Abstract
In this study, cultures of friable callus derived from hypocotyls explants of Helianthus annuus L. seedlings were readily obtained. It was observed that Murashige & Skoog medium supplemented with (BA) Benzyl adenine and (NAA) Naphthaleneacetic acid with different concentration encouraged the formation of callus. This friable callus used in obtaining cell suspension cultures in liquid MS medium containing 1.0 mg/ L BA, 2.0 mg /L NAA. The cells started their first division after 24hours and continued their division. Density of these cells reached to 7.33-8.50 x 103 cell / ml at the fourth day of age. The results of culturing cell suspension by embedding them in agar using Multiple Drop Array (MDA) technique proved the suitability of this method. Cells begin the first division within 5-6 days and continued their division until the formation of cell colonies, Which then developed to form callus primordia. The work have studied the effect of exposing cell suspension to heat shock. The treated suspensions were cultured by following MDA technique. Results indicated that heat shocked cell begin the first division at 2-5 days and increase the total number of cell colonies and callus primordias compared to the untreated samples (control).
