IMPORTANCE OF THE IRON CHELATE FORMULA FOR MICROPROPAGATION OF ROSA-HYBRIDA L MONEYWAY

In vitro propagation of the rose rootstock 'Moneyway' was investigated on the following media: Murashige and Skoog (MS), Quoirin and Lepoivre (QL) and Woody Plant (WP). Growth, which was measured as length of shoots after a 6-week period, was faster on MS and QL than on WP, In spite of the better growth, chlorosis of newly formed leaves occurred from the third week on and was correlated with a lower chlorophyll content of shoots. Replacement of FeEDTA by FeEDDHA in QL and MS resulted in the development of green shoots for more than 3 months. The occurrence of chlorosis was not pH directed since the pH of QL with FeEDTA or FeEDDHA had not changed after 6 weeks of growth. Addition of the light absorbing dye fast yellow 9 to QL with FeEDTA also resulted in green shoots with a higher chlorophyll content. It is suggested that FeEDDHA is a more photostable chelate than FeEDTA, resulting in a higher availability of iron for the rose shoots. The impact of the iron chelate formula on the micropropagation of plant species that are susceptible to iron deficiency is discussed.