Thin cell layer technology for induced response and control of rhizogenesis in chrysanthemum

Abstract

Chrysanthemum (Dendranthema Xgrandiflora Ramat. Kitamura) stem transverse thin celllayers (tTCLs) were used to obtain defined morphogenic programs with selectedplant growth regulators. A rhizogenic pathway could be manipulated invitro by the application of a single auxin (2,4-D, NAA, IBA or IAA,in increasing order of rhizogenic response), or by the addition of coconutwater, with light or darkness playing a significant role. The addition of TIBAeliminated the rhizogenic capacity of all the auxins tested, but not that ofcoconut water, while the addition of activated charcoal was inhibitory. Theabsence of sucrose resulted in a limited rhizogenic response. Results clearlyindicate the importance of auxins, media additives and light in the activationof a rhizogenic program in chrysanthemum tTCLs. Due to their restricted size andmedium-dependant nature, the capacity to control rhizogenesis and/ororganogenesis in chrysanthemum (and indeed any plant species) by TCLs hasfar-reaching consequences and applications in the floricultural andpharmaceutical sectors. Since all factors (exogenously-applied hormones andother growth-stimulating or growth-inhibiting substances, light, temperature,humidity and other environmental cues) may be strictly controlled invitro, TCL technology allows for the establishment of protocols aimedat chrysanthemum flower improvement through genetic engineering, the success ofwhich lies in its first step i.e. programmable morphogenesis and regeneration.