Physiological responses of bread and durum wheat seeds to osmotic stress and salinity in the early germination stage

Determining the mechanisms underlying tolerance to osmotic stress and salinity during the germination period is an essential task in order to improve agricultural production in arid and semi-arid areas. In this work, the seeds of bread and durum wheat cultivars were treated with different concentrations of polyethylene glycol (PEG)-6000 and NaCl for 1 week, and half-maximal inhibitory concentrations (IC50) of germination were calculated. The seeds were then exposed to IC50 values of NaCl and PEG-6000 for 2 days in order to assess their physiological and biochemical properties. Alpha and beta amylase enzyme activities, the reducing sugar, total sugar, proline, protein, and H2 O2 contents, and DPPH radical scavenging activity of the seeds were determined by spectrophotometric methods. The results showed that the bread wheat seeds had a much higher tolerance to excess salt and osmotic stress than the durum wheat seeds. In particular, the average IC50 value of NaCl for the bread wheat cultivars was almost twice that for the durum wheat cultivars. The imbibition test revealed that the water uptake capacity of the seeds did not explain the difference in tolerance to these stress conditions. On the other hand, the bread wheat seeds exhibited constitutively higher proline, total sugar, and H2 O2 contents as well as antioxidant capacity compared to the durum wheat seeds (p < 0.05). In conclusion, the current findings suggest that the interplay of oxidative metabolism and compatible solutes may contribute to improving germination tolerance under water deficit and salinity conditions in wheat

Boron toxicity tolerance in barley may be related to intrinsically higher levels of reactive oxygen species in the shoots

There is considerable intra-and interspecific variation in boron (B) toxicity tolerance in crop plants. In this study, we aimed to investigate the mechanisms involved in tolerance to excess B in barley (Hordeum vulgare) in the early stages of plant development. To do this, B-sensitive (Bülbül-89) and B-tolerant (Tarm-92) barley cultivars were grown hydroponically under control and B stress conditions (10 mM H3 BO3 ) for 4 or 7 days. The hydrogen peroxide (H2 O2 ), malondialdehyde (MDA), total phenolic, total flavonoid, anthocyanin, proline, and total sugar contents, as well as DPPH radical scavenging capacity, were then determined for both cultivars. Our results showed that B treatment led to significant increases in the B concentration of the barley cultivars for both exposure times. However, there were no drastic differences in the B concentration of the roots and shoots between the sensitive and tolerant cultivars. While the dry root weight of Bülbül-89 was reduced after 7 days of B stress (p < 0.05), such a decrease was not observed in Tarm-92. The H2 O2 , MDA, proline, total sugar, and anthocyanin contents of both cultivars increased considerably in response to excess B during at least one treatment period (p < 0.05). The H2 O2 content of Tarm-92 under control and B stress conditions was significantly greater than that of Bülbül-89, but there was no difference in the MDA content and radical scavenging capacity between the two cultivars. Finally, a 35% increase was found in the total flavonoid content of the Tarm-92 seedlings exposed to B stress for 4 days. In conclusion, the findings of this study suggest that tolerance to B toxicity in barley seedlings may be related to their capacity to tolerate higher levels of reactive oxygen species

Effect of fire-derived chemicals on germination and seedling growth in Mediterranean plant species

The promoting effect of smoke-derived chemicals (e.g. karrikinolide and cyanohydrin) on germination in many plants from Mediterranean-type ecosystems such as South Africa and south-western Australia is well documented. However, very little is known about (1) the relative importance of different compounds and their possible interactive effects, (2) their role in enhancing seedling growth in wild plants, and (3) their effect on the germination of plants in the Mediterranean Basin. To fill these gaps in knowledge, we performed experiments to evaluate the effect of smoke water, karrikinolide, mandelonitrile (a cyanohydrin analogue), potassium nitrate and gibberellic acid on the germination and seedling growth of 37 species from the Mediterranean Basin. The results suggest that germination and/or seedling growth of 21 species are enhanced by at least one of the fire-derived chemicals. There were positive correlations between most of the compounds tested in terms of germination response, but synergetic and inhibitory effects were also detected. Stimulation of germination was most prominent in species with annual life cycles. Fire-derived chemicals were more effective in stimulating root growth than shoot growth. In conclusion, we provide novel evidence that the recruitment of different Mediterranean species may be enhanced by different smoke compounds, and that synergetic and inhibitory effects of chemical compounds are important in the germination ecology of plants.This study was financially supported by the Scientific Research Projects Coordination Unit of Muğla Sıtkı Koçman University (grant number 15/153)Peer reviewe