Kinetin has been reported to exert inhibitory effect when used in tissue culture and in some cases reverse the action of auxin and cause growth inhibition and retardation of root formations. Kinetin also acts as ‘mitotic poison’, mimicking the effect of pesticides and toxic chemicals and interferes in mitosis mechanism of plants. The effect of kinetin on size of cell and nucleus as well as chromosome behaviour in root tip meristems of Agapanthus praecox ssp. minimus was studied. The results showed that prolong exposure to kinetin caused chromosome abnormalities to occur more frequently. Chromosome breakage yielded fragmented chromosomes, while abnormal spindle fibers caused delay in chromosome movement, termed as laggard chromosomes. Abnormal nucleus was also observed with kinetin treatments, such as micronucleus, binucleated and tripolar cells.
This paper discussed on the effectiveness of BAP and NAA growth hormones on establishment of plant regeneration for selected ornamentals; Agapanthus praecox, Justicia betonica and Celosia cristata. Various explants (leaf, stem, shoot tip and bulb) derived from one-month-old aseptic seedlings of A. praecox and C. cristata, as well as explants from intact plants of J. betonica were utilized to achieve complete plant regeneration of these species. MS medium supplemented with various hormones, with an emphasis on BAP and NAA was tested to obtain direct and indirect regeneration. Both A. praecox (bulbs) and C. cristata (shoots) formed complete plantlets on MS added with 0.5-2.0 mg/L BAP and NAA, while direct regeneration was achieved for J. betonica on MS media containing BAP. Several methods were attempted to acclimatize the regenerants, with A. praecox gave the highest percentage of survival rates (96.67%), followed by J. betonica (80.00%) and C. cristata (75.00%).