Effect of different forms of nitrogen, on pH value of culture medium during somatic embryogenesis of tomato (Solanum lycopersicon L.) plant

Backgrounds and one of the most important factors that effect on formation and development of somatic embryogenesis is culture medium composition and the most important compound is nitrogen. Pervious researches evaluated effect of different forms of nitrogen on somatic embryogenesis and cell suspension culture, but they didn’t evaluate the effect of each form separately or in combination with other forms. Therefor present study conducted to evaluate different forms of nitrogen, singly, in combination to other forms and in different ratios.
in this study in order to evaluate the effect of different forms of nitrogen on somatic embryogenesis of tomato, an experiment conducted in a complete randomized design (CRD) with eight treatments and four replications in tissue culture laboratory of Agricultural sciences and natural resources university of Gorgan. Applied treatments includes: B5 medium contained nitrate or ammonium or casein hydrolysate as sole nitrogen, B5 medium contained two forms of nitrogen together such as ammonium with nitrate, ammonium with casein hydrolysate or nitrate with casein hydrolysate, B5 medium with no nitrogen content. Complete B5 medium with all three nitrogen forms candidate as control. In this experiment hypocotyl segments of tomato seedlings cultured in modified B5 medium (based on treatments) that contained 2-4, D. after 25 days in order to embryo realization, explants transferred into modified B5 medium without 2-4, D. Thirty five days after realization phase characters such as number of somatic embryos. Secondary pH value of culture medium at the end of both induction and realization phase and Chlorophyll content of plant materials measured.
results of present study showed that different forms and different portion of nitrogen remained different effects on somatic embryogenesis. The most reduction in pH value of medium occurred in medium contained ammonium as sole nitrogen source and the minimum reduction of pH happened in medium contained casein hydrolysate. Results showed that there were significant differences in number of embryo and development of them in a way that the maximum number of embryos formed in complete B5 medium and medium contained both nitrate and casein hydolysate. Results also showed that different nitrogen treatments significantly affected chlorophyll content of plant materials presented in culture medium in a way that the maximum total chlorophyll, chlorophyll a and b obtained in medium contained nitrate and casein hydrolysate and complete B5 medium respectively.
different forms of nitrogen in combination with other forms and in different relative portions remained different effects on formation and development of somatic embryos that regenerated from hypocotyl segments of tomato. Due to results obtained in this study it can be concluded that using proper form and portion of nitrogen could enhance embryogenesis frequency and somatic embryos development.