Promoting root induction and growth of in vitro macadamia (Macadamia tetraphylla L. ‘Keaau’) plantlets using CO2-enriched photoautotrophic conditions

Plant Cell Tissue and Organ Culture (Impact Factor: 2.13). 09/2011; 106(3):435-444. DOI: 10.1007/s11240-011-9940-8


In this study, a rooting protocol was developed for macadamia plantlets with healthy roots and enhanced growth performance,
along with enhanced photosynthetic capability. In vitro-grown shoots rooted in vented vessels containing vermiculite as the
supporting material exhibited 100% frequency of root induction, whereas when shoots were grown in non-vented vessels containing
a solidified Murashige and Skoog (MS) medium, the frequency of root induction was less than 30%. The formation of root with
callus, hyperhydricity, and leaf necrosis was observed in this photomixotrophic closed system. The modification of the vented
photoautotrophic system with different concentrations of CO2 and sucrose were investigated using vermiculite as the supporter. The number of roots, root length, root surface area, fresh
weight, and dry weight were significantly higher in plantlets grown in CO2-enriched (1,000μmolCO2mol−1) photoautotrophic conditions. The water content in both root and shoot tissues of plantlets cultured under photoautotrophic
conditions was maximized. In addition, shoot and leaf performances were enhanced in plantlets cultured under CO2-enriched photoautotrophic conditions. The supplementation of sucrose (29–88mM) to culture media in both ambient and elevated
CO2 conditions affected a reduction in the shoot and root performance of in vitro plantlets. Chlorophyll a, chlorophyll b, and
total carotenoids in the leaf tissues of plantlets acclimatized in CO2-enriched photoautotrophic conditions were enriched, leading to increasing photosynthetic abilities, including chlorophyll
fluorescence and net photosynthetic rate. From this investigation, a root induction protocol was established and the production
of healthy macadamia plantlets was successfully implemented using CO2-enriched photoautotrophic conditions.

KeywordsEnriched CO2
–Net photosynthetic rate–Photoautotrophic conditions–Sucrose–Water content–Vermiculite

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    • "Photoautotrophic in vitro propagation has been successfully applied to numerous species, including P. glomerata (Iarema et al. 2012), Macadamia tetraphylla (Cha-um et al. 2011), Oplopanax elatus (Park et al. 2011), Solanum tuberosum (Badr et al. 2011), Actinidia deliciosa (Arigita et al. 2010), Cymbidium Music Hour " Maria " (Norikane et al. 2010), Populus deltoids (Mingozzi et al. 2009), Phalaenopsis " Amaglade " (Yoon et al. 2009), Limonium latifolium (Xiao and Kozai 2006), Hypericum perforatum (Couceiro et al. 2006), and Spathiphyllum cv. Merry (Silva et al. 2006). "
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    ABSTRACT: The aim of the present study was to evaluate the effects of forced ventilation and CO2 enrichment (360 or 720 μmol mol−1 CO2) on the in vitro growth and development of Pfaffia glomerata, an endangered medicinal species, under photomixotrophic or photoautotrophic conditions. P. glomerata nodal segments showed substantial differences in growth, relative water content and water loss from leaves, photosynthetic pigments, stomatal density, and leaf anatomical characteristics under these different treatments. CO2 enrichment led to increased photosynthetic pigments and reduced stomatal density of in vitro cultivated P. glomerata. A lack of sucrose in the culture medium increased 20-hydroxyecdysone levels, but the increase in CO2 levels did not further elevate the accumulation of 20-hydroxyecdysone. All growth increased in a CO2-enriched atmosphere. In addition, CO2 enrichment, with or without sucrose, gave a lower relative water loss from leaves. This finding indicates that either a photoautotrophic or photomixotrophic system in a CO2-enriched atmosphere may be suitable for large-scale propagation of this species.
    Full-text · Article · Aug 2013 · In Vitro Cellular & Developmental Biology - Plant
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    • "Macadamia is grown extensively in commercial plantations in Australia, South Africa, Brazil, Hawaii, Kenya and Costa Rica, and most cultivars have been derived from selection programmes in Hawaii and Australia that identified superior-yielding seedling trees (Nagao and Hirae, 1992; Stephenson and Gallagher, 2000; Peace et al., 2003; Steiger et al., 2003; Hardner et al., 2009). These cultivars are propagated clonally by grafting onto seedling rootstocks, although tissue culture methods have been developed recently for macadamia seedlings (Cha-um et al., 2011). Orchards are typically comprised of two or more cultivars, often with a principal cultivar and the other cultivars planted in 'pollinator' rows. "
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    ABSTRACT: Macadamia is a widely-grown tree crop that produces edible kernels with high oil content. The macadamia kernel is the single embryo of the fruit, and so factors that influence fruit set and embryo development are critical regulators of yield and quality. This review summarises over 75 years of research on floral induction, floral structure, pollen transfer, the breeding system and fruit development of macadamia, highlighting features such as insect pollination and partial self-incompatibility that limit orchard productivity and affect kernel quality.
    Full-text · Article · Feb 2013 · Scientia Horticulturae
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    • "Typically, in vitro propagated plants show peculiar characteristics, such as poorly developed shoots, less epicuticular and cuticular wax, tissues with low mechanical strength, higher water content, non-functional stomata and small, thin leaves with fewer trichomes and low photoautotrophic activity (Kozai and Kubota 2001; Cha-um et al. 2011; Xiao et al. 2011). The high relative humidity and CO 2 concentration inside a jar (because of reduced gas exchange) may influence anatomical, physiological and morphological plant characteristics, and can result in great losses during acclimatization (Kitaya et al. 2005). "
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    ABSTRACT: Pfaffia glomerata (Spreng.) Pedersen is a medicinal species of great interest because it produces the phytoecdysteroid 20-hydroxyecdysone (20E). Generally, because of atypical growing conditions, in vitro propagated plants function less efficiently as autotrophs and have poorly developed morphological structures. This study analyzed the autotrophic potential of P. glomerata propa-gated in vitro and evaluated the influence that this has on 20E biosynthesis. Physiological and structural parameters of plants subjected to heterotrophic, photomixotrophic and photoautotrophic growth conditions were evaluated. Levels of 20E were measured by HPLC. Plants were acclimatized in a mixture of soil, sand and substrate, in a greenhouse. Conditions that provided higher carbon input led to an increase in plant growth, and the presence of sucrose was critical, in closure systems without a gas permeable membrane, for normal anatomical development of the micropropagated plants. The absence of sucrose increased photosynthesis and conditions that enhanced photoauto-trophy induced greater levels of 20E. The increase of 20E levels by the photoautotrophic system offers new prospects for increasing the commercial production of this species, and for studies that could elucidate the biosynthetic path-way of phytoecdysteroids in plants.
    Full-text · Article · Aug 2012 · Plant Cell Tissue and Organ Culture
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