Annual bedding plants are the largest (45%) segment of the U.S. commercial floriculture industry with a reported wholesale value of $1.76 billion in 2007 (U.S. Department of Agriculture, 2008). In the past decade, annual and perennial crops have increasingly been propagated by shoot-tip cuttings; in 2006, U.S. greenhouse growers imported 878 million nonrooted cuttings of annuals and perennials with a reported wholesale value of U.S. $61 million (U.S. Department of Agriculture, 2007). In the United States, cuttings of bedding plants are typically received from offshore production facilities and propagated in greenhouses from December to March for sales to consumers in spring and early summer. During propagation, the integrated photosynthetic photon flux (PPF) [daily light integral (DLI)] outdoors can range from 5 to 20 mol·m−2·d−1 across the northern half of the United States (Korczynski et al., 2002). In greenhouses, light levels can be 50% or less of that outdoors because of structures, glazing, shading, and obstructions (Hanan, 1998). Therefore, the DLI during propagation can be as low as 1 to 5 mol·m−2·d−1 and even lower during extended periods of cloudy weather.
Vegetative cuttings require a minimum quantity of photosynthetic light to provide a supply of carbohydrates for callus and adventitious root initiation and development (Haissig, 1986; Veierskov, 1988). Light intensities below this minimum can delay root growth and development, leading to an extended rooting period and increased probability of rooting failure. Adventitious root formation and growth were influenced by the PPF and photosynthesis during propagation of pea (Pisum sativum L.) (Davis and Potter, 1981), geranium (Pelargonium ×hortorum L.H. Bail.) (Rapaka et al., 2005) and rose (Rosa ×hybrida L.) cuttings (Costa and Challa, 2002). However, rooting of geranium was also positively correlated with the preharvest leaf sucrose concentration when propagation PPF was low (Druege et al., 2004) such as less than 100 μmol·m−2·s−1 (Rapaka et al., 2005). Conversely, stomatal closure, reduced turgor, and lower osmotic potential (ψS) from excessive light can inhibit root formation because of water and temperature stress and photoinhibition (Eliasson and Brunes, 1980; Enfield, 2002; Grange and Loach, 1985).
Numerous studies have been performed to understand the effects of DLI or light intensity on propagation of seedlings, cuttings, or microshoots. These studies have species-specific results and primarily focused on either shoot growth (e.g., stem elongation and shoot biomass) or rhizosphere growth (e.g., rooting percentage, root number, and biomass) and subsequent flowering in herbaceous and woody species. In herbaceous cuttings and seedlings such as celosia (Celosia argentea L.), seed impatiens (Impatiens wallerana Hook. f.), salvia (Salvia splendens Sell ex Roem. & Schult.), marigold (Tagetes patula L.), pansy (Viola ×wittrockiana Gams.) (Pramuk and Runkle, 2005a), baby's breath (Gypsophila paniculata L.) (Islam and Willumsen, 2001), petunia (Cabaleiro and Economou, 1992), and phlox (Phlox paniculata L.) (Enfield, 2002), rooting and shoot biomass and quality generally increased with increasing DLI or light intensity. For example, rooting percentage and dry weight of baby's breath cuttings were greater after 3 weeks in a propagation greenhouse when plants were provided with a DLI of 12 mol·m−2·d−1 compared with 7 mol·m−2·d−1 (Islam and Willumsen, 2001). In addition, cuttings propagated under a DLI of 12 mol·m−2·d−1 subsequently flowered 14 d earlier than cuttings propagated under a DLI of 7 mol·m−2·d−1.
To our knowledge, no studies have been published on the effects of DLI after 8 to 16 d of propagation on shoot and root biomass accumulation and the effects on subsequent development of vegetatively propagated bedding crops. Petunia (Petunia ×hybrida hort. Vilm.-Andr.) and New Guinea impatiens (Impatiens hawkeri Bull.) are two of the most valuable annual bedding crops commonly propagated from cuttings (U.S. Department of Agriculture, 2008). The objective of this study was to quantify the effects of DLI during propagation on rooting, growth, and quality (cutting height and biomass accumulation) of each species during the rooting stage and to determine whether there were any residual effects of DLI on subsequent growth and development after transplant. In addition, three cultivars of each species were chosen to determine the responses to DLI within a species.
Behrens, V. 1988 Influence of light intensity on the propagation success of Acer palmatum ‘Atropurpureum’ propagated by cuttings Acta Hort. 226 321 326
Costa, J.M. & Challa, H. 2002 The effect of the original leaf area on growth of softwood cuttings and planting material of rose Scientia Hort. 95 111 121
Davis, T.D. & Potter, J.R. 1981 Current photosynthate as a limiting factor in adventitious root formation on leafy pea cuttings J. Amer. Soc. Hort. Sci. 106 278 282
Dole, J.M. & Hamrick, D.J. 2006 Propagation basics 3 16 Dole J. & Gibson J. Cutting propagation: A guide to propagating and producing floriculture crops Ball Publishing Batavia, IL
Druege, U. , Zerche, S. & Kadner, R. 2004 Nitrogen- and storage-affected carbohydrate partitioning in high-light adapted Pelargonium cuttings in relation to survival and adventitious root formation under low light Ann. Bot. (Lond.) 94 831 842
Enfield, A.L. 2002 Flower induction and cultural requirements for quick-cropping of the herbaceous perennials Veronica spicata, Phlox paniculata, Leucanthemum ×superbum, Achillea, Gaura lindheimeri, and Campanula Dept. of Horticulture, Michigan State Univ East Lansing MS Thesis.
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Enfield, A.L. 2002 Flower induction and cultural requirements for quick-cropping of the herbaceous perennials Veronica spicata, Phlox paniculata, Leucanthemum× superbum, Achillea, Gaura lindheimeri, and Campanula Dept. of Horticulture, Michigan State Univ East Lansing MS Thesis.
Erwin, J. , Mattson, N. & Warner, R. 2004 Light effects on annual bedding plants 62 71 Fisher P. & Runkle E. Lighting up profits: Understanding greenhouse lighting Meister Media Worldwide Willoughby, OH
Haissig, B.E. 1986 Metabolic processes in adventitious rooting of cuttings 141 189 Jackson M.B. New root formation in plants and cuttings Martinus Nijhoff Publishers Dordrecht, The Netherlands
Islam, N. & Willumsen, K. 2001 Effects of photoperiod and daily light integral on rooting, subsequent growth, flowering and yield of flowering stems in Gypsophila paniculata L. ‘Perfecta’ Gartenbauwissenschaft 66 225 228
Korczynski, P.C. , Logan, J. & Faust, J.E. 2002 Mapping monthly distribution of daily light integrals across the contiguous United States HortTechnology 12 12 16
Lopez, R.G. 2007 Stock plant and propagation photosynthetic daily light integral and storage influences postharvest performance of herbaceous cuttings Dept. of Horticulture, Michigan State Univ East Lansing PhD Diss.
Pramuk, L.A. & Runkle, E.S. 2005a Photosynthetic daily light integral during the seedling stage influences subsequent growth and flowering of Celosia, Impatiens, Salvia, Tagetes, and Viola HortScience 40 1336 1339
Pramuk, L.A. & Runkle, E.S. 2005b Modeling growth and development of Celosia and Impatiens in response to temperature and photosynthetic daily light integral J. Amer. Soc. Hort. Sci. 130 813 818
Rapaka, V.K. , Bessler, B. , Schreiner, M. & Druge, U. 2005 Interplay between initial carbohydrate availability, current photosynthesis, and adventitious root formation in Pelargonium cuttings Plant Sci. 168 1547 1560
U.S. Dept. of Agriculture 2007 Floriculture and nursery crops yearbook: Report Econ. Res. Service Washington, DC 27 June 2008 <http://usda.mannlib.cornell.edu/usda/ers/FLO-yearbook//2000s/2007/FLO-yearbook-10-04-2007.pdf>.
U.S. Dept. of Agriculture 2008 Floriculture crops 2007 summary Nat. Agr. Sta. Service Washington, DC 27 June 2008 <http://usda.mannlib.cornell.edu/usda/current/FlorCrop/FlorCrop-04-24-2008.pdf>.
Veierskov, B. 1988 Relations between carbohydrates and adventitious root formation 70 78 Davis T.D. , Haissig B.E. & Sankhla N. Adventitious root formation in cuttings Dioscorides Press Portland, OR
Yuan, M. , Carlson, W.H. , Heins, R.D. & Cameron, A.C. 1998 Effect of forcing temperature on Coreopsis grandiflora, Gaillardia ×grandiflora, Leucanthemum ×superbum, and Rudbeckia fulgida HortScience 33 663 667