Effects of Silicon Fertilization in Phalaenopsis

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Effects of Silicon Fertilization in Phalaenopsis
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Wajsbrot,Charles,Sr
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Master's ( M.S.)
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University of Florida
Degree Disciplines:
Horticultural Science, Environmental Horticulture
Committee Chair:
Moore, Kimberly A
Committee Members:
Broschat, Timothy K
Vendrame, Wagner A

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Environmental Horticulture -- Dissertations, Academic -- UF
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Abstract:
The effect of Silicon (Si) fertilization applied from week 24 to 34 on Phalaenopsis orchids was studied (24 to 28 week was considered the liner stage while weeks 29 to 34 were post liner stage). Three experiments were conducted. In the first experiment, Si was applied from week 29 to 34. In experiment 2, Si was applied from week 24 to 28. In experiment 3, Si was applied from week 24 to 34. In all three experiments Si was applied as 10ml of solution per plant once a week with potassium silicate (KSiO3) as a drench at three different concentrations (0.25, 0.5, 1 mg of Si per plant per application). In experiment 1, Phalaenopsis root and shoot dry weight (DW) increased as Si application rate of Si increased from 0 to 0.5 mg, but then decreased. In experiment 2, at week 34 plants that received 1 mg of Si had higher shoot DW than other treatments while root DW was greatest at 0.25 mg of Si. In experiment 3, shoot and root DW increased as Si concentration increased from 0 to 0.5 mg and then decreased from 0.5 mg to 1 mg. In all three experiments, Si concentrations in shoot and root tissues was higher in Si treated plants than control plants. This study indicates that Phalaenopsis plants appear to be Si accumulators but further work needs to be conducted as to the long term benefits of Si applications to Phalaenopsis.
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by Charles Wajsbrot.
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Thesis (M.S.)--University of Florida, 2011.
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Adviser: Moore, Kimberly A.
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1 EFFECTS OF SILICON FERTILIZATION IN PHALAENOPSIS By CHARLES WAJSBROT A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF M ASTER OF S CIENCE UNIVERSITY OF FLORIDA 2011

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2 2011 Charles Wajsbrot

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3 To my family, my greatest treasure

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4 ACKNOWLEDGMENTS the plants during the first 28 weeks; a lso to Kerry cMillan for providing the plants. My appreciation to Luci Fisher and Michelle To m es as well as Joanne Korvick. I would also like to thank my graduate committee members: Dr. Timothy Broschat, Dr. Wagner Vendrame and Dr. Kimberly A. Moore for t heir support and guidance. Thanks for my wife, Dalia, for the help with the statistical analyses.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF FIGURES ................................ ................................ ................................ .......... 7 LIST OF ABBREVIATIONS ................................ ................................ ............................. 8 ABSTRACT ................................ ................................ ................................ ..................... 9 CHAPTER 1 INTRODUCTION ................................ ................................ ................................ .... 10 2 LITERATURE REVIEW ................................ ................................ .......................... 12 Silicon ................................ ................................ ................................ ..................... 12 Silicon Uptake M echanism ................................ ................................ ...................... 13 Benefits of Silicon ................................ ................................ ................................ ... 15 Orchids ................................ ................................ ................................ ................... 18 3 MATERIAL AND METHODS ................................ ................................ .................. 19 Phase I (Weeks 24 to 28) ................................ ................................ ....................... 19 Phase II (Weeks 29 to 34) ................................ ................................ ...................... 20 Statistical Methods ................................ ................................ ................................ .. 21 Phase I ................................ ................................ ................................ ............. 21 Phase II ................................ ................................ ................................ ............ 21 4 RESULTS AND DISCUSSION ................................ ................................ ............... 24 Phase I (W eeks 24 28) ................................ ................................ ........................... 24 Phase II (Weeks 29 34) ................................ ................................ ......................... 24 5 CONCLUSION ................................ ................................ ................................ ........ 32 LIST OF REFERENCES ................................ ................................ ............................... 33 BIOGRAPHICAL SKETCH ................................ ................................ ............................ 39

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6 LIST OF TABLES Table page 3 1 Concentrations of Silicon (Si) applied to 200 Phalaenopsis orchid liners from week 24 to 28 ................................ ................................ ................................ ..... 22 3 2 Treatment combinations for applications of Silicon (Si) during weeks 29 to 34 ................................ ................................ ................................ ...................... 23 4 1 Substrate pH, electrical conductivity (EC) and Silicon (Si) at week 28 t .............. 27 4 2 Concentration of Silicon (Si) in Phalaenopsis root and shoot tissue at week 28 and at week 34 ................................ ................................ .............................. 28

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7 LIST OF FIGURES Figure page 4 1 Root (rfw) and shoot (sfw) FW at week 28 ................................ ........................ 29 4 2 Length and width of largest leaf and length of longest root ............................... 29 4 3 Root (rdw) and shoot (sdw) DW at week 28 ................................ ...................... 30 4 4 Root (rdw) and shoot d ry weight (sdw) at week 34 of Phalaenopsis plants that did not receive Silicon (Si) during liner production (weeks 24 to 28) .......... 30 4 5 Root (rdw) and shoot dry weight (sdw) at week 34 of Phalaenopsis plants that received Silicon (Si) during liner production (weeks 24 to 28) .................... 31 4 6 Root (rdw) and shoot dry weight (sdw) at week 34 of Phalaenopsis plants that received Silicon (Si) during liner production (weeks 24 to 28) as well as from weeks 29 to 34 ................................ ................................ .......................... 31

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8 LIST OF ABBREVIATIONS DW dry weight EC electro conductivity FW fresh weight K m Michaelis Constant mg milligrams pH concentration of H ions rdw root dry weight sdw shoot dry weight Si silicon SME saturated media extraction V max maximal tr ansport rate VWC volume tric water concentration

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9 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial F ulfillment of the Requiremen ts for the Degree of Master of S cience EFFECTS OF SILICON FERTILIZATION IN PHALAENOPSIS By Charles Wajsbrot August 2011 Chair: Kimberly Moore Major: Horticultural Science The effect of Silicon (Si) fertilization applied from week 24 to 34 on Phalaenopsis orchids was studied (24 to 28 week was considered the liner stage while weeks 29 to 34 were post liner stage) T hree experiments were conducted. In the first experiment, Si was applied from week 29 to 34 In experiment 2, S i was applied from week 24 to 28. In experiment 3, Si was applied from week 24 to 34. In all three experim ents Si was applied as 10ml of s olution per plant once a week with potassium silicate (KSiO 3 ) as a drench at three different conc entrations (0.25, 0.5 1 mg of Si per plant per application ) In e xperiment 1, Phalaenopsis root and shoot dry weight (DW) increased as Si application rate of Si increased from 0 to 0.5 mg, but then decreased. In experiment 2 at week 34 plants that received 1 mg of Si had hig her shoot DW than other treatments while root DW was greatest at 0.25 mg of Si. In experiment 3, shoot and root DW increased as Si concentration increased from 0 to 0.5 mg and then decreased from 0.5 mg to 1 mg. In all three experiments, Si concentrations in shoot and root tissues was higher in Si treated plants than control plants. This study indicate s that Phalaenopsis plants appear to be Si accumulators but further work needs to be conducted as to the long term benefits of Si applications to Phalaenopsi s

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10 CHAPTER 1 INTRODUCTION Silicon (Si) is the second most abundant element after oxygen in soil. Silicon dioxide comprises 50 70% of the soil mass. As a consequence, all plants rooting in soil contain some Si in their tissues. However, the role of Si in p lant growth and development was overlooked until the beginning of the 20th century (Richmond and Sussman 2003). Silicon is not considered an essential element, but Si can reach levels in plants similar to those of macronutrients (Epstein, 1994). Its impor tance as a nutrient has been demonstrated in numerous studies reporting the beneficial effects of Si supplementation to agronomic crops, such as rice and sugar cane (Datnoff and Snyder, 1991; Ma and Takahashi, 2002; Gao et al., 2004) the dry weight increa sed from 6% to 80% depending on species (Chen et al., 2000, 2001). Orchid production has increased for the past 15 years due to their popularity, the rapid expansion of the market, and the interest of growers and customers for new and improved hybrids. Orc hid production reached 8% of the global floriculture trade by 2006 (Martin and Madassery, 2006 ) Vendrame at al. (2010) reported that Phalaenopsis orchids liners accumulate Si. They reported increased liner shoot and root dry weights when Si was applied a t 1% concentration as compared to controls. The effects of Si application in Phalaenopsis orchids past the liner stage have not been evaluated. Hypothesis : Silicon applications in Phalaenopsis commercial production settings past the liner stage can impro ve overall plant grow th

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11 Objective : The objective of this experiment was to evaluate the effects of different concentrations of Si in Phalaenopsis growth when applied during the 24 th to 34 th weeks of production in a commercial greenhouse.

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12 CHAPTER 2 LITER ATURE REVIEW Silicon Silicon is a non essential element with beneficial effects reported for several crops Oryza sativa L.). In Japan Si is a requirement for obtaining high y ields of rice (Ma and prophylactic role against several stresses observed in a variety of plant species (Epstein and Bloom, 2005). Silicon is the second most prevalent element within the soil. Although deemed a non essential nutrient for the majority of plants, Si uptake by plants provides many benefits such as improved pest and pathogen resistance (Ishiguro, 2001; Meyer and Keepeing, 2001), drought tolerance (Lux et al. ,2002), heavy metal tolerance (Neuman and Nieden, 2001),and improved agricultural crop quality and yield (Korndofer and Lepsch, 2001). As the effects and benefits of Si absorption vary from species to species, and are usually only noted under conditions of biotic and abiotic stress, a comprehensive view of Si plant biology and its role in plant health has not been for med (Richmond & Sussman, 2003). The current knowledge of Si metabolism in higher plants lags behind that in other organisms, such as diatoms (Zurzo lo and Bowler,2001; Falciatore and Bowler,2002) making plant research with Si important form and is always combined with other elements, usually form ing oxides or silicates (Richmond and Sussman, 2003). Si licon is absorbed by plants in the form of uncharged silicic acid, Si(OH) 4 and is ultimately irreversibly precipitated throughout the plant as

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13 amorphous silica (SiO 2 nH 2 plants). Although S i is plentiful, most sources of Si are insoluble and not in a plant available form (Ric h mond & Sussman, 2003). Silicon Uptake M echanism Plant species differ greatly in Si accumulation, ranging from 0.1% to 10% i n shoot dry weight (Epstein, 199 4; Ma & Taka hashi, 2002).This difference was attributed to the difference in the ability of roots to take up Si (Takahashi et al., 1990). Rice can accumulate Si to the level of up to 10% of shoot dry weight, which is several times higher than that of essential macronu trients such as nitrogen (N), phosphorus (P) and potassium (K) (Savant et al., 1997). to group the high intermediate and non Si accumulators. The groupings were based up on measurements (on a dry weight basis) of Si and the Si to calcium (Ca) ratio in plant tissue, and illustrate how Si accumulation varies widely between species. After analyzing more than 147 species for Si content, different modes of Si uptake (active, pa ssive and rejective) were suggested to account for accumulator, intermediate and excluder groups, respectively (Takahashi et al. 1990). Silicon contents of more than 0.5% suggested that the plants were using an active uptake or sequestration mechanism to ac quire Si (Sangstter and Hodson,1992; Mayland et al,1993). Ma and Takahashi, (2002) showed that there was a characteristic distribution of Si accumulation in the plant kingdom. In higher plants, plants in Gramineae and Cyperacea e show high Si accumulation. Plants in Cucurbita ceae Urtica ceae and Commelinaceae show intermediate Si accumulation, whereas most other plants species show low Si accumulation. Plants with an active mode of uptake take up Si faster than water,

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14 resulting in a depletion of Si in the u ptake solution. Plants with a passive mode of uptake take up Si at a rate that is similar to the uptake rate of water; thus, no significant changes in the concentration of Si in the uptake solution are observed. By contrast, plants with a rejective mode of uptake tend to exclude Si, which is demonstrated by the increasing concentration of Si in the uptake solution. In a study using rice, cucumber and tomato, species that accumulate high, medium and low levels of Si, respectively, it was found that transport ation of Si from the external solution to the cortical cells was mediated by a similar transporter with a Km (Michaelis constant substrate concentration on which the reaction rate is at half maximum) ) value of 0.15 mM in all three species (Mitani and Ma, 2 005). However, the Vmax ( maximum rate achieved at maximum substrate concentration ) differed with plant species (i.e. rice > cucumber > tomato), suggesting that the density of the transporter differs among plant species. It seems that this transport process is energy dependent because metabolic inhibitors and low temperature inhibit transport (Mitani and Ma, 2005). Furthermore, the Si concentration in the xylem sap was much higher in rice than it was in cucumber and tomato. Unlike in rice, where xylem loadin g of Si was mediated by a kind of transporter, xylem loading was mediated by diffusion in cucumber and tomato. These results indicate that xylem loading was the most important determinant for a high level of Si to accumulate in rice shoots. The much lower accumulation of Si in cucumber and tomato might be explained by a lower density of the transporter to transport Si from the external solution to the cortical cells, and a defective or absence of transporter to transport Si from cortical cells t o the xylem (Ma and Yamaji, 2006)

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15 Depositions of opal occur throughout the plant in cell walls, cell lumens, tric homes intracellular spaces, roots, leaves and reproductive organs. It has been thought that these depositions primarily occur through evapotranspiration (Motomura et al., 1996 ), a hypothesis that is partially based on the fact that the common locations of opal coincide with major evapotranspiration sites. However, there is some evidence that plant macromolecules participate in forming an organic matrix for silica deposition (Harrison,1996;Inanaga and Okasaka,1995;Inanaga et al.,1995). Such molecules have already been identified in other organisms t hat deposit silica (Kroger et a l, 2000; Kroger et al., 2001; Kroger et al., 2002). Benefits of Silicon Several studies have indica ted a relationship between Si and disease suppression of horticultural crops like cucumber ( Cucumis sativus L.), miniature roses ( Rosa sp.), and zinnia ( Zinnia elegans Jacq.) (Cherif et al., 1992; Datnoff et al., 2006; Dik et al., 1998; Locke et al., 2006; Menzies et al.,1991). Silicon supplemented melon ( Cucumis melo L.) contained higher chlorophyll levels and reduced transpiration rates compared with untreated plants (Lu and Cao, 2001). Silicon sprays significantly reduced the occurrenc e and severity of bract necrosis of poinsettia ( Euphorbia pulcherrima Willd. ex. Klotzsch), a physiological disorder caused by calcium deficiency. This effect was attributed to reduced evapotranspiration (McAvoy and Bernard, 1996). Silicon is a predominant element in mineral soils. However, in greenhouse floriculture production, most plants are cultivated using soilless substrates in which Si availability is limited (Voogt and Sonneveld, 2001).

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16 Some beneficial effects of Si may occur even if Si is not taken up in appreciable amounts (Voogt and Sonnenfeld 2001). Silicon can also alleviate imbalances between zinc and phosphorus supply (Marschner et al. 1990). Silicon plays an important role in increasing the resistance of plants to pathogens such as blast on r ice ( Oryza sativa L.) (Datnoff et al., 1997). Silicon is effective in preventing lodging in rice by increasing the thickness of the culm wall and the size of the vascular bundles (Shimoyama, 1958), thereby enhancing the strength of the stems. Silicon also a lleviates the effects of other abiotic stresses including salt stress, metal toxicity, drought stress, radiation damage, nutrient imbalance, high temperature, and freezing (Epstein, 1999; Ma and Tahakashi, 2002; Ma, 2004). Savvas et al. (2002) reported tha t gerbera ( Gerbera jamesonii ) plants amended with Si in the nutrient solution had significantly thicker flower stems and a higher proportion of flowers graded Class I. Moreover, Richter (2001) revealed that vase life of different gerbera cultivars could be extended and the number of flowers with bent neck could be reduced by supplying plants with Si. Foliar and root applications of Si reduced the number of colonies of powdery mildew developing in cucurbits such as cucumber ( Cucumis sativus L.) muskmelon ( C ucumis melo L.) and zucchini squash ( C u curbita maxima Duch.) (Menzies et al., 1992). Powdery mildew colony number in grape ( Vitis vinifera L.) leaves was reduced to 11% of the control leaves when foliar Si sprays were used (Bowen et al., 1992). Powdery mil dew development in Arabidopsis thaliana was observed rarely when plants were watered with a nutrient solution containing soluble Si (Ghanmi et al., 2004). Application of Si to soil or in hydroponic cultivation resulted in suppression of powdery mildew in t ( Fragraria fresco )

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17 cultivar (Kanto et al., 2004; 2006). Belanger et al. (2003) found that Si amendments to the soil mix or added to the nutrient solution protected wheat ( Triticum aestivum ) from powdery mildew. T he protective role of Si has been attributed to the accumulation of Si in the leaves, which creates a physical barrier to pathogens (Adatia and Besford, 19 86; Samuels et al., 1991 ). defense mechanisms (Fauteux et al., 2006; Remus Borel et al., 2005; Rodrigues et al., 2004; 2005). For instance, Fawe et al. (1998) demonstrated that the addition of Si to cucumber ( Cucumis sativa L. ) plants enhanced resistance to powdery mildew by increas ing antifungal activity in the plant. Similarly, Liang et al. (2005) and Rodrigues et al. (2005) found that root applied Si enhanced the activity of pathogenesis related (PR) proteins and thus increased resistance to pathogen attack on cucumber and rice ( O ryza sativa ) plants, respectively. In the Netherlands, Si supplementation of the hydroponic solution was recommended for the production of crops like cucumber ( Cucumis sativus L.) and roses ( Rosa sp .) to avoid negative effects of Si deprived plants (De Kre ij et al., 1999). Addition of Si to recirculated nutrient solution in a closed hydroponic system, ameliorated most of the negative effects of recirculation on cut rose production, resulting in better stem quality (Ehret et al., 2005). Silicon supplementati on in the form of external foliar treatments has proven to increase pathogen resistance of plant species that do not take up Si efficiently ( Bowen et al,1992; Menzies et al,1992). Silicon is an element that does not cause severe injury to plants when prese nt in excess and can provide multiple benefits (Ma et al,2001).

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18 Orchids In many orchid plants, silica bodies have been observed as longitudinal rows along the veins of the leaves. They were spherical or conical in shape depending on the species (Zhou,1995) After it is taken up, Si is translocated to the shoot in the form of monomeric silicic acid (Case y et al.,2003; Mitani et al. ,2005) and is finally deposited on cell wall material as a polymer of hydrated, a morphous silica Vendrame et al.(2010) reported that Phalaenopsis are Si accumulators. According to the AOS (American Orchid Society) in the U S, there are over 130 reported plant diseases affecting one or mo re orchid genera, caused by pathogens such as nematodes, fungi, bacteria, and viruses. Several studies have reported relationship between Si and d isease suppression However, li mited studies report on the use of supplemental Si applications as it relates to disease suppression in Phalaenopsis A previous study by Vendrame et al. (2010) indicates th at Si has a potential for improving Phalaenopsis growth and development.

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19 CHAPTER 3 MATERIAL AND METHODS Phase I (W eek s 24 to 28) Eight hundred Phalaenopsis plugs from germination bottles were randomly planted as 25 plugs per 12 in X12 in (25 cm X 25 cm) tray filled with a 60% in pine bark and 40% coconut coir medium (by volume). Plants were grown for 28 weeks at VWC plants were irrigated with 20N 8.7P 16.6K (Peters 20 20 2 0; J.R. Peters, Allentown, PA). After 28 weeks, the 800 plants were divided into four groups of 200 plants. Silicon was randomly applied at rates of 0, 0.5, 1 or 2 times the dilution suggested by the supplier to each group of 200 plants respectively 0, 0 2 5, 0.5, 1 (mg ) of Si (Table 3 1). Each p lant received 10 ml of solution once a week for 4 weeks, from week 24 to 28. Silicon was applied as AgSil 25 PQ Corp. (Valley Forge PA) starting on January12, 2011 (week 24). This product supplied Si as KSiO 3 co nsisting of 6.9% of K and 9.7% of Si 70.9% water, pH 11.3. The average light intensity in the greenhouse during phase I under the 55 % shade was 150 mol.m 2 with an average temperature of 17.68 o C (63.83 o F) and an average RH of 83%. At the end of phase I (week 28), 25 plants per group were harvested to record the length and width of the longest leaf, length of the longest root, root and shoot fresh weight (FW) and dry weight (DW). Shoots and roots were oven dried at 75 o C f or 48 H and DW was determined. R oot and shoot Si was determined by Florida Spectrum Environmental Inc (Ft Lauderdale, FL) to det ermine the amount of total Si in these tissues. Media samples were also collected at this time and sent to Florida Spectrum

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20 Environmental Services Inc.(Ft Laud erdale, FL) to determine extractable Si concentrations according to their method EPA 6010B. One substrate sample w as collected per group to determine pH and electrical conductivity (EC). Substrates were extracted with distilled water using the saturated media extraction method (SME). The pH was measured using a pH meter Milwaukee (Rocky Mount) SM 100 and EC using a Milwaukee (Rocky Mount, NC) EC meter T 75. Phase II (W eek s 29 to 34) At week 29 (February 14, 2011) ery Inc. to the University of Florida Ft Lauderdale Research and Education Center (FLREC) teaching greenhouse. The remaining 700 (100 were harvested for analysis) plants from phase I were divided into three experiments (Table 3 2). For experiment 1, plan ts that did not receive Si during phase I randomly received 0, 0.5, 1, or 2 x the recommended rate respectively 0, 0. 2 5, 0.5, 1 (mg ) of Si for weeks 29 to 34. Experiment 2 consisted on plants that received 0.5, 1, or 2x the Si during phase I did not rece ive any additional Si during weeks 29 to 34. Experiment 3 consisted of plants that received 0.5, 1, and 2x Si in phase I and continued to receive the same rates for weeks 29 to 34. Average light intensity in the greenhouse at FLREC was 240 mol.m 2 with a n average temperature of was 22.1 o C ( 71.8 o F ) and average RH% of 73%. Plants received ferti gation once a week with 11N 35P AgSil25 was applied once a week, as shown in table 3 2. At week 34, 10 plants were harvested per treatment to determine DW, and Si % in root and shoots. Tissue samples were sent to Florida Spectrum Environmental Inc for analysis.

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21 Statistical Methods Phase I The following nine varia bles were measured at the end of Phase I (week 28) : Root fresh weight (FW) and dry weight (DW), shoots FW and DW, length and width of longest leaves, length of roots and total number of roots and shoots. For each variable, one ANOVA analysis was performed t o evaluate the effect of treatment group (Si solution concentrations). Mean separations were performed using the Tukey method. The dose response relationship between treatment group and each variable, if any, was evaluated using a quadratic equation, and t he R 2 coefficient was used to measure the quality of this adjustment. Phase II Root and shoot DW and FW were measured at week 34. Plants from phase I were divided into three experiments (Table 3 2). Data was analyzed separately for each experiment using AN OVA, Tukey mean separation and quadratic regression equations.

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22 Table 3 1 Concentrations of Silicon (Si) applied to 200 Phal a enopsis orchid liners from 34 at University of Florida, Ft Lauderdale. Silicon was applied at 0, 0. 2 5, 0.5, 1 ( m g ) Silicon was supplied as AgSil 25 PQ Corp. (Valley Forge PA) 0 0.5 X 1 X 2 X no Si 1/2 commercial recommendation commercial recommendation twice commercial recommenda tion m g of Si per 10 ml of the solution 0 0 25 0 5 1 .0 ml of solution per plant per application 0 10 10 10 ml of AgSil25 per liter to mix 0 20 40 80 m g of Si per application that the plant is receiving 0 0 25 0 5 1 .0

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23 Table 3 2 Treatment combinations for applications of Silicon (Si) during weeks 29 to 34 of Phal a enopsis growth at the University of Florida Fort Lauderdale greenhouse. Silicon was supplied as AgSil 25 PQ Corp. (Val ley Forge PA) at 0 m g, 0.25 m g, 0.5 m g, and 1 m g pe r application These treatments were randomly applied to 175 plants per experiment based on the application of Si applied from 24 to 28 weeks and then Si application from 29 to 34 weeks. Treatment Phase I (24 28 weeks) Phase II (29 to 34 weeks) Experimen t 1 Si (g) 1 0 0 2 0 0. 2 5 3 0 0.5 4 0 1 Experiment 2 Si (g) 5 0. 2 5 0 6 0.5 0 7 1 0 Experiment 3 Si (g) 8 0. 2 5 0. 2 5 9 0.5 0.5 10 1 1

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24 CHAPTER 4 RESULTS AND DISCUSSI ON Phase I (W eek s 24 28) A ccording to Kamenidou et al. (2008), the effect of Si su pplements on sunflower height and flower diameter varied depending on Si source and concentration. During phase I, as Si increased from 0 to 0.5 m g Phal a enopsis root and shoot FW, root and shoot DW, width of longest leaf and root length increased and then decreased (Figs. 4 1, 4 2, and 4 3). Vendrame et al. (2010) reported similar resu lts during liner production. Earlier reports provided a wide range of acceptable EC for Phalaenopsis ranging from 0.63 and 3.8 dS m 1 (Wang 1996; Wang and Gregg, 1994). I n general, plant growth is reduced as EC levels increase in the substrate (Wootton et al.,1981). The EC in the substrate increased as the levels of Si applied increased (Table 4 1). It is possible that high EC when using 1 m g of Si per application contribut ed to poor growth in Phalaenopsis acceptable range (Table 4 1). Silicon concentrations in the root and shoot tissue increased as Si app lication increased from 0 to 1 m g (Table 4 2) The concent ration of Si was higher in roots than it was in shoots (Table 4 2). This confirms that Phalaenopsis is indeed a Si accumulator species. Vendrame et al. (2010) also reported that Si concentration in roots and shoots increased as Si applica tion rate increas ed Phase II (W eek s 29 34) Experiment 1: Plants did not receive any Si d uring 24 to 28 weeks but received Si duri ng 29 to 34 weeks. As Si concentration increased from 0 to 1 m g Phal a enop s is root and shoot dry weight increased (Fig 4 4). Silicon concentra tions in root and shoot

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25 tissues increased as application rate of Si increased from 0 to 0.5 m g, and then decreased (Table 4 2). Experiment 2: Plants received Si weeks 24 to 28 but did not receive any additional Si from weeks 29 to 34 At week 34, plants t hat received 1 m g of Si during weeks 24 to 28 had greate st shoot DW but root DW was greate st at 0.25 mg (Fig 4 5) Silicon concentration in the roots increased as applica tion rate increased from 0 to 1 m g (Table 4 2). However Si concentrations in the sh oots increased as application rate increased from 0 to 0. 2 5 mg and then decreased (Table 4 2). Experiment 3: Plants received Si at 0. 2 5 m g 0.5 m g, and 1 m g from week 24 to 34 As observed during the first 4 weeks, shoot and root DW increased as Si con cent ration increased from 0 to 0.5 m g and then decreased (Fig 4 6). Unlike the data collected at week 28, w h ere Si in tissues linearly increased as application rate increased, Si concentrations in root and shoot tissues was greatest for plants treated with 0. 2 5 m g and 0.5 m g respectively at week 34 (Table 4 2). As reported by Vendrame et al. (2010) reduced growth parameters in Phalaenopsis orchid liners were possibly related to the applied concentration of Si and the elevated EC value. Although substrate EC le vels appeared to be in an acceptable range for most ornamentals, we did observe symptoms of salt damage at the higher application rates of Si. It appears that the most adverse effect from Si application during liner phase was due to increased EC l evels. A ccording to Wang (1998) the most obvious adverse effect of increasing salinity was the degree of root injury. In this study roots died, suggesting that Phalaenopsis may be more susceptible to high salinity concentrations than previously described.

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26 Another possible explanation for decreased Phalaenopis growth at high Si levels could be an induced magnesium (Mg) defeiciency). According to Kamenidou et al. (2009), apparent antagonism between K + supplied by potassium silicate sources lead to Mg deficiency in sunflower ( Helianthus annuus L.) and zinnia ( Zinnia elegans ) We did not observe any symptoms of Mg deficiency in this experiment. Because we did not run a K control, i t is possible that the improved g row th of Phalaenopsis in this study was due to K ferti lization and not Si. Silicon supplementation effects on greenhouse produced sunflowers can vary from beneficial to detrimental depending on the applied source and concentration of Si (Kame n idou et al.,2008).

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27 Table 4 1 Substrate p H, electrical conductivity (EC) and Sil i con (Si) at week 28. Phalaenopsis liners were treated from week 24 to 28 with AgSil 25 PQ Corp. (Valley Forge PA) applied at 0, 0. 2 5, 0.5 or 1 (mg ) plant/week Silicon concentrations in the substrate were determined by Florida Spectrum Environmental Inc while pH and EC were determined on the extracted solution from the saturated media extraction method. One sample per treatment Si Treatment pH EC (dS/m) Si (mg/Kg) 0 5.8 2.58 72.2 0. 2 5 6.1 2.66 81.6 0.5 6.9 2.79 9 0.9 1 7.2 2.89 133.0

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28 Table 4 2 Concentration of Silicon (Si) in Phal a enopsis root and shoot tissue at week 28 and at week 34. During weeks 24 to 28, plants received Si applied at 0, 0. 2 5, 0.5 or 1 (mg ) plant/week During weeks 2 9 to 34 plants were divided into three experiments. In experiment 1 plants did not receive Silicon (Si ) during liner production (weeks 24 to 28) but received Si applied at 0,0. 2 5, 0.5 or 1 ( m g ) plant/week during weeks 29 to 34. In experiment 2 plants recei ved Si during liner production (weeks 24 to 28) at 0, 0. 2 5, 0.5 or 1 ( m g ) plant/week but did not receive any Si application during weeks 29 to 34. In experiment 3, plants received Si during liner production (weeks 24 to 28) as well as from weeks 29 to 34 at 0, 0. 2 5, 0.5 or 1 ( m g ) plant/week Silicon was supplied as AgSil 25 PQ Corp. (Valley Forge PA). Concentrations of Si in the tissue were determined by Florida Spectrum Environmental Inc 10 plants per treatment were analyzed Week 24 to 28 Week 29 to 34 Root Si (mg/Kg) Shoot Si (mg/Kg) 0 109.0 73.3 0. 2 5 137.0 114.0 0.5 135.0 106.0 1 198.0 145.0 Exp 1 0 0 110.0 77.7 0 0. 2 5 229.0 127.0 0 0.5 199.0 102.0 0 1 187.0 98.8 Exp 2 0 0 110.0 77.7 0. 2 5 0 168.0 120.0 0.5 0 156.0 90.1 1 0 194.0 89.2 E xp 3 0 0 110.0 77.7 0. 2 5 0. 2 5 190.0 124.0 0.5 0.5 181.0 126.0 1 1 167.0 81.0

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29 Figure 4 1 Root (rfw) and shoot (sfw) FW at week 28 after Phalaenopsis liners had received Silicon (Si) applied at 0 ,0. 2 5, 0.5 or 1 ( m g ) per plant/week from week 24 to 28 (phase I) Silicon was supplied as AgSil 25 PQ Corp. (Valley Forge PA). Data are means of 25 plants. Figure 4 2 Length and width of largest leaf and length of longest root of Phalaenopsis l iners that had received Silicon (Si) applied at 0, 0. 2 5 0.5 or 1 ( m g ) per plant/week from week 24 to 28 (phase I) Silicon was supplied as AgSil 25 P Q Corp. (Valley Forge PA). Data are means of 25 plants. 4.27 7.38 5.82 4.94 7.35 10.65 10.93 7.88 y = 7.8145x 2 + 7.8936x + 4.7132 R = 0.5572 y = 14.251x 2 + 14.583x + 7.4986 R = 0.9737 0 2 4 6 8 10 12 0 0.2 0.4 0.6 0.8 1 1.2 fresh weight (g) Silicon (mg applied weekly) rfw sfw 76.92 89.76 96.16 82.36 40.36 47.72 49.88 43.52 96.88 123.04 103.68 100.12 y = 16.189x 2 + 35.231x + 76.721 R = 0.9977 y = 8.1636x 2 + 17.818x + 40.494 R = 0.996 y = 12.985x 2 + 24.469x + 101.56 R = 0.3517 0 20 40 60 80 100 120 140 0 0.5 1 1.5 measurment (mm) silicon(mg applied weekly) longest leaf length longest leaf width longest length root

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30 Figure 4 3 Roo t (rdw) and shoot (sdw) DW at week 28 after Phalaenopsis liners had received Silicon (Si) applied at 0, 0. 2 5, 0.5 or 1 ( m g ) per plant/week from week 24 to 28 (phase I) Silicon was supplied as AgSil 25 PQ Corp. (Valley Forge PA). Data are m eans of 25 plant s. Figure 4 4 Root (rdw) and shoot dry weight (sdw) at week 34 of Phal a enopsis plants that did not receive Silicon (Si) during liner production (weeks 24 to 28) but received Si applied at 0, 0. 2 5, 0.5 or 1 ( m g ) per plant /week during weeks 29 to 34 (Experiment 1) Silicon was supplied as AgSil 25 PQ Corp. (Valley Forge PA). Data are m eans of 10 plants. 0.39 0.51 0.44 0.41 0.42 0.53 0.54 0.42 y = 0.2836x 2 + 0.2789x + 0.4085 R = 0.492 y = 0.5091x 2 + 0.5033x + 0.4244 R = 0.9825 0 0.1 0.2 0.3 0.4 0.5 0.6 0 0.2 0.4 0.6 0.8 1 1.2 Dry Weigth (g) silicon(mg applied weekly) rdw sdw 0.418 0.49 0.515 0.591 0.337 0.432 0.403 0.517 y = 0.0181x 2 + 0.1196x + 0.4226 R = 0.9834 y = 0.0007x 2 + 0.0816x + 0.3518 R = 0.839 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0 0.2 0.4 0.6 0.8 1 1.2 Dry Weigth (g) silicon(mg applied weekly) rdw sdw

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31 Figure 4 5 Root (rdw) and shoot dry weight (sdw) at week 34 of Phal a enopsis plants th at received Silicon (Si) during liner production (weeks 24 to 28) at 0,0. 2 5, 0.5 or 1 ( m g ) per plant/week but did not receive any Si application during weeks 29 to 34 (Experiment 2) Silicon was supplied as AgSil 25 PQ Corp. (Valley Forge PA). Data are m eans of 10 plants. Figure 4 6 Root (rdw) and shoot dry weight (sdw) at week 34 of Phal a enopsis p lants that received Silicon (Si ) during liner production (weeks 24 to 28) as w ell as from weeks 29 to 34 (Experiment 3) a t 0, 0. 2 5 0.5 or 1 ( m g ) per plant/week Silicon was supplied as AgSil 25 PQ Corp. (Valley Forge PA). Data are m eans of 10 plants. 0.337 0.634 0.727 0.61 0.418 0.665 0.835 0.481 y = 0.2675x 2 + 0.666x + 0.3454 R = 0.9897 y = 0.3645x 2 + 0.7688x + 0.4054 R = 0.9817 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 0.2 0.4 0.6 0.8 1 1.2 Dry Weigth (g) silicon(mg applied weekly) sdw rdw

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32 CHAPTER 5 CONCLUSION Based on the results of this study, the addition of Si to Phalaenopsis indicates that Phalaenopsis appear to acc umulate Si and support the work reported by Vendrame et al (2010). Silicon appears to have a positive impact on overall growth T he liner stage appears to be very sensitive to over application of Si due to increased salinity concentrations in the growing substrate. Past the liner stage plants seem to be less sensitive to salinity. However as salinity increases more roots die (Wang, 1998). At week 34 plants from experiment two showed no negativ e effects of salinity while still showing Si accumulation i n the root This suggests a higher tolerance to salinity for Phalaenopsis plants at a more advanced stage of vegetative growth. According to Tamai and Ma 2003, the uptake of Si involves at least two processes; the transport of Si from external solution t o cortical cells, and from cortical cells to the xylem. Roots died possibly compromising Si uptake and consequently the final DW of tissue. The higher concentration of Si in the roots as compared to the shoots could indicate a higher concentration of Si tr ansporters from the external solution to the cortical cell than that of transporters to xylem cells. It seems that at the liner stage Si has to be applied in a lower concentration to avoid salinity damage. Further studies need to be performed to determine recommended levels of Si that prevent salinity damage, but also promote positive growth results. Additional studies on the benefits of Si in flower development and quality are also warranted.

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36 McAvoy, R.J., and B.B. Bernard. 19 9 6. Silica spray reduce the incidence and severity of bract necrosis in poinsettia. HortScience 31:1146 1149. Marschner, H., H. Oberle, I. Cakmak, and V. Romheld. 1990. Growth enhancement by Si lcon in cucumber ( Cucumis sativus ) plants depends on imbalan ce in phosphorus and zinc supply. Plant and Soil 124:211 219 Martin, K.P. and J. Madassery. 2006. Rapid in vitro propagation of Dendrobium Hybrids through direct shoot formation from explants, and protocorm like bodies. Sci Hort. 108:95 99. Mayland H F D.A. Johnson K.H. Asay and J.J. Read. 1993. Ash, carbon isotope discrimination, and Si lcon as estimators of transpiration efficiency in crested wheatgrass. Aust J Plant Phys 20:361 369. Menzies, J., P. Bowen, D. Ehret, and D. M. Glass. 1992. Foliar app lication of potassium silicate reduce severity of powdery mildew on cucumber, muskmelon, and zucchini squash. J Amer Soc Hort Sci 117: 902 905. Menzies, J.G., D.L. Ehret, A.D.M. Glass, T. Helmer, C. Koch, and F. Seywerd. 1991. Effects of soluble Si lco n on the parasitic fitness of Sphaerotheca fuliginea on Cucumis sativus Phytopathology 81:84 88. Meyer J H and M.G. Keeping MG. 2001. Past, present and future research of the role of Si for sugarcane in southern Africa. In : Datonoff L, Korndorfer G, S ynder G (eds). Silicon in Agriculture. Elsevier Science New York. Mitani N., and J.F. Ma. 2005. Uptake system o f Si lcon in different plant species. J. Exp. Bot. 56 : 1255 1261. Mitani, N., J.F. Ma, and T. Iwashita. 2005. Identification of Si licon form in t he xylem of rice ( Oryza sativa L. ). Plant Cell Phys . 46: 279 283. Motomura H N. Mita, and M. Suzuki. 1996. Silica accumulation in long lived leaves of Sasa veitchii (Carriere) Rehder ( Poaceae Bambusoideae ). Ann Bot 90:149 152. Neumann D and U. z ur Nieden 2001. Si licon and heavy metal tolerance of higher plants. Phytochem 56:685 692. Remus Borel, W., J. G Menzies, and R. R Belanger. 2005. Si licon induced antifungal compounds in powdery mildew infected wheat. Phys Mo l Plant Path 66(3):108 1 15. Richmond, K.E. and M. Sussman. 2003. Got Si licon ? The non essential beneficial plant nutrient Curr. Opin. Plant Bio. 6, 268 272 Ritcher,M.. 2001. Silicium verbessert haltbarkeit bei Gerbera [Si fertilization and vase life of gerbera]. Das Magazin fur Z ierpflanzenbau 22:42 44.

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39 BIOGRAPHICAL SKETCH Charles Wajs brot was born in Sao Paulo, Brazil. The younger of two children, he grew up in Sao Paulo, Brazil, graduating from Renascenca Hig h School in 1984. He earned a bachelor s degree in b iology in 2001from Uninove in Sao Paulo, Brazil. Charles started as an entrepreneur after graduating from high school H e worked on a family business un til 1997 when he started his own recycling factory. In 1999 he started to manufacture pipes from recycled plastic produced by his company, and later his company specialized in pipes for telecommunication Th e company also produced plastic bags for garbage with the recycled material. In 2004 he moved to N ew J ersey, and in 2008 he sold his company and decide d to go back to school to pursue a Master s of Science degree. He received his master s degree and star t ed a PhD program in fall 2011 to continue his work with o rchids Charles has been ma rried to Dalia Ballas Wajsbrot for 15 years and they have t wo children, Victoria, age 14 and Daniel age 9.