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Adventitious rooting of cuttings is a critical and very important process in horticultural mass production either in traditional vegetative multiplication or with propagation in vitro. Several factors affecting rhizogenesis of Rosa sp. shoots and other species have been reported in this review. External factors, which are relatively easy to control (temperature, light, medium composition) and internal factors (endogenous level of growth regulators, phenolic compounds) resulting from ontogenic stage and genotype are presented. The comparison of the different rooting procedures in vitro and ex vitro, and preparation of the microcuttings to the rooting through improving their quality and rooting ability are also discussed.
Micropropagation of roses has been widely applied for mass production, introduction of new cultivars, selection of new lines and elimination of rose viruses by meristem tip culture. The effects of cultural factors affecting shoot multiplication of rose - the ingredients of the medium, environmental influences and culture systems, have been briefly reported. Also the problem of senescence of shoot culture and possibility of prevention of this process has been described.
Microcuttings of easy-to-root dwarf rose cv. Starina, showing early symptoms of leaf senescence and shoot-tip necrosis in rooting stage, were chosen for the study. The effects of inhibitors of ethylene biosynthesis (AOA, AIB) and action (AgNO₃), and Ca²⁺ and Mg²⁺ were studied in relation to rooting, leaf senescence and shoot-tip necrosis. The effects of these substances were examined with respect to IAA presence in a medium, which stimulated leaf yellowing and shoot-tip necrosis. AOA strongly inhibited rooting of microcuttings, but did not affect ethylene biosynthesis. AIB at 250 mg·l⁻¹ and AgNO₃ 2.5 mg·l⁻¹ in the presence of IAA did not affect rooting but effectively prevented leaf senescence. Ca²⁺ alone or combined with Mg²⁺ at raised concentration, or an ethylene action inhibitor Ag⁺, reduced shoot-tip necrosis in microcuttings treated with IAA. Addition of Ag⁺ to IAA medium drastically increased ethylene production by the shoots. Interaction between endogenous levels of auxin, ethylene and calcium in relation to rooting, shoot-tip necrosis and leaf senescence was discussed. Ethylene could enhance tissue sensitivity to auxin. Moreover, the tissue of rose shoots is very sensitive in the in vitro condition on standard medium because of the calcium deficiency. Thus, the raised Ca/Mg level counteracted shoot-tip necrosis through enhancing cell membrane and wall resistance to ethylene and IAA.
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