Abstract
Seeds germination and seedlings growth of Cucumis sativus and Solanum lycopersicum were monitored in in vitro and in vivo experiments after application of different concentrations of NaCl (25, 50, 100 and 200 mM). Photosynthetic pigments content and the biochemical responses of C. sativus and S. lycopersicum were assessed. Salinity stress slightly delayed the seeds germination rate and significantly reduced the percentage of germination as well as shoot length under the highest salt concentration (200 mM) in cucumber. Furthermore, root length was decreased significantly in all treatments. Whereas, in tomato, a prominent delay in seeds germination rate, the germination percentage and seedlings growth (shoot and root lengths) were significantly influenced under all concentrations of NaCl. Fresh and dry weights were reduced prominently in tomato compared to cucumber. Photosynthetic pigments content was reduced but with pronounced decreasing in tomato compared to cucumber. Secondary metabolites profiling in both plants under stress was varied from tomato to cucumber. The content of saponins, proline and total antioxidant capacity was reduced more prominently in tomato as compared to cucumber. On the other hand, the content of phenolics and flavonoids was increased in both plants with pronounced increase in tomato particularly under the highest level of salinity stress. The metabolomic profiling in stressful plants was significantly influenced by salinity stress and some bioactive secondary metabolites was enhanced in both cucumber and tomato plants. The enhancement of secondary metabolites under salinity stress may explain the tolerance and sensitivity of cucumber and tomato under salinity stress. The metabolomic evaluation combined with multivariate data analysis revealed a similar mechanism of action of plants to mediate stress, with variant level of this response in both plant species. Based on these results, the effect of salinity stress on seeds germination, seedlings growth and metabolomic content of plants was discussed in terms of tolerance and sensitivity of plants to salinity stress.
Highlights
One third of irrigated lands all over the world are significantly affected by salinity
Homogenized size of C. sativus and S. lycopersicum seeds were soaked in distilled water for 30 min. 70% ethanol was used for seeds surface sterilization for 30 s
Plants are smart for responding to abiotic stress which is specific to plant species by responding differently or at different levels through metabolomic alterations
Summary
One third of irrigated lands all over the world are significantly affected by salinity. Salinity is a serious problem causing decrease of crop productivity through its negative effect on seeds germinations and seedlings growth. It affects plant growth through disturbing plant osmosis, Plants 2020, 9, 1626; doi:10.3390/plants9111626 www.mdpi.com/journal/plants. Plants 2020, 9, 1626 imbalance nutrition channels and ionic toxicity [2,3] The alteration in these main mechanisms leads to metabolic and physiological changes and poses a negative impact on seed’s germination, seedling’s growth as evident from retarded shoot and root length, fresh and dry weight, chlorophyll content and its synthesis [2,4,5,6,7]
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