Propagation Daily Light Integral and Root-Zone Temperature Influence Rooting of Single-internode Pennisetum ×advena Culm Cuttings

The objectives were to characterize and compare shrinkage (i.e., transplant loss) and growth of tissue-cultured blueberry (Vaccinium corymbosum) transplants acclimated in greenhouses or indoors under 1) different photosynthetic photon flux densities (PPFDs) (Expt. 1); or 2) spectral changes over time using broad-spectrum white (W; 400 to 700 nm) light-emitting diodes (LEDs) without or with red or far-red (FR) radiation (Expt. 2). In Expt. 1, ‘Emerald’ and ‘Snowchaser’ transplants were acclimated for 8 weeks under PPFDs of 35, 70, 105, or 140 ± 5 µmol·m‒2·s‒1 provided by W LED fixtures for 20 h·d−1. In another treatment, PPFD was increased over time by moving transplants from treatment compartments providing 70 to 140 µmol·m‒2·s‒1 at the end of week 4. Transplants were also acclimated in either a research or a commercial greenhouse (RGH or CGH, respectively). Shrinkage was unaffected by PPFD, but all transplants acclimated indoors had lower shrinkage (≤4%) than those in the greenhouse (15% and 17% in RGH and CGH, respectively), and generally produced more shoot and root biomass, regardless of PPFD. Growth responses to increasing PPFD were linear in most cases, although treatment effects after finishing were generally not significant among PPFD treatments. In Expt. 2, ‘Emerald’ transplants were acclimated for 8 weeks under constant W, W + red (WR), or W + FR (WFR) radiation, all of which provided a PPFD of 70 ± 2 μmol·m−2·s−1 for 20 h·d−1. At the end of week 4, a group of transplants from WR and WFR were moved to treatment compartments with W (WRW or WFRW, respectively) or from W to a research greenhouse (WGH), where another group of transplants were also acclimated for 8 weeks (GH). Shrinkage of transplants acclimated indoors was also low in Expt. 2, ranging from 1% to 4%. In contrast, shrinkage of transplants acclimated in GH or under WGH was 37% or 14%, respectively. Growth of indoor-acclimated transplants was generally greater than that in GH or under WGH. Although growth responses were generally similar indoors, plants acclimated under WFR had a higher root dry mass (DM) and longer roots compared with GH and WGH.

Section: Discussionsupporting

confidence: 90%

Radiation Intensity and Quality Affect Indoor Acclimation of Blueberry Transplants

Gómez

Poudel

Yegros

et al. 2021

“…Wilkerson et al (2005) suggested that the poinsettia rooting percentage is greatest when root zones are 27 to 29°C, and declines at higher or lower temperatures. Owen and Lopez (2018) showed that both root-zone temperature and light impact rooting percentage of purple fountain grass (Pennisetum •advena). At a low DLI (4-10 mol • m -2 • d -1 ), increasing temperature increased rooting percentage, whereas at a higher DLI (8-16 mol • m -2 • d -1 ), rooting percentage increased up to an optimum temperature of 23°C and then declined (Owen and Lopez, 2018).…”

Section: Resultsmentioning

confidence: 99%

“…Owen and Lopez (2018) showed that both root-zone temperature and light impact rooting percentage of purple fountain grass (Pennisetum •advena). At a low DLI (4-10 mol • m -2 • d -1 ), increasing temperature increased rooting percentage, whereas at a higher DLI (8-16 mol • m -2 • d -1 ), rooting percentage increased up to an optimum temperature of 23°C and then declined (Owen and Lopez, 2018). Greater root-zone temperatures in submist and combination systems might, in part, account for their increased quality of root systems relative to overhead mist, but lower aerial temperatures in combination systems might, in turn, account for the increased rooting percentage in combination systems relative to submist alone.…”

Section: Resultsmentioning

confidence: 99%

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

Sanchez¹,

Burnett²,

Peterson³

2020

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.

“…Enfield et al (2003) reported that garden phlox (Phlox paniculata) cuttings required at least 3.5 mol • m -2 • d -1 for rapid, uniform rooting. Owen and Lopez (2018) propagated fountain grass (Pennisetum •advena) culm cuttings at DLIs from 4 to 16 mol • m -2 • d -1 and reported that the most efficient rooting occurred at 8-10 mol • m -2 • d -1 , whereas the highest DLI (16 mol • m -2 • d -1 ) had lower culm and root density. Currey et al (2012) examined the effect of DLI after callus formation on the cuttings of nine annual species.…”

Section: Discussionmentioning

confidence: 99%

Daily Light Integral: A Research Review and High-resolution Maps of the United States

Faust

Logan

2018

The National Renewable Energy Laboratory developed the National Solar Radiation Database to provide accessible solar radiation data to the research community for various uses. Previously, we created a series of monthly daily light integral (DLI) maps to provide a tool for horticulturists to estimate the potential growth and flowering responses for various plants throughout the year. The original DLI maps were based on solar radiation data from 239 sites recorded from 1961 to 1990. The DLI maps presented in this article were created from an updated database that included data from 1998 to 2009. This database provides higher resolution data modeled from satellite images of cloud cover. The data are presented in pixels with each pixel representing 100 km2 of land across the lower 48 United States and Hawaii, whereas the Alaska data are 1600 km2 pixels. The database provided global horizontal irradiance data that were converted to DLI (mol·m−2·d−1) using the conversion factor of 0.007265 mol (400–700 nm)·Wh−1 (400–2700 nm), which assumes that 45% of the solar radiation is in the photosynthetically active radiation (PAR, 400–700 nm) region and 4.48 μmol·J−1 is the conversion from radiometric to quantum units. The updated DLI maps provide more geographically precise data reflecting recent weather patterns. We present a comprehensive review of recent research exploring the growth and flowering responses of horticultural crops to DLI.