Papaya (Carica papaya L.) is grown throughout the equatorial regions of the world (Crane, 2008; Morton, 1987; Nakasone and Paull, 1998), and the species is an important horticultural crop on Guam and other nearby islands. Many of the regions where papaya is grown experience chronic trade winds, and quality of papaya is improved by wind protection during orchard development (Davey, 1958). Under Guam's conditions, wind protection improves absolute growth and increases leaf photosynthesis in young papaya plants (Clemente and Marler, 2001).
Biomechanical properties of plants improve as a result of exposure to non-catastrophic wind (Cullen, 2002; de Langre, 2008; Niklas, 1998; Schaetzl et al., 1989). Therefore, reduced absolute growth interplays with improved structural strength when plants are exposed to wind. The relative benefits of improved biomechanical properties may depend on stresses imposed after moderate wind exposure. For the regions in the northwestern Pacific Ocean, tropical cyclones are dominant forces in shaping agricultural, natural, and urban landscapes (Marler, 2001). As a result, allowing trade winds to impact a papaya orchard during establishment may decrease the extent of damage in the event of a subsequent tropical cyclone.
Phenotypic plasticity is an important means by which plants cope with environmental heterogeneity; therefore, understanding variation in plant traits is important to predict responses to variable environments. More detailed studies on crop responses to wind may improve management decisions (e.g., Koizumi et al., 2008). Consequently, a series of experiments was conducted on young papaya plants to determine the influence of ambient wind exposure on rapid leaf, stem, and root growth responses and a second set of experiments to determine the degree of asymmetry of rapid root and stem responses to wind direction. Root physiology, morphology, and development are under genetic control (Zobel, 1975), so two cultivars derived from separate breeding programs were included in each experiment. Objectives were to compare the rapidity and extent of plasticity of growth under ambient wind exposure among papaya leaves, stems, and roots to more fully understand how these responses are coordinated among these various organs. This information may improve management decisions for establishing an orchard in windy environments, inform approaches for long-term field experimental design, and improve general understanding of biomechanical properties of this giant herb.
Berthier, S. & Stokes, A. 2005 Phototropic response induced by wind loading in maritime pine seedlings (Pinus pinaster Ait.) J. Expt. Bot. 56 851 856
Clemente, H.S. & Marler, T.E. 2001 Trade winds reduce growth and influence gas exchange patterns in papaya seedlings Ann. Bot. (Lond.) 88 379 385
Crane, J.H. 2008 Papaya growing in the Florida home landscape. Univ. of Florida IFAS Fact Sheet HS-11
Fisher, J.B. & Mueller, R.J. 1983 Reaction anatomy and reorientation in leaning stems of balsa (Ochroma) and papaya (Carica) Can. J. Bot. 61 880 887
Friend, A.L., Coleman, M.D. & Bebrands, J.G. 1994 Carbon allocation to root and shoot systems of woody plants 245 273 Davis T.D. & Haissig B.E. Biology of adventitious root formation Plenum Press New York, NY
Givnish, T.J. 1995 Plant stems: Biomechanical adaptation for energy capture and influence on species distributions 3 49 Gartner B.L. Plant stems Academic Press New York, NY
Kaufman, P.B., Carlson, T.F., Dayanandan, P., Evans, M.L., Fisher, J.B., Parks, C. & Wells, J.R. 1989 Plants—Their biology and importance Harper and Row New York, NY
Nicoll, B.C. & Ray, D. 1996 Adaptive growth of tree root systems in response to wind action and soil conditions Tree Physiol. 16 891 898
Retuerto, R. & Woodward, F.I. 1993 The influences of increased CO2 and water supply on growth, biomass allocation and water use efficiency of Sinapis alba L. grown under different wind speeds Oecologia 94 415 427
Russell, R.S. 1977 Relationship between roots and shoots 9 27 Wilkins M.B. Plant root systems: Their function and interaction of the soil McGraw-Hill London, UK
Schaetzl, R.J., Johnson, D.L., Burns, S.F. & Small, T.W. 1989 Tree uprooting: Review of terminology, process, and environmental implications Can. J. For. Res. 19 1 11
Sellier, D. & Fourcaud, T. 2005 A mechanical analysis of the relationship between free oscillations of Pinus pinaster Ait. Saplings and their aerial architecture J. Expt. Bot. 56 1563 1573
Smith, V.C. & Ennos, A.R. 2003 The effects of air flow and stem flexure on the mechanical and hydraulic properties of the stems of sunflowers Helianthus annuus L J. Expt. Bot. 54 845 849
Stokes, A., Salin, F., Kokutse, A.D., Berthier, S., Jeannin, H., Mochan, S., Kokutse, N., Dorren, L., Abd.Ghani, M. & Fourcaud, T. 2005 Mechanical resistance of different tree species to rockfall in the French Alps Plant Soil 278 107 117
Watkinson, A.R. & White, J. 1986 Some life-history consequences of modular construction in plants Philos. Trans. R. Soc. Lond. B Biol. Sci. 313 31 51
Zobel, R.W. 1975 The genetics of root development 261 275 Torrey J.G. & Clarkson D.T. The development and function of roots Academic Press New York, NY