Abstract
Seed priming has proved to be an effective method in imparting stress tolerance to plants using natural and/or synthetic compounds to treat the seeds before germination. The present study was designed to investigate the physiological mechanism of seed priming with ZnSO4 (osmopriming) and distilled water (hydropriming) on sugar beet genotypes (‘Shokofa’, ‘Sina’, ‘Paya’, ‘Turbata’, and ‘Aria’) germination indices, seedling growth parameters, and biochemical properties under salinity stress (0, 2, 5, and 12 dS/m NaCl). A significant reduction in germination percentage (33.23%), germination rate (77.2%), chlorophyll a, b, and total contents (43.9, 31.9, and 39.9%, respectively) while, a significant increase in radical, plumule, and seedling length (57.1, 44.4, and 51.2%, respectively), seedling vigour index (48.9%), superoxide dismutase activity (61.3%), proline (54.0%) and sugar (56.3%) contents were achieved at 12 dS/m NaCl in compared to the control treatment. Seed hydropriming and osmopriming caused significant improvements in photosynthetic pigments, antioxidant enzyme activity, and proline content reflected in high germination percentage and rate as well as seedling vigour index and reduced mean germination time under salinity. ‘Paya’ and ‘Aria’ genotypes had a superiority according to the germination percentage and seedling vigour index, respectively. The hydropriming of ‘Paya’ genotype resulted in the highest germination percentage (95%) under high level of salinity (12 dS/m) which 11.84% increase compared to the control treatment. Hydropriming of ‘Sina’ seeds showed the highest chlorophyll a and total, and carotenoids under non-stress conditions (22.89, 31.65, and 2116.6 µg/g FW). Also, hydropriming by increases chlorophyll b content led to the modulation of the negative effects of high salinity stress (12 dS/m). In conclusion, different seed priming treatments in sugar beet seeds improved the salinity tolerance by physiological characteristics nonetheless hydropriming was the most effective treatment to get higher germination indices in ‘Paya’ and ‘Aria’ genotypes.
Highlights
Sugar beet (Beta vulgaris L.) is one of the most recently domesticated crops, belongs to the order Caryophyllales (Skorupa et al, 2019)
Germination parameters The effects of genotypes, salinity, and priming as well as interaction genotype × salinity × priming was significant on germination percentage (GP), mean germination time (MGT), germination rate (GR), germination uniformity (GU), radical length (RL), plumule length (PL), seedling length (SL), and seedling vigour index (SVI)
Results indicated that a moderate level of salinity (5 dS/m) had the highest seedling growth parameters such as RL, PL, SL, and SVI compared to the non-stress conditions
Summary
Sugar beet (Beta vulgaris L.) is one of the most recently domesticated crops, belongs to the order Caryophyllales (Skorupa et al, 2019). It is an important root crop in the world for sugar production, where its taproots are used. Detrimental effects include (i) reduced water availability, due to an osmotic effect from high concentrations of soluble salts in the root medium, (ii) ion toxicity, as a result of the accumulation of Na+ and Cl, (iii) oxidative stress, resulting from an overproduction of reactive oxygen species (ROS) and (iv) acute K+ deficiency as a result of massive K+ leak from depolarized cells (Moreno et al, 2018). Plant survival is likely the most vital indicator of salinity tolerance, whereas afterward yield and growth reduction may be considered as the final tolerance criterion (Saadat and Homaee, 2015)
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