Protocols for Micropropagation of Woody Trees and Fruits

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M. BERUTO AND P. CURIR
Figure 14. Gradual acclimatization of rooted tree peony plantlets to in vivo conditions.
Plantlets have been grown on vessels filled with a mixture of sterilized milled peat and perlite
under the usual conditions in the culture room a) (step 1; see text). At the end of the culture
period (4 weeks), plantlets show an improved development of leaves and roots b) and are
transferred to peat-pot c) and d) under greenhouse conditions (step2; see text).
Step 2
1. Fill the peat pot (10 cm in diameter) with a mixture of milled peat (80%),
pumice (15%), bentonite (2%) and slow release plant fertilizer (3%).
2. Transfer the plantlets into the pots and water widely (Figure 14C,D). Since
this step, plantlets are grown under unheated greenhouse conditions.
3. Cover the plantlets with a white polypropylene film (17 g/m 2 ) for 2 weeks.
During this period, plantlets should be watered taking care to avoid excessive
humidity.
2.5. Notes on the Following in Vivo Growth Phase
Scanty literature is available on the development of tree peony in vitro plants due to
an arrest of shoot growth which even prevents the survival during the acclimatization
phase (Bouza et al., 1994b).
The ex vitro plantlets obtained in the present work, showed a continuously
developing root system and growth of leaves and shoots till complete flowering
(Figure 15). After the acclimatization phase, plantlets have been grown under
greenhouse (unheated), watered and fertilized according to the normal cultural
practices advised for tree peony (Rogers, 1995). Once a month a 0.1% solution of
Rovral (Iprodione 270 g L –1 ) was applied to avoid fungal contamination and after
about 1 year the developed plants were transferred to plastic pots (14 cm in diameter).
About one year after the acclimatization, plants increased in size and they
had a pronounced development of roots and leaves (Figure 15A1,A2,B1,B2,C1,C2).