Time‐course analysis of salicylic acid effects on ROS regulation and antioxidant defense in roots of hulled and hulless barley under combined stress of drought, heat and salinity

Abstract

Greater crop losses can result from simultaneous exposure to a combination of drought, heat and salinity in the field. Salicylic acid (SA), a phenolic phytohormone, can affect a range of physiological and biochemical processes in plants and significantly impacts their resistance to these abiotic stresses. Despite numerous reports involving the positive effects of SA by applying each abiotic stress separately, the mechanism of SA-mediated adaptation to combined stresses remains elusive. This study, via a time-course analysis, investigated the role of SA on the roots of hulled and hulless (naked) barley (Hordeum vulgare L. 'Tarm' and 'Özen', respectively), which differed in salt tolerance, under the combined stress of drought, heat and salt. The combined stress caused marked reductions in root length and increases in proline content in both genotypes; however, Tarm exhibited better adaptation to the triple stress. Under the first 24 h of stress, superoxide dismutase (SOD; EC.1.15.1.1) and peroxidase (POX; EC.1.11.1.7) activity in the Tarm roots increased remarkably, while decreasing in the Özen roots. Furthermore, the Tarm roots showed higher catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.11) and glutathione reductase (GR; EC 1.6.4.2) activity than the Özen during the combined stresses. The sensitivity of hulless barley roots may be related to decreasing SOD, POX, CAT and GR activity under stress. Over 72 h of stress, the SA pretreatment improved the APX and GR activity in Tarm and that of POX and CAT in Özen, demonstrating that exogenously applied SA regulates antioxidant defense enzymes in order to detoxify reactive oxygen species. The results of this study suggest that SA treatment may improve the triple-stress combination tolerance in hulled and hulless barley cultivars by increasing the level of antioxidant enzyme activity and promoting the accumulation of proline. Thus, SA alleviated the damaging effects of the triple stress by improving the antioxidant system, although these effects differed depending on characteristic of the hull of the grain.

NtMYB4 and NtCHS1 Are Critical Factors in the Regulation of Flavonoid Biosynthesis and Are Involved in Salinity Responsiveness

“…It is well documented that salt stress usually results in the excessive accumulation of ROS, which have deleterious effects on plant cells (Ashraf and Harris, 2004; Torun, 2018). Thanks to their antioxidant capacity, flavonoids play an important role against oxidative injury caused by salt stress (Dixon and Paiva, 1995).…”

Root Growth Adaptation to Climate Change in Crops

“…To counteract this response, plants accumulate a great quantity of proline and other osmoprotectants, and increase the expression and activity of ROS scavenging enzymes. SA may have a role in this tolerance process by promoting the biosynthesis of osmoprotectants and regulating the activity of several ROS scavenging enzymes (Torun, 2019). On the contrary, in tomato, heat seems to alleviate salinity damage by increasing evapotranspiration and photosynthetic rates.…”

Effectiveness of different methods of salicylic acid application on growth characteristics of tomato seedlings under salinity

“…Salicylic acid has important regulatory functions in plant growth, particularly under adverse stressful conditions [9,25,35,46]. Salicylic acid has roles in flower induction, general growth and development, various enzyme biosynthesis, stomata movements, membrane protections, and cell respiration [4,9,21,39,45]. One of the most prominent roles of salicylic acid is in stress tolerance of plants, where it can act as a signaling molecule that induces resistance [18,22,43,46].…”