Abstract
An investigation was undertaken to determine whether various light reduction and shoot banding treatments could increase rooting on stem cuttings of Lindera benzoin [(L.) Blume] (northern spicebush), a difficult-to-root woody plant. Stock plants were grown under one of three light conditions (light, shade, or etiolation). Emerging shoots received either no treatment or a banding treatment that involved adhering a hook-and-loop fastener coated with varying concentrations of indole-3-butyric acid (IBA) around the shoot base to create a localized etiolated zone before taking cuttings. Data on rooting percentage and number of roots per cutting were analyzed using logistic and Quasi-Poisson regression, respectively. Etiolated cuttings treated with a band without IBA had the highest rooting probability and number of roots; however, etiolated cuttings across all banding treatments had similarly successful results. Additionally, there were several significant differences in rooting probabilities and root numbers between banding treatments within the shade- and light-grown groups. This research evaluated asexual propagation approaches for use with northern spicebush and provides a framework for the adoption and development of this taxon as a nursery crop.
There is great variability among woody plants in their responses to asexual propagation techniques. Although some species root readily from stem cuttings, others are much more difficult to propagate, which can limit their commercial production despite the desirable traits they may bring to the landscape. For these difficult-to-root plants, a variety of practices have been developed to stimulate root formation on stem cuttings, most notably full or localized etiolation or shading, application of synthetic growth regulators, and the use of stock plants with juvenile shoot growth.
Several studies have provided evidence that etiolation, the growing of plants in the absence of light or under heavy shade, may promote physiological changes in developing stem tissues that increase the rooting potential of subsequent stem cuttings. For instance, Maynard and Bassuk (1996) observed that European hornbeam (Carpinus betulus L.) plants grown under etiolation displayed a reduction in the lignification of the secondary xylem and thickness of the periderm, as well as an increase in sclereid-free gaps in the sclerenchyma sheath. These changes were correlated with increased rooting percentage and root numbers in stem cuttings (Maynard and Bassuk 1996). Other factors associated with an improved rooting response following etiolation include reduced callus formation at the cutting base (Husen 2011; Wu et al. 2006) and an increase in the availability of carbohydrates that provide energy for rhizogenesis and cell growth (Husen 2008; Klopotek et al. 2010).
The positive effects of etiolation on rooting of stem cuttings have been observed in numerous taxa, including Saskatoon serviceberry [Amelanchier alnifolia (Nutt.) Nutt. Ex M. Roem.] (Nelson 1987), bigtooth maple (Acer grandidentatum Nutt.) (Richards and Rupp 2012), several oak (Quercus L.) species (Hawver and Bassuk 2000), and certain azalea (Rhododendron L.) cultivars (Apine et al. 2013). Cuttings taken from etiolated stock plants have been treated with a synthetic auxin—namely, indole-3-butyric acid (IBA) or 1-naphthaleneacetic acid (NAA), to promote rooting further.
The level of light exclusion needed to achieve increased rooting may vary by species. Maynard and Bassuk (1992) found that stem cuttings of C. betulus ‘Fastigiata’ displayed the best rooting response when stock plants were grown under 95% shade rather than complete (>99%) shade; likewise, increased rooting of cuttings has also been displayed in European smoketree (Cotinus coggygria Scop.) at 96% light exclusion (Pacholczak et al. 2005). Significantly improved rooting of cuttings has also been observed in plants grown in much lower shade levels, including creeping juniper (Juniperus horizontalis Moench) grown at 50% and 70% irradiance, redosier dogwood (Cornus alba L.) grown at 50% irradiance, and Japanese maple (Acer palmatum Thunb. ‘Atropurpureum’) grown at 40% to 50% irradiance (Behrens 1988; Hansen 1997; Pacholczak et al. 2017).
A complement or alternative to whole-plant etiolation or shading is banding, a procedure in which light is excluded from the portion of the stock plant shoot that will become the cutting base using an opaque band to create a localized etiolated zone. Bands can be applied to shoots from plants grown under etiolation, which are then brought into the light to allow the shoots to “green up” except for where bands have been applied. Alternatively, bands can be applied to light-grown shoots that are subsequently “blanched” by the band due to light exclusion (Maynard and Bassuk 1987). IBA is often added to the bands to promote rooting. Herman and Hess (1963) applied the blanching method to red kidney bean (Phaseolus vulgaris L.) and Chinese hibiscus (Hibiscus rosa-sinensis L.) by covering the bases of new shoots with black bands, taking cuttings at the shoot base, and dipping the blanched cuttings in IBA before rooting under mist. This procedure significantly increased root numbers in both species. Blanching followed by a quick dip in IBA has also been used to increase rooting percentage in softwood cuttings of apple rootstock (Malus domestica Borkh.) (Sun and Bassuk 1991), cherry rootstock (Prunus cerasus L. × Prunus canescens Bois) (Gulen et al. 2004), and king protea [Protea cynaroides (L.) L.] (Wu et al. 2006).
Maynard and Bassuk (1985) introduced a technique of banding shoots with squares of black, self-adhering hook-and-loop fasteners (VELCRO® Sew On Fasteners; VELCRO® Brand, Manchester, NH, USA). Both sides of the open band are dipped in a talc IBA preparation and then are firmly pressed around the base of the stem so that the two sides adhere, and the hooks are forced into the tender stems. This serves to wound underlying stem tissue lightly and facilitate the application of IBA, thereby increasing root formation. Blanching with such a band coated in IBA powder led to the highest rooting percentage among several taxa, including English oak (Quercus robur L.), northern red oak (Quercus rubra L.), and common lilac (Syringa vulgaris L. ‘Belle de Nancy’ and ‘President Grevy’) (Maynard and Bassuk 1987). Increased rooting of cuttings from shoots blanched with hook-and-loop bands has also been observed in 2-year-old greenhouse-grown seedlings of sugar maple (Acer saccharum Marshall) (Richer et al. 2004).
In many cases, the combination of full etiolation plus banding leads to optimal rooting results. In apple cultivar Bramley’s Seedling, complete shading of stock plants followed by banding with black tape significantly increased rooting percentages (Delargy and Wright 1979). Maynard and Bassuk found that, compared with etiolation alone or banding alone, etiolation followed by banding with hook-and-loop fasteners (VELCRO®) dipped in IBA led to the highest rooting in A. saccharum, paper birch (Betula papyrifera Marshall), European hornbeam, Chinese chestnut (Castanea mollissima Blume), and scarlet oak (Quercus coccinea Münchh) (Maynard and Bassuk 1987, 1992). Similar results were observed in American hazelnut (Corylus americana Walter), European beech (Fagus sylvatica L.), Oyama magnolia (Magnolia sieboldii K. Koch), and fragrant epaulette tree (Pterostyrax hispida Siebold & Zucc.) (Bassuk et al. 1986).
Propagule position and the cutting back of stock plants also play an important role in the rooting of stem cuttings. In woody plants, the rooting potential of cuttings is influenced by the “cone of juvenility,” which holds that the most physiologically juvenile tissues of a plant are in regions closest to the base. Cuttings taken from these regions typically produce more adventitious roots than those from mature tissues (e.g., branches and the distal end of the stem) (Beyl 2008). For instance, this effect has been observed in northern red oak (Fishel et al. 2003) and several larch (Larix Mill.) hybrid families (Peer and Greenwood 2001), wherein the rooting response of cuttings was greatest in shoots taken from basal stem sections and declined with increasing distance from the tree base production of physiologically invigorated she. Additionally, the pruning or cutting back of stock plants may stimulate thoots that root more easily when taken as cuttings (Pijut et al. 2011). Amissah and Bassuk (2009) found that severely pruning swamp white oak (Quercus bicolor Willd.) stock plants to 4 cm and allowing new epicormic shoots to form improved the rooting response of subsequent cuttings and layers. Similar results were observed in mature yerba mate (Ilex paraguariensis St. Hil.) plants subjected to girdling and coppicing near the trunk base (Bisognin et al. 2018) as well as a bloodwood hybrid (Corymbia torelliana × C. citriodora) continuously pruned to 15 cm to maintain clonal juvenility (Wendling et al. 2015).
An appropriate subject for tests of adventitious root-stimulating factors of stem cuttings is northern spicebush [Lindera benzoin (L.) Blume]. L. benzoin is a dioecious shrub native to a large swath of North America from Maine west to Ontario and Kansas and south to Florida and Texas. Typically found in moist soils along streams and in the forest understory, L. benzoin grows 1.8 to 3.6 m tall and equally as wide with a loosely rounded form. Ornamental value is provided in the form of clusters of small, yellow flowers in the spring and bright scarlet, oval drupes in the fall (Dirr 2009). Historically, L. benzoin has been propagated from seed due to low rooting percentages produced from cuttings (Dirr and Heuser 2006). However, research from Lenze (2020) provided preliminary evidence that rooting success could be improved through etiolation and banding treatments. The objective of this research was to determine the most successful combination of lighting and banding treatments for increased rooting of L. benzoin stem cuttings, making rapid commercial production of this species more feasible.
Materials and Methods
Twenty-nine L. benzoin stock plants were left in an unheated polyhouse in Ithaca, NY, USA (lat. 42°27′31.86″N, long. 76°27′54.72″W) from mid-October 2021 through late February 2022. The average ambient temperature ranged from –5.77 to 4.20 °C during this period. All plants were potted in soilless media (LM-111 All Purpose Mix; Lambert, Rivière-Ouelle, Canada) in a standard #3 round plastic container (10.4 L, 27.9 cm in diameter) and had a caliper measurement of ∼1.59 cm (5/8″). After 4 months, plants were moved to a greenhouse with temperatures of 23.9/18.3 °C day and night and 27% to 95% relative humidity. At the first sign of bud swell, the apical meristems of all plants were removed and plants of each size were trimmed to a uniform height of ∼33.0 cm.
Each stock plant was randomly assigned to one of three light treatments: full light, etiolation (>99% light exclusion), or shade (50% light exclusion). Relative light levels were determined using a sensor that measured PAR (PAR) in µmol·m−2·s−1 (LI-190R; LI-COR, Inc., Lincoln, NE, USA). The plants to be etiolated were placed on a bench enclosed with a tent of opaque black shadecloth topped with a layer of reflective cloth to prevent overheating. Plants in the shade group were placed on a bench under a tent of one layer of 50% mesh shadecloth, and those in the light group were left under full natural light.
As shoots emerged and grew to 5 to 7 cm long, each was randomly assigned one of four banding and hormone treatments: no banding, banding with 3000 mg·kg−1 IBA in talc, banding with 8000 mg·kg−1 IBA in talc, or banding without IBA. Within the three light levels, roughly equal numbers of shoots received each banding treatment (18 to 23 replicate shoots per banding treatment in etiolated plants, 34 to 37 in shade-grown plants, and 42 to 47 in light-grown plants) with different shoots on the same plant often receiving varying treatments (Fig. 1). The banding treatment involved firmly affixing a 2.5-cm square of hook-and-loop fastener (VELCRO®) around the base of each shoot. The bands either had no IBA applied or were coated in 3000 mg·kg−1 IBA (Hormodin® 2; OHP, Inc.; Morrisville, NC, USA) or 8000 mg·kg−1 IBA (Hormodin® 3; OHP, Inc.) before being firmly affixed around the shoot bases. IBA was applied to the bands by pressing both the hook and loom sides of the fabric into a dish of fresh IBA powder and tapping them against the dish to remove excess, creating an even coating. A final group of shoots had no band applied (see Table 1 for a summary of treatments).
Images of experimental design and procedure. (A) Lindera benzoin stock plant on a bench with varying banding and indole-3-butyric acid treatments applied to the shoots. (B) Shoot with band removed showing successful blanching of underlying tissue. (C) Cuttings under intermittent mist.
Citation: HortScience 58, 5; 10.21273/HORTSCI17022-22
Summary of light and banding treatments applied to Lindera benzoin stock plants and stem cuttings.
Stock plants under the light and shade treatments remained on their respective benches for the duration of the experiment. Plants under the etiolation/black cloth treatment, however, were moved to the shade bench immediately after their shoots were treated to allow them to green up. On all plants, if any shoot grew longer than 10 cm, the apical meristem was trimmed to maintain uniform cutting length. All plants were irrigated as necessary with municipal tap water and fertilized five times per week with Jack’s Professional® Acid (JR Peters, Allentown, PA, USA) 21N–3.1P–5.8K water-soluble fertilizer [21% N (derived from ammonia and urea), 7% P2O5, 7% K2O] and a 7N–0P–0K–10Fe iron chelate (derived from sodium iron pentetic acid) applied via fertigation at a rate of 150 mg·L−1. A one-time drench of a 4N–0P–0K–6Fe iron chelate (derived from sodium iron ethylenediamine-N, N′-bis) was applied at 22 mg·L−1 to correct a suspected iron deficiency.
Three weeks after the initial banding treatment, shoots were excised from the mother plant directly below the band or equivalent location on light-grown plants. Bands were removed and bases of all cuttings were dipped in 8000 mg·kg−1 IBA (Hormodin® 3) before being planted in trays filled with a mix of perlite and soilless media (LM 111) at a 2:1 ratio by volume. Trays were placed on a mist bench with a layer of 50% mesh shadecloth overhead to prevent water stress, where they received 4 s of mist every 10 min. No fertilizer was applied to the cuttings at this stage. After 7 weeks, each cutting was removed from its tray and assessed for rooting success, and, if rooted, number of roots.
Statistical analysis.
Statistical analysis of the rooting data were carried out using statistical software [RStudio ver. 2022.07.0 (RStudio Team 2022)]. To determine the effects of light and banding treatments on rooting success, a generalized linear model with a binomial distribution and a logit link was fitted to the data (logistic regression). Data on the number of roots per cutting were analyzed using a Quasi-Poisson regression model, which was selected over an ordinary least squares model to account for overdispersion. An alpha level of 0.05 was used to determine statistical significance.
Additionally, post-hoc testing was completed to assess the effect of band treatment on rooting within each light level. Using the R Package emmeans (Lenth 2022), Z-tests were conducted to make pairwise contrasts of least-squared means by banding treatment. For instance, among etiolated plants, the least-squares means of unbanded cuttings vs. cuttings treated with a band with 3000 mg·kg−1 IBA (Hormodin® 2) were compared to determine if one group rooted better than the other. P values were adjusted for multiple comparisons using Tukey’s test (using P ≤ 0.05).
Results
Rooting success.
A total of 403 cuttings were obtained from L. benzoin stock plants across all treatments. Seventy-one percent of cuttings rooted, with notable variation by light and banding treatment group (Table 2). Rooting by overall light treatment was highest among cuttings from etiolated stock plants, followed by those from the shade- and light-grown plants, at 92%, 72%, and 60%, respectively. The highest rooting percentage by light and banding treatment occurred in etiolated cuttings treated with a band without IBA (96%), whereas the lowest percentage was in light-grown cuttings treated with a band without IBA (43%).
Observed percent rooting of Lindera benzoin stem cuttings 7 weeks posttreatment under intermittent mist.
Analysis of deviance of the fitted binomial model showed that stock plant light level had a significant effect on the rooting of cuttings (P < 0.05). Band treatment and the overall interaction between band treatment and light were not significant (Table 3).
Analysis of deviance results showing effects of light and banding treatments on rooting probability of Lindera benzoin stem cuttings.
Within the light-grown treatment group, there were a number of significant differences in rooting probability based on banding treatment, as revealed by a pairwise comparison of least-squares means. Light-grown cuttings that received a band with 3000 mg·kg−1 IBA (Hormodin® 2) or 8000 mg·kg−1 IBA (Hormodin® 3) had a significantly higher probability of rooting than those receiving a band with no IBA. Also in the light group, cuttings treated with a band with 8000 mg·kg−1 IBA had a significantly higher probability of rooting than cuttings that did not receive a band. Additionally, the difference between cuttings treated with a band with 3000 mg·kg−1 IBA vs. unbanded cuttings was nearly significant at P = 0.051 (Table 4).
Pairwise contrasts of rooting probability of Lindera benzoin stem cuttings by band treatment within light, shade, and etiolation light treatment groups.
In the etiolated and shade groups, there were no significant differences in rooting probability by banding treatment. This is reflective of the observed data, in which cuttings in these light groups displayed similar rooting percentages across all banding treatments (87% to 96% among etiolated cuttings and 62% to 89% among shade-grown cuttings).
A summary of the modeled probability of rooting by light and banding treatment is displayed in Fig. 2. Overall, etiolated cuttings treated with a band without IBA had the highest predicted probability of rooting at 96%, whereas the lowest probability was in light-grown cuttings treated with a band without IBA (43%).
Predicted probability of rooting of Lindera benzoin stem cuttings by light and band treatment based on logistic regression model. H2 refers to 3000 mg·kg−1 indole-3-butyric acid (IBA) (Hormodin® 2), and H3 refers to 8000 mg·kg−1 IBA (Hormodin® 3). Error bars represent calculated standard error. Within each light level, different letters represent significant differences in predicted mean rooting probability (P ≤ 0.05, Z-tests with Tukey adjustment for comparison of multiple means).
Citation: HortScience 58, 5; 10.21273/HORTSCI17022-22
Number of roots.
Across all treatment groups, cuttings yielded a mean of 18 roots per cutting. However, there were notable differences across treatments: Plants that were grown under black cloth, shade, and light yielded a mean of 39, 16, and 11 roots per cutting respectively across all banding treatments. See Fig. 3 for photos of rooting in light-grown vs. etiolated cuttings. The highest mean number of roots per cutting was observed in etiolated cuttings treated with a band without IBA (50 roots), whereas the lowest number was seen in light-grown cuttings with no banding treatment (six roots) (Table 5).
Images of successfully rooted Lindera benzoin cuttings 7 weeks post-treatment under intermittent mist. (A) Cutting received etiolation and a band without indole-3-butyric acid (IBA). (B) Cutting received light and a band without IBA.
Citation: HortScience 58, 5; 10.21273/HORTSCI17022-22
Observed average number of roots per stem cutting of Lindera benzoin seven weeks posttreatment under intermittent mist.
Light and band treatment were found to have a significant effect on number of roots per cutting at P < 0.001. The interaction between light and band treatment was also significant at P = 0.019 (Table 6). Shade and etiolation treatments were shown to have a significant positive effect on the number of roots per cutting, compared with light-grown plants. Additionally, band treatments with 3000 mg·kg−1 IBA (Hormodin® 2) and 8000 mg·kg−1 IBA (Hormodin® 3) had a significant positive effect on number of roots per cutting, relative to shoots that received no banding. Figure 4 displays the estimated number of roots per cutting by light and banding treatment based on the Quasi-Poisson regression model.
Predicted number of roots per Lindera benzoin cutting by light and band treatment based on Quasi-Poisson regression model. H2 refers to 3000 mg·kg−1 indole-3-butyric acid (IBA) (Hormodin® 2), and H3 refers to 8000 mg·kg−1 IBA (Hormodin® 3). Error bars represent calculated standard error. Within each light level, different letters represent significant differences in predicted mean number of roots per cutting (P ≤ 0.05, Z-tests with Tukey adjustment for comparison of multiple means).
Citation: HortScience 58, 5; 10.21273/HORTSCI17022-22
Analysis of deviance results showing effects of light and banding treatments on number of roots per Lindera benzoin cutting.
Additionally, pairwise contrasts of least-squares means showed that within a given light treatment, there were significant differences in the number of roots per cutting by banding treatment (Table 7). For shade-grown stock plants, cuttings treated with bands plus 3000 mg·kg−1 IBA (Hormodin® 2) or 8000 mg·kg−1 IBA (Hormodin® 3) had twice the predicted number of roots than cuttings treated with a band without IBA (P = 0.033 and 0.045, respectively). In the light group, banding plus 8000 mg·kg−1 IBA was associated with an increase in roots compared with no banding (P = 0.019). Banding plus 3000 mg·kg−1 IBA also had higher predicted root numbers compared with no banding, though not significant at P = 0.066. Among etiolated plants, cuttings treated with a band without IBA had significantly more roots than cuttings that were not banded (P = 0.050).
Pairwise contrasts of number roots per Lindera benzoin stem cutting by band treatment within light, shade, and etiolation light treatment groups.
Discussion
Etiolation led to the highest rooting probability and average number of roots per cutting, followed by shade and light treatments. The general correlation between the degree of stock plant shading and the increased rooting of cuttings has been observed in numerous difficult-to-root taxa, such as creeping juniper ‘Andorra’ (Hansen 1997), European hornbeam ‘Fastigiata’ (Maynard and Bassuk 1992), and azalea cultivars (Apine et al. 2013). Of particular note in this experiment is the fact that among cuttings from etiolated stock plants, there were no significant differences in rooting probability by banding treatment (Fig. 2). In the observed data, even unbanded cuttings rooted as consistently as cuttings that received bands with and without IBA (87% to 96% of cuttings rooted across all banding treatments) (Table 2). This outcome differed from previous L. benzoin propagation research in which only 33% of etiolated stem cuttings that did not receive a band rooted during a 3-week period under mist (Lenze 2020). Cuttings in the present experiment were left to root for 7 weeks, suggesting that although adventitious root formation may be delayed among unbanded etiolated cuttings, with adequate time, etiolation alone may still promote increased rooting in this species.
As for the number of roots per etiolated cutting, banding without IBA led to the highest average (50 roots), but there were no significant differences in root numbers between these cuttings and cuttings receiving bands with 3000 or 8000 mg·kg−1 IBA (Table 7). Additionally, although unbanded etiolated cuttings yielded significantly fewer roots than cuttings receiving a band without IBA (Fig. 2), they still produced more roots than light- and shade-grown cuttings across all banding treatments (Table 5). Considering these results, etiolation without banding or etiolation with a band without IBA are appropriate methods of propagating L. benzoin with relatively low effort. These techniques save the step of dipping bands in talc-based IBA (Hormodin®) while still resulting in high rates of well-rooted cuttings, an effect also observed in Saskatoon serviceberry ‘Pembina’ (Nelson 1987) and Norway maple (Acer platanoides L.) (Tomov 2017).
When growing L. benzoin stock plants under sun or a shadecloth, the importance of banding and IBA application for the promotion of adventitious rooting increases. For instance, in shade-grown cuttings, although band treatment did not significantly affect rooting probability (Fig. 2), banding with 3000 or 8000 mg·kg−1 IBA increased the average number of roots per cutting to 21 and 20 roots per cutting, respectively, compared with nine roots in cuttings receiving a band without IBA (Table 5). In light-grown stock plants, unbanded cuttings had a 48% rooting probability and six roots per cutting. Banding with 8000 mg·kg−1 IBA significantly increased both the predicted rooting probability to 77% and number of roots per cutting to 15 (Fig. 2, Table 5).
Although the combination of partial stock plant shading and shoot banding has not been extensively studied, shading in general has been shown to have favorable effects on the rooting of cuttings of many woody plants (Pacholczak et al. 2017; Hansen 1997; Maynard and Bassuk 1992). It is also well established that among light-grown stock plants, banding with or without IBA can improve the rooting response of cuttings from many taxa (Maynard and Bassuk 1987; Richer et al. 2004; Tomov 2017; Wu et al. 2006). However, studies of kola nut (Cola anomola K. Schum) have provided evidence that stock plants grown under increased irradiance have a reduced sensitivity to IBA and therefore need higher concentrations to produce a favorable rooting response (Kanmegne et al. 2017). This would seem consistent with the findings of this experiment, wherein cuttings from stock plants grown under higher irradiance (full sun and 50% shade) required a higher concentration of IBA on the bands to produce a favorable rooting response, compared with cuttings from etiolated stock plants.
These results provide evidence that it is possible to substantially increase the rooting percentage and number of roots per cutting of Lindera benzoin using etiolation, shading, and banding techniques. In particular, etiolation without banding and etiolation combined with a band without IBA promote the greatest rooting response in cuttings with relatively little effort. However, among shade- and light-grown cuttings, banding and IBA treatments can also significantly increase rooting, so commercial growers can determine the optimal propagation method for L. benzoin based on their facilities, budgets, and labor constraints.
Improved understanding of asexual propagation techniques will allow the horticulture industry to make more clonal selections for desirable ornamental traits and bring L. benzoin and other underused woody plants to a wider market. The propagation methods implemented in this experiment have been widely used across numerous genera and species (Pijut et al. 2011) and further investigations should be undertaken to study their effectiveness in new taxa.
References Cited
Amissah, JN & Bassuk, NL 2009 Cutting back stock plants promotes adventitious rooting of stems of Quercus bicolor and Quercus macrocarpa J Environ Hortic. 27 3 159 165 https://doi.org/10.24266/0738-2898-27.3.159
Apine, I, Freidenfelds, K, Megre, D, Dokane, K & Kondratovics, U 2013 The effect of stock plant etiolation on rooting and overwinter survival of deciduous azalea cuttings Acta Hortic. 990 465 472 https://doi.org/10.17660/ActaHortic.2013.990.60
Bassuk, NL, Maynard, BK & Creedon, J 1986 Stockplant etiolation and banding for softwood cutting propagation: Working towards commercial application Combined Proc Int Plant Propagators’ Soc. 36 599 602
Behrens, V 1988 Influence of light intensity on the propagation success of Acer palmatum ‘Atropurpureum’ propagated by cuttings Acta Hortic. 226 321 326 https://doi.org/10.17660/ActaHortic.1988.226.39
Beyl, CA 2008 Juvenility and its effect on macro- and micropropagation 151 156 Beyl, CA & Trigiano, RN Plant propagation concepts and laboratory exercises. CRC Press Boca Raton, FL, USA
Bisognin, DA, Lencina, KH, da Luz, LV, Fleig, FD & Gazzana, D 2018 Adventitious rooting competence and rescue of adult mate plants by cuttings Rev Arvore. 42 3 https://doi.org/10.1590/1806-90882018000300012
Delargy, JA & Wright, CE 1979 Root formation in cuttings of apple in relation to auxin application and to etiolation New Phytol. 82 2 341 347 https://doi.org/10.1111/j.1469-8137.1979.tb02659.x
Dirr, MA 2009 Manual of woody landscape plants: Their identification, ornamental characteristics, culture, propagation and uses 6th ed. Stipes Publishing LLC Champaign, IL, USA
Dirr, MA & Heuser, CW 2006 The reference manual of woody plant propagation: From seed to tissue culture 2nd ed. Timber Press Portland, OR, USA
Fishel, DW, Zaczek, JJ & Preece, JE 2003 Positional influence on rooting of shoots forced from the main bole of swamp white oak and northern red oak Can J Res. 33 4 705 711 https://doi.org/10.1139/x02-201
Gulen, H, Eris, A & Erbil, Y 2004 Improved rooting of Gisela-5 softwood cuttings following banding and IBA application HortScience. 39 6 1403 1405 https://doi.org/10.21273/hortsci.39.6.1403
Hansen, OB 1997 Improved rooting in woody species by reducing stock plant irradiance Combined Proc Int Plant Propagators’ Soc. 47 368 373
Hawver, G & Bassuk, NL 2000 Improved adventitious rooting in Quercus through the use of a modified stoolbed technique Combined Proc Int Plant Propagators’ Soc. 50 307 313
Herman, DE & Hess, CE 1963 The effect of etiolation upon the rooting of cuttings Combined Proc Int Plant Propagators’ Soc. 13 42 62
Husen, A 2008 Stock-plant etiolation causes drifts in total soluble sugars and anthraquinones, and promotes adventitious root formation in teak (Tectona grandis L. f.) coppice shoots Plant Growth Regulat. 54 13 21 https://doi.org/10.1007/s10725-007-9222-y
Husen, A 2011 Rejuvenation and adventitious rooting in coppice-shoot cuttings of Tectona grandis; as affected by stock-plant etiolation Am J Plant Sci. 02 03 370 374 https://doi.org/10.4236/ajps.2011.23042
Kanmegne, G, Mbouobda, HD, Fotso, Kamtat, GF & Omokolo, DN 2017 Interaction of stockplants shading and exogenous auxin on the propagation of Cola anomala K. Schum (Malvaceae) by cuttings S Afr J Bot. 112 246 252 https://doi.org/10.1016/j.sajb.2017.06.005
Klopotek, Y, Haensch, K-T, Hause, B, Hajirezaei, M-R & Druege, U 2010 Dark exposure of petunia cuttings strongly improves adventitious root formation and enhances carbohydrate availability during rooting in the light J Plant Physiol. 167 7 547 554 https://doi.org/10.1016/j.jplph.2009.11.008
Lenth, RV 2022 emmeans: Estimated Marginal Means, aka Least-Squares Means R package version 1.7.5. https://CRAN.R-project.org/package=emmeans
Lenze, BL 2020 Effects of light with banding and layering techniques on rooting difficult-to-root woody species (MPS project report) Cornell University Ithaca, NY, USA
Maynard, BK & Bassuk, N 1985 Etiolation as a tool for rooting cuttings of difficult-to-root woody plants Combined Proc Int Plant Propagators’ Soc. 35 488 495
Maynard, BK & Bassuk, NL 1987 Stockplant etiolation and blanching of woody plants prior to cutting propagation J Am Soc Hortic Sci. 112 2 273 276 https://doi.org/10.21273/jashs.112.2.273
Maynard, BK & Bassuk, NL 1992 Stock plant etiolation, shading, and banding effects on cutting propagation of Carpinus betulus J Am Soc Hortic Sci. 117 5 740 744 https://doi.org/0.21273/JASHS.117.5.740
Maynard, BK & Bassuk, NL 1996 Effects of stock plant etiolation, shading, banding, and shoot development on histology and cutting propagation of Carpinus betulus L. fastigiata J Am Soc Hortic Sci. 121 5 853 860 https://doi.org/10.21273/JASHS.121.5.853
Nelson, SH 1987 Effects of stock plant etiolation on the rooting of saskatoon berry (Amelanchier alnifolia Nutt.) cuttings Can J Plant Sci. 67 1 299 303 https://doi.org/10.4141/cjps87-043
Pacholczak, A, Jędrzejuk, A & Sobczak, M 2017 Shading and natural rooting biostimulator enhance potential for vegetative propagation of dogwood plants (Cornus alba L.) via stem cuttings S Afr J Bot. 109 34 41 https://doi.org/10.1016/j.sajb.2016.12.009
Pacholczak, A, Szydło, W & Łukaszewska, A 2005 The effect of etiolation and shading of stock plants on rhizogenesis in stem cuttings of Cotinus coggygria Acta Physiol Plant. 27 4 417 https://doi.org/10.1007/s11738-005-0046-y
Peer, KR & Greenwood, MS 2001 Maturation, topophysis and other factors in relation to rooting in Larix Tree Physiol. 21 4 267 272 https://doi.org/10.1093/treephys/21.4.267
Pijut, PM, Woeste, KE & Michler, CH 2011 Promotion of adventitious root formation of difficult-to-root hardwood tree species Janick, J Horticultural Reviews. Vol. 38 John Wiley & Sons 213 251
RStudio Team., PM, Woeste, KE & Michler, CH 2022 RStudio: Integrated Development for R RStudio, PBC Boston, MA, USA
Richards, MR & Rupp, LA 2012 Etiolation improves rooting of bigtooth maple cuttings HortTechnology. 22 3 305 310 https://doi.org/10.21273/HORTTECH.22.3.305
Richer, C, Rioux, JA, Tousignant, D & Brassard, N 2004 Improving vegetative propagation of sugar maple (Acer saccharum Marsh.) Acta Hortic. 630 167 175 https://doi.org/10.17660/ActaHortic.2004.630.20
Sun, WQ & Bassuk, NL 1991 Effects of banding and IBA on rooting and budbreak in cuttings of apple rootstock “MM.106” and Franklinia J Environ Hortic. 9 1 40 43 https://doi.org/10.24266/0738-2898-9.1.40
Tomov, V 2017 Rooting of Norway maple (Acer platanoides L.) cuttings For Ideas. 23 1 57 64
Wendling, I, Warburton, PM & Trueman, SJ 2015 Maturation in Corymbia torelliana × C. citriodora stock plants: Effects of pruning height on shoot production, adventitious rooting capacity, stem anatomy, and auxin and abscisic acid concentrations Forests. 6 10 3763 3778 https://doi.org/10.3390/f6103763
Wu, HC, du Toit, ES & Reinhardt, CF 2006 Etiolation aids rooting of Protea cynaroides cuttings S Afr J Plant Soil. 23 4 316 317 https://doi.org/10.1080/02571862.2006.10634772
