High NO3-N to NH4-N Ratios Promote Growth and Flowering of a Hybrid Phalaenopsis Grown in Two Root Substrates

in HortScience

Young, bare-root plants (three leaves, 15 cm in leaf spread) from a vegetatively propagated clone of Phalaenopsis Blume x Taisuco Kochdian were imported in late May and planted in a mix consisting of three parts medium-grade Douglas fir bark and one part each of perlite and coarse peat (by volume) or in pure Chilean sphagnum moss. All plants were given 221 N, 124 P, 515 K, 100 Ca, and 50 Mg (all in mg·L−1) when being irrigated. The total N varied from 0%, 25%, 50%, 75%, to 100% NO3-N with the balance being NH4-N. Plants were fertigated when the substrate became dry. For both substrates, as the percentage of NO3-N increased, plants produced slightly fewer leaves. Regardless of the NO3-N to NH4-N ratio, plants grown in moss produced one extra leaf than those planted in the bark mix during an 8-month period. There was a tendency of increasing top leaf length and width as well as the whole-plant leaf spread as NO3-N increased from 0% to 100% in either substrate. Plants receiving 50% or more NO3-N in either substrate spiked and flowered 2 weeks earlier than those given 25% or 0% NO3-N. When grown in the bark mix, flower count, flower diameter, and inflorescence length all increased as NO3-N increased from 0% to 75%. Flower stem (inflorescence, 5 cm from the base) became progressively thicker as NO3-N increased from 0% to 100%. Only two among the 24 plants grown in moss and receiving 100% NH4-N bloomed. These results suggest that Phalaenopsis does not grow well with 100% NH4-N and must be provided with NO3-N at no less than 50%, preferably 75%, of the total N for improved growth and flowering.

Abstract

Young, bare-root plants (three leaves, 15 cm in leaf spread) from a vegetatively propagated clone of Phalaenopsis Blume x Taisuco Kochdian were imported in late May and planted in a mix consisting of three parts medium-grade Douglas fir bark and one part each of perlite and coarse peat (by volume) or in pure Chilean sphagnum moss. All plants were given 221 N, 124 P, 515 K, 100 Ca, and 50 Mg (all in mg·L−1) when being irrigated. The total N varied from 0%, 25%, 50%, 75%, to 100% NO3-N with the balance being NH4-N. Plants were fertigated when the substrate became dry. For both substrates, as the percentage of NO3-N increased, plants produced slightly fewer leaves. Regardless of the NO3-N to NH4-N ratio, plants grown in moss produced one extra leaf than those planted in the bark mix during an 8-month period. There was a tendency of increasing top leaf length and width as well as the whole-plant leaf spread as NO3-N increased from 0% to 100% in either substrate. Plants receiving 50% or more NO3-N in either substrate spiked and flowered 2 weeks earlier than those given 25% or 0% NO3-N. When grown in the bark mix, flower count, flower diameter, and inflorescence length all increased as NO3-N increased from 0% to 75%. Flower stem (inflorescence, 5 cm from the base) became progressively thicker as NO3-N increased from 0% to 100%. Only two among the 24 plants grown in moss and receiving 100% NH4-N bloomed. These results suggest that Phalaenopsis does not grow well with 100% NH4-N and must be provided with NO3-N at no less than 50%, preferably 75%, of the total N for improved growth and flowering.

Differential growth responses to N sources have been reported for many crops. Although Rhododendrum obtusum (Lindl.) Planch ‘Hexe’ (azalea) prefers NH4-N (Colgrave and Roberts, 1956), Viburnum plicatum Miq. tomentosum Thunb. had improved growth with NO3-N over NH4-N at low pH but not at high pH (Dirr, 1975). Plant species have different sensitivities to NH4-N. Spinacea oleracea L. is highly sensitive to NH4-N and requires NO3-N to grow well, whereas Pisum sativum L. is tolerant to NH4-N (Lisa et al., 2001).

Growth of the tropical foliage species Maranta leuconeura did not respond to N being 5% to 75% as NH4-N (Strojny, 1999). Brassia actinophylla Endl., Calathea makoyama E. Morr., and Philodendrum selloum C. Koch had best growth and quality with NH4-N or urea than with NO3-N (Conover and Poole, 1982). Similarly, growth and grade of Aglaonema Schott. × Silver Queen and Philodendrum scadens oxicardium (Schott) Bunt. were improved when the N they received contained 25% NH4-N or 100% urea as opposed to NO3-N (Conover and Poole, 1986). However, Dieffenbachia maculata (Lodd.) G. Don. ‘Camille’ and Nephrolepis exaltata (L.) Schott. grew equally well regardless of their N sources. There exists a wide diversity in plants' responses to N sources, and how one species responds to various N sources or ratio of N sources cannot be used to predict how another species would respond.

Hybrids of Phalaenopsis Blume. have become an economically important pot orchid on all continents and its production is fast increasing (Wang, 2004). This orchid requires high fertility for optimum growth and flowering (Wang, 1994, 1996; Yoneda et al., 2000). Although high N is required, there have been no efforts to examine how NO3-N and NH4-N regulate the performance of this important crop under greenhouse production conditions. A recent study showed that Phalaenopsis had good vegetative growth under K-deficient conditions, but plants started dying after they became reproductive (Wang, 2007). Therefore, it is critical to study how nutrients affect plant growth in both phases.

The objective of this study was to characterize how a hybrid Phalaenopsis responded to several NO3-N to NH4-N ratios during vegetative growth and flowering in each of two root substrates that differed in their physical and chemical properties.

Materials and Methods

Bare-root, vegetatively propagated plants (averaged 15 cm in leaf spread) of a white-flowered Phalaenopsis Blume × Taisuco Kochdian clone were imported in late May. Plants were potted in 11.4-cm round plastic pots (600-mL volume) filled with a mix consisting of three parts medium-grade ground Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] bark and one part each of perlite and coarse Canadian sphagnum peat (by vol.) or in 10.2-cm pots (450 mL vol.) filled with pure Chilean sphagnum moss (Sphagnum magellanicum Brid.). The uppermost leaf on each plant was marked for determining the number of new leaves to be produced.

The greenhouse had transparent polycarbonate sheets on the roof and sides. A layer of black polypropylene shade fabric was installed inside the greenhouse allowing for the transmission of 18% to 20% of full sunlight. Maximum photosynthetic photon flux at solar noon was 420 μmol·m−2·s−1 in June and 260 μmol·m−2·s−1 in December. Average temperatures were 30 day/25 night °C in the summer and 25 day/17 night °C during the winter.

Fertilizer solutions were made from 11N–3.2P–14.9K–7Ca–1.6Mg–0S (NO3-N) or 11N–3.2P–14.9K–0Ca–1.6Mg–16S (NH4-N) (Jack Peters, personal gifts) to provide 100%, 75%, 50%, 24%, and 0% nitrate-N. All fertilizer solutions contained, in mg·L−1, 221N, 124P, 515K, 140Ca, and 54Mg. CaCl2 was used to balance Ca in all solutions. The solutions containing 100%, 75%, 50%, 25%, and 0% NO3-N had 32, 88, 176, 264, and 352 mg·L−1 S, respectively. MgSO4·7H2O was added to the 100% nitrate solution to provide 32 mg·L−1 S. All other macroelement cations were balanced among the nutrient solutions. Pots were fertigated only when the substrate had become dry. Plants in the bark mix were given 100 mL nutrient solution at each fertigation and those planted in moss were provided with 300 mL of a fertilizer solution to avoid salt accumulation. No supplemental micronutrients were used.

The date on which the flower stem emerged from the base of a leaf (mostly the third acropital leaf) was recorded as the spiking date. Flowering data were collected on plants grown in the bark mix only. When the first flower bud on a plant opened, that date was recorded as the flowering date (anthesis). Flower count, the natural horizontal spread of the first flower on a plant, the internodal length between the first and second flowers, the length of the flower stem between the base and the first flowering node, and the distance between the first flowering node and the tip of that inflorescence were recorded after all flowers had opened. The thickness of the flowering stem was measured at ≈5 cm from the base with an electronic digital caliper (MAX-CAL; Fowler, Brownwood, TX). The number of new leaves and their combined lengths were determined. The length and width of the uppermost mature leaf were measured and recorded.

Treatments were arranged in a randomized complete block design. One plant in a pot represented an experimental unit that was replicated 24 times. Linear and quadratic regression analyses were performed with SAS programming (SAS Institute, Cary, NC) using the percentage nitrate-N as the independent variable.

Results

For both substrates, as the percentage of NO3-N increased, plants produced slightly fewer leaves (Fig. 1A); However, the differences were small for plants grown in the bark mix, i.e., 3.5 leaves at 100% NH4-N and 3.1 at 100% NO3-N (Fig. 1A). Regardless of the NO3-N to NH4-N ratio, plants grown in moss produced one extra leaf than those planted in the bark mix. Whole-plant leaf spread increased as NO3-N increased from 0% to 100% in both substrate (Figs. 1B and 1C). The top mature leaves on plants receiving 100% NO3-N and planted in bark mix were approximately two-thirds larger in area than those receiving 100% NH4-N. In both media, the combined length of the new leaves on a plant increased as NO3-N increased from 0% to 75% and then declined slightly at 100% NO3-N (Fig. 1D). Leaf span became larger as NO3-N increased form 0% to 100% (Figs. 2 and 3A).

Fig. 1.
Fig. 1.

Effect of NO3-N to NH4-N ratio on vegetative growth of a Phalaenopsis Blume × Taisuco Kochdian clone grown in pure sphagnum moss or a bark mix substrate. (A) New leaves; (B) top leaf length; (C) top leaf width; (D) total leaf length. The vertical bars represent se of the mean. L and Q = linear and quadratic response. *, **, and ***, significance at P = 0.05, 0.01, and 0.001, respectively.

Citation: HortScience horts 43, 2; 10.21273/HORTSCI.43.2.350

Fig. 2.
Fig. 2.

Appearance of plants grown in a bark mix (top) or pure sphagnum moss substrate (bottom).

Citation: HortScience horts 43, 2; 10.21273/HORTSCI.43.2.350

Fig. 3.
Fig. 3.

Effect of NO3-N to NH4-N ratio on leaf span and spiking date of a Phalaenopsis Blume × Taisuco Kochdian clone grown in pure sphagnum moss or a bark mix substrate. (A) Leaf span; (B) days to spiking. The vertical bars represent se of the mean. L and Q = linear and quadratic response. *, **, and ***, significance at P = 0.05, 0.01, and 0.001, respectively.

Citation: HortScience horts 43, 2; 10.21273/HORTSCI.43.2.350

In both substrates, plants spiked 2 weeks earlier (Fig. 3B) when NO3-N increased from 0% to 50% with no additional change as NO3-N increased to 100% . In bark mix, plants flowered 3 weeks earlier when given 50% to 100% NO3-N (Fig. 4A). Flower count increased from 4.5 to 7.0 as NO3-N increased from 0% to 75% (Fig. 4B). Flower diameter was 16% wider and the area of a flower was 38% larger when plants were given 75% NO3-N compared with those receiving 100% NH4-N (Fig. 4C).

Fig. 4.
Fig. 4.

Effect of NO3-N to NH4-N ratio on flowering characteristics of a Phalaenopsis Blume × Taisuco Kochdian clone grown in a bark mix substrate. (A) Days to flowering; (B) flower count; (C) flower diameter; (D) spike length, base to first flower. The vertical bars represent se of the mean. L and Q = linear and quadratic response. *, **, and ***, significance at P = 0.05, 0.01, and 0.001, respectively.

Citation: HortScience horts 43, 2; 10.21273/HORTSCI.43.2.350

The length of the flower stem between the base and the first flower increased with increasing NO3-N to 50% (Fig. 4D), whereas the length between the first flower and the tip increased with increasing percentage of NO3-N to 75% (Fig. 5A). As a result, the total inflorescence length was longest at 75% NO3-N (Fig. 5B). The length of the internode between the first two flowers increased with increasing NO3-N to 100% (Fig. 5C). Flower stem diameter at 5 cm above the base was 22% larger when provided with 50% or higher NO3-N (Fig. 5D).

Fig. 5.
Fig. 5.

Effect of NO3-N to NH4-N ratio on flower stem of a Phalaenopsis Blume × Taisuco Kochdian clone grown in a bark mix substrate. (A) Spike length, first flower to tip; (B) total inflorescence length; (C) flower stem diameter; (D) flower internode length. The vertical bars represent se of the mean. L and Q = linear and quadratic response. *, **, and ***, significance at P = 0.05, 0.01, and 0.001, respectively.

Citation: HortScience horts 43, 2; 10.21273/HORTSCI.43.2.350

Discussion

In some previous studies that determined the effects of N sources or pH on plant growth, the concentrations of other major elements were not balanced among the nutrient solutions used or not reported (Andrews and Hammer, 2006; Bernstein et al., 2005; Conover and Poole, 1986; Ganmore-Neumann and Hagiladi, 1990; Hanne and Schuch, 2006). Although authors described treatment effects, it was not clear if it was the treatments or the varying concentrations of other macroelements that resulted in the differences in plant responses. In this current study, the solutions containing 100%, 75%, 50%, 25%, and 0% NO3-N had 32, 88, 176, 264, and 352 mg·L−1 S, respectively. It was reported that 32 mg·L−1 S is far more than adequate to avoid S deficiency and for good growth in Euphobia pulcherrima Willd. (Dale et al., 1990) and Dendrothema grandiflora (Huang et al., 1997). S at 900 mg·L−1 did not cause phytotoxicity to Pelagonium ×hortorum L. H. Bailey ‘Red Elite’ (Compton, 2006). Therefore, it is very likely the differences that were observed at various NO3-N and NH4-N ratios were truly the result of treatment effects (Lisa et al., 2001).

Alder and Wilcox (1995) showed that, in muskmelon (Cucumis melo L.), NH4-N completely inhibited K absorption. In mineral soils, NH4 + may fix K so that K uptake by plants is lowered as a result of reduced availability (Barker, 1967; Maynard et al., 1968). The absorption of all macronutrients by Phalaenopsis young seedlings in vitro (Kubota et al., 2000) and by Colocasia esculanta L. Schott cv. Bun Long (taro; Osorio et al., 2003) was reduced as percentage of NH4-N increased. However, symptoms of K deficiency such as lower leaf yellowing, bronze coloration, necrosis, and leaf death (Wang, 2007) were not observed on Phalaenopsis plants in either substrate that received 100% NH4-N. This suggests that the absorption of K was likely not severely reduced by applying 100% NH4-N to Phalaenopsis.

Phalaenopsis is tropical in origin and was grown under relatively high temperature during this study. Roots of plants supplied with only NH4-N have high demands for carbon skeletons for ammonium assimilation (Arnozis et al., 1988) and high O2 consumption (Matsumoto and Tamura, 1981), resulting in low sugar concentration in the roots and poor plant growth compared with NO3-N-fed plants. This may have resulted in smaller plants when given high percentages of NH4-N. Spiking (the emergence of the potential flower stem) is associated with high sugar concentration in leaves after being exposed to inductive temperatures (Lee and Lee, 1996). It may be possible that the delayed spiking in plants receiving 75% or 100% NH4-N was the result of low sugar concentration in the foliage.

In another monocot species Colocasia esculanta, 75% or higher N in the nitrate form promoted growth (Osorioet al., 2003). Plants that were provided with NH4-rich nutrient solutions had retarded growth and small leaf area. Kubota et al. (2000) reported that Phalaenopsis seedlings being propagated in vitro preferred 80% or higher of the total nitrogen being in the nitrate form for highest leaf number, largest leaf area, and more and longer roots. There was little or no difference in the growth of Zea maize plants resulting from various proportions of NO3- and NH4-N at low N concentrations (Xu et al., 1992). However, at higher N concentration, plant growth increased as NO3-N increased from 0% to 75% and then declined. That was similar to the results found in this study at a high total N concentration of 221 mg·L−1, which was previously reported to result in optimum growth and flowering (Wang, 1994, 1996).

When high fertility is provided to Phalaenopsis, whether grown in pure sphagnum moss or in a bark mix, the data suggest that a minimum of equal proportion of NO3-N and NH4-N must be provided. Providing 75% NO3-N and 25% NH4-N further improves vegetative growth and flowering of Phalaenopsis.

Literature Cited

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    • Search Google Scholar
    • Export Citation
  • AndrewsP.H.HammerP.A.2006Response of zonal and ivy geraniums in root medium pHHortScience4113511355

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    • Export Citation
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    • Search Google Scholar
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    • Search Google Scholar
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  • WangY.T.1994Medium and fertilizer affect the performance of Phalaenopsis orchids during two flowering cyclesHortScience29269271

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  • WangY.T.2007Potassium concentration affects growth and flowering of Phalaenopsis in a bark mix or sphagnum moss substrateHortScience4215631567

    • Search Google Scholar
    • Export Citation
  • XuQ.F.TsaiC.L.TsaiC.Y.1992Interaction of potassium with the form and amount of nitrogen nutrition on growth and nitrogen uptake of maizeJ. Plant Nutr.152333

    • Search Google Scholar
    • Export Citation
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    • Search Google Scholar
    • Export Citation

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Contributor Notes

Phalaenopsis plants were personal gifts from Clone Biotechnology Company, Pintung, Taiwan. Assistance from Bianchi and Davis Greenhouses, Riverhead, NY, to import these plants is appreciated. Acknowledgments to Amy Tsai and Christine Yen for technical assistance.

Current address: Matsui Nursery, 1645 Old Stage Road, Salinas, CA 93908.

To whom reprint requests should be addressed; e-mail yintung.wang@gmail.com

Article Sections

Article Figures

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    Effect of NO3-N to NH4-N ratio on vegetative growth of a Phalaenopsis Blume × Taisuco Kochdian clone grown in pure sphagnum moss or a bark mix substrate. (A) New leaves; (B) top leaf length; (C) top leaf width; (D) total leaf length. The vertical bars represent se of the mean. L and Q = linear and quadratic response. *, **, and ***, significance at P = 0.05, 0.01, and 0.001, respectively.

  • View in gallery

    Appearance of plants grown in a bark mix (top) or pure sphagnum moss substrate (bottom).

  • View in gallery

    Effect of NO3-N to NH4-N ratio on leaf span and spiking date of a Phalaenopsis Blume × Taisuco Kochdian clone grown in pure sphagnum moss or a bark mix substrate. (A) Leaf span; (B) days to spiking. The vertical bars represent se of the mean. L and Q = linear and quadratic response. *, **, and ***, significance at P = 0.05, 0.01, and 0.001, respectively.

  • View in gallery

    Effect of NO3-N to NH4-N ratio on flowering characteristics of a Phalaenopsis Blume × Taisuco Kochdian clone grown in a bark mix substrate. (A) Days to flowering; (B) flower count; (C) flower diameter; (D) spike length, base to first flower. The vertical bars represent se of the mean. L and Q = linear and quadratic response. *, **, and ***, significance at P = 0.05, 0.01, and 0.001, respectively.

  • View in gallery

    Effect of NO3-N to NH4-N ratio on flower stem of a Phalaenopsis Blume × Taisuco Kochdian clone grown in a bark mix substrate. (A) Spike length, first flower to tip; (B) total inflorescence length; (C) flower stem diameter; (D) flower internode length. The vertical bars represent se of the mean. L and Q = linear and quadratic response. *, **, and ***, significance at P = 0.05, 0.01, and 0.001, respectively.

Article References

  • AlderR.A.WilcoxG.E.1995Ammonium increases the net rate of sodium influx and partitioning to the leaf of muskmelonJ. Plant Nutr.1819511962

    • Search Google Scholar
    • Export Citation
  • AndrewsP.H.HammerP.A.2006Response of zonal and ivy geraniums in root medium pHHortScience4113511355

  • ArnozisP.A.NelemansJ.A.FindeneggG.R.1988Phosphoenolpyruvate carboxylase activity in plants grown with either NO3 or NH4 + as inorganic nitrogen sourceJ. Plant Physiol.1322327

    • Search Google Scholar
    • Export Citation
  • BarkerA.V.1967Growth and nitrogen distribution in bean (Phaseolus vulgaris L.) plants subjected to ammonium nutrition. II. Effects of potassium in a calcium carbonate buffered systemAdv. Front. Plant Sci.18722

    • Search Google Scholar
    • Export Citation
  • BernsteinN.LoffeM.BrunerM.NishriY.LuriaG.GoriI.MatanE.Philosoph-HadasS.UmielN.HagiladiA.2005Effects of supplied nitrogen form and quantity on growth and postharvest quality of Ranunculus asiaticus flowersHortScience4018791886

    • Search Google Scholar
    • Export Citation
  • ColgraveH.A.RobertsA.N.1956Growth of azalea as influenced by ammonium and nitrate nitrogenJ. Amer. Soc. Hort. Sci.68522536

  • ComptonM.2006Growth of Geranium plants in soilless media containing sphagnum peat and anaerobic digestion-derived biosolidsHortScience41979(abstr.).

    • Search Google Scholar
    • Export Citation
  • ConoverC.A.PooleR.T.1982Influence of nitrogen source in growth and tissue nutrient content on three foliage plantsProc. Fla. State Hort. Sci.95151153

    • Search Google Scholar
    • Export Citation
  • ConoverC.A.PooleR.T.1986Nitrogen source effects on growth and tissue content of selected foliage plantsHortScience2111081109

  • DaleM.E.PaparozziE.T.CarrJ.D.1990Sulfur deficiency in poinsettiaHortScience25424426

  • DirrM.A.1975Effect of nitrogen form and pH on growth, NO3-N, NH4-N and total N content of container-grown double-file Viburnum J. Amer. Soc. Hort. Sci.100216218

    • Search Google Scholar
    • Export Citation
  • Ganmore-NeumannR.HagiladiA.1990Effect of the NO3 /NH4 + ratio in nutrient solution on Pelargonium stock plants: Yield and quality of cuttingsJ. Plant Nutr.1312411256

    • Search Google Scholar
    • Export Citation
  • HanneK.S.SchuchU.K.2006Nitrogen form and concentration affect nitrogen leaching and seedling growth of Prosopis velutina HortScience41239243

    • Search Google Scholar
    • Export Citation
  • HuangL.C.PaparozziE.T.GotwayC.1997The Effect of altering nitrogen and sulfur supply on the growth of cut chrysanthemumJ. Amer. Soc. Hort. Sci.122559564

    • Search Google Scholar
    • Export Citation
  • KubotaS.YonedaK.SuzukiY.2000Effects of ammonium to nitrate ratio in culture medium on growth and nitrate absorption of Phalaenopsis seedlings in vitroEnviron. Control in Biol.38281284

    • Search Google Scholar
    • Export Citation
  • LeeN.LeeC.H.1996Changes in carbohydrate in Phalaenopsis during flower induction and inflorescence developmentJ. Chinese Soc. Hort. Sci.42262275

    • Search Google Scholar
    • Export Citation
  • LisaB.FrechillaS.LamsfusC.Aparicio-TejoP.M.2001The sensitivity to ammonium nutrition is related to nitrogen accumulationScientia Hort.91143152

    • Search Google Scholar
    • Export Citation
  • MatsumotoH.TamuraK.1981Respiratory stress in cucumber roots treated with ammonium or nitrate nitrogenPlant Soil60195204

  • MaynardD.N.BarkerA.V.LachmanW.H.1968Influence of potassium on the utilization of ammonium by tomato plantsProc. Amer. Soc. Hort. Sci.92537542

    • Search Google Scholar
    • Export Citation
  • OsorioN.ShuaiX.MiyasakaS.WangB.ShireyR.L.WangmoreW.J.2003Nitrogen level and form affect taro growth and nutritionHortScience383640

    • Search Google Scholar
    • Export Citation
  • StrojnyZ.1999Effect of nutrient solution concentration and NH4:NO3 ratio on Maranta growthScientia Hort.80105112

  • WangY.T.1994Medium and fertilizer affect the performance of Phalaenopsis orchids during two flowering cyclesHortScience29269271

  • WangY.T.1996Effects of six fertilizers on vegetative growth and flowering of Phalaenopsis orchidsScientia Hort.65191197

  • WangY.T.2004Flourishing market for potted orchidsFlowerTECH725

  • WangY.T.2007Potassium concentration affects growth and flowering of Phalaenopsis in a bark mix or sphagnum moss substrateHortScience4215631567

    • Search Google Scholar
    • Export Citation
  • XuQ.F.TsaiC.L.TsaiC.Y.1992Interaction of potassium with the form and amount of nitrogen nutrition on growth and nitrogen uptake of maizeJ. Plant Nutr.152333

    • Search Google Scholar
    • Export Citation
  • YonedaK.KubotaS.YonemotaF.MatsumotoT.2000Effect of various irrigation methods on growth and inflorescence emergence in Phalaenopsis and Doritaenopsis J. Chinese Soc. Hort. Sci.46297304

    • Search Google Scholar
    • Export Citation

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