Abstract:

In vitro rhizogenesis of Juglans regia cotyledons from mature or near mature fruit was investigated. The top, middle and basal sections of the cotyledon showed different rooting capacity. On 1/4 DKW basal medium supplemented no plant growth regulators, the rooting ratio of the top section was 100%, while the middle and basal had no rhizogeneesis. The endogenous indoleacetic acid (IAA) level in the rooting top sections presented as increasing at the culture beginning, then maintaining at a level during the differentiation of root primordia, and increasing again to form a peak when the primordia started to grow (4 days after culture). However, the IAA in the middle and basal sections without rhizogenesis showed decreasing dramatically at the culture beginning, then maintaining at a certain level. SDS-PAGE demonstrated that 62.8 and 38.4 kDa were the rooting related protein bands in walnut cotyledon. Former up_expressed and later down-expressed in the rhizogenesis. Application of exogenous indolebutyric acid (IBA)(0.5～10 mg·L^-1)in the medium had effects to induce the middle and basal sections to root and to regulate their endogenous IAA changes similar to that happened in the rooting of the top section. Meanwhile it up-regulated the expression of the 62.8 kDa proteins and down-regulated 38.4 kDa protein bands. Exogenous 6-benzylaminopurine (BAP) inhibited the rooting of cotyledon top section and restrained the rooting-related changes on IAA and proteins. The system that IBA induced J.regia cotyledon rooting by regulating rooting-related IAA and proteins could be taken as a good research model for the further investigations on molecular rhizogenesis mechanism of woody plants.

Key words: Juglans regia, In vitro culture, Cotyledon, Rhizogenesis, Hormone regulation, Protein band