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Rolston St. Hilaire and Carlos A. Fierro Berwart

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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Rolston St. Hilaire and Carlos A. Fierro Berwart

The effects of 1H-indole-3-butyric acid (IBA), cutting position on stock plants, the date of propagation, the type of rooting substrate and temperature on rooting of mussaenda (Mussaenda erythrophylla Schumach. & Thonn. `Ashanti Blood' and `Rosea', and Mussaenda philippica A. Rich `Aurorae') stem cuttings were determined. Cuttings of `Ashanti Blood' produced the largest number of roots when treated with 15 mmol (3000 ppm) IBA and rooted in perlite at 29 °C (84 °F). Cutting position on stock plants did not affect rooting in any of the three cultivars. Propagation date and temperature of the rooting medium affected root numbers in `Aurorae'. With `Rosea', only the type of rooting substrate affected root number. Rooting percentage was 22%, 48%, and 39% in `Ashanti Blood', `Aurorae', and `Rosea' respectively. After 30 days of propagation average root length was 4, 12, and 4 mm (0.2, 0.5, and 0.2 inch) in `Ashanti Blood', `Aurorae', and `Rosea' respectively. Growers must determine precise rooting conditions for each cultivar to obtain consistent rooting of cuttings. This process may not be economically feasible on a commercial basis because rooting percentages are relatively low. We conclude that other methods of clonal propagation need to be evaluated before uniform rooted stem cuttings of mussaenda can be produced economically.

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Rolston St. Hilaire, Carlos A. Fierro Berwart, and Carlos A. Pérez-Muñoz

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 mmol IBA, or distilled water, and sampled every 2 days over 26 days to observe adventitious root formation and development. Adventitious roots initiated from phloem parenchyma cells. Cuttings treated with 15 mmol IBA had a mean of 18 root primordia per basal 1 cm of cutting after 10 days. Primordia were absent in nontreated cuttings at 10 days. These results suggest that nontreated cuttings are difficult to root because few primordia are produced. Chemical name used: 1H-indole-3-butyric acid (IBA).