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The effects of four propagation moisture management 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 ψ and the greatest water vapor density deficit of air surrounding the cuttings (VDDA), but ψ and VDDA were otherwise not consistently associated with success of rooting in other treatments. Midday ψ 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. Cuttage is an extensively practiced and economical means of vegetative propagation for a wide range of woody plants cultivated for use as ornamental, fruit, or agroforestry crops. The development of intermittent mist systems and their widespread commercial availability in developed countries has greatly increased the range of species that can be propagated by cuttage. On the other hand, rural farmers, especially in developing countries, often do not have access to mist technology due to the expense or unavailability of the necessary hardware components and/or the lack of electricity and/or piped water supply. When automatic misting is not available, moisture management in cutting propagation is often the factor limiting success. Nonmist propagation systems involving passive moisture barriers in the form of polyethylene or glass enclosures have long been used to minimize moisture loss from cuttings. Recently, researchers at the Institute for Tropical Ecology have developed and characterized a nonmist propagation system appropriate for vegetative propagation of tropical woody plants when electricity and piped water are not available (Leakey et al., 1990; Newton and Jones, 1993a, 1993b). The goal of successful moisture management in a cutting propagation facility is to minimize transpirational water loss while maximizing water uptake by cuttings. This can be achieved by maintaining high relative humidity (RH) of the air surrounding the cuttings either by the use of mist or a moisture barrier like polyethylene, and by the use of shade and/or mist to avoiding high air temperature (TA) and high leaf to air temperature differences for publication 15 June 1994. Accepted for publication 4 Oct. 1994. The blishing this paper was defrayed in part by the payment of page charges. tal regulations, this paper therefore must be hereby marked advertisey to indicate this fact. repring requests should be addressed. with Monsanto Agricultural Group, Monsanto Co., St. Louis. he Faculty of Agriculture. (TL–A). Loach (1977, 1988) and coworkers (Grange and Loach, 1983a, 1983 b), and Newton and Jones (1993b) have used cutting water potential (ψ) as an indicator of the effects of environmental manipulations on the moisture status of cuttings. Polyethylene moisture barriers are usually raised above the surface of the cuttings by at least several centimeters, by means of a wood or metal framework, to create a tent. A modification of raised polyethylene systems known as contact polyethylene (Loach, 1988) involves laying a thin sheet of polyethylene directly on top of, in direct contact with, the foliage of cuttings. Loach (1977) reported that cuttings frequently root better under contact polyethylene than in a polyethylene tent because TL, TA, and TL–A tend to be lower in the former. In the western highlands of Kenya, where our research was conducted, cuttage is used to propagate a number of woody crops used for food (cassava), beverage (tea), as ornamentals (bougainvillea), or for agroforestry [Sesbania sesban (L.) Merrill]. Because small scale rural farmers do not have access to electricity, piped water, and/or mist system components, cuttings are frequently stuck in soil or a suitable rooting medium (sand), out in the open, under shade, where high VDDs prevail. Under such conditions only relatively easy-to-root species can be successfully rooted. The objective of this research was to compare propagation success and cutting water stress for two low-tech nonmist cutting propagation systems—polyethylene tent and contact polyethylene —with the locally common practice of open propagation, and to compare the performance of all three low-tech systems to that of a relatively high-tech mist propagation system. Materials and Methods The species used in these experiments were Hibiscus rosasinensis L. (hibiscus), Bougainvillea x Buttiana ‘Mrs. Butt’ (bouJ. AMER. SOC. HORT. SCI. 120(3):366–373. 1995. Table 1. Effect of four moisture management systems on the roots/rooted cutting (RRC) and percent rooting (% R) of semihardwood and hardwood cuttings. In the case of bougainvillea, only a single block shade structure was used. For hibiscus and kei apple, treatment means within blocks are presented if there was a significant block effect or block × treatment interaction; otherwise treatment means pooled across blocks are presented. zLetters differing within a column denote significant differences (P = 0.05), using Duncans multiple range test. gainvillea), and Dovyalis caffra (kei apple). These were chosen because they are in high demand in Kenya for hedge and/or ornamental plantings. Bougainvillea and hibiscus, which are moderately difficult and easy to root, respectively, are commonly propagated in this region by sticking cuttings in the open under shade. Kei apple is typically propagated from seed, which is only available for a limited period each year and, even then, may not be available in sufficient quantities. Experimental design. The experiments with hibiscus and kei apple were randomized complete-block designs with four moisture management treatments including contact polyethylene, polyethylene tent, mist, and open. Each species was treated as a separate experiment. For hibiscus and kei apple, two blocks in each experiment corresponded to two separate yet identical shade structures (described below), each containing all four treatments. In the case of bougainvillea, the experiment was not blocked (only one shade structure was used) because only a limited number of cuttings were available at a given time. The four moisture management treatments were each randomly assigned to one of the four propagation beds within each shade structure. For a given species (experiment), one wooden flat of cuttings consisting of five rows of eleven cuttings each, was placed in each of the moisture management treatments (beds) within a shade structure. The experiment was repeated at two times for hibiscus and bougainvillea, but only once for kei apple. Propagation (shade) structures. Two identical, wood-framed, outdoor shade structures were built against the outside wall of a greenhouse at the Dept. of Horticulture, Egerton Univ., Njoro, J. AM E R. SO C. HO R T. SC I. 120(3):366-373. 1995. Kenya (elevation 2600 m). Each shade structure was divided into four adjacent rectangular cutting propagation beds, 1 m wide x 2 m long x 0.5 m high, corresponding to the four moisture management treatments (contact polyethylene, polyethylene tent, mist, and open). For shade, split bamboo poles (≈5 cm in diameter) were placed horizontally, side by side, on a wooden frame, 1 m above ground level. Although the bamboo poles were in contact with each other, irregularities along their length created 1-to 3-mm gaps, through which narrow bands of direct sunlight passed to the otherwise shaded cutting beds. At midday on a typical cloudless day, irradiance (PAR), measured with a quantum sensor (LI– 190SB; Licor, Lincoln, Neb.) was 1811 μmol·m·s in full sunlight outside the shade structure. Within the shade structure, irradiance was 91 and 1158 μmol·m·s in full shade and sun gaps, respectively. Each of the four beds within each structure was filled to a depth of 15 cm with coarse gravel to facilitate drainage. For the mist treatment, a l-cm-id. PVC pipe, plumbed to a tap (well) water source, was run lengthwise down the center of the bed, 80 cm above ground level (≈45 cm above the top of the cuttings). Two mist nozzles were located 1 m apart along the 2-m-long mist bed to supply uniform and complete mist coverage of the cuttings. To minimize fluctuations in RH, polyethylene sheeting was placed around the four sides of each mist bed to a height of 80 cm, but the top was left open. Mist was applied during daylight hours only. The system was controlled by a solenoid valve connected to an electronic interval timer that was set manually to mist for 6 sec at intervals varying between 2 to 20 min, depending upon prevailing irradiance and temperature conditions on a given day.

Comparison of Four Moisture Management Systems for Cutting Propagation of Bougainvillea, Hibiscus, and Kei Apple