Compared with fruit and vegetable crops, the effects of potassium (K) on growth and performance of ornamental and floral crops have not been studied as extensively. K deficiency is a widespread disorder on many palm species worldwide (Chase and Broschat, 1991) that can lead to the death of the plant if supplemental K is not applied (Broschat, 1990).
In field studies, flower production of Anthurium andraeanum Linden. (Higaki et al., 1992) and Gerbera jamesonii H. Bolus ex Hook.f. (Dufault et al., 1990) increased when K was at 375 and 110 to 220 kg·ha−1, respectively, compared with lower rates. In a greenhouse study, increasing K concentration from 0.25 to 10 meq·L−1 (10 to 390 mg·L−1) in the recirculating nutrient solution resulted in more flowers, longer stem, and whole-plant fresh weight of Rosa hybrida ‘Forever Yours’ (Woodson and Boodley, 1982). Shoot dry weight and leaf area of Salvia splendens F. Sellow ‘Bonnfire’ increased as K concentration increased from 25 to 300 mg·L−1 (Eakes et al., 1991). The tropical foliage species Aglaonema commutatum Schott, however, did not respond to increased K from 80 to 320 mg per 15-cm pot per month (Poole and Conover, 1977).
Phalaenopsis Blume. hybrids are the most popular pot orchids on the market around the world. Individual flowers of these orchids often last 3 to 4 months (Wang, 1997, 2000). Their relatively rapid growth and short juvenile period (Lee, 1991) are advantageous for breeders to improve this crop by crossbreeding and cloning. Several studies found that Phalaenopsis plants require high nutrient concentrations for optimal growth under warm environmental conditions (Lee and Lin, 1988; Wang, 1996; Wang and Gregg, 1994).
Leaves of healthy Phalaenopsis plants may remain on the plant for 2 or more years and contain 3% to 8% K on a dry-weight basis (Lee, 1988; Wang, 1998; Wang and Konow, 2002). In recent years, a physiological disorder has been observed on Phalaenopsis leaves. The affected plants had irregular yellowish areas on the second or third basipetal leaves (Chen, 2001; Lee, 2001; Lee and Lee, 2000). Symptoms of this disorder became much more severe after vegetative plants have been induced to initiate the flowering process by exposing them to cool air. The yellowed leaf tissues were found to have extremely low levels of K (0.40% to 0.64%) (Lee, 2001). No controlled studies have been conducted to quantify Phalaenopsis K requirements and to characterize the specific symptoms of K deficiency.
As a result of the long production time from seed, millions of Phalaenopsis plants of varying sizes are imported to the United States each year from overseas suppliers. Although nearly all overseas Phalaenopsis suppliers grow this crop in straight sphagnum moss (moss), most growers in the United States produce this orchid in media largely made of ground douglas fir [Pseudotsuga menziesii (Mirb.) Franco] bark. Because it is obvious that these two materials have markedly diverse water retention characteristics, Phalaenopsis grown in these media may have different requirements for K concentration in the nutrient solution being applied.
The objectives of this study were 1) to determine the growth and flowering of Phalaenopsis in response to a wide range of K concentrations when grown in two media drastically different in water and nutrient retention characteristics and 2) to characterize the K deficiency symptoms.
Broschat, T.K. 1994 Removing potassium-deficient leaves accelerates rate of decline in Phoenix roebelenii O'Brien HortScience 29 823
Chen, Y.J. 2001 Effect of mineral nutrition on growth, mineral composition, and leaf quality during stalk emergence of Phalaenopsis sp Dept. of Hort., National Taiwan Univ Taipei, Taiwan Master's Thesis
Dufault, R.J. , Phillips, T.L. & Kelly, J.W. 1990 Nitrogen and potassium fertility and plant populations influence field production of gerbera HortScience 25 1599 1602
Eakes, D.J. , Wright, R.D. & Seiler, J.R. 1991 Water relations of Salvia splendens ‘Bonfire’ as influenced by potassium nutrition and moisture stress conditioning J. Amer. Soc. Hort. Sci. 116 712 715
Figdore, S.S. , Gabelman, W.H. & Gerloff, G.C. 1989 Influence of potassium efficiency, sodium substation capacity, and sodium accumulation in tomatoes grown under low potassium stress J. Amer. Soc. Hort. Sci. 114 322 327
Gartner, J.A. 1969 Effect of fertilizer nitrogen on a dense sward of Kikuy. Paspalum and carpet grass. 2. Interactions with phosphorus and potassium Queensland J. Agr. Animal Sci. 26 365 372
Higaki, T. , Imamura, J.S. & Paull, R.E. 1992 N, P, and K rates and leaf tissue standards for optimum Anthurium andraeanum flower production HortScience 27 909 912
Lee, B.J. & Lee, N. 2000 Potassium, light, and temperature on Phalaenopsis leaf yellowing J. Chinese Soc. Hort. Sci. 46 491 (abstr.).
Lee, N. 1988 The growth and flowering physiology of Phalaenopsis plants 13 27 Proc. of Improving Phalaenopsis Production Symposium. Taitung Agricultural Improvement Station Taitung, Taiwan
Lee, N. 1991 Juvenility in Phalaenopsis 77 86 Proc. of a Symposium on Growth Regulation of Horticultural Crops II. Taichung District Agricultural Improvement Station Taichung, Taiwan
Lee, N. 2001 Phalaenopsis photosynthesis, flowering physiology, and leaf yellowing. Industry scientific development and collaboration reports Taiwan Sugar Corporation, Taipei, Taiwan. I 22 35
Lee, N. & Lin, G.M. 1988 Controlling the flowering of Phalaenopsis 27 44 Proc. of a symposium on forcing culture of horticultural crops. Taichung District Agricultural Improvement Station Taichung, Taiwan Special Publication No. 10
Poole, D.T. & Conover, C.A. 1977 Nitrogen and potassium fertilization on Aglaonema commutatum Schott cvs. Fransher and Pseudobrateatum HortScience 12 570 571
Sharma, C.P. & Singh, S. 1990 Sodium helps overcome potassium deficiency effects on water relations of cauliflower HortScience 25 458 459
Wang, Y.T. 1996 Effects of six fertilizers on vegetative growth and flowering of Phalaenopsis orchids Scientia Hort. 65 191 197
Wang, Y.T. 2000 Impact of a high phosphorus fertilizer and timing of termination of fertilization on flowering of a hybrid moth orchid HortScience 35 60 62
Wang, Y.T. & Gregg, L.L. 1994 Medium and fertility affect the performance of Phalaenopsis orchids during two flowering cycles HortScience 29 269 271
Wang, Y.T. & Konow, E.A. 2002 Fertilizer source and medium composition interact to affect vegetative growth and mineral nutrition of a hybrid moth orchid J. Amer. Soc. Hort. Sci. 127 442 447
Widders, I.E. & Lorenz, O.A. 1979 Tomato root development as related to potassium nutrition J. Amer. Soc. Hort. Sci. 104 216 220
Woodson, W.R. & Boodley, J.W. 1982 Influence of potassium on growth, flowering, and chemical composition of greenhouse roses grown in recirculating nutrient solutions HortScience 17 46 47
Yeh, D.M. , Lin, L. & Wright, C.J. 2000 Effects of mineral nutrient deficiencies on leaf development, visual symptoms and shoot-root ratio of Spathiphyllum Acta Hort. 86 223 233
Yoneda, K. , Suzuki, N. & Hasegawa, I. 1999 Effects of macroelement concentrations on growth, flowering, and nutrient absorption in an Odontoblossum hybrid Scientia Hort. 80 259 265