COMPARISON OF FOUR MOISTURE MANAGEMENT SYSTEMS FOR CUTTING PROPAGATION OF BOUGAINVILLEA, HIBISCUS, AND KEI APPLE

摘要

The effects of four propagation moisture manage ment systems on the water relations and rooting of cuttings of three tropical woody crops were investigated at a relatively cool, but high irradiance site. Leafy semihardwood or leafless hardwood cuttings of Bougainvillea x Buttiana Holtt. & Standl. (bougainvillea), and leafy semihardwood cuttings of Hibiscus rosa-sinensis L. (hibiscus), and Dovyalis caffra (Hook. f. et Harv.) Warb. (kei apple) were propagated in shade under contact tent polyethylene enclosures or in the open with or without intermittent mist. Xylem water potential and leaf and air temperatures and relative humidity were monitored during the rooting period, Hardwood cuttings rooted better than softwood cuttings of bougainvillea. The best rooting of softwood cuttings of all three species was consistently associated with contact polyethylene, whereas open-propagated, nonmisted cuttings rooted poorly or not at all. The poor rooting of open-propagated nonmisted cuttings was associated with the most negative midday psi and the greatest water vapor density deficit of air surrounding the cuttings (VDDA), but psi and VDDA were otherwise not consistently associated with success of rooting in other treatments, Midday psi of cuttings under contact polyethylene was either less negative or not different from that of other treatments despite the fact they exhibited the greatest daytime leaf and leaf to air temperature differences, Because ambient night temperatures were suboptimal for rooting, the warm air trapped beneath the polyethylene enclosures at night may have contributed to improved rooting in these treatments.