He-Ne Laser Enhances Seed Germination and Salt Acclimation in Salvia officinalis Seedlings in a Manner Dependent on Phytochrome and HO.

In the current study the role of HO in He-Ne laser-induced effects on seed germination and post-germinative performance of Salvia officinalis seedlings was assessed under both non-stress and saline conditions. Salinity had adverse impacts on seed germination and root length and decreased seed germination tolerance index. Seed priming with HO and He-Ne laser impacted the seed germination and vigoration in a dose-dependent manner. The optimal effects were gathered by energy dose of 6 J/cm laser and concentration of 5 mM HO. These pre-treatments enhanced seed germination due to increasing contents of total soluble and reducing sugars and the amylase activity in seeds and improved seedling performance under saline and non-saline conditions. Furthermore, Phy B transcripts were upregulated, salt-accrued oxidative stress was mitigated, and the activities of POD and CAT increased in seedlings primed with HO and laser. Interestingly, applying diphenyleneiodonium (DPI as an inhibitor of NADPH oxidase activity) and N, N-dimethyl thiourea (DMTU as a HO scavenger) arrested the upregulation of phy B gene and abolished stimulatory impact of laser priming on the aforementioned attributes under both non-stress and saline conditions. These novel findings suggest that HO as a downstream signal modulates the impacts of He-Ne laser on seed germination, seedling performance and salt acclimation in sage seedlings, and likely phy B also is involved in these responses.