In vitro application of tryptophan on auxin accumulation and some physiological parameters of tobacco (Nicotina rustica L.) plant

Auxins are important and critical phytohormones for plant growth and development. Indole-3-acetic acid (IAA) is a natural auxin in plant tissues that plays an important role in physiology and differentiation of plants. Tryptophan (Trp) an aromatic amino acid serves as a precursor of IAA biosynthesis pathway. It is also used as a component of proteins, and various secondary metabolites synthesis in plants. In this study tobacco plantlet were cultured in MS medium supplemented with tryptophan at 0, 0/025 and 0/05 M concentrations. After 4 weeks post treatment, the IAA content was measured in apical leaves. The IAA content after Tryptophan treatments showed significant difference compared with untreated plants. Results showed that the highest level of IAA in the plants cultured on tryptophan free medium while, the lowest level of IAA was found in the plants in the culture medium with 0/05 M tryptophan. When photosynthetic pigments were measured, results of chlorophyll pigments and carotenoids showed no difference in treated capered with untreated plants.. The same pattern was observed for other physiological parameters. In plants treated with Trp compared with untreated a 40 KD protein showed up regulation.