Overhead mist (OM) facilitates the propagation of stem cuttings past preventing transpirational water loss. However, drawbacks to OM include the application of large volumes of water, potentially unsanitary conditions, irregular misting coverage, and leaching of foliar nutrients. We explored three alternatives to OM that might avert these issues by applying wet below, rather than overhead. These included i) a submist (SM) aeroponic organization configured to provide intermittent mist only to the rooting zone, 2) a subirrigation (SI) system that provided water via capillary activeness through perlite from a reservoir maintained beneath the base of each cutting, and 3) a subfog (SF) aeroponic system that was configured to provide constant fog only to the rooting zone. To initiate each system, nosotros wetted perlite or filled reservoirs using either water or quarter-strength Hoagland solution. Stem cuttings of 'Wizard Mix' coleus (Plectranthus scutellarioides) were propagated in the systems for 21 days. Cuttings in the SM system produced more than iii times as many roots every bit cuttings in the OM organization, with roots more than six times the length. Root dry out weights averaged 28 mg for cuttings in the SM system, compared with just three.5 mg among cuttings receiving OM. The SF and SI systems produced results broadly comparable to the OM. Fertilizer did not consistently improve rooting measures across the systems. Although we observed few fine roots on cuttings rooted using SM, they transplanted well into a soilless substrate and rapidly produced new root growth. The SM system used less than 1/v the h2o used by the SI system, and less than one/50 the water used by the SF system. In comparing, a unmarried OM nozzle operating for 10 seconds released about one-third of the total water lost through transpiration from each SM system over the unabridged experiment. Our results testify that SM systems merit further evaluation for propagation of plants by stem cuttings.
Overhead mist revolutionized the propagation manufacture by providing reliable means to manage transpirational h2o losses by leafy stem cuttings. This system slows transpiration of cuttings primarily by decreasing foliage temperatures through evaporative cooling from the leaf surface (Hartmann et al., 2011). However, OM has potential drawbacks, including the use of large volumes of h2o, potentially unsanitary conditions created by persistent water films on leaves (Preece, 2003), the potential for anaerobic conditions in the rooting zone, the depression of root-zone temperatures by evaporative cooling (Hartmann et al., 2011), nonuniform misting coverage, leaching of foliar nutrients (Preece, 2003), difficulty controlling cutting nutrition during propagation (Hartmann et al., 2011; Zhang and Graves, 1995), and the demand to extensively acclimate cuttings to a depression-humidity, mist-free environment.
Several authors have considered alternatives to OM for propagation of plants by stem cuttings, which nosotros refer to here equally SI, SM, and SF (Zhang and Graves, 1995). Graves and Zhang (1996) evaluated the suitability of SI for the propagation of several woody and herbaceous plant species, and establish that such a system tin exist an effective alternative to OM. Moreover, Zhang and Graves (1995) found rooting could be improved in SI when a fertilizer solution was used instead of h2o. Another alternative organisation that merits investigation relies on the awarding of mist from below the cut, to the base of the stem inserted into an enclosed chamber. Several such aeroponic systems are bachelor on the market place for use by domicile gardeners, just do non seem to be marketed for commercial propagation. Several authors have evaluated SM aeroponic systems for propagation of plants by stem cuttings, with promising results (Mehandru et al., 2014). Another aeroponic production on the market (Whirlwind Ultrasonic Fogger; FutureGarden, Lindenhurst, NY) tin be used to supply a fog of nebulized water or fertilizer solution to the bases of cuttings inserted into a rooting chamber. To our knowledge, the potential efficacy of this arrangement for propagation has not been formally evaluated in the academic literature.
We speculated that each of these systems might offer several of the following advantages to OM for the propagation of plants past leafy stem cuttings. These include express water usage, increased sanitation and reduced foliar illness pressures, superior oxygenation to the rooting zone, maintenance of loftier root-zone temperatures in the absence of evaporative cooling, compatible application of h2o to each cutting, no leaching of nutrients, efficient commitment of water-soluble fertilizer during propagation, and a reduction in acclimation requirements typical of cuttings accustomed to receiving foliar mist. Moreover, in 2 of the systems (SM and SF), root development could be assessed in situ without disturbing frail, developing roots. Our aim here was to conduct a proof-of-concept evaluation to explore the general claim of each system.
The primary objective of this study was to compare rooting and posttransplant performance of coleus propagated in four propagation systems: traditional OM, SM aeroponic, SF aeroponic, and a modified SI system. The second objective was to decide whether the addition of h2o-soluble fertilizer was benign in any of these systems.
Materials and methods
We built iv propagation systems: traditional OM, aeroponic SM, aeroponic SF, and SI. The traditional OM system consisted of a single depression-pressure nozzle (Vibro-Spreader; Rain-Tal, Or-kiva, Israel) mounted on the top of a 22-inch-alpine polyvinyl chloride (PVC) riser. Mist was turned on for x s every x min using a ordinarily airtight 24-VAC solenoid valve (Netafim, Fresno, CA) connected to an electronic timer (Gemini 6A; Phytotronics, Earth Metropolis, MO). Cuttings grown in this system were inserted basally into open trays (xl × 40 × 13 cm) containing coarse perlite (Whittemore Co., Lawrence, MA) initially wetted with tap h2o or fertilizer solution.
The SI organisation was a modified version of the organization Graves and Zhang (1996) described. In this system, 32 L of coarse perlite was placed in water-tight blackness PVC tubs (64 × 45 × xiv cm) leveled on greenhouse benches. Water or fertilizer solution was filled to a depth of ii.5 inches to ensure that the basal end of each cutting was ≈1 inch above the h2o or solution. During the experiment, additional water was added every 1–ii d as needed to maintain water or fertilizer solution to the initial volume of ≈16 L.
The SM system consisted of 16 mist nozzles (Botanicare 330° Micro Sprayer; American Agritech, Chandler, AZ) tapped into a 3/four-inch PVC manifold with dimensions of 56 × 33 cm within a 27-gal plastic tub with dimensions of 74 × 52 × 37 cm (Commander Black Tote; Centrex Plastics, Findlay, OH). Hooked to the manifold was a submersible pump (Eco-plus ECO-396; Sunlight Supply, Vancouver, WA) continued to a timer (Titan Controls Apollo 12 Timer; Sunlight Supply), which operated the pump for 10 s every 10 min. Holes of iii/8 inch bore were drilled in the lid of the tub to insert the cuttings, and a 1/2-inch-thick canvass of rigid foam insulation with one/four-inch holes was placed over the hat to secure cuttings in place. The level of water was checked daily; more water was added as needed to maintain a uniform volume (32 50) throughout the experiment.
The SF organization was constructed using a commercially available fog generator that nebulizes water by vibrating ceramic discs (Cyclone Ultrasonic Fogger). A large black plastic tub identical to those used for the SM systems served as a reservoir for h2o or fertilizer solution, and a shop vacuum hose continued the fog outlet of the ultrasonic fogger to the headspace in the tub, which doubled equally the rooting chamber. The lid of each tub was modified in the same mode every bit those used on the SM systems. Each SF aeroponic system, which operated continuously, was checked daily and the large reservoir was refilled with water as needed to maintain the 32-L volume initially filled with h2o or fertilizer solution.
3 replications of each system were operated using tap water lone, whereas three additional replications of each organization were initiated with a liquid fertilizer solution of quarter-strength modified Hoagland solution, which provided ≈52 mg·Fifty−1 nitrogen initially to each system (Hoagland and Arnon, 1950). For the latter replications, we applied fertilizer at the start of the experiment to fill tubs (SM and SF systems) or saturate perlite (OM and SI systems). Thereafter, we replenished the lost fertilizer solution from each system with tap water. Our goal was to evaluate whether initially increasing fertility of the rooting zone would better the rooting of stem cuttings.
On 29 Jan. 2016, cuttings that were ≈12 cm long were taken from stock plants of 'Magician Mix' coleus, grown from seed (Fedco Seeds, Waterville, ME). Because the cultivar was a mix, we collected cuttings from plants of five cultivars (Maroon, Coral Sunrise, Scarlet, Jade, and Velvet Red) with two cuttings of each cultivar placed in each replicate arrangement.
On 19 Feb. 2016, root rating (from 0 = no roots to 5 = superior rooting) and length of the longest root were recorded from every cut. Half of the cuttings (one of each cultivar) were destructively harvested, the total number of roots was counted, and the roots and shoots were dried in a room maintained at ≈68 °C for one week to measure out root and shoot dry weights and root:shoot. On the aforementioned day, the other one-half of the cuttings were transplanted into 5-inch azalea pots (Kord, Toronto, ON, Canada) containing a commercial peat-based growing medium (Fafard 1-PV; Sun Gro Horticulture, Agawam, MA). After transplant, plants were hand-watered as needed, and on 2 Mar. 2016, they were acme-dressed with v thousand of 14N–4.2P–11.6K controlled-release fertilizer (Osmocote; Everris, Dublin, OH). On i Apr. 2016, we measured the plant summit from the surface of the medium to the tallest indicate on the plant, and harvested and dried each establish in a drying room, to record shoot and root dry weights and root:shoot.
The cuttings and container plants were grown in a Quonset greenhouse covered with a triple layer polycarbonate glazing. During propagation, cuttings were shaded with 50% Mylar shadecloth. When plants were grown in containers, they were non shaded. The average daily temperature from 19 February. until 24 Mar. 2016, measured using a weather condition station (WatchDog 1650 Micro Station; Spectrum Technologies, Aurora, IL), was 21.7 °C. Photosynthetically active radiation was measured using a breakthrough light sensor attached to the aforementioned weather station; daily light integral (DLI) was calculated from this data by multiplying μmol·m−ii·s−ane by ane,000,000 and dividing this number by 86,400 to obtain mol·m−two·d−1. DLI averaged 10.19 mol·m−ii·d−one.
The study was analyzed every bit a split up-plot experiment with propagation arrangement on the level of the main plot, fertilizer handling on the level of the split up plot, and three blocks that each independent ane replication of each system and fertilizer combination. During the study, there was no show that response variables differed past cultivar; measurements from all cuttings (subsamples) within each replication system were but averaged before data assay. For each organisation and fertilizer combination, v or ten subsamples constituted the average, depending on the variable (detailed above). Analysis of variance was used in the agricolae parcel for R (version 0.98.1103; RStudio, Boston, MA) to exam for the main effects of system, and Fisher'south to the lowest degree significant difference was used for means separation among those systems operated without fertilizer. Adjacent, t tests using pooled variances tested for an upshot of fertilizer by comparison each arrangement initiated with fertilizer solution to the baseline responses obtained using water lonely.
Results
All four systems maintained the turgor of the cuttings for the duration of the experiment. Cuttings in the SF system, in which modest wilting was observed for the first couple days, recovered and did not wilt once again. Cuttings from all four systems produced roots, with those produced in SI and OM systems somewhat thicker and with more than evident fine roots than those produced in the SM and SF systems (Fig. 1).
Fig. 1.
Representative cuttings of coleus after 3 weeks in each of the four propagation systems: overhead mist (OM), submist (SM), subirrigation (SI), and subfog (SF). Cuttings in the SM systems produced longer, thinner roots than cuttings in the other systems, and typically produced roots more uniformly around the stem and in a higher place the stem.
Representative cuttings of coleus after iii weeks in each of the four propagation systems: overhead mist (OM), submist (SM), subirrigation (SI), and subfog (SF). Cuttings in the SM systems produced longer, thinner roots than cuttings in the other systems, and typically produced roots more uniformly effectually the stem and college upward the stem.
In the comparison of systems operated with h2o solitary, coleus cuttings in SM outperformed those in the other systems for all 4 measures of rooting (Tabular array 1). Cuttings in SM had roots more than seven times the length of those in the OM treatment, and root ratings and root numbers were most four times equally neat. Finally, the root dry weights of cuttings rooted in the SM system were ≈xv times that of the cuttings propagated with OM (Table 1). Plants rooted in SI had root lengths and subjective root ratings greater than those produced past OM and SF. The SF organisation produced rooting values on cuttings that were similar to those receiving OM (Table i).
Table 1.
Boilerplate root length, root rating, root number, and root dry weight among cuttings of coleus after 21 d in one of four propagation systems.
Cuttings from all 4 systems transplanted readily to a peat-based greenhouse medium. However, those cuttings rooted in SM established and grew more quickly, producing plants that were both taller and with greater root dry weights than plants propagated with OM (Table 2). Plants originating in SM likewise produced greater shoot dry weights than plants from the three other systems.
Tabular array 2.
Average measures of growth among cuttings of coleus transplanted from one of the four propagation systems into a greenhouse medium and grown for 34 d with a slow-release fertilizer applied.
The use of h2o-soluble fertilizer had express influence on root evolution of cuttings during propagation, regardless of organization (Table i). However, we did record a fertilizer effect in the SM organization after transplant into a peat-based medium. Cuttings that were rooted in the SM arrangement with fertilizer later developed into taller plants with more than than twice the root dry out weight, and nearly twice the shoot dry weight, of cuttings rooted in SM with water (Table ii).
Discussion
To our noesis, this is the first written report to compare the efficacy of these four propagation systems simultaneously, and to assess the do good of fertilizer solution on adventitious rooting of cuttings in each. Our results illustrate how SM may exist an effective alternative to OM for the propagation of herbaceous crops past stem cuttings. Cuttings of coleus in SM produced root systems of greater weight, with longer and more numerous roots, than cuttings in the iii other systems (Tabular array one). Moreover, cuttings from SM transplanted readily and continued to develop robust root systems in a soilless medium (Table 2), with root tips reaching the wall of the container inside one week. Previous authors have successfully propagated plants including winged yam (Dioscorea alata), white yam (Dioscorea rotundata), paimpa (Caralluma edulis), jeewanti (Leptadenia reticulata), and dambel (Tylophora indica) in SM or aeroponic systems without OM (Maroya et al., 2014; Mehandru et al., 2014). In comparison with propagation using OM, our results with SM seem to concord with those of Soffer and Burger (1989), who demonstrated that an aero-hydroponic system produced measures of rooting in chrysanthemum (Chrysanthemum ×morifolium) and weeping fig (Ficus benjamina) stem cuttings that were superior to those obtained by using OM.
Subirrigation is also a viable method for propagating coleus in the absenteeism of OM, performing intermediately to SM and OM in measures of rooting. Our results concur with those of Zhang and Graves (1995), who found that coleus and 'Charm' chrysanthemum propagated in a SI arrangement were similar to those propagated in an OM system (Zhang and Graves, 1995). Notwithstanding, 'Frank'southward Red' scarlet maple (Acer rubrum) propagated in SI had greater root dry weight than cuttings propagated by using OM (Zhang and Graves, 1995). The least promising culling to OM was the SF arrangement, which produced measures of rooting comparable with OM in our study (Table 1). Subfog does not seem similar a practical approach for commercial propagation, every bit the water in this system had to be refilled most daily, a process that could be readily automated but that nonetheless uses large volumes of water.
Root ratings were college when coleus was propagated in SM compared with all other systems (Table 1). Subirrigation systems produced plants that had higher root quality compared with fog and OM merely that were still inferior to plants propagated in SM (Tabular array ane). Root quality of many herbaceous plants, including 'Stained Glass' coleus is influenced by factors that include the season when cuttings are harvested (Crawford et al., 2016). Our results demonstrate that the type of propagation system also impacts quality of the root organisation.
Initiating the systems with a fertilizer solution was not of import for the production of well-rooted cuttings in this study, as differences in rooting betwixt fertilized and unfertilized cuttings were minimal in all systems (Table ane). Although fertilizer increases shoot growth of herbaceous cuttings during propagation under OM (Currey and Lopez, 2014), the importance of fertilizer in root development during propagation is less clear. Practical fertilizer may increase, decrease, or have no upshot on root dry weight of herbaceous stem cuttings during propagation (Currey and Lopez, 2014; Santos et al., 2009). As nosotros just applied fertilizer in one case at the beginning of the propagation cycle, we expected that differences in rooting betwixt fertilizer treatments were about likely for those systems that retained the fertilizer solution over the course of the report. Liquid fertilizer was probably lost virtually rapidly in the SF systems when the initial solution was nebulized and discharged from the organization. As well, any solution used to initiate the OM system was probably leached if it was not apace taken upwardly by cuttings. Surprisingly, although SM and SI systems retained the applied fertilizer solution, consequential differences in rooting were not observed between these fertilized and unfertilized systems (Table ane). We are interested in farther exploring the differences in fertilizer applied during a sustained period in the time to come. Still, it would be challenging to adequately compare fertility in SM and OM systems, since h2o-soluble fertilizer leaches out of substrates in OM but is retained in the SM reservoir, and deadening-release fertilizer is unsuitable for use in a SM organization.
Although fertilizer solutions did not obviously bear on root formation during propagation, a delayed but dramatic benefit of fertilizer during SM propagation manifested after establishment in a greenhouse medium. Submist cuttings propagated using fertilizer solution later grew 15% taller, with 113% more than root weight and 85% more shoot weight (Table 2), than cuttings propagated without fertilizer, despite the uniform awarding of tiresome-release fertilizer to all plants following transplantation. Therefore, it is of import to consider not only the effect that fertilizer might have on root evolution during propagation, but also its potential "priming effect" on subsequent growth in containers.
We encountered challenges in the implementation of several of these systems. For example, in the construction of the SI organisation, nosotros needed to carefully level the tub acting every bit a reservoir, and the perlite within it, so that all cuttings were the aforementioned meridian from the saturated zone. In the implementation of the SM and SF systems, securing cuttings through the lid of the chamber in a removable manner was a challenge. At the stop of the experiment, some holes in the hat had to be manually enlarged with a razor blade to allow the removal of rooted cuttings. Some growers and hobbyists use cream pucks inserted into larger holes, an approach that seems likewise expensive and time- and labor-intensive for commercial propagation. We are exploring alternative methods to secure cuttings in these systems in such a manner as to make insertion and removal of cuttings rapid, without a high cost per cutting.
Nearly of the issues we encountered were with the SF system, which required substantial troubleshooting to operate effectively. The cost of the fog generators nosotros used made these the most expensive systems to implement. The generators themselves were susceptible to malfunctioning if their ceramic nebulizer discs were non installed at the proper depth relative to the h2o level in the organisation, which happened initially considering of shifting of these units inside the fog generator during shipping. Therefore, nosotros had to disassemble the generators to correct the orientation of these units earlier they would function correctly. Next, the placement of the hose connecting the fog output to the headspace of the tub was critical; if any portion of the hose settled lower than both ends, condensation pooling in the hose soon blocked the flow of fog to the chamber. Finally, nosotros needed to construct the organisation with a degree of "leakiness" because an airtight rooting chamber would return the fan in the fog generator ineffective at delivering fog to the bedchamber. The holes into which cuttings were inserted were somewhat wider than the cuttings, assuasive fog to freely escape the system and prevent a buildup of pressure.
One potential reward we observed in the utilise of SM for propagation instead of traditional OM is that SM systems lose water but through transpiration through the cuttings instead of direct to the atmosphere by evaporation during misting and from surfaces in the greenhouse. Although we did not measure the amount of water the OM system used over the duration of the study, nosotros noted the amount of water nosotros added to the SM systems. Each SM system, which only lost water considering of cutting transpiration, used the same corporeality of water during the entire study as a single OM nozzle operating for 30 due south. This observation justifies scaling up the system for direct comparisons of water use during propagation on a commercial calibration.
Our next goals are to extend the present inquiry to boosted herbaceous and woody institute species to reply questions related to the implementation and efficacy of SM systems, to explore the biological science underlying the positive results of cuttings propagated in SM systems, and explore the potential for SM systems in the propagation of difficult-to-root plants. One particularly important claiming of such a system for greenhouse crops might be the fact that cuttings are not rooted into plugs of solid media, which may brand transplanting more fourth dimension consuming or modify electric current transplanting systems. This business seems less problematic for plant nursery crops, which are oft blank-rooted later propagation to be overwintered in common cold storage.
Conclusions
This inquiry has the potential to outcome in profitability for the green manufacture because propagation is a major component of horticulture crop production. The Census of Horticulture Specialties (U.S. Section of Agriculture, 2016) indicated that propagation solitary was valued at $695 one thousand thousand in 2014. This research may contribute substantially to improvement in propagation technology. By eliminating many of the shortcomings of OM, SM could fix a new standard for plant propagation technology and augment the range of plants that can be propagated from stem cuttings. In this study, cuttings in SI and SF systems produced rooting comparable to those in OM, whereas cuttings rooted in the SM aeroponic systems produced dramatically more roots, longer roots, and root systems of greater dry weight than cuttings in the OM systems. Cuttings rooted in SM transplanted finer and grew rapidly in containers of solid media. Finally, despite non affecting root development during propagation, the use of fertilizer solution in SM propagation systems seemed to prime cuttings for increased growth once transplanted into a solid medium.
Unit of measurement
Literature cited
Crawford,B.D., Dole,J.One thousand. & Bergman,B.A.2016Influences of season and cut week within a propagation cycle on rooting of 'Stained Drinking glass' coleus shoot tip cuttings are non overcome by rooting compound treatmentHortTechnology26620627
Crawford,B.D.Dole,J.Thousand.Bergman,B.A.2016Influences of season and cutting week within a propagation cycle on rooting of 'Stained Drinking glass' coleus shoot tip cuttings are non overcome by rooting chemical compound treatmentHortTechnology26620627
)| false
Search Google Scholar
Consign Citation
Currey,C. & Lopez,R.2014Controlled-release fertilizer during cutting propagation affects growth and tissue nutrient concentrations of rooted cuttings of almanac bedding plantsHortScience49152159
Currey,C.Lopez,R.2014Controlled-release fertilizer during cutting propagation affects growth and tissue food concentrations of rooted cuttings of almanac bedding plantsHortScience49152159
)| false
Search Google Scholar
Export Citation
Graves,W.R. & Zhang,H.1996Relative water content and rooting of subirrigated stem cuttings in four environments without mistHortScience31866868
Graves,Westward.R.Zhang,H.1996Relative water content and rooting of subirrigated stem cuttings in 4 environments without mistHortScience31866868
Maroya,Northward.Balogun,Yard.Asiedu,R.Aighewi,B.Lava Kuma,P.Augusto,J.2014Yam propagation using 'aeroponics' engineering scienceAnnu. Res. Rev. Biol.four38943903
)| imitation
Search Google Scholar
Export Citation
Mehandru,P., Shekhawat,Due north.Due south., Rai,One thousand.K., Kataria,Five. & Gehlot,H.South.2014Evaluation of aeroponics for clonal propagation of Caralluma edulis, Leptadenia reticulata, and Tylophora indica – Three threatened medicinal AsclepiadsPhysiol. Mol. Biol. Plantstwenty365373
Mehandru,P.Shekhawat,N.S.Rai,M.One thousand.Kataria,V.Gehlot,H.Southward.2014Evaluation of aeroponics for clonal propagation of Caralluma edulis, Leptadenia reticulata, and Tylophora indica – Three threatened medicinal AsclepiadsPhysiol. Mol. Biol. Plantsxx365373
)| false
Search Google Scholar
Consign Citation
Preece,J.E.2003A century of progress with vegetative plant propagationHortScience3810151025
Preece,J.E.2003A century of progress with vegetative plant propagationHortScience3810151025
)| faux
Search Google Scholar
Consign Citation
Santos,K.M., Fisher,P.R. & Argo,W.R.2009Stem versus foliar uptake during propagation of Petunia ×hybrida vegetative cuttingsHortScience4419741977
Santos,K.M.Fisher,P.R.Argo,W.R.2009Stem versus foliar uptake during propagation of Petunia ×hybrida vegetative cuttingsHortScience4419741977
)| false
Search Google Scholar
Export Citation
Soffer,H. & Burger,D.W.1989Institute-propagation using an aero-hydroponics systemHortScience24154
Soffer,H.Burger,D.W.1989Found-propagation using an aero-hydroponics systemHortScience24154
)| fake
Search Google Scholar
Export Citation
U.Southward. Department of Agriculture2016
Zhang,H. & Graves,W.R.1995Subirrigation to root stem cuttings: Comparison to intermittent mist and influence of fertilizationHortTechnology5265268
Zhang,H.Graves,Westward.R.1995Subirrigation to root stem cuttings: Comparison to intermittent mist and influence of fertilizationHortTechnology5265268
0 Response to "Peer Reviewed Journals on Root Formation on Coleus Cutting in Response to Fertilizer"
Post a Comment