The structure and quality of the adventitious root system formed on a microcutting stem is crucial to the successful acclimation, survival, and ultimate performance of micropropagated plants. Despite increasing evidence that the rooting method impacts on the character of the framework root system, very little research has elucidated the consequences of standard rooting methods on plant quality and performance. Root initiation on microcuttings is handled by a wide range of strategies in commercial practice. In comparison to in vitro roots, ex vitro roots have smaller root diameters, larger vascular diameters, greater length, more branch root development, and root hairs. One important microenvironmental parameter - light - was investigated to determine its contribution to root character. Typically, in vitro root systems are exposed to light throughout the root initiation period. Parallel treatments were established of in vitro light and dark rooting and ex vitro rooting of four woody species. Regardless of light exposure, the overall diameter of adventitious roots was larger for in vitro treatments than the ex vitro treatment. Vascular development was significantly more advanced ex vitro. These results suggest that light is not a major influence contributing to the differences between ex vitro and in vitro root character.
Renee Timmermann and M.A.L. Smith
Maria Papafotiou and Aekaterini N. Martini
ex vitro axillary buds ( Al-Qudah et al., 2011 ) and cryopreservation ( Rabba’a et al., 2012 ). It has also been reported that micropropagation of the ornamental medicinal Teucrium fruticans from shoot-tip explants ( Frabetti et al., 2009 ) and of
Carmen Valero Aracama*, Michael E. Kane, Nancy L. Philman, and Sandra B. Wilson
A sea oats (Uniola paniculata L.) micropropagation protocol was previously developed for 28 genotypes that favored multiplication and rooting of shoots in vitro. However, microcutting size, morphology, and acclimatization ex vitro varied considerably among genotypes. In the present study we evaluated the effect of Stage III duration on in vitro morphology, biomass production, and ex vitro survivability of easy-(EK 16-3) and difficult-to-acclimatize (EK 11-1) sea oats genotypes. After 3, 6, and 9 weeks at Stage III, survivability of microcuttings was 85%, 96% and 98% for EK 16-3, and 2%, 27% and 40% for EK 11-1, respectively. After 9 weeks Stage III, EK 16-3 microcuttings had higher shoot dry weights but lower root dry weights than in EK 11-1. Moreover, roots in EK 11-1 were fewer but longer than in EK 16-3. Leaf production was similar in both genotypes. However, leaf elongation was significantly inhibited in EK 11-1, in which 95% of the leaves were ≤ 15 mm long in contrast with EK 16-3, with 50% leaves ≥ 16 mm long after 9 weeks Stage III. Light microscopy examinations showed anatomical similarities between EK 16-3 in vitro leaves and mature ex vitro leaves. Conversely, short in vitro leaves of EK 11-1 exhibited mesophyll disruption and reduced cuticle development. Conceivably, the short leaves had limited photosynthetic competency, thereby reducing ex vitro survival of rooted EK 11-1 microcuttings.
Jeffrey Adelberg, Maria Delgado, and Jeffrey Tomkins
total of 6 weeks ex vitro, survival and whole plant FW was determined. The experiment was a completely randomized design with four genotypes, two BA concentrations, two ANC concentrations, two sucrose concentrations, and two explant densities (4 × 2
Lauren E. Deans, Irene E. Palmer, Darren H. Touchell, and Thomas G. Ranney
), and H. serrata ‘MAK20’ ( C ) plants during their third ex vitro growing season. A comparison of floral characteristics showed that induced tetraploidy caused a significant decrease in inflorescence number for all cultivars ( P < 0.05), with an
Yulan Xiao and Toyoki Kozai
A photoautotrophic or sugar-free medium micropropagation system (PAM) using five large culture vessels (volume = 120 L each) with a forced ventilation unit for supplying CO2-enriched air was developed and applied to commercial production of calla lily (Zantedeschia elliottiana) and china fir (Cunninghamia lanceolata) plantlets. The culture period of calla lily plantlets in the PAM was reduced by 50%, compared with that in a conventional, photomixotrophic micropropagation system (PMM) using small vessels each containing a sugar-containing medium. Percent survival ex vitro of calla lily plantlets from the PAM was 95%, while that from the PMM was 60%. The production cost of calla lily in the PAM was reduced by about 40%, compared with that in the PMM, and the initial investment per plantlet for the PAM was ≈10% lower than that for the PMM. The sales price of ex vitro acclimatized calla lily plantlet was increased by 25% due to its higher quality, compared with plantlets produced in the PMM.
John L. Edson, David L. Wenny, and Annette Leege-Brusven
In vitro—derived microshoots of antelope bitterbrush, incubated for 1 month in media supplemented with 0.44 μm BA, grew 0.8 and 1.1 cm longer in woody plant medium (WPM) compared to full-strength and half-strength Murashige and Skoog (MS) media, respectively. Explants cultured in WPM supplemented with 0.44 μm BA and 0.54 μm NAA produced a mean of five axillary shoots per explant. Explants dipped in 0.1% IBA or 0.1% NAA rooted best in 0.1% IBA with 89% success ex vitro vs. 60% success in vitro. Survival of acclimatized plantlets rooted ex vitro was 95%, while 50% survived when rooted in vitro. After 1 year of greenhouse growth, 98% of plantlets survived and flowered. Chemical names used: benzyladenine (BA), 3-indolebutyric acid (IBA), 1-naphthaleneacetic acid (NAA).
Ribo Deng and Danielle J. Donnelly
Micropropagated `Festival' red raspberry (Rubus idaeus L.) shoots were rooted in specially constructed plexiglass chambers in ambient (340 ± 20 ppm) or enriched (1500 ±50 ppm) CO2 conditions on a medium containing 0, 10, 20, or 30 g sucrose/liter. Plantlet growth and leaf 14CO2 fixation rates were evaluated before and 4 weeks after ex vitro transplantation. In vitro CO2 enrichment promoted in vitro hardening; it increased root count and length, plantlet fresh weight, and photosynthetic capacity but did not affect other variables such as plantlet height, dry weight, or leaf count and area. No residual effects of in vitro CO2 enrichment were observed on 4-week-old transplants. Sucrose in the medium promoted plantlet growth but depressed photosynthesis and reduced in vitro hardening. Photoautotrophic plantlets were obtained on sucrose-free rooting medium under ambient and enriched CO2 conditions and they performed better ex vitro than mixotrophi plantlets grown with sucrose. Root hairs were more abundant and longer on root tips of photoautotrophic plantlets than on mixotrophic plantlets. The maximum CO2 uptake rate of plantlet leaves was 52% that of greenhouse control plant leaves. This did not change in the persistent leaves up to 4 weeks after ex vitro transplantation. The photosynthetic ability of persistent and new leaves of 4-week-old ex vitro transplants related neither to in vitro CO2 nor medium sucrose concentration. Consecutive new leaves of transplants took up more CO2 than persistent leaves. The third new leaf of transplants had photosynthetic rates up to 90% that of greenhouse control plant leaves. These results indicate that in vitro CO2 enrichment was beneficial to in vitro hardening and that sucrose may be reduced substantially or eliminated from red raspberry rooting medium when CO2 enrichment is used.
Suzanne M. Dethier Rogers and Sharon Banister
A micropropagation system was developed for micropropagation and rooting of Notholaena spp. Shoot cultures were initiated from mature sori on leaflets of the Notholaena cultivar Sun-Tuff and cultured on gelled Murashige and Skoog (MS) medium without hormones. Rooting and plant growth were evaluated on gelled MS, vermiculite moistened with liquid MS, or vermiculite moistened with water. Vermiculite wetted with MS was superior in promoting frond and root development. High humidity was not needed to acclimatize the plants ex vitro.
Jeffrey Adelberg, Kazuhiro Fujiwara, Chalermpol Kirdmanee, and Toyoki Kozai
Two triploid clones of melon from the same tetraploid parent were grown in vitro with and without sugar, rooted without sugar in media both in a laboratory controlled environment chamber (in vitro) and a greenhouse acclimatization unit (ex vitro), and compared for subsequent nursery growth in the greenhouse unit. The clone `(L-14 c B) × L-14' produced more shoots in both photomixotrophic (with sucrose) or photoautotrophic (sugar-free) conditions. Both genotypes were equally likely to root in sugar-free media, and `(L-14 × B) × L-14' rooted as well from either photoautotrophic and photomixotrophic shoots but `(L-14 × B) × Mainstream' rooted less frequently from photoautotrophic shoots. Seventy-six percent (76%) of the shoots were able to root photoautotrophically in vitro, whereas 47% of the ex vitro shoots were rooted. About 85% of plantlets from all treatments survived after transfer to the nursery. After growth in the greenhouse nursery, the sizes of plants (fresh and dry weight, leaf area) were the same for either clone, from either photoautotrophic or photomixotrophic shoots. Also, after growth in the nursery, plantlets that had been rooted in vitro were larger than those rooted ex vitro. Photoautotrophic rooting demonstrates a concept for integrating micropropagation and plug-type vegetable transplant production.