Omethoate treatment mitigates high salt stress inhibited maize seed germination.

Omethoate (OM) is a highly toxic organophophate insecticide, which is resistant to biodegradation in the environment and is widely used for pest control in agriculture. The effect of OM on maize seed germination was evaluated under salt stress. Salt (800mM) greatly reduced germination of maize seed and this could be reversed by OM. Additionally, H2O2 treatment further improved the effect of OM on seed germination. Higher H2O2 content was measured in OM treated seed compared to those with salt stress alone. Dimethylthiourea (DTMU), a specific scavenger of reactive oxygen species (ROS), inhibited the effect of OM on seed germination, as did IMZ (imidazole), an inhibitor of NADPH oxidase. Abscisic acid (ABA) inhibited the effect of OM on seed germination, whereas fluridone, a specific inhibitor of ABA biosynthesis, enhanced the effect of OM. Taken together, these findings suggest a role of ROS and ABA in the promotion of maize seed germination by OM under salt stress.

[Effects of Enhanced Ultraviolet B Irradiation on Photosynthetic and Antioxidant System of Sorghum Seedlings].

The UV-B radiation on the surface of our planet has been enhanced due to gradual thinning of ozone layer. The change of solar spectrum UV-B radiation will cause damage to all kinds of terrestrial plants at certain degree. In this paper, taking breeding sorghum (Sorghum bicolor (L.Moench))variety Longza No.5 as sample, 40 µW·cm-2 UV-B radiation treatment was conducted on sorghum seedlings at two-leaf and one-heart stage and different time courses; then after a 2 d recovering, photosynthetic parameters were measured with a photosynthetic apparatus; the activities of antioxidant enzymes were detected as well. Our results revealed that, as the dosages of UV-B increasing, leaf browning injury was aggravated, plants dwarfing and significantly were reduced fresh weight and dry weight were observed; anthocyanin content was significantly increased; chlorophyll and carotenoid content significantly were reduced and net photosynthetic rate and chlorophyll fluorescence parameters were decreased. Meanwhile, with the increase in UV-B dosages, stomatal conductance, intercellular CO2 concentration and transpiration rate showed "down - up - down" trend; the activities of SOD and GR presented "down - up" changes; activities of POD and CAT demonstrated "down - up - down", and APX, GPX showed an "up - down - up" pattern. It is worth to note that, under the four-dose treatment, a sharp decline in net photosynthesis in sorghum seedlings was observed at 6 h UV-B treatment (equals to 2.4 J·m-2), and an obvious turning point was also found for other photosynthetic parameters and activities of antioxidant enzymes at the same time point. In summary, the results indicated that the enhanced UV-B radiation directly accounted for the damages in photosynthesis system including photosynthetic pigment content, net photosynthetic rate and chlorophyll fluorescence parameters of sorghum; the antioxidant system showed different responses to UV-B radiation below or above 6 h treatment: ASA-GSH cycle was more sensitive to low-dose UV-B radiation, while high-dose UV-B radiation not only undermined the photosynthesis system, but also triggered plant enzymatic and non-enzymatic antioxidant systems, resulting in leaf browning and necrosis,biomass accumulation reduction, plant dwarfing and even death.