Some herbicide agents like oryzalin are widely used for in vitro polyploidization because of their depolymerization effects on microtubules, which usually direct the polar distribution of sub-cellular components. These herbicides hinder plant growth by inhibiting cell division and elongation. To determine the effect of oryzalin on the in vitro growth of gerbera plantletsm,an experiment on the cultivar\"Red explosion\" with five concentration of oryzalin(0,30,60,120 qnd 240 M) in liquid medium and three exposure periods(12,24 and 48 hours) was established. After these treatments, planlets were directed to solid Murashigue and Skoog media with three concentations of kinetin(4,6 and 8 mg/l). Number of new leaves produced, and fresh mass zccumulation of cultured plantlets were used to determine the growth inhibition effects of oryzalin. The lowest number of leaves were produced on the treatment of 120 micro molar oryzalin for 24h on medium containing 4 mg/l kinetin whearse minimum fresh weight was obtained on the treatment of 240 M oryzalin for 48h on medium containing 4 mg/l kinetin.

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