Propagation of Ornamental Plants
14(4): 171-176, 2014
DOES SHOOT ANATOMICAL HETEROGENEITY INFLUENCE EX VITRO ADVENTITIOUS ROOT FORMATION IN RHODODENDRON MICROCUTTINGS?
Kristine Dokane1*, Dace Megre1,3, Madara Lazdane2, and Uldis Kondratovics1
1 Faculty of Biology, University of Latvia, 4 Kronvalda Boulv., 1586 Riga, Latvia, *Fax: + 371-67034862, *E-mail: firstname.lastname@example.org
2 Plant Biology Laboratory, Botanical Garden, University of Latvia, 2 Kandavas str., 1083 Riga, Latvia
3 National Botanical Garden, 1 Miera str., 2169 Salaspils, Latvia
Rhododendrons (Rhododendron L., Ericaceae) are among the most popular ornamental plant species in Latvia. Mostly they are propagated by rooting of macrocuttings or microcuttings ex vitro. Sometimes the result of ex vitro adventitious rooting is unsuccessful even when using morphologically uniform microcuttings and identical propagation conditions. Thus the aim of this study was to determine how the successive adventitious rooting phases are achieved and to check whether there are any initial anatomical differences between microshoots that could affect rooting. Elepidote rhododendron ‘Nova Zembla’ adventitious shoots were multiplied in vitro and rooted ex vitro. Anatomical observations were done during the experiment and measurements of vascular cylinder : shoot diameter and phloem : xylem width were done. The initial plant material was very heterogeneous – different stem developmental stages were observed. Some microshoots had a continuous vascular ring while others had separate vascular bundles. First rooting related changes were visible on day 4, when groups of dividing meristematic cells were observed in cambial region. First root primordia were found on day 12, and first roots were observed on day 16. During the whole experiment shoots were morphologically uniform but both the vascular cylinder : shoot ratio and phloem : xylem ratio differed. Microshoots that formed meristemoids had larger phloem : xylem ratio. Those microshoots which did not undergo any rooting-related changes had smaller phloem : xylem ratio. Thus we suggest that the development of microshoot vascular system might play significant role in adventitious rooting processes.
Key words: anatomy, ex vitro, microshoot heterogeneity, propagation, rhizogenesis, Rhododendron