Potassium plays a key role in plant growth and physiology, specifically in the activation of enzymes, stomata regulation, plant water relations, and mobility of ions and other solutes within the plant (Mengel and Kirkby, 2001). Potassium deficiency affects primary and secondary metabolism (Armengaud et al., 2009), leading to increased susceptibility to pest and disease (Amtmann et al., 2008), leaf edge scorching, and reduced growth and marketability of a range of ornamental species (Karimi et al., 2009; Wang, 2007; Yi Lin and Ming Yeh, 2008).
Knowledge of critical nutrient demands is of major importance for the design of sustainable horticultural production systems. Nutrient requirement is defined in terms of a critical concentration derived from growth or yield response curves over a wide range of nutrient supply (Genc et al., 2002). The response curves are usually separated into four phases: 1) a deficiency phase in which plant growth increases markedly with slight incremental increases in nutrient concentration; 2) a sufficiency phase in which growth is maximized (Salifu and Timmer, 2003); 3) an adequate phase in which further growth is not achieved despite the increase in nutrient availability as a result of luxury consumption; and 4) a toxicity phase in which nutrient concentration continues to increase but plant growth declines (Isaac and Kimaro, 2011; Marschner, 1995; Salifu and Timmer, 2003). Nutrient concentration is defined as sufficient or as the critical optimum concentration (Marschner, 1995) when plants exhibit 90% to 95% of maximum growth or yield (Ulrich and Hills, 1993), whereas the concentration at which growth declines is considered as the critical toxicity level (Marschner, 1995).
Lilium (Lilium sp.) is a widely cultivated ornamental geophyte. Studies on Lilium nutrition have been reported (Argo and Biernbaum, 1994) and tissue nutrient levels (mmol·kg−1) of high-quality lilium plants are 1700 to 2900 nitrogen (N), 32 to 226 phosphorus (P), 512 to 1279 K, 50 to 100 calcium (Ca), and 125 to 833 Mg (Dole and Wilkins, 2005). However, there is little information available on lilium cultivation for cut flower purposes in hydroponic systems. Ornamental geophytes pose a challenge for plant nutrition research because the bulb stores reserves of carbohydrates and mineral elements; thus, the response to external nutrient concentrations may not be comparable to that of non-geophytic species. The present study was conducted to determine the response of Lilium sp. L cv. Arcachon in perlite cultures to varying K levels in the nutrient solution with the objective of defining the critical internal and external K concentration. Because no reports have been published, on the present research we also assessed the relationship of K nutrition with leaf water potential (ψw), photosynthetic rate, leaf anatomy, and plant nutritional status.
Amtmann, A., Troufflard, S. & Armengaud, P. 2008 The effect of potassium nutrition on pest and disease resistance in plants Physiol. Plant. 133 682 691
Argo, W.R. & Biernbaum, J.A. 1994 Irrigation requirements, root-medium pH, and nutrient concentrations of easter lilies grown in five peat-based media with and without an evaporation barrier J. Amer. Soc. Hort. Sci. 119 1151 1156
Armengaud, P., Sulpice, R., Miller, A.J., Stitt, M., Amtmann, A. & Gibon, Y. 2009 Multilevel analysis of primary metabolism provides new insights into the role of potassium nutrition for glycolysis and nitrogen assimilation in Arabidopsis roots Plant Physiol. 150 772 785
Bremner, J.M. 1996 Nitrogen-total, p. 1085−1121. In: Bigham, J.M. (ed.). Methods of soil analysis. Soil Science Society of America, Madison, WI
Dole, J.M. & Wilkins, H.F. 2005 Floriculture, principles and species. 2nd Ed. Prentice Hall, NJ
Egilla, J.N., Davies, F.T. & Boutton, T.W. 2005 Drought stress influences leaf water content, photosynthesis, and water-use efficiency of Hibiscus rosa-sinensis at three potassium concentrations Photosynthetica 43 135 140
Fricke, W. & Flowers, T.J. 1998 Control of leaf cell elongation in barley. Generation rates of osmotic pressure and turgor, and growth-associated water potential gradients Planta 206 53 65
Fricke, W., Leigh, R.A. & Tomos, A.D. 1994 Concentrations of inorganic and organic solutes in extracts from individual epidermal, mesophyll and bundle-sheath cells of barley leaves Planta 192 310 316
Genc, Y., McDonald, G.K. & Graham, R.D. 2002 Critical deficiency concentration of zinc in barley genotypes differing in zinc efficiency and its relation to growth responses J. Plant Nutr. 25 545 560
Isaac, M.E. & Kimaro, A.A. 2011 Diagnosis of nutrient imbalances with vector analysis in agroforestry systems J. Environ. Qual. 40 860 866
Karimi, E., Abdolzadeh, A. & Sadeghipour, H.R. 2009 Increasing salt tolerance in Olive, Olea europaea L. plants by supplemental potassium nutrition involves changes in ion accumulation and anatomical attributes Intl. J. Plant Prod. 3 49 60
Marschner, H. 1995 Mineral nutrition of higher plants. 2nd Ed. Academic Press, Inc., London, UK
Mengel, K. & Kirkby, E.A. 2001 Principles of plant nutrition. 5th Ed. Kluwer Academic Publishers, The Netherlands
Qi, Z. & Spalding, E.P. 2004 Protection of plasma membrane K+ transport by the salt overly sensitive1 Na+-H+ antiporter during salinity stress Plant Physiol. 136 2548 2555
Rus, A., Lee, B., Muñoz-Mayor, A., Sharkhuu, A., Miura, K., Zhu, J.K., Bressan, R.A. & Hasegawa, P.M. 2004 AtHKT1 facilitates Na+ homeostasis and K+ nutrition in planta Plant Physiol. 136 2500 2511
Salifu, K.F. & Timmer, V.R. 2003 Optimizing nitrogen loading of Picea mariana seedlings during nursery culture Can. J. For. Res. 33 1287 1294
Shabala, S., Babourina, O. & Newman, I. 2000 Ion-specific mechanisms of osmoregulation in bean mesophyll cell J. Expt. Bot. 51 1243 1253
Soltanpour, P.N., Johnson, G.W., Workman, S.M., Benton Jones, J. & Miller, R.O. 1996 Inductively coupled plasma emission spectrometry and inductively coupled plasma-mass spectrometry, p. 91−139. In: Bigham, J.M. (ed.). Methods of soil analysis. Soil Science Society of America, Madison, WI
Spalding, E., Hirsch, R.E., Lewis, D.R., Qi, Z., Sussman, M.R. & Lewis, B.D. 1999 Potassium uptake supporting plant growth in the absence of AKT1 channel activity: Inhibition by ammonium and stimulation by sodium J. Gen. Physiol. 113 909 918
Ulrich, A. & Hills, F.J. 1993 Principles and practices of plant analysis, p. 11–24. In: Westerman, R.L. (ed.). Soil testing and plant analysis. Part II. Soil Sci. Soc. Amer., Madison, WI
Wang, Y.T. 2007 Potassium nutrition affects growth and flowering of Phalaenopsis grown in a bark mix or sphagnum moss substrate HortScience 42 1563 1567