grains under Cd and drought stress: A field study

Toxic metals present in soil and water severally affect the food crops and create serious health concerns. The current field study was focused on the impacts of foliar spray of zinc oxide nanoparticles (ZnO NPs) (100 mg/L) and soil applied co-composted biochar (0.5% w/w) on yield and cadmium (Cd) accumulation by grains of wheat ( Triticum aestivum L.) under simultaneous Cd and water limited stress. After 60 days of seeds sowing, drought stress was initiated in half plots by alternate irrigation compared to normal irrigation. Plants were harvested after 122 days and various physiological parameters were measured. Results showed that drought and Cd stress collectively decreased plant dry weight and chlorophyll contents and caused oxidative stress in leaves. While application of NPs and co-composted biochar improved the plants biomass and chlorophyll contents by overcoming the oxidative stress and alterating the antioxidants enzymatic activities in stressed plants. Combined application of NPs and co-composted biochar restricted the Cd uptake below its threshold level in grains (0.2 mg/kg). The current study concluded that the combination of ZnO NPs and co-composted BC was helpful to improve wheat growth and biomass, chlorophylls contents, antioxidant enzyme activities by scavenging ROS and reducing Cd uptake by plants under simultaneous Cd and drought stress. • Cadmium and drought stress inhibited wheat growth under field conditions. • NPs and co-composted biochar improved wheat growth and chlorophyll contents under stress. • The amendments enhanced activities of antioxidants enzymes in wheat plants. • The amendments reduced the Cd concentration in wheat grains.

Effect of Shading and Mowing on the Growth of Indonesia’s Native Zoysia grass in Silty Clay Soil

&lt;p&gt;In general, turfgrass grows well and forms high quality turf under full sun exposure. It is very difficult, however, to grow a warm season turfgrass under shaded condition. Zoysia grass is a popular warm season grass that commonly grow under full sun exposure condition. There are limited information regarding the growth response and turf quality of zoysia grass when grown under shaded condition. This study aims to observe the growth and quality of various zoysia grass local cultivars at different shading intensities and different mowing. This research was carried out using 10 zoysia grass cultivars planted in the rice fields’ vertisol clay with randomized complete block design. The shading used were control, shade-nets with 25% and 65% hole densities. Zoysia grass was fertilized using NPK; 4:1:3 and mowed three times. The results showed that plants without shade, 25% and 65% received on average solar irradiance of 25,141; 12,456 and 3,727 lux. The increase in shade level decreased the shoot fresh weight, dry weight, root dry weight and the plant height. Shading and frequent mowing effected the plant height. Mowing has more effect on plant height in 25% shading than in 65% shading. The increase in shading, in mowed grass showed increased plant height and decreased plant dry weight. Mowing three times can reduce plant height in all shades. The grasses under 25% shading resulted the highest plant dry weight; whereas and shading 65% resulted the lowest. Plant dry weight and uniformity of turf were affected by the cultivars.&lt;/p&gt;

Impact of some industrial solid wastes on the growth and heavy metal uptake of cucumber (Cucumis sativus L.) under salinity stress

This study was conducted to investigate the effect of industrial solid wastes (ISWs) and salinity on growth and heavy metals uptake by cucumber (Cucumis sativus L.). The soil was treated with 5% and 10% of the ceramic factory (CFW), stone cutting (SCW) and sugar factory (SFW) wastes. Plant of cucumber was grown under greenhouse conditions in control and ISWs treated soils and stressed with electrical conductivities of 0, 4 and 8 dS m−1. Plants were harvested after 2 months and separated into root, shoot, and fruit. Then, dry weights and heavy metals contents in each fraction of plants were determined. The addition of all ISWs in soil increased total heavy metals content in the soil. In all treatments, growth parameters of cucumber decreased when irrigated with saline waters. As compared to control soil, the addition of CFW and SCW to soil decreased plant dry weight, while, it was improved with the addition of the SFW. The result of plant analysis showed that there was an increase in the contents of heavy metals (except Cr) in all parts of cucumber with the addition of ISWs. Salinity decreased the content of Zn uptake and increased another heavy metal uptake by all parts of the plants. The application of ISWs and salinity did not show a significant effect on bioconcentration (BCF) and transfer factor (TF) of heavy metals in plants. The health risk index (HRI) values of all heavy metals for both adults and children were found to be less than 1, so, the health risk of heavy metal for people who consume cucumber grown in these industrial areas was generally assumed to be safe.

Screening of jute and kenaf varieties for salinity tolerance

A study was conducted in the Department of Agronomy, Bangladesh Agricultural University (BAU), Mymensingh from April to August 2012 to examine the salinity tolerance of eight jute varieties (CVE-3, C-83, CVL-1, BJC-7370, O-795, O-9897, OM-1, O-72) and two kenaf varieties (HC-95 and HC-2). Initially germination of these varieties were evaluated under six salinity levels viz. 0mM, 20mM, 40mM, 60mM, 80mM, and 100mM NaCl in the seed laboratory of the Department of Agronomy. Afterwards, all the varieties was grown in pots in the net house under four salinity levels viz. 0mM, 25mM, 50mM, and 75mM. The results from the germination study revealed that under control condition (0mM NaCl) all the jute varieties showed germination more than 80% both at 7 and at 14 days after seed sowing, whereas kenaf varieties had germination a little less than 80%. Among the jute varieties, O-72 showed the highest germination (92%), which was statistically similar with those of OM-1(91%), O-795 (90%), and C-83(87%). Salinity stress decreased germination drastically in all of the jute and kenaf varieties. A salinity level of 100mM caused the highest germination inhibition (74.70%) in jute variety CVL-1, which was very close to those of BJC-7370 and O-72. On the other hand, the lowest germination inhibition (51.11%) was recorded in jute variety O-795. The results of the pot trail showed that the plant characters of jute and kenaf varieties were affected significantly by salinity stress. All the varieties produced their respective plant height, number of leaves per plant, and plant dry weight under control condition (no salinity). Among these varieties, CVE-3 produced the highest plant height (145.2cm), and total dry weight (22.55g), whereas O-72 produced the highest number of leaves per plant (24.67). All these plant characters decreased sharply due to salinity stress irrespective of variety. However, the rate of decrease of plant characters occurred differentially in the jute and kenaf varieties. The highest rate of decrease in number of leaves (74.22%) was found from the variety CVE-3, whereas the lowest one was recorded from the variety HC-2 (51.68%). Salinity stress caused the highest decrease in total plant dry weight (73.68%) in the variety CVL-1 and plant height (73.64%) also in the variety CVL-1. On the contrary, the lowest decrease in plant dry weight (50.99%) was found in the variety O-9897 and plant height also in variety O-9897 (50.88%). Based on the results from germination test and pot trail, it can be inferred that jute variety O-9897 appeared to be the most salt tolerant followed by O-795, HC-2, HC-95, CVE-3, O-72, C-83, BJC-7370, OM-1, and CVL-1.

Arbuscular mycorrhiza improves nitrogen use efficiency in soybean grown under partial root-zone drying irrigation

ABSTRACTArbuscular mycorrhizal (AM) fungi can form symbiotic association with the roots of plants that acquire carbon (C) exclusively from the host plants and supply nitrogen (N) to the plants. In this study, our objective was to investigate the effects of the AM fungus on plant growth, C and N partitioning and accumulation of Glycine max L. grown under water stress in pot experiment. Soybean seedlings were inoculated or not inoculated with the AM fungus, and were exposed to three irrigation treatments including full irrigation, deficit irrigation and partial root-zone drying irrigation (PRD). The 15N isotope labeling was used to trace soybean N accumulation. Results showed that water stress significantly decreased plant dry weight. Compared with non-AM fungus, AM fungus increased root N and 15N concentration, and decreased stem, leaf and pod N and 15N concentrations under PRD. AM colonization decreased C and N partitioning into stem and leaf, and increased C and N partitioning into root under PRD. AM plants had greater C accumulation and N use efficiency than non-AM plants. It was concluded that AM symbiosis plays an important role in C and N dynamics of soybean grown under water stress.

The Effects of Different Surfactants to Dry Weight Wheat

Surfactant is used as wetting agent, dispersant, emulsifier, foaming agent, bactericide in detergent, soap, herbicide and insecticides. The pollution from their residue in nature affects agricultural products as well. In this study was performed to determine the effects of anionic, cationic and nonionic surfactants on the dry weight of wheat ( Triticum aestivum). This research was conducted as randomized split parcels with 3 repetetives in greenhouse. Surfactants were applied at 0, 180, 360, 540 and 720 mg kg –1 concentration after sowing, it was harvested on the 50 th day. Anionic surfactant caused to decrease the dry weight (p < 0.05) of wheat plant. While cationic surfactant caused to decrease the dry weight (p < 0.05), the application of nonionic surfactant did not. According to study results; anionic and cationic surfactants have a negative impact on the growth of plant roots of wheat. Therefore experiencing difficulties in the acquisition of plant nutrients can be attributed to a decrease in plant dry weight.

Evaluation of the Impacts of Salinity on Biomass and Nutrient Levels of Agave Species with Agricultural Potential in Semiarid Regions

Long used as a source of food, beverages, and fiber, Agave exhibits potential to be cultivated as a crop to produce alternative sweeteners, bioenergy, and a variety of other end uses. However, little is known regarding the productivity levels of Agave when grown in saline soils in semiarid regions. Hydroponic experiments were carried out to evaluate the effects of salinity on biomass accumulation and nutrient levels of young plants of Agave parryi, Agave utahensis ssp. kaibabensis, Agave utahensis ssp. utahensis, and Agave weberi. Salinity treatments (0.6, 3.0, 6.0, and 9.0 dS·m−1) were imposed in each experiment. Both subspecies of A. utahensis were sensitive to salt treatments. In the higher salinity treatments, A. utahensis ssp. utahensis exhibited high mortality; both subspecies had lower plant dry weights. Agave parryi was more tolerant, but experienced a decrease in plant dry weight in the 9.0 dS·m−1 treatment. The biomass of A. weberi was unaffected by any level of salinity. Calcium, Mg, S, and Mn levels decreased in both A. parryi and A. weberi at higher salinity levels. Potassium and P levels in A. parryi decreased in the higher salt treatments. Decreases in nutrients were not severe enough to cause any apparent nutrient deficiencies in A. parryi and A. weberi. Agave parryi and A. weberi tolerated salinity at higher levels than expected, and may show promise for cultivation in saline soils.

Role of the extracytoplasmic function sigma factor CarQ in oxidative response of Bradyrhizobium japonicum.

As a nitrogen-fixing bacterium, Bradyrhizobium japonicum can establish a symbiotic relationship with the soybean plant (Glycine max). To be a successful symbiont, B. japonicum must deal with plant defense responses, such as an oxidative burst. Our previous functional genomics study showed that carQ (bll1028) encoding extracytoplasmic function (ECF) sigma factor was highly expressed (107.8-fold induction) under oxidative stress. Little is known about the underlying mechanisms of how CarQ responds to oxidative stress. In this study, a carQ knock-out mutant was constructed using site-specific mutagenesis to identify the role of carQ in the oxidative response of B. japonicum. The carQ mutant showed a longer generation time than the wild type and exhibited significantly decreased survival at 10 mM H(2)O(2) for 10 min of exposure. Surprisingly, there was no significant difference in expression of oxidative stress-responsive genes such as katG and sod between the wild type and carQ mutant. The mutant also showed a significant increase in susceptibility to H(2)O(2) compared to the wild type in the zone inhibition assay. Nodulation phenotypes of the carQ mutant were distinguishable compared to those of the wild type, including lower numbers of nodules, decreased nodule dry weight, decreased plant dry weight, and a lower nitrogen fixation capability. Moreover, desiccation of mutant cells also resulted in significantly lower percent of survival in both early (after 4 h) and late (after 24 h) desiccation periods. Taken together, this information will provide an insight into the role of the ECF sigma factor in B. japonicum to deal with a plant-derived oxidative burst.

Carbon trading for phosphorus gain: the balance between rhizosphere carboxylates and arbuscular mycorrhizal symbiosis in plant phosphorus acquisition

Two key plant adaptations for phosphorus (P) acquisition are carboxylate exudation into the rhizosphere and mycorrhizal symbioses. These target different soil P resources, presumably with different plant carbon costs. We examined the effect of inoculation with arbuscular mycorrhizal fungi (AMF) on amount of rhizosphere carboxylates and plant P uptake for 10 species of low-P adapted Kennedia grown for 23 weeks in low-P sand. Inoculation decreased carboxylates in some species (up to 50%), decreased plant dry weight (21%) and increased plant P content (23%). There was a positive logarithmic relationship between plant P content and the amount of rhizosphere citric acid for inoculated and uninoculated plants. Causality was indicated by experiments using sand where little citric acid was lost from the soil solution over 2 h and citric acid at low concentrations desorbed P into the soil solution. Senesced leaf P concentration was often low and P-resorption efficiencies reached >90%. In conclusion, we propose that mycorrhizally mediated resource partitioning occurred because inoculation reduced rhizosphere carboxylates, but increased plant P uptake. Hence, presumably, the proportion of plant P acquired from strongly sorbed sources decreased with inoculation, while the proportion from labile inorganic P increased. Implications for plant fitness under field conditions now require investigation.

NaCl differently interferes with Cd and Zn toxicities in the wetland halophyte species Kosteletzkya virginica (L.) Presl.

Hydroponic experiments were carried out using seedlings of the wetland halophyte species Kosteletzkya virginica (L.) Presl. exposed to 10 μM Cd or 100 μM Zn in the absence or presence of 50 mM NaCl. Interaction between salinity and heavy metals was analysed in relation to plant growth, water status and tissue ion contents (Na, K and Ca). Results showed a strong inhibition effect of Cd on leaf emergence, lateral branch development and leaf expansion. Heavy metals induced a significant decrease in plant dry weight, water content, osmotic potential (Ψ S) and leaf water potential (Ψ w). Cadmium and Zn accumulated to higher extent in the roots than in the shoots. Cadmium increased the leaf K concentration while Zn had an opposite effect. Salinity strongly reduced Cd uptake and translocation from roots to shoots: it mitigated the Cd impact on lateral branch emergence but had no effects on plant dry weight and water status. Cadmium drastically reduced Na translocation in salt-treated plants while Zn increased it. It is concluded that complex interactions exist between heavy metals and monovalent cations in salt conditions and that Cd and Zn display contrasting behaviour in this respect. Stress-induced modification of ion content did not fully explain growth inhibition in Kosteletzkya virginica.

Effects of Salinity on the Response of the Wetland Halophyte Kosteletzkya virginica (L.) Presl. to Copper Toxicity

Kosteletzkya virginica (L.) Presl. is a perennial wetland halophyte which could be exposed to heavy metals in polluted salt marsh environments. In order to investigate the interaction between salinity (50 mM NaCl) and heavy metal, young plants were exposed in hydroponic culture to 10 μM Cu in the presence or absence of 50 mM NaCl. Copper strongly inhibited the leaf emergence and lateral branch development as well as leaf expansion, and induced a significant decrease in plant dry weight (DW), water content (WC), osmotic potential (Ψs) and leaf water potential (Ψw). Copper treated plants accumulated significantly higher level of Cu in the roots than in the shoots although Cu intake rates decreased with the duration of stress exposure. Additions of NaCl in the absence of Cu excess had no detrimental impact on plant growth. In the presence of Cu excess, NaCl decreased Cu accumulation in roots and stems but had no positive impact on plant growth. Copper induced a large decrease in K concentration in roots and stems as well as a decrease in Ca concentration in the leaves. The impact of Cu and NaCl appeared to be additive on leaf Ψs and leaf quaternary ammonium compounds concentrations. It is concluded that K. virginica exhibits a high bioconcentration factor for Cu which could be, at least partly, responsible for its sensitivity to this toxic element. The impact of stress on K and Ca homeostasis is discussed in relation to ion distribution and presence of mucilage in the plant.

Effect of Salt Stress on Growth and Essential Oil of Matricaria chamomilla

A pot experiment based on complete blocks design was carried out to investigate the effect of salinity on growth traits and essential oil content of chamomile (Matricaria chamomilla L.). Four levels of salinity including control (0 mM), 50, 150 and 250 mM Nacl and CaCl2 in 5 : 1 molar ratio were used. Result indicated that increased salinity caused reduction in plant height, number of branches per plant, number of flowers per plant. Increased salinity also significantly decreased plant dry weight, flower dry weight and essential oil content. The highest values of growth traits such as number of flower per plant, flower dry weight and essential oil content were observed under control condition (non-salinity stress). The effect of salinity on flower dry weight is greater than other traits. Flower dry weight of plants at low (50mM) level of salinity was decreased 12.2 % compared to control (non-stressed plant) while essential oil content increased 18.2 % at the same salt concentration. At the highest level of salt stress (250mM) flower dry weight and essential oil content was decreased by 79.8 and 45.5 % compared to non stressed plants, respectively. Number of flower per plant was decreased by 16.1 and 69.2 % at lowest (50 mM) and highest (250 mM) salinity concentration respectively. Salinity affects flowering time of plants. Flowering time of non-stressed plants started 50 days after plant transplanting while flowering time of plants treated by 250 mM salinity started 64 days after seedlings transplanting to pots.

Root morphology and physiological characteristics in Carya cathayensis seedlings with low phosphorus stress.

Phosphorus（P） deficiency is one of the limiting factors to plant growth. However，scarce information is available about the effect of P deficiency on the growth of Carya cathayensis. To study root morphology，leaf photosynthesis characteristics，leaf acid phosphatase，and root secreted acid phosphatase of Carya cathayensis seedlings，a hydroponic culture experiment with treatments of sufficient P（0.1 mmolL－1） or deficient P（0.02 mmolL－1） was conducted. Results showed that compared to sufficient P，the low P treatment significantly decreased（P＜0.05） plant dry weight，plant P concentration，plant P accumulation，root length，root surface area，root volume leaf photosynthetic rate，and stomatal conductance； however，there were no significant differences for intercellular CO2 concentration. Additionally，the low P treatment significantly increased （P＜0.05） leaf acid phosphatase （by 135%） and root secreted acid phosphatase （by 159%）. Thus，the low P treatments with decreases in leaf photosynthetic rate and stomatal conductance，but no differences for intercellular CO2 concentration，showed that leaf photosynthetic rate was not due to stomatal limitation. Also，for C. cathayensis an increase in acid phosphatase activity induced by a P deficiency could be an adaptive mechanism to low P stress.［Ch，4 fig. 1 tab. 28 ref.］