Multiculture process
Callus age, plantlet age and pretreatment duration on the medium containing growth
regulators were proved to give different rooting abilities. Pontaroli and Camadro [2005]
applied 18-month-old and approximately 20-month-old calluses for two experiments.
The latter one gave better plant regeneration ability. Yang and Clore [1974] investigated
the effect of plantlet age on the rooting rate. They found that plantlets older than
4 weeks (8, 12, 16 and 20 weeks) could have more rooting percentage (>75%) after
subculturing in MS + 0.1 ppm NAA+ KT for 2 weeks or more. A study conducted by
Wu et al. [2006] clarified that when shoot tips were pretreated in MS + 0.5 mg·L-1 BA
+ 0.05 mg·L-1 KT + 1 mg·L-1 PP333 + 3% sucrose + 0.8% agar for 12 days before subculture
in MS basal medium for 10 days, rooting rate peaked to 80%. Extending the
pretreatment time did not increase rooting rate any more. Hence, 12 days pretreatment
culture was considered to be beneficial for plantlet rooting.