Intermittent Mist Research Articles

Mechanisms of enhanced heat transfer of piston oscillating cooling in a heavy-duty diesel engine

The thermal load and reliability of pistons become major concerns with the increase of power density of internal combustion engines. The oscillating cooling technology is often adopted to enhance the heat transfer of pistons in heavy-duty diesel engines. To understand the heat transfer mechanisms, this study developed an optical oscillating cooling piston based on a real heavy-duty engine. The characteristics of two-phase oscillating flows were optically observed under different conditions. As engine speed increased from 100 to 700 r/min or oil supply pressure decreased from 0.2 to 0.8 bar, the oscillation intensity of the two-phase flow gradually increased and the oscillating flow pattern developed from slug to intermittent mist flow. Furthermore, computational fluid dynamics simulations were performed to analyze the heat transfer mechanisms of oscillating cooling and optimize the structure of the piston. The results showed that the heat transfer coefficient of oscillating cooling can be decomposed into three components, namely conventional flow, oscillation enhanced and jet flushing parts. The conventional flow part accounts for the largest proportion of the total heat transfer coefficient, whose value is positively correlated with oil flow rate. The oscillation enhanced part is optimal when the oil filling rate is between 40 % and 60 %. The jet flushing part can lead to a higher temperature gradient in the outer cooling gallery and thus increased thermal stress. The cooling capacities of inner and outer galleries are mainly influenced by the diameters of the oil outlet and distributor pipes, respectively. The jet flushing part can be controlled by changing the inclination angle of the distributor pipe. Finally, optimization achieved an improvement of 8.3 % in cooling capacity of inner cooling gallery and a reduction of 27.5 % of heat dissipation inhomogeneity in the piston.

Mist Spraying as an Outdoor Cooling Spot in Hot-Humid Areas: Effect of Ambient Environment and Impact on Short-Term Thermal Perception

Mist spraying is an active cooling technology used to alleviate heat stress during hot summers. However, there is limited experimental research on the relationship between ambient thermal parameters and spray cooling efficiency, as well as the transient and short-term thermal perceptions of local residents. In this study, an intermittent mist spraying system was set up, and environmental measurements, coupled with questionnaire surveys, were conducted under typical high temperature and still air conditions. The aim was to investigate the relationship among environmental factors, spray cooling effects, and dynamic improvements in human thermal perception. The results showed that higher ambient temperatures resulted in a more significant cooling effect, with a maximum value of 5.68 °C. Upon entering the spraying area, people experienced a large perceptual change, with the mean thermal sensation and thermal comfort change covering 73% and 62% of the total change ranges, respectively. This study indicated that the mist spray system can be activated if the ambient temperature exceeds 32.5 °C, helping local residents maintain a physiological state close to slightly hot and neutral comfort. These findings suggest that mist spraying can be applied in environmental design as an outdoor cooling spot to mitigate urban overheating, providing valuable insights for the application of mist spray systems in actual outdoor settings in hot-humid areas.

Micropropagation of Hemp (Cannabis sativa L.)

Hemp (Cannabis sativa L.) is commonly grown for the medicinal secondary metabolites produced by pistillate inflorescences. Micropropagation is a valuable method of propagating hemp plants because of the aseptic process and the production of true-to-type propagules. The hemp cultivar TJ’s CBD was used for a series of experiments to compare media inputs and practices for the clonal micropropagation of hemp. For stage I, shoot tips harvested from stock plants that were grown in a growth chamber produced less endogenous contamination in newly established cultures than shoot tips harvested from the greenhouse. In addition, stage I disinfection treatments with 20%, 40%, and 60% bleach (7.5% sodium hypochlorite) for 10 minutes had no differences in surface contamination rates. All concentrations were able to clean explants equally, and no damage to the explants was observed. For stage II, there were no differences in growth and multiplication rate between shoot tip or nodal explants. In addition, no differences were observed between the gelling agent’s agar, agargellan, and gellan gum at standard rates. When basal nutrient formulations were compared at standard rates and with their respective vitamins, Murashige and Skoog, Linsmaier & Skoog, and Driver & Kuniyuki Walnut media were found to be superior to Lloyd & McCown Woody Plant Medium. Media pH levels of 4.0, 5.0, 5.8, 6.0, and 7.0 were compared, and no differences were observed in final fresh weights, shoot lengths, or quality ratings. The pH levels of 5.8, 6.0, and 7.0 generated a greater number of lateral nodes. Sucrose levels of 0%, 1.5%, 3.0%, 4.5%, and 6.0% (wt/vol) were also compared, with the 1.5% and 3.0% rates showing greater fresh weights, shoot lengths, and quality ratings. Growth room temperatures of 22, 24, 26, and 28 °C were compared, with temperatures of 28 and 26 °C generating greater fresh weights, shoot lengths, numbers of nodes, and quality ratings compared with cooler temperatures. The cytokinins 6-enzylaminopurine (BA), 6-(γ,γ-dimethylallylamino) purine (2iP), and thidiazuron (TDZ) were compared at 1.0, 5.0, and 10.0 μM concentrations. The 5.0-μM TDZ treatment generated greater fresh weights and numbers of lateral nodes; however, it also produced the shortest shoot lengths and lowest quality ratings. The 2iP treatments at 1.0 and 5.0 μM, and the BA treatment at 1.0 μM produced the greatest quality ratings. The 5.0-μM 2iP level was considered the best treatment for stage II multiplication based on high ratings, in addition to the greater final fresh weights, shoot lengths, and numbers of nodes that were produced. For stage III experiments, the auxins indole 3-butyric acid (IBA) and 1-naphthylacetic acid (NAA) were compared at concentrations of 0.25, 0.5, and 2.5 μM. Auxin treatments of 0.25 μM NAA, 0.5 μM NAA, and 2.5 μM IBA generated the greatest final shoot fresh weights, root fresh weights, and numbers of nodes. However, the 2.5-μM IBA treatment resulted in a higher overall rating. For stage IV, ex vitro rooting and acclimation trials compared a dome and an intermittent mist system, as well as treated the unrooted cuttings with an externally applied auxin. Acclimating with a dome produced greater shoot heights, fresh shoot weights, and overall ratings compared with the mist system. The auxin treatment mildly increased fresh root weight, but was not as important to acclimation success as the domed environment. It has been concluded that a micropropagation system that uses lower rates of sucrose, higher growing temperatures, and lower rates of the cytokinins BA and 2iP are optimal for the micropropagation of hemp. In addition, when acclimating hemp plants from tissue culture, an in vitro stage III can be bypassed and plants can be rooted ex vitro during stage IV acclimation with a dome with or without additional auxin treatments.

Evaluation of an intermittent mist spray cooling system for improving greenhouse eggplant cultivation

Cultivation of crops in greenhouses faces the issue of overheating, which can harm yields. A low-cost solution is evaporative cooling, which also reduces the vapor pressure deficit. Fine mist sprays can significantly reduce temperature and vapor deficit. However, the fast evaporation rate could cause air saturation and wetting of plants, causing damage. A simple method to control the effect is intermittent spraying. In this research, air temperature was continuously measured at 20 locations for a misted 98m2 greenhouse during eggplant cultivation, as well as a control greenhouse without mist, while also evaluating the resulting crops. An array of 28 high pressure hydraulic nozzles, spraying 2.6kg/h each, intermittently sprayed 20 seconds on, then 10 seconds off throughout the day. The temperature in the misted greenhouse averaged 2.2K to 4.8K cooler than the control greenhouse. In the misted greenhouse, the total yield (+26%) and marketable fruits (+143%) were higher than the control. The cooling effect of the misted greenhouse compared to the control case tended to correlate with outdoor wind speed. The comparison of the misted greenhouse to its own initial condition did not. Evaluations of evaporation cooling may yield better understanding if compared to a control greenhouse at the same site.

Direct synthesis of submillimeter-sized few-layer WS2 and WS0.3Se1.7 by mist chemical vapor deposition and its application to complementary MOS inverter

This study investigated the direct synthesis of submillimeter-sized few-layer tungsten disulfide (WS2) and tungsten sulfoselenide (WS0.3Se1.7) using the mist chemical vapor deposition (CVD) method as a channel layer for metal-oxide-semiconductor field-effect transistors (MOSFETs). The atomic mono/bilayers WS2 and WS2−x Se x were deposited on thermally grown SiO2 and mist-CVD-grown high-κ amorphous aluminum titanium oxide coated on p+-Si substrates by an intermittent mist supply in a closed quartz tube from (NH4)2WS4 dissolved in N-methyl-2-pyrrolidone. Further, the furnace temperatures, supply/storage times of the precursor mist per cycle, and precursor concentration were considered variables. Consequently, few-layer WS2 and WS0.3Se1.7 with grain sizes of 700–800 μm were obtained on the high-κ a-Al0.74Ti0.26O y dielectric layers through adjustments to the deposition conditions. Subsequently, this few-layer WS2 and WS0.3Se1.7 were applied as channel layers in MOSFETs, which showed n- and p-channel behaviors using gold and platinum source/drain electrodes, respectively. Further, average mobilities of ∼52 and ∼41 cm2 V−1 s−1 were obtained with a threshold voltage of −0.2 (0.3) V and on-off ratios of ∼1 × 106 and ∼6 × 105 in n-WS2 and p-WS0.3Se1.7 channel FETs, respectively. Moreover, this n- and p-channel FETs were used to design an electrically isolated complementary inverter circuit, and a gain of 4–5 was obtained. The findings of this study suggest that mist CVD can be a consistent manufacturing technique for both the channel and gate insulating layers applied in FETs.

Impact of Indole-3-butyric Acid Concentration and Formulation and Propagation Environment on Rooting Success of ‘I3’ Hemp by Stem Cuttings

As the industrial hemp (Cannabis sativa L.) market grows, there is a need for methods to clonally propagate parental breeding stock and new cultivars. Information is lacking on vegetative cutting propagation of hemp. We evaluated how propagation environment (intermittent mist vs. subirrigation under a humidity dome), indole-3-butyric acid (IBA) formulation (talc rooting powder vs. IBA in solution), and IBA concentration (0, 3000, or 8000 ppm) affected stem cuttings from ‘I3’, a cannabinoid-free cultivar of industrial hemp. Under mist or domes, rooting quality and percent declined at 8000 ppm IBA. Root and shoot quality and rooting percentage also were reduced in 3000 ppm IBA in solution treatment compared with talc. Our data show that for the cultivar tested, cuttings rooted at the highest percentage and produced the highest-quality roots and shoots with either no hormone or 3000 ppm talc powder. These treatments did equally well under humidity domes or intermittent mist.

Sustainable Exploitation of Greek Rosmarinus officinalis L. Populations for Ornamental Use through Propagation by Shoot Cuttings and In Vitro Cultures

Rosmarinus officinalis L. belongs to the Lamiaceae family and is cultivated worldwide due to its diverse uses as an ornamental evergreen shrub in gardening, as well as a food seasoning and a natural medicine. The present research was conducted to study the morphological traits of seven wild-grown rosemary populations in Greece, as well as the propagation of two selected populations with the most desirable ornamental characteristics, by the use of shoot cuttings and in vitro cultures. From the study of the morphological traits of the seven populations, those with interesting features were grown in the areas of Amaliada and Piperia and, thus, were chosen for studying their propagation. Rooting of the shoot cuttings was carried out during the four seasons of the year, using potassium salt Indole-3-butyric acid (K-IBA) at concentrations of 0.5 and 1 g·L−1, in various substrates under the intermittent mist or fog system. It was found that the shoot cuttings rooted easily in all four seasons, but there were better results for the population of ‘Piperia’ in autumn, with 1 g·L−1 K-IBA (80%), and ‘Amaliada’ in spring, with 0.5 g·L−1 K-IBA (82.5%), while higher rooting percentages were achieved in the fog system, on a substrate consisting of perlite and peat, in a ratio of 2:1 (85%). For the in vitro cultures, shoot tips excised from the two selected populations were successfully disinfested by pre-soaking in an antioxidant solution and then, by sterilizing them in 0.6% (w/v) NaOCl, followed by transferring them onto a Murashige and Skoog (MS) nutrient medium. ‘Amaliada’ cultures proved to be the most productive population (2.1 shoots per explant), with the highest shoot formation frequency (91.6%), when cultivated on the MS nutrient medium without plant growth regulators. For ‘Piperia’ cultures, the highest shoot formation frequency (66.6%) was achieved on the MS nutrient medium supplemented with 0.25 or 0.5 mg·L−1 6-Benzyloaminopurine (BAP) and 0.1 mg·L−1 Indole-3-acetic acid (IAA). Spontaneous root formation frequency was noticed on the MS nutrient medium, containing 0.5 mg·L−1 BAP and 0.1 mg·L−1 IAA, for both ‘Amaliada’ and ‘Piperia’ cultures (50% and 41.6%, respectively) in a single stage, with root lengths of 7.1 and 5.3 cm, respectively. Rosemary plantlets, with roots formed in vitro after transplanting them in soilless substrate, were acclimatized adequately in the greenhouse environment (~70%).

Propagation Methods for the Conservation and Preservation of the Endangered Whorled Sunflower (Helianthus verticillatus).

Helianthus verticillatus Small, the whorled sunflower, is a perennial species only found at a few sites in the southeastern United States and was declared federally (USA) endangered in 2014. The species spreads locally via rhizomes and can produce copious seeds when sexually compatible genotypes are present. Vegetative propagation of the species via cuttings and the optimum conditions for seed germination have not been determined. To investigate asexual propagation via cuttings, stem sections were harvested in late May, June, and July in Knoxville, Tennessee (USA) and trimmed to a minimum of two nodes. The base of the cuttings was treated with either auxin or water, and grown in a Promix BX potting medium with intermittent mist and 50% shade for one month. Seeds were harvested from a population of multiple genotypes in Maryville, Tennessee and used to determine viability and the range of temperatures suitable for germination. A clonal population was developed and used for three years to assess sexual compatibility at three locations in Knoxville, Tennessee. Ninety-five percent of the cuttings from May rooted in two-to-three weeks and formed more than 20 adventitious roots per cutting with auxin and 18 with water treatments. The ability of cuttings to root decreased in June to about 20%, and none rooted in July with either water or auxin pretreatments. Pre-germination tetrazolium tests indicated that about 91% of seeds (achenes) were viable. Subsequent germination tests revealed high germination at varying temperatures (96 to 99% of seeds (achenes) germinated at 22/11, 27/15, and 29/19 °C), whereas germination was significantly inhibited by 33/24 °C. Fifty percent of the seeds germinated at 22/11 °C in 7.5 days, whereas only 2.0 to 2.5 days were required for 50% germination at 27/15, 29/19, and 33/24 °C. Seeds were not produced at any of the clonal planting locations during the three years. Vegetative propagation via rooted cuttings was successful in the mid-spring, seed germination was possible over a wide range of temperatures, and self-incompatibility was evident in this species. The results of this study will permit fast and efficient propagation of multiple and selected genotypes for conservation, commerce, and breeding of elite cultivars with disease resistance or other desirable attributes.

Adventitious rooting of cultivars and clonal selections of Prunus spp. rootstock under intermittent mist system

To reduce peach tree losses due the Peach Tree Short Life (PTSL), the main research line in Brazil is to select tolerant rootstock and perpetuate it by cloning methods. The objective was to evaluate adventitious rooting capacity of softwood cuttings of three cultivars and several clonal rootstock selections of Prunus spp., under intermittent mist system. Two trials were conducted and ‘Capdeboscq’, ‘Okinawa’ (P. persica) and ‘Sharpe’ [‘Chickasaw’ (P. angustifolia Marsh.) x Prunus spp.] were used as reference cultivars. After 53 days (trial 1) and 72 days (trial 2) from the cutting setting, we conclude that softwood cuttings under intermittent mist system are a feasible way to propagate peach rootstock selections of 2010/2011 PTSL selection cycle. Root quality was satisfactory in most selections, with high percentages of cuttings suitable for transplanting and excellent root number and root length. OS-GRA-10-17, VEH-GRA-10-31, VEH-GRA-10-32, VEH-GRA-10-37 and VEH-GRA-10-38 selections had the highest mortality and the lower percentages of live rooted cuttings. The ease of vegetative propagation must be taken into account in more promising rootstock.

EFFICIENCY OF VEGETATIVE PROPAGATION OF CAJÁ-DE-JABUTI UNDER CONCENTRATIONS OF INDOLEBUTYRIC ACID AND GRAFTING METHODS

ABSTRACT The objectives of the tests were to evaluate concentrations of indolebutyric acid (IBA) combined with different types of cuttings and grafting methods on the vegetative propagation of cajazeira-dejabuti (S. testudinis). The experiment with stem cuttings was conducted in a greenhouse with an intermittent misting system. The experimental design was completely randomized in a 5 x 6 factorial arrangement consisting of five cutting types: apical, medial, basal, stratified, and tanchan, and six IBA concentrations: 0, 1,000, 2,000, 3,000, 4,000, and 5,000 mg kg-1, with four replications of ten cuttings. The experiment with the root cuttings followed a randomized block design composed of six IBA concentrations (0, 1,000, 2,000, 3,000, 4,000, and 5,000 mg kg-1) with four replications, evaluating after 120 days the percentages of live, sprouted, rooted, and calloused cuttings, and the number and dry mass of roots and sprouts. Five grafting methods (chip budding, shield budding, cleft grafting, wedge grafting, and splice grafting) were tested by evaluating the graft success and sprouting percentages at 30 and 60 days after grafting, respectively. Statistical analyses were performed using the Kruskal-Wallis non-parametric test. The IBA concentrations of 0, 2,000, 3,000, and 5,000 mg kg-1 increased the number of sprouts in tanchan cuttings. The tanchan cuttings showed the highest survival and percentage of sprouts regardless of the IBA concentration. The IBA concentration of 2,200 mg kg-1 promotes higher rooting rates in root cuttings. Splice grafting provides higher graft success and sprouting rates.

Concentrations of indolebutyric acid on air-layering of guava cv. Paluma

Nowadays, the predominant technique for the commercial propagation of guava seedlings is through cuttings, using herbaceous cuttings that need a specialized infrastructure with intermittent misting, clean water, exhausters, water filters, and fans. As an alternative to plant propagation by cuttings, this study aimed to evaluate the influence of concentrations of indolebutyric acid (IBA) on the rooting of branches of the guava cv. Paluma by air-layering. The experimental design was in randomized blocks, with four replications and 10 air layers per plot. The treatments consisted of six concentrations of IBA powder mixed with industrial talcum: 0, 1,000, 2,000, 3,000, 4,000, and 5,000 mg.kg-1. Four adult guava parents that were in the off-season period were used. For the preparation of the air layers, the stems were girdled with a 4.0 cm width, using a steel blade, by removing the bark until exposing the cambium region, followed by IBA application and wrapping of the branches with a plastic bag containing moist organic substrate. The following variables were evaluated 120 days after air-layering: percentage of rooted and callused air layers, longest root length, and root dry matter. The analysis of variance indicated no significant differences between the IBA concentrations for all variables, but the rooting percentages were high (68.6 to 92.2%) regardless of the application of the exogenous auxin.

An approach for the mass propagation of Cupressus sempervirens L. (Cupressaceae), for quality propagule production

The scenarios of climate change in Mediterranean regions bring back the need for tree species tolerant to drought and disease, for agro- and urban-forestry purposes, landscape rehabilitation, as well as for post-fire and quarry restoration plans. Therefore, forest industries focus on selecting, propagating and growing superior trees. The Cupressus sempervirens L. is such a coniferous tree species, with a fundamental ecological, financial and ornamental role in the Mediterranean region. The aim of this study was to develop an efficient macropropagation protocol, which would lead to mass-selected genotypes or phenotypes of C. sempervirens f. sempervirens. For this purpose the axillary shoot multiplication method was used, by adopting both cutting propagation and intermittent mist methods. These methods were used for the first time in the macropropagation of C. sempervirens f. sempervirens. For shoot proliferation, 24 different modified macropropagation treatments at different concentrations and combinations were tested: shoot cuttings, concentrations of K-IBA and rooting systems. The elongation and root induction was carried out in an intermittent mist system for 50 days, then the new plantlets were moved for acclimatization for 15 days in a greenhouse. The current workflow presents an effective preliminary protocol with clear steps and treatments for macropropagation of C. sempervirens f. sempervirens. The developed protocol for macropropagation of tree species ensures cost- and time-efficient propagation. Produced plantlets were developed efficiently under in vivo conditions, allowing to propagate and store genetic material for conservation and domestication. This protocol can be generated for other tree species of the Cupressus genus and the Cupressaceae family.

Shooting and Rooting Behaviour in Relation to Season, Age and Growing Conditions of Dendrocalamus asper Backer

The experiment was conducted at Agroforestry Research Centre, of G. B. Pant University of Agriculture and Technology, Pantnagar to assess the effect of age (one and two year old), growing condition (intermittent misting and no misting) and different seasons (summer, monsoon, autumn and spring) on rooting and shooting of culm cuttings of Dendrocalamus asper. The experiment was laid out in factorial randomized block design with three replications. The findings indicated that in D. asper, one year old culm cuttings in the intermittent misting condition showed good results. The findings also indicated that shooting and rooting per cent of culm cuttings planted in different season showed response as Spring (March)> Summer (June)> Monsoon (August)> Autumn (October).

Propagation of Sweetgale, Rhodora, and Catberry by Stem Cuttings

Sweetgale (Myrica gale), rhodora (Rhododendron canadense), and catberry (Ilex mucronata) are shrubs of eastern North America that may have potential for broader use in horticultural landscapes. Because information on their vegetative propagation is scarce, we conducted experiments over 2 years to evaluate the effects of cutting collection date, wounding, substrate composition, and the concentration of applied potassium salt of indole-3-butyric acid (K-IBA) on rooting of each species. In 2015, we collected cuttings of each species on three dates to obtain both softwood and semihardwood cuttings. Cuttings were unwounded or wounded with a razor blade, and treated by dipping into water containing K-IBA at concentrations ranging from 0 to 15,000 mg·L−1, after which they were inserted into a substrate of 3:1 perlite:peat (by volume) and placed under intermittent mist. In 2016, semihardwood cuttings of each species were all wounded, treated with K-IBA from 0 to 15,000 mg·L−1, and inserted into substrates of 100%, 75%, or 50% perlite, with the remaining volume occupied by peat. In both years, the greatest percentage of sweetgale cuttings rooted when no K-IBA was applied. K-IBA application also reduced root ratings, root dry weights, and root lengths of sweetgale. For rhodora and catberry, maximal responses for all measures of rooting occurred when 5000 to 15,000 mg·L−1 K-IBA was applied. We recommend that growers use no exogenous auxin to propagate sweetgale, and 5000 to 10,000 mg·L−1 K-IBA to propagate rhodora and catberry. Cuttings of all three species can be collected from softwood or semihardwood shoots. Finally, sweetgale can be rooted in perlite alone, whereas rhodora and catberry required the addition of peatmoss for satisfactory root development.

Collection period and indolebutyric acid on the rooting of adult pecan plant cuttings

Abstract: The objective of this work was to evaluate the effect of the collection period and of the exogenous application of indolebutyric acid (IBA) on the rooting of cuttings from adult pecan (Carya illinoinensis) plants. The experiment was carried out in a greenhouse with intermittent mist irrigation, from December 2017 to October 2018. The experimental design was completely randomized, in a 4x5 factorial arrangement, with four collection periods (spring, summer, autumn, and winter) and five concentrations of IBA (0, 2,000, 4,000, 6,000, and 8,000 mg L-1). For the cuttings collected during summer and autumn, there was a linear relationship between rooting and the increase of the IBA concentration. The best results for rooting, callus formation, mean number of roots, mean root length, and root dry and fresh mass are obtained for the cuttings collected during summer, with the application of 8,000 mg L-1 IBA on the base of each cutting, under a mist irrigation system. The rooting of cuttings from adult pecan plants with the application of IBA is possible, being an alternative propagation method for the species.

Vegetative rescue of Camu-Camu from epicormic sprouts of detached branches

Abstract The cloning of camu-camu by cuttings has shown distinct and sometimes controversial results. The use of juvenile materials has been indicated for difficult rooting species. Thus, this work aimed to evaluate the emission of epicormic sprouts in mega-cuttings and cuttings of detached branches, as well as the cloning of camu-camu from these sprouts. The research was developed by conducting four experiments, the first two being related to the emission of epicormic sprouts, while the others referred to the cloning of camu-camu from these sprouts. In experiments evaluating sprout emission, the following factors were studied: mother plant x branch position; mother plant x substrate. In the other tests, using standard cuttings with two pairs of leaves made from epicormic sprouts, the following factors were evaluated: mother plant x cutting type x indolbutyric acid concentration (IBA); mother plant x hydroretentive polymer x environment. The number and speed of sprouts vary depending on the mother plant. IBA has negative influence on cutting and cuttings from the lower portion of sprouts have greater rooting potential than those from the upper portion. Environment with intermittent mist irrigation is more suitable for the propagation of camu-camu by cuttings. Vegetative rescue by means of epicormic sprouts in mega-cuttings and cuttings of detached branches presents potential application for the clonal propagation of camu-camu, requiring improvement in order to increase efficiency.

Environment, Photosynthesis, and Adventitious Rooting of Manchurian Lilac Cuttings Propagated in Overhead Mist, Submist, and Combination Systems

We propagated manchurian lilac (Syringa pubescens subsp. patula ‘Miss Kim’) vegetatively from stem cuttings using overhead mist, submist, and combination propagation systems. Cuttings were collected when terminal buds were already set, after the period of tender growth that is optimal for lilac propagation. Net photosynthesis (Pn) was recorded to assess whether differences in rooting could be attributed to differences in photosynthetic activity of cuttings within each system. The propagation environment differed significantly among systems, with vapor pressure deficit (VPD) substantially greater for submist systems than for overhead mist or combination systems, and root zones warmer in submist and combination systems than in overhead mist. Pn of cuttings did not differ among systems and was initially low, but increased about when the first root primordia were visible. Rooting percentages were 90% among cuttings in the combination system, with cuttings in overhead mist and submist rooting at lower, but similar, percentages (68% and 62%, respectively). Cuttings in the combination and submist systems produced significantly more and longer roots than those in the overhead mist system, and retained nearly all of their leaves. Overall, the use of systems that provide intermittent mist to the basal end of each cutting was effective for propagating manchurian lilac. Our results demonstrate that cuttings in submist alone experience a much greater VPD than those in overhead mist, but may nonetheless root at comparable percentages and produce superior measures of root system quality. Combination systems show promise for rooting of species like manchurian lilac, because cuttings rooted at high percentages and with consistent root system quality, despite having been collected after the optimal spring period for lilac propagation.

Rooting response of Prunus wild relative semi-hardwood cuttings to indole-3-butyric acid potassium salt (KIBA)

Wild Prunus germplasm is an important resource for pest and disease resistance traits for the continued improvement of almond and other Prunus rootstocks. Evaluation of resistance in these wild species requires clonal replicates that are traditionally produced by rooting cuttings. Over two consecutive years, leafy cuttings of 20 genotypes of the following wild Prunus species were collected in mid-late May and treated with a 15 s dip in 0, 500, 1000, 2000 or 4000 mg/L of the potassium salt of indole-3-butyric acid (KIBA): almonds (P. argentea (one genotype), P. bucharica (two genotypes), P. dulcis (two genotypes), P. tangutica (three genotypes)), peaches (P. davidiana (two genotypes), P. kansuensis, P. mira (two genotypes), P. persica (three genotypes including a commercial peach rootstock, ‘Lovell’)), and plums (P. cerasifera (two genotypes), P. salicina (two genotypes)).. The cuttings were planted in a perlite-vermiculite medium under intermittent mist and periodically checked for roots. The plum species rooted at a higher percentage, and produced more roots than the peach species; and the almond species generally failed to root. The plums produced the most roots at 2000−4000 mg/L KIBA, although rooting in both P. cerasifera and P. salicina was genotype dependent. The plum cuttings that rooted generally produced from 2 to 14 roots that averaged 0.74–1.73 cm long when the cuttings were harvested; one accession produced 60 roots/cutting when treated with 4000 mg/L KIBA. The wild peach species produced the most roots at 1000−4000 mg/L KIBA, with cuttings of P. kansuensis and P. mira having significantly higher rooting percentages than P. davidiana and P. persica cuttings. All of the wild almond species tested did not root or rooted a very low percentage.

Prairie Dropseed Germination Highest with Warm, Moist Conditions

We tested prairie dropseed (Sporobolus heterolepis) using six different germination treatments and found the best results with cold (40 °F), dry storage followed by direct seeding into a commercial germination mix placed in a 75 °F glass-glazed greenhouse with intermittent mist (5 seconds of mist every 8 minutes), and 600-W high-pressure sodium lighting with a 16-hour daylength. We found commercial laboratory viability analysis from tetrazolium staining did not correspond to germination results. Cold (34 °F), moist (2.3 g seed moistened with 2.5 mL deionized water) treatment, also known as cold conditioning, produced significantly less germination and fewer transplantable seedlings, and is not recommended for prairie dropseed.

Propagation of Comptonia peregrina L. from stem cuttings

Comptonia peregrina is a desirable native ornamental plant for challenging landscapes, but it cannot be produced using conventional softwood stem cuttings. We demonstrate that C. peregrina can be successfully propagated using young shoots (6 to 8 cm in length) recently emerged from rhizomes taken as cuttings. Although significantly more cuttings rooted using intermittent mist (99%) than propagation dome (70%), cuttings under propagation domes had greater shoot counts. Due to the drier and warmer conditions under propagation domes, cutting shoot tips were killed, which relieved apical dominance and stimulated lateral budbreak. Cuttings rooted under propagation domes produced plants having greater height, width, and size after 90 d than cuttings rooted under intermittent mist. Treatment of cuttings with talc-based rooting hormone at 3000 and 8000 ppm indole-3-butyric acid (IBA) significantly improved rooting percentage and shoot count over untreated cuttings. Cuttings treated with 8000 ppm IBA produced the most roots. Container plants grown from cuttings and pruned to 7 cm in height produced twice as many shoots as unpruned plants. Using cuttings taken from young shoots (6 to 8 cm) produced from rhizomes, 3000 or 8000 ppm IBA, and intermittent mist nursery growers can achieve rooting percentages for C. peregrina above the 80% benchmark preferred for commercial plant production.