Effect of Nitric Oxide and Arbuscular Mycorrhiza on some Physiological Traits of Liquorice (Glycyrrhiza glabra L.) Plant under Salinity Stress

The salinity affliction of land constitutes a major threat amongst the various forms of soil degradation. Arbuscular mycorrhiza fungus can be useful as a bio-fertilizer in providing plant nutrition and reducing the effects of environmental stresses on plants. On the other hand, nitric oxide plays a role in many environmental and non-environmental stresses, including drought and salinity stresses. Liquorice (Glycyrrhiza globra Linn.), commonly known as Mulahatti and Yashtimadhu, is the highest priority value crop which can be successfully cultivated on salt-affected and degraded lands. It is a small perennial leguminous herb of the family Fabaceae (Papilionaceae) native to the Mediterranean region and central and southwest Asia, and cultivated in Italy, Russia, France, UK, USA, Germany, Spain, China, Pakistan, Afghanistan, Iran, Iraq, Uzbekistan, Turkey, Turkmenistan and north-western India. This research was carried out with the aim of investigating the effect of nitric oxide modification on coexistence with arbuscular mycorrhizal fungus on some of the physiological traits of licorice under the salt stress of sodium chloride. This research was a factorial experiment based on completely randomized block design with three replications. Factors consisted of five levels of NaCl-salinity (0 as control, 50, 100, 150 and 200 mM), two levels of nitric oxide (0 and 0.2 mM) and two levels of mycorrhizal fungi (the presence and absence of mycorrhizal). To do this, 10 kg pot of pumice mixture and pumice (1 to 1 ratio) were poured into 60 plastic containers (30 x 20 cm; 10 L) and sterilized by alcohol. The seeds germinated in petri dishes after adequate growth, they were transferred to the pots (all seeds were germinated and grown in the same conditions). In each pot, five seedlings were cultured and irrigated with distilled water until a two-leaf stage. After that, the treatment was carried out by a Hoagland solution. Application of saline treatments and nitric oxide (from sodium nitroproced as nitric oxide source) was performed 45-days. Finally, after 60 days of planting, sampling was carried out to measure the physiological traits from the middle leaves of each pot, and after being placed in an aluminum foil with ice-containing flux, it was transferred to the laboratory and then transferred to 80 o C. The evaluated traits were leaf flavonoids by Swain (52) method, proline content by Bates et al. (6) method, MDA with Ohkawa et al. (40) method, CAT activity by Pereira et al. (44) method, POD activity by Korori (28) method and SOD activity by Giannopolitis and Reis (21) method. The data were analyzed by SPSS 22 (IBM SPSS Statistics 22.0) software application. The data was normalized and inferential statistics such as analysis of variance and mean comparison of treatments were calculated using Duncan's multiple range test. The results showed that the salinity stress had significant effect on flavonoid content, proline content, malondialdehyde rate and antioxidant activity of catalase, peroxidase and superoxide dismutase. Salinity had increased levels of malondialdehyde, proline content, and the activity of antioxidant enzymes (catalase, peroxidase, and superoxide dismutase). The coexistence of mycorrhiza fungus in combination with nitric oxide or alone reduced the number of flavonoids and increased proline content at each level of salinity stress. Nitric oxide had no significant effect on measured traits but was more effective in combination with Mycorrhiza fungi. In general, sodium chloride salinity stress had a negative effect on the physiological traits of liquorice, but the use of nitric oxide with arbuscular mycorrhizal fungus reduced the negative effects of stress. In general, it can be said that the removal and decontamination of active oxygen species is an important part of salinity tolerance in plants. In the present study, salinity stresses have significantly increased the amount of MDA, which is an indicator of plant response to stress. In addition to salinity stress, nitric oxide stress has been induced to reduce the effects of high salt concentration on some of the indices, thus reducing nitric oxide in high concentrations of MDA. Application of saline treatment significantly increased the activity of the three antioxidant enzymes CAT, POD, and SOD. The results showed that salinity stress had a decreasing effect on studied traits, but the application of arbuscular mycorrhizal fungus with nitric oxide reduced the negative effects of sodium chloride salinity stress on liquorice plant.