Springer Science and Business Media LLC

The recommended field dose (RFD) of isoproturon induced significant accumulations of H2O2 in the leaves of 10-d-old maize seedlings throughout the following 20 d; the accumulation increased with time and also with herbicide dose. Meanwhile, low doses significantly increased ascorbic acid, glutathione and thiols while high doses caused diminutions. Superoxide dismutase (SOD; EC 1.15.1.1) activity was significantly enhanced up to the 12th d whereas ascorbate peroxidase (APX; EC 1.11.1.7) activity was significantly reduced after the fourth d onwards. Catalase (CAT; EC 1.11.1.6) and guaiacol peroxidase (GPX; EC 1.11.1.7) activities were similarly increased during the first 4 d but decreased from the 12th and the eighth d, respectively. Low doses increased SOD and GPX activities but high doses led to diminutions whereas CAT and APX were reduced by all doses. The activities of γ-glutamyl-cysteine synthethase (γ-GCS; EC 6.3.2.2) and glutathione synthethase (GSS; EC 6.3.2.3) were enhanced for 4 d; high doses caused general reductions. Isoproturon significantly reduced activities of glutathione S-transferase (GST; EC 2.5.1.18) isoforms [GST(CDNB), GST(ALA), or GST(MET)] after the fourth d, however, it had no effect on GST(ATR). Similar reductions in activities of glutathione peroxidase (GSPX; EC 1.15.1.1) and glutathione reductase (GR; EC 1.6.4.2) were detected up to the 16th and the 12th d, respectively. The activities of GST isoforms, GSPX and GR were reduced by high doses. These changes seemed to be related and might point to an oxidative stress state that exacerbated with prolonged time and/or increased isoproturon dose.

The effect of a moderate (PEG −0.75 MPa) and severe (PEG −1.5 MPa) water deficit on SA content in leaves and roots as well as the effect of pre-treatment with SA on reaction to water stress were evaluated in two barley genotypes — the modern cv. Maresi and a wild form of Hordeum spontaneum. Water deficit increased SA content in roots, whereas SA content in leaves did not change. The level of SA in the roots of control plants was about twofold higher in ‘Maresi’ than in H. spontaneum. After 6 hours of a moderate stress the level of SA increased about twofold in H. spontaneum and about two and a half-fold in ‘Maresi’. Under severe stress conditions the level of SA increased about twofold in the both genotypes, but not before 24 hrs of the stress. Plant treatment with SA before stress reduced a damaging action of water deficit on cell membrane in leaves. A protective effect was more noticeable in H. spontaneum than in ‘Maresi’. SA treatment increased ABA content in the leaves of the studied genotypes. An increase of proline level was observed only in H. spontaneum. The obtained results suggest that ABA and proline can contribute to the development of antistress reactions induced by SA.

Pepper (Capsicum annuum L.) is an important vegetable crop that can be improved using plant tissue culture and biotechnology. However, it is difficult to develop appropriate breeding material by in vitro cultivation in this species. Haploid plant production is useful in the breeding programs to facilitate recovery of recessive mutations and unique genetic recombinations. In embryogenesis, haploid formation from pollen in anther culture is a scientifically advanced, but controversial system. Various techniques for haploid plant regeneration are used to establish an efficient double haploid production method. The purpose of this article is to summarize, through comparison, results in pepper anther culture, problems associated with work in this field, and the influence of critical factors for successful embryo formation and plantlet development.

Heat stress is one of the most detrimental environment stresses for plants. Hydrogen peroxide (H2O2) is produced quickly in response to various stresses and likely plays a positive role in transmitting stress signal in organisms. This investigation addressed whether an exogenous H2O2 application would affect the heat response of turfgrasses and induce acclimation. Tall fescue (Festuca arundinacea cv. Barlexas) and perennial ryegrass (Lolium perenne cv. Accent), two important cool-season turfgrasses and forages, were sprayed with 10 mM H2O2 before they were treated with heat stress (38/30 °C, day/night) and compared with plants maintained at control temperatures (26/15 °C, day/night). Prior to the initiation of heat stress, H2O2 pretreatment increased the activities of guaiacol peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) and glutathione-dependent peroxidase (GPX) and the ascorbate and glutathione pool, and it decreased the GSH/GSSG ratio. During the heat stress process, pretreated plants from both grasses exhibited higher turfgrass quality and relative water content, and they experienced lower oxidative damage and H2O2 levels. Moreover, the activities of APX, GR, GPX and glutathione-S-transferase increased significantly in response to H2O2 pretreatment under heat stress. These results suggested that H2O2 most likely participated in the transduction of redox signaling and induced the antioxidative defense system, including various enzymatic and nonenzymatic H2O2 scavengers. The scavengers played important roles in improving the thermotolerance of tall fescue and perennial ryegrasses.

Three approaches were successfully used to manipulate content of flavonoids in transgenic plants. Overexpressing either the adaptor 14-3-3 protein or genes coding the key enzymes of the flavonoid biosynthesis pathway resulted in a significant increase in the compound content in potato tuber epidermis. The opposite effect was observed in transgenic plants in which these proteins were repressed; this strongly supports the view that the gene construct determines transgenic plant features. The most effective construct was, however, the one containing single dihydroflavonol reductase (DFR) gene in sense orientation. In all cases the increase in flavonoid content resulted in the expected enhancement of the antioxidant capacity of tuber extract. At the biochemical level a decrease in the starch content in transgenic plant overexpressing proteins regulating flavonoid biosynthesis was detected. In the case of glucosyl transferase (GT) gene overexpression, the content of phenolic compounds remained at the control level, however, the antioxidant capacity of tuber extracts significantly decreased. The GT plants grew faster and were more resistant to pathogen attacks, the tuber yield was significantly higher than that of nontransformants. Thus it is speculated that it is the chemical structure and degree of glucosylation of flavonoids rather than their quantity which determines transgenic plant features.

This study aims to determine the low temperature resistance of dormant buds at nodes with or without lateral shoots of Karaerik grape cultivar, and explain the relationship between the resistance and biochemical parameters in this grape cultivar. In this study, the mean values of high temperature exotherms (HTEs), low temperature exotherms (LTEs), water, reducing sugar, total soluble protein contents and antioxidant enzyme activities of dormant buds taken from nodes with or without lateral shoots were determined. The experiment has been found that buds in nodes with lateral shoots showed HTE and LTE at higher temperatures (HTE average −6.7 °C and LTE average −8.3 °C) than buds (HTE average −7.9 °C and LTE average −11.5 °C) in nodes without lateral shoots; therefore, buds in nodes with lateral shoots had less tolerance to low temperature. Additionally, lower sugar (average 41.05 mg g−1), protein (average 1.61 mg g−1), superoxide dismutase (average 425.27 EU g−1 tissue), peroxidase (average 2516.1 EU g−1 tissue) and polyphenol oxidase (average 7283.1 EU g−1 tissue) were determined for buds taken from nodes with lateral shoots. Due to the fact that dormant buds taken from nodes with lateral shoots decreased the resistance to low temperatures, this research suggests that these lateral shoots should be excised with the summer pruning at the regions, where low temperatures caused the damages.

Cultivation of alfalfa (Medicago sativa L.), one of the most extensive forages around the world, is important for animal feeding and ecological conservation in Northwest China. Seed soaking with salicylic acid (SA) facilitates germination and improves morphological and physiological traits. Thus, it is necessary to investigate the effect of SA on alfalfa seed germination, as it may be beneficial for seedling establishment and field production. In this study, the influence of SA at different concentrations (C: 0, 0.4, 0.8, and 1.2 mM) and seed soaking times (ST: 8, 16, 24, and 32 h) on alfalfa cultivars (CV: Eureka + , WL525HQ, Central, Kehan) was investigated using an orthogonal experimental design. The results showed that the effect was dependent on C, CV, and ST. In addition, SA enhanced seed germination by improving seed vigor, reducing lipid peroxidation, promoting osmotic regulation, and enhancing antioxidant levels. More importantly, model analysis revealed that 0.77 mM SA and 25.5 h ST were the optimal seed soaking conditions.

This study, for the first time, investigated the total protein changes and protease activity pattern of three cultivars of kiwifruit including Abbott, Allison and Hayward, cultivated in the north of Iran, during 6 months of fruit development from July to December 2008. During the last month of sampling, fruits were stored in ambient temperature. According to the result of fruit extracts, pattern of changes in total protein concentration showed three significant steps: low concentration of protein during the early stages of fruit development until middle of July for Allison and Hayward and early August for Abbott, increasing protein concentration until middle of October for Allison and Hayward and late October for Abbott, and steady state level of protein concentration until harvesting time. During storage time of fruits, all three cultivars showed increasing level of total protein concentration. Among the cultivars, Hayward and Allison showed the lowest and highest total protein concentration, respectively. Protease activity showed increasing pattern in all of the investigated cultivars significantly until harvesting time. During postharvest time, Hayward did not show any significant change in protease activity but, the other two cultivars had increasing pattern from 10 to 20th of storage and then decreased significantly. Among the cultivars, Abbott showed the lowest and Allison the highest level of total protease activity at harvesting and postharvesting time. SDS-PAGE, ion-exchange chromatography and zymogram native-PAGE of fruits extraction showed that dominant protein and protease activity in these cultivars during fruit development and ripening process is related to actinidin.