Mussaendas (Mussaenda spp.) are ornamental shrubs, and some cultivars are difficult to root. This study was conducted to explore how adventitious roots initiate and develop in the cultivar Rosea, and to determine if anatomical events are associated with difficulty in rooting stem cuttings. Stem cuttings were treated with 5, 10, 15 mm 1H-indole-3-butyric acid (IBA), or distilled water, and sampled every 2 days over 26 days to observe adventitious root formation and development. For analysis by light microscopy, the basal 1 cm of cuttings was embedded in wax and stained with safranin-fast green. Adventitious roots initiated from phloem parenchyma cells and from basal callus in nontreated cuttings. Cuttings treated with 15 mm IBA had a mean of 18 root primordia per basal 1 cm of cutting after 10 days. Root primordia were not observed in non-treated cuttings at 10 days. Root primordia that developed in non-treated cuttings lacked clear vascular connections. These results suggest that non-treated cuttings are difficult to root because few primordia are produced.
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