Search

Abscisic acid (ABA) is an important plant hormone that plays significant roles in cold tolerance regulation. However, whether ABAimproves cold tolerance by increasing the activities of antioxidant enzymes in wheat remains unknown. In this study,the activities of antioxidant enzymes of the winter wheat variety ‘dongnongdongmai 1ʹ (‘dn1ʹ)afterthe application of exogenous ABA under low temperature (0°C, −10°C, −20°C, and −25°C) were investigated. Results showed that cold stress significantly increased H(2)O(2) and relative conductivity, whileABA significantly reduced this effect. ABA enhanced cold tolerance in both leaves and rhizomes at −10°C and −20 °Cby increasing CAT, SOD, POD, APX, GR, DHAR, and MDHAR. However, this tolerance was weakenedat −25°C with decreasing ASA, GSH, APX, DHAR, and MDHARthan at-10°C and −20°C.POD, GR, and DHARlevels peaked at −10°C, while CAT, SOD, GSH, APX, and MDHAR content in rhizomes peaked at −20°C. The rate of returning green was significantly increased after ABA treatment than in controls (93.5% vs 83.6 %). In ‘dn1ʹ, rhizomes had a higher cold tolerance than leaves. Thereby, exogenous ABA could enhance cold tolerance byincreasing the activities of antioxidant enzymes.

“Dongnongdongmai 1” is a cultivated winter wheat which can endure cold temperature as low as −30 °C with a reviving rate of 85 %. We aimed to explore the involvement of antioxidant protection system in salicylic acid (SA)-enhanced cold resistance of winter wheat. Seedlings were prayed with 0.1 mM SA at three-leaf stage, followed by cold acclimation at tillering stage (4 °C for 5 days) prior to cold treatment at 4, 0, −10 or −20 °C for 2 days. Under low temperature, the relative electrical conductivity (REC) of rhizomes and H2O2 content in rhizomes were lower compared with leaves, while in the reactive oxygen species (ROS) removal system, only the POD activity was higher. Foliar spray with SA significantly inhibited the cold-increased REC of rhizomes at −20 °C and REC of leaves at −10 and −20 °C. In addition, application of SA prior to −10 or −20 °C treatment suppressed the increase in H2O2 content both in rhizomes and leaves. SA enhanced the activities of SOD, POD, and CAT in wheat following low-temperature treatment, especially at −10 and −20 °C. In addition, spray with SA resulted in 1.1-to-4.9-fold enhanced activities of the key enzymes in AsA–GSH cycle, including APX, DHAR, and MDHAR. Our results suggested that SA could improve the resistance of winter wheat against extreme low temperature by enhancing the activities of antioxidases to eliminate ROS and maintain the redox homeostasis. In addition, the less damage to rhizomes in comparison with leaves may be attributed to enhanced POD activity.

Not giving mathematical details but the simple principles, we present two types of techniques for both depth and time prestack migration velocity analysis. The first type of the techniques is based on the migration velocity spectrum, and the second is based on the migration velocity scanning. The accuracy of the picked/selected velocities can be tested by the common image gathers with a common-shot style. An alternate approach, based on the so-called zero-timedifference gathers computed by reflection or scattering ray tracing regarding to the migrated horizon(s), is proposed to be used as an additional way for migration velocity testing in complex areas.