Showing papers on "Shoot published in 2013"

Melatonin promotes water‐stress tolerance, lateral root formation, and seed germination in cucumber (Cucumis sativus L.)

Abstract: A comprehensive investigation was carried out to determine the changes that occurred in water-stressed cucumber (Cucumis sativus L.) in response to melatonin treatment. We examined the potential roles of melatonin during seed germination and root generation and measured its effect on reactive oxygen species (ROS) levels, antioxidant enzyme activities, and photosynthesis. Melatonin alleviated polyethylene glycol induced inhibition of seed germination, with 100 μm melatonin-treated seeds showing the greatest germination rate. Melatonin stimulated root generation and vitality and increased the root:shoot ratio; therefore, melatonin may have an effect on strengthening cucumber roots. Melatonin treatment significantly reduced chlorophyll degradation. Seedlings treated with 100 μm melatonin clearly showed a higher photosynthetic rate, thus reversing the effect of water stress. Furthermore, the ultrastructure of chloroplasts in water-stressed cucumber leaves was maintained after melatonin treatment. The antioxidant levels and activities of the ROS scavenging enzymes, i.e., superoxide dismutase, peroxidase, and catalase, were also increased by melatonin. These results suggest that the adverse effects of water stress can be minimized by the application of melatonin.

Do plants need nitrate? The mechanisms by which nitrogen form affects plants

Abstract: The literature on nitrogen (N) form effects on plants at different stages of their development has been critically reviewed, assessing the possible mechanisms of these effects. In particular, nitrate (NO3−) was compared with the other forms of N utilised by plants. It is concluded that the form of N available to plants can affect their time and rate of seed germination, leaf expansion and function, dry matter partitioning between shoot and root, and root architecture. The magnitude of these effects is dependent on environmental factors outside the supply of N. The mechanism of these effects is variable. Assessment of the importance of root or shoot NO3− assimilation under different environmental conditions is an important area for further study.

Cytokinin-producing, plant growth-promoting rhizobacteria that confer resistance to drought stress in Platycladus orientalis container seedlings.

Abstract: One of the proposed mechanisms through which plant growth-promoting rhizobacteria (PGPR) enhance plant growth is the production of plant growth regulators, especially cytokinin. However, little information is available regarding cytokinin-producing PGPR inoculation on growth and water stress consistence of forest container seedlings under drought condition. This study determined the effects of Bacillus subtilis on hormone concentration, drought resistance, and plant growth under water-stressed conditions. Although no significant difference was observed under well-watered conditions, leaves of inoculated Platycladus orientalis (oriental thuja) seedlings under drought stress had higher relative water content and leaf water potential compared with those of noninoculated ones. Regardless of water supply levels, the root exudates, namely sugars, amino acids and organic acids, significantly increased because of B. subtilis inoculation. Water stress reduced shoot cytokinins by 39.14 %. However, inoculation decreased this deficit to only 10.22 %. The elevated levels of cytokinins in P. orientalis shoot were associated with higher concentration of abscisic acid (ABA). Stomatal conductance was significantly increased by B. subtilis inoculation in well-watered seedlings. However, the promoting effect of cytokinins on stomatal conductance was hampered, possibly by the combined action of elevated cytokinins and ABA. B. subtilis inoculation increased the shoot dry weight of well-watered and drought seedlings by 34.85 and 19.23 %, as well as the root by 15.445 and 13.99 %, respectively. Consequently, the root/shoot ratio significantly decreased, indicative of the greater benefits of PGPR on shoot growth than root. Thus, inoculation of cytokinin-producing PGPR in container seedlings can alleviate the drought stress and interfere with the suppression of shoot growth, showing a real potential to perform as a drought stress inhibitor in arid environments.

Arbuscular mycorrhizal fungi native from a Mediterranean saline area enhance maize tolerance to salinity through improved ion homeostasis

Abstract: Soil salinity restricts plant growth and productivity. Na + rep- resents the major ion causing toxicity because it competes with K + for binding sites at the plasma membrane. Inocula- tion with arbuscular mycorrhizal fungi (AMF) can alleviate salt stress in the host plant through several mechanisms. These may include ion selection during the fungal uptake of nutrients from the soil or during transfer to the host plant. AM benefits could be enhanced when native AMF isolates are used.Thus, we investigated whether native AMF isolated from an area with problems of salinity and desertification can help maize plants to overcome the negative effects of salinity stress better than non-AM plants or plants inoculated with non-native AMF. Results showed that plants inoculated with two out the three native AMF had the highest shoot dry biomass at all salinity levels. Plants inoculated with the three native AMF showed significant increase of K + and reduced Na + accumulation as compared to non-mycorrhizal plants, concomitantly with higher K + /Na + ratios in their tissues. For the first time, these effects have been correlated with regula- tion of ZmAKT2, ZmSOS1 and ZmSKOR genes expression in the roots of maize, contributing to K + and Na + homeostasis

Brassica napus Growth is Promoted by Ascophyllum nodosum (L.) Le Jol. Seaweed Extract: Microarray Analysis and Physiological Characterization of N, C, and S Metabolisms

Abstract: Despite its high capacity to take up nitrate from soil, winter rapeseed (Brassica napus) is characterized by a low N recovery in seeds. Thus, to maintain yield, rapeseed requires a high fertilization rate. Increasing nutrient use efficiency in rapeseed by addition of a biostimulant could help improve its agroenvironmental balance. The effects of marine brown seaweed Ascophyllum nodosum on plant growth have been well described physiologically. However, to our knowledge, no study has focused on transcriptomic analyses to determine metabolic targets of these extracts. A preliminary screening of different extracts revealed a significant effect of one of them (AZAL5) on rapeseed root (+102 %) and shoot (+23 %) growth. Microarray analysis was then used on AZAL5-treated or nontreated plants to characterize changes in gene expression that were further supported by physiological evidence. Stimulation of nitrogen uptake (+21 and +115 % in shoots and roots, respectively) and assimilation was increased in a similar manner to growth, whereas sulfate content (+63 and +133 % in shoots and roots, respectively) was more strongly stimulated leading to sulfate accumulation. Among the identified genes whose expression was affected by AZAL5, MinE, a plastid division regulator, was the most strongly affected. Its effect was supported by microscopic analysis showing an enhancement of chloroplast number per cell and starch content but without a significant difference in net photosynthetic rate. In conclusion, it is suggested that AZAL5, which promotes plant growth and nutrient uptake, could be used as a supplementary tool to improve rapeseed agroenvironmental balance.

Environmental effects of nanosilver: impact on castor seed germination, seedling growth, and plant physiology

Abstract: Increasing use of nanoparticles in daily products is of great concern today, especially when their positive and negative impact on environment is not known. Hence, in current research, we have studied the impact of silver nanoparticle (AgNPs) and silver nitrate (AgNO3) application on seed germination, root, and shoot length of castor bean, Ricinus communis L. plant. Silver nanoparticles had no significant effects on seedling growth even at higher concentration of 4,000 mg L(-1), while the silver in bulk form as AgNO3 applied on the castor bean seeds inhibited the seed germination. Silver uptake in seedlings of the castor seeds on treatment with both the forms of silver was confirmed through atomic absorption spectroscopy studies. The silver nanoparticle and silver nitrate application to castor seeds also caused an enhanced enzymatic activity of ROS enzymes and phenolic content in castor seedlings. High-performance liquid chromatography analysis of individual phenols indicated enhanced content of parahydroxy benzoic acid. These kinds of studies are of great interest in order to unveil the movement and accumulation of nanoparticles in plant tissues for assessing future applications in the field or laboratory.

5-Aminolevulinic Acid Ameliorates the Growth, Photosynthetic Gas Exchange Capacity, and Ultrastructural Changes Under Cadmium Stress in Brassica napus L.

Abstract: Heavy-metal toxicity in soil is one of the major constraints for oilseed rape (Brassica napus L.) production. One of the best ways to overcome this constraint is the use of growth regulators to induce plant tolerance. Response to cadmium (Cd) toxicity in combination with a growth regulator, 5-aminolevulinic acid (ALA), was investigated in oilseed rape grown hydroponically in greenhouse conditions under three levels of Cd (0, 100, and 500 μM) and three levels of foliar application of ALA (0, 12.5, and 25 mg l−1). Cd decreased plant growth and the chlorophyll concentration in leaves. Foliar application of ALA improved plant growth and increased the chlorophyll concentration in the leaves of Cd-stressed plants. Significant reductions in photosynthetic parameters were observed by the addition of Cd alone. Application of ALA improved the net photosynthetic and gas exchange capacity of plants under Cd stress. ALA also reduced the Cd content in shoots and roots, which was elevated by high concentrations of Cd. The microscopic studies of leaf mesophyll cells under different Cd and ALA concentrations showed that foliar application of ALA significantly ameliorated the Cd effect and improved the structure of leaf mesophyll cells. However, the higher Cd concentration (500 μM) could totally damage leaf structure, and at this level the nucleus and intercellular spaces were not established as well; the cell membrane and cell wall were fused to each other. Chloroplasts were totally damaged and contained starch grains. However, foliar application of ALA improved cell structure under Cd stress and the visible cell structure had a nucleus, cell wall, and cell membrane. These results suggest that under 15-day Cd-induced stress, application of ALA helped improve plant growth, chlorophyll content, photosynthetic gas exchange capacity, and ultrastructural changes in leaf mesophyll cells of the rape plant.

Exogenous application of moringa leaf extract modulates the antioxidant enzyme system to improve wheat performance under saline conditions

Abstract: Amongst naturally occurring plant growth stimulants, moringa (Moringa oleifera Lam.) has attained enormous attention being rich in cytokinin, antioxidants and macro–micro nutrients in its leaves. In this study, potential of foliar applied moringa leaf extract (MLE; 30 times diluted), benzyl amino purine (BAP; 50 mg L−1) and hydrogen peroxide (H2O2; 120 μM) at tillering, jointing, booting and heading growth stages was evaluated to induce salt resistance in wheat. Water spray treatment was taken as control. Wheat cv. Sehar-2006 was grown under normal (4 dS m−1), medium (8 dS m−1) and high (12 dS m−1) soil saline conditions. Application of these stimulants decreased the shoot Na+ and Cl− contents, with simultaneous increase in shoot K+ contents. Maximum shoot K+ (48.62 %) contents were recorded with MLE application under high salinity. Activities of leaf antioxidants viz. superoxide dismutase, peroxidase and contents of total soluble phenolics were increased at medium salinity level; whereas ascorbate contents were also improved by MLE application at high salinity level. However, maximum increase in leaf total soluble protein (35.9 %) was observed with BAP application at medium salinity. The shoot length, shoot and root dry weights were decreased with increase in level of salt stress. Grain weight (18.5 %) and kernel yield (18.5 %) were also improved by MLE application under saline and normal conditions than other stimulators used. In conclusion, foliar applied moringa leaf extract could ameliorate salinity-induced adverse effects by activation of antioxidant defense system and decrease in accumulation of Na+ and Cl− into shoots under moderate saline conditions.

Effect of nanoparticles suspension on the growth of mung (Vigna radiata) seedlings by foliar spray method

Abstract: The present experimental investigation demonstrates the effect of nano-ZnO, nano-FeO and nano-ZnCuFe-oxide particles on the growth of mung ( Vigna radiata ) seedling. The study was carried out by spraying optimum concentrations of nanoparticles in suspension form on hydroponically grown test units and examining the effect on the shoot growth of seedlings. Based on biomass assay, it was found that the seedlings displayed good growth over control, demonstrating a positive effect of the nanoparticle treatment. The best performance was observed for nano-ZnCuFe-Oxide followed by nano-FeO and nano-ZnO. Absorption of nanoparticles by plant leaves was also detected by inductive coupled plasma/atomic emission spectroscopy.

Effects of arbuscular mycorrhiza inoculation on plant growth, biological and physiological parameters and mineral nutrition in pepper grown under different salinity and p levels.

Abstract: A study was conducted in a greenhouse, to investigate the effects of arbuscular mycorrhizal fungi (Glomus intraradices), soil salinity and P availability on growth (leaf area and dry weight), nutrient absorption and ion leakage, chlorophyll, soluble sugar and proline content and alkaline phosphatase activity of pepper plants (Capsicum annuum L) Plants were grown at four levels of salinity (0, 50, 100 and 200 mM NaCl) and two P levels (10 and 40 mg kg -1 ) Colonisation was 80% to 51% in non-stressed and high salt-stressed plants, respectively The mycorrhizal dependency was high and only reduced at the higher salinity level Mycorrhizal plants maintained greater root and shoot biomass at all salinity levels compared to non-mycorrhizal plants, regardless the P level Interactions between salinity, phosphorous and mycorrhizae were significant for leaf area, root and shoot dry mass Non-mycorrhizal plants accumulated higher Na and lower K and P compared to mycorrhizal plants The cell membrane integrity was greater in mycorrhizal plants than in non-mycorrhizal ones The proline content increases with increasing salt stress and was significantly higher in leaves than in roots The results indicate that the mycorrhizal inoculation is capable of alleviating the damage caused by salt stress conditions on pepper plants, to maintaining the membranes stability and plant growth, and this could be related to P nutrition

Endophytic Penicillium funiculosum LHL06 secretes gibberellin that reprograms Glycine max L. growth during copper stress

Abstract: Heavy metal pollution in crop fields is one of the major issues in sustainable agriculture production. To improve crop growth and reduce the toxic effects of metals is an ideal strategy. Understanding the resilience of gibberellins producing endophytic fungi associated with crop plants in metal contaminated agriculture fields could be an important step towards reducing agrochemical pollutions. In present study, it was aimed to screen and identify metal resistant endophyte and elucidate its role in rescuing crop plant growth and metabolism during metal stress. Fungal endophyte, Penicillium funiculosum LHL06, was identified to possess higher growth rate in copper (Cu) and cadmium contaminated mediums as compared to other endophytes (Metarhizium anisopliae, Promicromonospora sp. and Exophiala sp.). P. funiculosum had high biosorption potential toward copper as compared to cadmium. An endophyte-metal-plant interaction was assessed by inoculating the host Glycine max L. plants with P. funiculosum during Cu (100 μM) stress. The Cu application adversely affected the biomass, chlorophyll and total protein content of non-inoculated control plants. The control plants unable to synthesis high carbon, hydrogen and nitrogen because the roots had lower access to phosphorous, potassium, sulphur and calcium during Cu treatment. Conversely, P. funiculosum-association significantly increased the plant biomass, root physiology and nutrients uptake to support higher carbon, hydrogen and nitrogen assimilation in shoot. The metal-removal potential of endophyte-inoculated plants was significantly higher than control as the endophyte-association mediated the Cu uptake via roots into shoots. The symbiosis rescued the host-plant growth by minimizing Cu-induced electrolytic leakage and lipid peroxidation while increasing reduces glutathione activities to avoid oxidative stress. P. funiculosum-association synthesized higher quantities of proline and glutamate as compared to control. Stress-responsive abscisic acid was significantly down-regulated in the plant-metal-microbe association. The endophyte P. funiculosum symbiosis counteracted the Cu stress and reprogrammed soybean plant growth. Such growth promoting and stress mediating endophytes can be applied at field levels to help in bioremediation of the polluted agricultural fields.

Gamma radiation effects on seed germination, growth and pigment content, and ESR study of induced free radicals in maize (Zea mays)

Abstract: The effects of gamma radiation are investigated by studying plant germination, growth and development, and biochemical characteristics of maize. Maize dry seeds are exposed to a gamma source at doses ranging from 0.1 to 1 kGy. Our results show that the germination potential, expressed through the final germination percentage and the germination index, as well as the physiological parameters of maize seedlings (root and shoot lengths) decreased by increasing the irradiation dose. Moreover, plants derived from seeds exposed at higher doses (≤0.5 kGy) did not survive more than 10 days. Biochemical differences based on photosynthetic pigment (chlorophyll a, chlorophyll b, carotenoids) content revealed an inversely proportional relationship to doses of exposure. Furthermore, the concentration of chlorophyll a was higher than chlorophyll b in both irradiated and non-irradiated seedlings. Electron spin resonance spectroscopy used to evaluate the amount of free radicals induced by gamma ray treatment demonstrates that the relative concentration of radiation-induced free radicals depends linearly on the absorbed doses.

Effect of short-term heat stress on growth, physiology and antioxidative defence system in wheat seedlings

Abstract: An experiment was conducted to find out the effect of short-term heat stress on morpho-physiological characters and antioxidants in 10 diverse wheat genotypes. Seed were aseptically grown in test tubes containing filter paper whose lower half was dipped in one-fourth MS media. Heat stress conditions were created by exposing the seedlings at 45 °C for 2 h after 7 days of their germination. Measurements were taken after 3 days of treatment. Heat stress significantly reduced the shoot dry mass, root dry mass, shoot length and root length in all the genotypes. The chlorophyll content and membrane stability index decreased, whereas proline content increased in heat-treated plants. There was significant increase in the activity of catalase, guaiacol peroxidase and superoxide dismutase under stress conditions. The genotypic variations were also significant. On the basis of a coordinated simulation of all these parameters, wheat genotypes Raj 4037 and PBW 373 were identified as tolerant to high temperature stress. The study provides evidence that the tolerant genotypes were equipped with better management of physiological processes along with an efficient antioxidative defence system, sensitivity of which can be evaluated to a sufficient level of certainty at seedling stage.

Piriformospora indica rescues growth diminution of rice seedlings during high salt stress.

Abstract: Piriformospora indica association has been reported to increase biotic as well as abiotic stress tolerance of its host plants. We analyzed the beneficial effect of P. indica association on rice seedlings during high salt stress conditions (200 and 300 mM NaCl). The growth parameters of rice seedlings such as root and shoot lengths or fresh and dry weights were found to be enhanced in P. indica-inoculated rice seedlings as compared with non-inoculated control seedlings, irrespective of whether they are exposed to salt stress or not. However, salt-stressed seedlings performed much better in the presence of the fungus compared with non-inoculated control seedlings. The photosynthetic pigment content [chlorophyll (Chl) a, Chl b, and carotenoids] was significantly higher in P. indica-inoculated rice seedlings under high salt stress conditions as compared with salt-treated non-inoculated rice seedlings, in which these pigments were found to be decreased. Proline accumulation was also observed during P. indica colonization, which may help the inoculated plants to become salt tolerant. Taken together, P. indica rescues growth diminution of rice seedlings under salt stress.

Alleviation of salt stress-induced adverse effects on maize plants by exogenous application of indoleacetic acid (IAA) and inorganic nutrients - A field trial

Abstract: The effects of indoleacetic acid (IAA) and inorganic nutrients (K and P) on some physiological parameters and kernel yield of maize (Zea mays L.) cultivar DK 647 F1 were investigated in two parallel experiments conducted in the same growth season in a saline field. Sodium chloride equivalent to 100 mM was added to the irrigation water and saline water applied to the field using a drip irrigation system. Indoleacetic acid was applied as foliar spray. Potassium and P were applied to the soil at the sowing time as monopotassium phosphate at 200 kg ha -1 . Salinity significantly reduced shoot dry mass, cob yield, total kernel yield, weight of 1000 kernels, chlorophylls “a” and “b” and relative water content in the maize plants, but increased proline accumulation, activities of the key antioxidant enzymes superoxide dismutase (SOD; EC 1.15.1.1), peroxidase (POD; EC. 1.11.1.7), catalase (CAT; EC. 1.11.1.6) and polyphenol oxidase (PPO; 1.10.3.1), and electrolyte leakage. However, application of K and P or foliar spray of IAA mitigated the adverse effects of salinity on maize plants. The most promising effect of IAA or K and P on alleviation of salt stress on maize was found when they were applied in combination. Leaf sodium (Na + ) concentration increased substantially, but leaf K + , Ca 2+ and P concentrations decreased markedly in the salt stressed maize plants. However, exogenous application of nutrients, IAA, or their combination considerably reduced Na + concentration and significantly improved K + , Ca 2+ , and P levels in the salt stressed maize plants. The exogenously applied inorganic nutrient- or auxin-induced growth promotion in maize plants was found to be associated with increased photosynthetic pigment concentration and leaf Na + /K + ratio, reduced membrane permeability, and altered activities of

Ionomic responses and correlations between elements and metabolites under salt stress in wild and cultivated barley.

Abstract: A thorough understanding of ionic detoxification and homeostasis is imperative for improvement of salt tolerance in crops. However, the homeostasis of elements and their relationship to metabolites under salt stress have not been fully elucidated in plants. In this study, Tibetan wild barley accessions, XZ16 and XZ169, differing in salt tolerance, and a salt-tolerant cultivar CM72 were used to investigate ionomic profile changes in tissues in response to 150 and 300 mM NaCl at the germination and seedling stages. At the germination stage, the contents of Ca and Fe significantly decreased in roots, while K and S contents increased, and Ca and Mg contents decreased in shoots, after 10 d of treatment. At the seedling stage, the contents of K, Mg, P and Mn in roots and of K, Ca, Mg and S in shoots decreased significantly after 21 d of treatment. Moreover, Na had a significant negative correlation with metabolites involved in glycolysis, α-ketoglutaric acid, maleic acid and alanine in roots, and metabolites associated with the tricarboxylic acid (TCA) cycle, sucrose, polyols and aspartate in leaves. The salt-tolerant genotypes XZ16 and CM72 showed a lower Na content in tissues, and less reduction in Zn and Cu in roots, of Ca, Mg and S in leaves, and shoot DW than the sensitive genotype XZ169, when exposed to a higher salt level. The results indicated that restriction of Na accumulation and rearrangement of nutrient elements and metabolites in barley tissues are possibly attributable to development of salt tolerance.

Effect of azospirillum inoculation on maize (zea mays l.) under drought stress

Abstract: Azospirillum strains isolated from water stressed conditions can mitigate drought effects when used as inoculants. In this context, the research was designed to study the effects of Azospirillum lipoferum strain (Accession no. GQ255950) inoculation on biochemical attributes and growth of maize plant under drought stress. Effect of seed inoculation and rhizosphere inoculation were studied in two varieties of maize, which were subjected to drought stress at vegetative stage. Water deficiency affected accumulation of free amino acids, soluble sugars, proline and soluble protein contents. However, seed inoculated plants had an increased accumulation of 54.54 percent and 63.15 percent free amino acids and soluble sugars respectively, while rhizosphere inoculated plants showed 45.45 percent increase in free amino acids and 31.57 percent increase in soluble sugars as compared to control. The concentrations of soluble proteins on the contrary decreased in the similar order. The plants growth aspect i.e. shoot and root fresh weight, shoot and root dry weight, shoot length and root length, also showed results in consistence with the biochemical attributes. Thus Azospirillum strain showed promising effects and can be a potent inoculant for maize that can help the crop to endure limited water availability.

Effects of Exogenous Salicylic Acid and Nitric Oxide on Physiological Characteristics of Perennial Ryegrass Under Cadmium Stress

Abstract: The effects of Cd, in combination with salicylic acid (SA) and sodium nitroprusside (SNP), on ryegrass seedlings were studied. Exposure of plants to 0.1 mM CdCl2 for 2 weeks resulted in toxicity symptoms such as chlorosis and necrotic spots on leaves. The addition of 0.2 mM SA or 0.1 mM SNP slightly alleviated the toxic effects of Cd. After application of both SA and SNP, these symptoms significantly decreased. Treatment with Cd resulted in a decrease of dry weight of roots and shoots, chlorophyll content, net photosynthetic rate (Pn), transpiration rate (Tr), and the uptake and translocation of mineral elements. In Cd-treated plants, levels of lipoxygenase activity and malondialdehyde, hydrogen peroxide (H2O2), and proline contents significantly increased, whereas the activities of antioxidant enzymes, such as superoxide dismutase, guaiacol peroxidase, catalase, and ascorbate peroxidase, decreased in both roots and shoots. The results indicated that Cd caused physiological stresses in ryegrass plants. The Cd-stressed plants exposed to SA or SNP, especially to SA + SNP, exhibited improved growth compared with Cd-stressed plants. Application of SA or SNP, especially the combination SA + SNP, considerably reduced root-to-shoot translocation of Cd and increased the activities of antioxidant enzymes in both roots and shoots of Cd-stressed plants. The interaction of SA and SNP increased chlorophyll content, Pn and Tr in leaves, and the uptake and translocation of mineral elements, and decreased lipid peroxidation and H2O2 and proline accumulation in roots and shoots. These results suggest that SA or SNP, and, in particular, their combination counteracted the negative effects of Cd on ryegrass plants.

The activity of antioxidant enzymes in response to salt stress in safflower (Carthamus tinctorius L.) and sunflower (Helianthus annuus L.) seedlings raised from seed treated with chitosan.

Abstract: Background Salt tolerance is a complex trait which involves the coordinated action of many genes that perform a variety of functions, such as ion sequestration, metabolic adjustment, osmotic adjustment and antioxidative defence In this article, the growth and the generation and scavenging of reactive oxygen species (ROS) under normal (ECiw [Electrical conductivity of irrigation water] = 05 dS m−1) and salt stress conditions (ECiw = 34, 61, 86 and 108 dS m−1) in relation to the priming of seeds of the two important oil yielding crops, ie safflower and sunflower, with different concentrations of chitosan [0% (control), 025%, 050%, 075%] is discussed Results Induced salinity stress significantly decreased germination percentage, germination rate, length and weight of root and shoot, and protein content Proline content, malondialdehyde content (MDA), catalase (CAT) and peroxidase (POX) activity increased at 108 dS m−1 Under control conditions there were no significant differences in germination percentage among different concentrations of chitosan, whereas CAT and POX activity were increased by low concentrations of chitosan With increasing salt stress, low concentrations of chitosan increased germination percentage but decreased MDA and proline contents and CAT and POX activity Conclusion Generation of ROS seems to be unavoidable under normal conditions and the activity of antioxidant enzymes in plants varies in terms of ROS generation under salt stress However, the data indicate that plants subjected to salt stress-induced oxidative stress and the low concentrations of chitosan exhibited positive effects on salt stress alleviation through the reduction of enzyme activity in both crops © 2012 Society of Chemical Industry

Copper‐induced stress in Solanum nigrum L. and antioxidant defense system responses

Abstract: Solanum nigrum L. plants were exposed for 28 days to 100 and 200 μmol/L copper (Cu) in a hydroponic system to analyze the antioxidant defense response. A dose-dependent reduction in growth (fresh mass of root and shoot, shoot height, and root elongation) with increasing concentration of Cu was observed, whereas Cu treatments did funt affect total chlorophyll and carotefunids content. An enhanced lipid peroxidation, in terms of malondialdehyde (MDA) content, was quantified in shoots when the plants were subjected to the highest Cu level, while in roots MDA levels showed a dose-dependent increase along the increasing Cu concentrations applied. An increase of proline in roots of plants exposed to 200 μmol/L Cu was found. Antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) did funt show significant changes with respect to control, in both roots and shoots, despite mRNA-specific accumulations varied between Cu levels and organs. Ascorbate peroxidase (APX) was negatively affected in shoots by the highest Cu level. Gene expression of the subtype 2d metallothioneins (MT) revealed to be Cu-enhanced throughout the plant body and correlated with Cu tissue levels, with the other MT1 and MT2 gene members downregulated in roots and upregulated in shoots, contributing more as antioxidants in the latter organs than in Cu homeostasis. MT3s are not involved in Cu homeostasis and phytochelatin (PC) production was enhanced in roots of plants exposed to 200 μmol/L Cu, contributing to a higher Cu accumulation in these organs.

CAROTENOID CLEAVAGE DIOXYGENASE 7 modulates plant growth, reproduction, senescence, and determinate nodulation in the model legume Lotus japonicus

Abstract: Strigolactones (SLs) are newly identified hormones that regulate multiple aspects of plant development, infection by parasitic weeds, and mutualistic symbiosis in the roots. In this study, the role of SLs was studied for the first time in the model plant Lotus japonicus using transgenic lines silenced for CAROTENOID CLEAVAGE DIOXYGENASE 7 (LjCCD7), the orthologue of Arabidopsis More Axillary Growth 3. Transgenic LjCCD7-silenced plants displayed reduced height due to shorter internodes, and more branched shoots and roots than the controls, and an increase in total plant biomass, while their root:shoot ratio remained unchanged. Moreover, these lines had longer primary roots, delayed senescence, and reduced flower/pod numbers from the third round of flower and pod setting onwards. Only a mild reduction in determinate nodule numbers and hardly any impact on the colonization by arbuscular mycorrhizal fungi were observed. The results show that the impairment of CCD7 activity in L. japonicus leads to a phenotype linked to SL functions, but with specific features possibly due to the peculiar developmental pattern of this plant species. It is believed that the data also link determinate nodulation, plant reproduction, and senescence to CCD7 function for the first time.