This study was intended to detect optimum benefits of seed priming in tomato with respect to treatment solutions, after priming storage period and concomitant changes in certain osmolites. For this target, seeds of two varieties of tomato (Lycopersicon esculentum M..), namely Castle rock and Super strain B were osmoprimed for 7 days in PEG 6000 (20%), K2HPO4 (200 mM) and KNO3 (250 mM) solutions, at 25°C in dark. Air-dried primed seeds were sown either directly (without storage), or after dry storage for 2 or 4 weeks. PEG was superior in enhancement of the germination percentage and rate, as well as growth vigor and uniformity of transplants (45-day-old) at the different storage periods. The increased growth rate was concomitant with evoked levels of photosynthetic pigments in leaves of transplants. Significant results were also obtained on osmoconditioning with K2HPO4, but to a lower extent than PEG, whereby KNO3 exhibited least efficiency. Castle rock seeds showed higher positive responses to priming processes than those of Super strain variety. Maximum significance of the priming benefits was shown on direct sowing of seeds without storage period. This substantiated that the priming benefits of tomato seeds are gained during the hydration phase with no requirements to the following drying phase. Long storage periods of osmoprimed Castle rock seeds (in PEG or K2HPO4) up to six months indicated that priming benefits could be maintained till 2 months and then started fading out afterwards. The contents of soluble sugars, free amino acids, proline and glycine betaine were compared in the control seeds, hydroprimed and those osmoprimed in PEG or K2HPO4 after 8 h, 3 and 7 days. Interpretation of the results augmented variations between the control seeds channeled to germination and corresponding quiescent seeds in the osmotica from 8 h to 7 days.
Anisa I. Ismail, Magda M. El-Araby , Amal Z. A. Hegazi and Seham M. A. Moustafa , 2005. Optimization of Priming Benefits in Tomato (Lycopersicon esculentum M.) and Changes in Some Osmolytes During the
Hydration Phase. Asian Journal of Plant Sciences, 4: 691-701.