**5. Conclusion**

The purpose of tissue culture studies is to obtain high-frequency shoot regeneration that is also a prerequisite for an efficient transformation system and a clonal propagation of plants. The introduction of foreign genes which code agronomically important traits into plant cells has not got any meaning if transgenic plants are not recovered from the transformed cell(s). Forthis reason, tissues with high regeneration capacity should be used. Regeneration capacity of the tissue is the key factor affecting the success of transformation studies. Types, concen‐ trations and combinations of plant growth regulators affect *in vitro* explant growth signifi‐ cantly. Correct concentrations and combinations of auxins and cytokinins should be determined to obtain high frequency adventitious shoot regeneration for related genotype. However, determining the explant type, and the correct concentrations and the combina‐ tions of growth regulators is not sufficient for the high frequency shoot regeneration. Shoot regeneration frequency can always be higher than the one we obtain in theory, as every cell has got an ability to form a whole fertile plant under *in vitro* conditions. Many factors affecting regeneration capacity of explant have not been found out yet. Such as, a recently reported technique that utilizes competition among the explants is quite effective to increase shoot regeneration capacity [2]. In this way, the unknown factors affecting regeneration capacity of explants ought to be determined to increase the success of tissue culture studies. In this chapter, the importance of water on shoot regeneration capacity as a main component of all living cells was discussed. Results of research studies given in this chapter showed that enriching tissue with water give rise to higher values with respect to tissue culture re‐ sponse. On the contrary, water deficiency in tissue decreased the regeneration capacity of explant significantly. From now on, water content of the explant should be considered as one of the most important factors such as growth regulators and explant type regarding higher tissue culture response.
