The Effects of Poly-γ-Glutamic Acid on the Postharvest Physiology and Quality of Strawberry cv. Hongyan during Cold Storage.

This study investigated the effects of poly-γ-glutamic acid (γ-PGA) on the postharvest physiology and quality of the strawberry cv. Hongyan during cold storage. The results showed that all concentrations of γ-PGA improved decay control and strawberry preservation by enhancing antioxidant capacity, delaying the softening process, and maintaining fruit quality, especially for 100 mg·L-1 γ-PGA. After 14 days of treatment, compared with control, 100 mg·L-1 γ-PGA decreased weight loss, decay rate, and index by 21.9%, 75.0%, and 66.7% and increased the total antioxidant capacity by 43.5% through antioxidant enzymes. In addition, 100 mg·L-1 γ-PGA increased fruit firmness by 53.6% by decreasing the activities of polygalacturonase, pectin lyase, cellulase, and ß-galactosidase. In terms of color quality, 100 mg·L-1 γ-PGA improved the values of lightness and yellowness by 30.9% and 52.8%. As regards nutritional quality, 100 mg·L-1 γ-PGA increased the contents of protein, soluble sugars, vitamin C, and total phenols by 106.6%, 80.6%, 51.2%, and 78.4%. In terms of sensory quality, 100 mg·L-1 γ-PGA increased the soluble solids' content by 19.0% and decreased the titrated acids' content by 21.1%, which increased the sugar-acid ratio by 50.9%. Our findings suggest that 100 mg·L-1 γ-PGA can be used to improve the decay control and preservation of strawberry cv. Hongyan under cold storage.

H2S induces NO in the regulation of AsA-GSH cycle in wheat seedlings by water stress.

In current study, we investigated the relationship between hydrogen sulfide (H2S) and nitric oxide (NO) in the regulation of ascorbate-glutathione (AsA-GSH) cycle in wheat seedlings by water stress. Findings showed that water stress significantly stimulated the production of H2S and NO, the transcript levels and activities of enzymes in AsA-GSH cycle, as well as malondialdehyde (MDA) production and electrolyte leakage, but significantly decreased AsA/DHA and GSH/GSSG. Meanwhile, water stress significantly decreased plant height and dry biomass. Except MDA and electrolyte leakage, above changes induced by water stress were reversed by H2S synthesis inhibitor aminooxyacetic acid (AOA) and NO synthesis inhibitor NG-nitro-L-arginine methyl ester (L-NAME). However, AOA and L-NAME significantly enhanced MDA production and electrolyte leakage, which further decreased plant height and dry biomass of wheat seedlings under water stress. Application of exogenous H2S donor sodium hydrosulfide (NaHS) to AOA-treated plants and application of exogenous NO donor sodium nitroprusside (SNP) to L-NAME-treated plants reversed above effects of AOA and L-NAME, respectively. Application of L-NAME plus water stress significantly decreased NO production induced by water stress. However, application of L-NAME plus water stress had no obvious influence on H2S production induced by water stress, while application of AOA plus water stress significantly reduced the production of H2S and NO induced by water stress. Current findings suggested that H2S acted upstream of NO in the regulation of AsA-GSH cycle in wheat seedlings by water stress.

The roles of H2S and H2O2 in regulating AsA-GSH cycle in the leaves of wheat seedlings under drought stress.

This paper investigated the roles of hydrogen sulfide (H2S) and hydrogen peroxide (H2O2) and the possible relationship between them in regulating the AsA-GSH cycle in wheat leaves under drought stress (DS). Results showed that DS markedly increased the production of H2S and H2O2, the transcript levels and activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR); malondialdehyde (MDA) content; and electrolyte leakage (EL). Meanwhile, DS markedly reduced plant height and biomass. Above increases induced by drought stress except MDA content and EL were all suppressed by pretreatments with H2S synthesis inhibitor aminooxyaceticacid (AOA) and H2O2 synthesis inhibitor diphenylene iodonium (DPI). Besides, pretreatments with AOA and DPI further significantly increased MDA content and EL and significantly reduced plant height and biomass under DS. DPI reduced the production of H2O2 and H2S induced by DS. AOA also reduced the production of H2S and H2O2 induced by DS. Pretreatments with NaHS + AOA and H2O2 + DPI reversed above effects of AOA and DPI. Our results suggested that H2S and H2O2 all participated in the up-regulation of AsA-GSH cycle in wheat leaves by DS and possibly affected each other.

Jasmonic acid-induced NO activates MEK1/2 in regulating the metabolism of ascorbate and glutathione in maize leaves.

This study investigated the relationship between MEK1/2 and nitric oxide (NO) in jasmonic acid (JA)-regulated metabolism of ascorbate and glutathione in maize leaves. The results showed that JA increased the activities of APX, GR, MDHAR, DHAR, GalLDH, and γ-ECS; the contents of AsA and GSH; and the production of NO. Above increases except for γ-ECS activity and NO production were all suppressed by pre-treatments with MEK1/2 inhibitors PD98059 and U0126. Above increases were all suppressed by pre-treatments with nitric oxide synthase (NOS) inhibitor L-NAME and NO scavenger cPTIO. The results of western blot showed that JA enhanced the phosphorylation level of MEK1/2. Pre-treatments with L-NAME and cPTIO suppressed JA-induced phosphorylation level of MEK1/2. Our results suggested that JA-induced NO activated MEK1/2 by increasing the phosphorylation level, which, in turn, resulted in the upregulation of ascorbate and glutathione metabolism in maize leaves.

Screening and characterization of endophytic Bacillus and Paenibacillus strains from medicinal plant Lonicera japonica for use as potential plant growth promoters.

A total of 48 endophytic bacteria were isolated from surface-sterilized tissues of the medicinal plant Lonicera japonica, which is grown in eastern China; six strains were selected for further study based on their potential ability to promote plant growth in vitro (siderophore and indoleacetic acid production). The bacteria were characterized by phylogenetically analyzing their 16S rRNA gene similarity, by examining their effect on the mycelial development of pathogenic fungi, by testing their potential plant growth-promoting characteristics, and by measuring wheat growth parameters after inoculation. Results showed that the number of endophytic bacteria in L. japonica varied among different tissues, but it remained relatively stable in the same tissues from four different plantation locations. Among the three endophytic strains, strains 122 and 124 both had high siderophore production, with the latter showing the highest phosphate solubilization activity (45.6 mg/L) and aminocyclopropane-1-carboxylic acid deaminase activity (47.3 nmol/mg/h). Strain 170 had the highest indoleacetic acid (IAA) production (49.2 mg/L) and cellulase and pectinase activities. After inoculation, most of the six selected isolates showed a strong capacity to promote wheat growth. Compared with the controls, the increase in the shoot length, root length, fresh weight, dry weight, and chlorophyll content was most remarkable in wheat seedlings inoculated with strain 130. The positive correlation between enzyme (cellulose and pectinase) activity and inhibition rate on Fusarium oxysporum, the IAA production, and the root length of wheat seedlings inoculated with each tested endophytic strain was significant in regression analysis. Deformity of pathogenic fungal mycelia was observed under a microscope after the interaction with the endophytic isolates. Such deformity may be directly related to the production of hydrolytic bacterial enzymes (cellulose and pectinase). The six endophytic bacterial strains were identified to be Paenibacillus and Bacillus strains based on the results of 16S rRNA gene sequencing analysis and their physiological and biochemical characteristics. Results indicate the promising application of endophytic bacteria to the biological control of pathogenic fungi and the improvement of wheat crop growth.

Screening and characterization of endophytic Bacillus and Paenibacillus strains from medicinal plant Lonicera japonica for use as potential plant growth promoters

Abstract A total of 48 endophytic bacteria were isolated from surface-sterilized tissues of the medicinal plant Lonicera japonica, which is grown in eastern China; six strains were selected for further study based on their potential ability to promote plant growth in vitro (siderophore and indoleacetic acid production). The bacteria were characterized by phylogenetically analyzing their 16S rRNA gene similarity, by examining their effect on the mycelial development of pathogenic fungi, by testing their potential plant growth-promoting characteristics, and by measuring wheat growth parameters after inoculation. Results showed that the number of endophytic bacteria in L. japonica varied among different tissues, but it remained relatively stable in the same tissues from four different plantation locations. Among the three endophytic strains, strains 122 and 124 both had high siderophore production, with the latter showing the highest phosphate solubilization activity (45.6 mg/L) and aminocyclopropane-1-carboxylic acid deaminase activity (47.3 nmol/mg/h). Strain 170 had the highest indoleacetic acid (IAA) production (49.2 mg/L) and cellulase and pectinase activities. After inoculation, most of the six selected isolates showed a strong capacity to promote wheat growth. Compared with the controls, the increase in the shoot length, root length, fresh weight, dry weight, and chlorophyll content was most remarkable in wheat seedlings inoculated with strain 130. The positive correlation between enzyme (cellulose and pectinase) activity and inhibition rate on Fusarium oxysporum, the IAA production, and the root length of wheat seedlings inoculated with each tested endophytic strain was significant in regression analysis. Deformity of pathogenic fungal mycelia was observed under a microscope after the interaction with the endophytic isolates. Such deformity may be directly related to the production of hydrolytic bacterial enzymes (cellulose and pectinase). The six endophytic bacterial strains were identified to be Paenibacillus and Bacillus strains based on the results of 16S rRNA gene sequencing analysis and their physiological and biochemical characteristics. Results indicate the promising application of endophytic bacteria to the biological control of pathogenic fungi and the improvement of wheat crop growth.

Nitric oxide participates in the regulation of the ascorbate-glutathione cycle by exogenous jasmonic acid in the leaves of wheat seedlings under drought stress.

In this paper, we investigated whether nitric oxide (NO) participated in the regulation of the ascorbate-glutathione (AsA-GSH) cycle by exogenous jasmonic acid (JA) in the leaves of wheat seedlings under drought stress. The findings of our study showed that drought stress significantly enhanced the AsA-GSH cycle by upregulating the activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR). Drought stress also markedly increased electrolyte leakage (EL), malondialdehyde (MDA) content, NO content, and significantly reduced the ratios of reduced ascorbate/dehydroascorbic acid (AsA/DHA) and reduced glutathione/oxidized glutathione (GSH/GSSG) compared with control. Exogenous JA significantly increased the above indicators, compared with drought stress alone. All these effects of JA were inhibited by pretreatment with NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO). Meanwhile, exogenous JA markedly decreased MDA content and electrolyte leakage of wheat leaves under drought stress. Pretreatment with cPTIO reversed the above effects of exogenous JA. Our findings indicated that NO induced by exogenous JA upregulated the activity of the AsA-GSH cycle and had important role in drought tolerance.

The difference in antioxidant capacity of four alfalfa cultivars in response to Zn.

The aim of this study was to evaluate antioxidative responses in roots, stem and leaves of four alfalfa cultivars to different concentrations of zinc (Zn) (0, 300, 600 and 900 µM) for 23 days. Among the four cultivars, Aohan displayed the highest Zn concentrations in tissues and the largest Zn amount in aerial parts. Zn stress induced the production of H2O2 and increased the content of free proline and activities of antioxidative enzymes in roots, stem and leaves of Aohan. Based on the above results, we concluded that Aohan is superior to other three cultivars for Zn phyto-remediation, which indicated that Aohan is a novel Zn accumulator and able to tolerate Zn-induced toxicity by activating the antioxidative defense system.

The protein kinase MEK1/2 participates in the regulation of ascorbate and glutathione content by jasmonic acid in Agropyron cristatum leaves.

This study investigated the role of the protein kinase MEK1/2 in the regulation of ascorbate and glutathione content by jasmonic acid in Agropyron cristatum leaves. The results showed that JA induced increases in the transcript levels and activities of APX, GR, MDHAR, DHAR, GalLDH and γ-ECS, the contents of AsA, GSH, total ascorbate and total glutathione, and the ratios of AsA/DHA and GSH/GSSG, and reduced the E(GSSG/2GSH). The increases, except for the transcript level and activity of γ-ECS and the reduction in E(GSSG/2GSH,) were all suppressed by pre-treatment with the MEK1/2 inhibitors PD98059 and U0126. The results of western blot analyses showed that JA induced increases in the phosphorylation level of MEK1/2. Our results suggest that JA could induce the activation of MEK1/2 by increasing the phosphorylation level, which, in turn, resulted in the up-regulation of ascorbate and glutathione content in A. cristatum leaves.

[Characteristics of Robinia pseudoacacia water physiological ecology under different habitats in North Shaanxi gully areas of Loess Plateau].

With locust (Robinia pseudoacacia), the main tree species in afforestation, as test material, this paper studied the characteristics of its water physiological ecology and productivity under four habitats, i. e. , sunny, shady, semi-sunny and semi-shady hillsides, in the North Shaanxi gully areas of Loess Plateau. The mean water content in 0 - 500 cm soil layer was 8.87% (shady), 8.06% (semi-shady), 7.62% (semi-sunny), and 6.96% (sunny), respectively. There was a significant discrepancy between shady, semi-shady, semi-sunny and sunnyhilisides (a 0.01), and the difference between shady, semi-shady and semi-sunny, as well as between semi-sunny and sunny hillsides was also significant (a 0.05) . Remarkable relationships were found between leaf RWC, locus WSD and soil water content (SWC) . The leaf RWC and locust water potential under sunny hillside were lower, but those under shady hillside were higher. The daily mean transpiration was in order of shady (4.07 microg x cm(-2) x s(-1)) > semi-shady (3.89 microg x cm(-2) x s(-1)) > semi-sunny (3.05 microg x cm(-2) x s(-1)) > sunny (2.70 microg x cm(-2)s(-1)) hillside. The remarkable difference of transpiration appeared at 11:00 and 13:00, and there existed a remarkable relationship between transpiration and light intensity, RH and soil water content. All of these resulted in a diversity of locust biomass under different habitats, the highest under shady hillside, and the lowest under sunny hillside, and the differences between different habitats were all significant. It could be concluded that soil water content was the main factor affecting locust growth.