Thidiazuron-induced in vitro shoot formation from roots of intact seedlings of Albizzia julibrissin

Abstract

Seedlings of silktree (Albizzia julibrissin Durrazz .) were grown in vitro on MS-media containing B5 vitamins, 3% sucrose, 0.25% phytagel and various concentrations (0 .1-10 µM) of thidiazuron (TDZ) . Addition of TDZ to the culture medium greatly reduced shoot and root elongation but did not influence shoot production from the cotyledonary node or apex . Within 8-10 days the seedling roots split open, formed large masses of callus, and developed green patches which eventually grew into normal shoots while still within the culture medium containing TDZ at 0.1-1 .0 µM . Such callus and shoot formation did not occur in control cultures lacking TDZ . At higher TDZ concentrations (2 .5-10 ,tiM), the green patches formed in the callus did not further develop into shoots . Addition of other cytokinins (kinetin, benzylaminopurine, zeatin) to the culture medium also induced some shoot formation from the roots, but higher concentrations than TDZ were required to induce regeneration . Isopentenyladenine failed to induced shoot formation . Following excision and transfer to MS media with or without 4 .9 pM IBA, the shoots induced by kinetin or benzylaminopurine rooted 4-7 days earlier than those induced by TDZ, but all excised shoots developed into normal rooted plantlets within 3 weeks.Abbreviations : TDZ = thidiazuron

In vitro regeneration of silktree (Albizzia julibrissin) from excised roots

“…About 50% of the control root explants formed shoot buds within 15 days after placement on B5 medium (Table 1). This is in sharp contrast to our previous results using intact seedlings (Sankhla et al, 1994) where no adventitious shoot formation occurred from roots in control cultures.…”

“…Furthermore, we observed that higher concentrations of TDZ (0.1 and 1.0 #M) drastically inhibited the elongation of shoots formed on the excised roots. Thidiazuron has displayed many biological properties similar to purine cytokinins (Huetteman & Preece, 1993;Mok etal., 1987;Sankhla et al, 1994). In many cytokinin-dependent system TDZ exhibits a considerably higher degree of biological activity than purine-type cytokinins (Mok et al, 1987;Sankhla et al, 1994;Thomas & Katterman, t986) and is being evaluated for its morphogenic effects in several areas of tissue culture research (Gill & Saxena, 1993;Huetteman & Preece, 1993;Sankhla et al, 1994;Saxena et al, 1992).…”

Thidiazuron: A multi-dimensional plant growth regulator

“…Various plants may need altered incubation periods for differentiation and morphogenesis. This is probably due to the capacity of TDZ in stimulating endogenous cytokinin biosynthesis or in altering cytokinin metabolism (Sankhla et al, 1994;Zhou et al, 1994). Therefore, it is suggested that double stage culture procedure consisting of culture of plant tissue on TDZmedium for appropriate period (usually 10 to 20 days) followed by a secondary TDZ-free medium, is beneficial for shoot proliferation and/or somatic embryogenesis.…”

Frozen storage stimulates the formation of embryo-like structures and elongating shoots in explants from mature Larix decidua and L. x eurolepsis trees

“…This is not unique, a somewhat similar development occurred in cultures of other species. For example, seedling cultures of Albizzia julibrissin produced shoots from green nodules (Sankhla et al, 1994) and suspension cultures of Liriodendron tulipifera formed proembryogenic nodules that elongated into mature embryos (Merkle et al, 1993). Microspores and megagametophytes of Ginkgo biloba grew globules that developed into heart-or club-shaped embryos (Laurain et al, 1993a,b) while mature zygotic embryos of Sequoia sempervirens produced compact callus masses that generated somatic embryos, some of which germinated (Bourgkard and Favre, 1988).…”