The Effect of Picloram and 2,4-D in Callogenesis of Leaf, Petiole and Endosperm Explants of Cycas revoluta Thunb

Cycas reveluta Thunb. is a valuable ornamental plant, requiring special care for appropriate growth and development. This beautiful plant having been found for the first time in China, is typical in tropical areas. Considering the advantages of tissue culture for propagation of the plant, the present study was aimed at evaluating the effects of various kinds and concentrations of growth regulators 2,4-D (0, 1, 2 and 4 mg/l)‎ and Picloram (0, 1, 2.5, 5 and 10 mg/l)‎ as well as different types of explants (leaf, petiole, and endosperm)‎ on callus induction in C. revoluta as a vital stage in successful in vitro propagation of the plant. The evaluation was made an assessment through of callus weight, area, volume, callogenesis percentage, as well as callogenesis rate. Treatments were set up in a factorial arrangement based on completely randomized design of three replications. According to the obtained results, the highest callus area (3.39 cm2) and volume (5.8 cm3) in endosperm explants was obtained from the 10 mg/l picloram. In contrast, no callus was observed in leaf explants in 10 ml/l Picloram treatment. The highest callus weight (8.17 gr)‎ in petiole explants was achieved from 1 mg/l of Picloram treatment. On the other hand, 4 mg/l 2,4-D and 10 mg/l picloram were identified as the most suitable treatments for induction of the higher levels of callogenesis (98.3% and 98.7%, respectively)‎ in endosperm explants, whereas no callus was induced in leaf explants in 10 mg/l of Picloram. In 1, 2.5 and 5 mg/l Picloram, leaf and petiole explants exhibited a higher rate of callogenesis (12 days)‎. Overall, the most desirable response in all the studied explants was achieved in 4 mg/l 2,4-D, although the treatment of endosperm explants with 10 mg/l of Picloram ended up with better results. Throughout this study, the texture and color of the obtained calli turned out to be different; while calli obtained from 2,4-D were granulate and had yellowish cream color, those induced through picloram application were milky paste.