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34 Indonesian Journal of Agriculture 1(1), 2008: 34-43 A. Santi et al. IMPACT AND MODEL OF AIR POLLUTION BY SIMULATED ACID RAIN ON THE GROWTH OF ORCHID PLANTS1) A. Santia), M.S. Saenib), N.A. Mattjikb), T. Juneb), and H. Hardjomidjojob) a) Indonesian Ornamental Plants Research Institute, Jalan Raya Ciherang, PO Box 8 SDL, Segunung, Pacet, Cianjur 43252 b) Bogor Agricultural University, Kampus IPB Darmaga, Bogor 16680 ABSTRACT and fall down with rain water, so the rain water has low pH. Rain water at normal condition has pH 5.6. Acid rain is Acid rain is one of the secondary air pollutants that inhibits the commonly occurred at industrial areas as effect of releasing growth of orchid plants. The general purpose of this research was SO3 and NO2 pollutants to the air with high concentration to study response of vanda, dendrobium, and oncidium orchids (Finley 2001). to the simulated acid rain to determine the critical point of the plant growth. The specific purpose of this research was (1) to Sukarsono (1998) stated that plant group which detect the SO2 and NO 2 pollutants as the cause of acid rain in susceptible to pollutant in relatively low concentration is research location, (2) to analyze total stomata, chlorophyl, ornamental and vegetable crops (horticulture), where the nitrogen, sugar, and acidity of leaves, and (3) to develop the pollutants caused chlorosis and necrosis. Generally, model of air pollution by simulated acid rain on the growth of ornamental and vegetable crops have leaf structure which orchid plants. This research was conducted in the paranet house at Agriculture and Forestry Provincial Office of DKI Jakarta from more sensitive to pollutants. It is assumed that plant with July 2003 to July 2005. The experiment was arranged in a factorial wider leaves had more stomata, so absorption of pollutants randomized block design with orchid plant genera (vanda, was higher and it caused leaves more sensitive to dendrobium, and oncidium) as the first factor, acidity of acid rain pollutants than plant with narrower leaves. (pH 4.3, 4.9, and 5.8) as the second factor, and frequency of acid Treshow (1984) explained that each pollutant is rain (once a week and twice a week) as the third factor. Each dangerous in different concentrations, and every plant treatment was held in three replications. Results of the research showed that there was no significant difference between acidity species gives different responses to each pollutant. Leaf and frequency of acid rain treatment on plant height and leaf damage that is indicated by visible damage is a final result length increment. The growth of three orchid plants were not of various processes initiated by entering pollutants into inhibited in the range of acidity (pH) apllied in the treatments. leaves and through some reactions in leaf cells. The The ranges of rain acidity were extended from 2.0 to 5.6 to know pollutants enter to the plant tissue through leaf stomata the resistance of orchid plants to the rain acidity. Growth of oncidium was inhibited at application of rain acidity (pH) ≤ 3.0, then go into intracellular part, affect water pH in cell, and while vanda and dendrobium were still in a normal growth at 3.0 finally react with mesophyl cell wall. Pollutants generally rain acidity application. Visual Basic 6.0 version used for model react with cell membrane especially protein component. development simulation of the program indicated that critical At high air pollution condition, plant chlorophyll will point of plant growth response for oncidium was occurred when N decrease as result of plant stress. Plant with high total concentration in the leaf was 5.28 mg/l and H concentration was chlorophyll at polluted air condition will be more tolerant 0.14 mg/l of acid rain. Vanda and dendrobium had no response to simulated acid rain, meanwhile oncidium was more sensitive to air pollution (Singh et al. 1991). to simulated acid rain. Orchids are one of ornamental plant species having high economic value. The plant growth requires good [Keywords: Vanda, dendrobium, oncidium, air pollution, model maintenance and suitable environmental condition. The simulation of acid rain; critical point] acidity of growing media (pH) extremely affects plant growth due to the inhibition of root growth. Acidity of INTRODUCTION growing media suitable to orchid growth is 5-6. Too low pH will damage the plant and finally decrease production Acid rain is decrease of acidity (pH) of rain water due to and quality of flower (Widiastoety and Santi 1997). the reaction between pollutants and water which forms According to Munzuroglu et al. (2005), vitamin A, E, and new chemical composition in the air having acid properties C contents in strawberry fruit decreased with declining of rain water pH after 24-hour treatment. The decrease vitamin 1) Article in bahasa Indonesia has been published in Jurnal content was due to the formation of oxygen free radical in Hortikultura (Special Edition) No. 2, 2007, p. 162-175. plant as result of acid effect. Impact and model of air pollution ... 35 Plant damage by acid rain in wider orchid plantation as the third factor. Each treatment comprised of three plants, areas will cause plants suffer or do not produce flower at so there were 54 experimental units. Tukey significant all resulting in economical crop losses. Even though data different test was used to find out treatment factor level on acid rain impact on orchid production have not available influencing observed response. yet, farmers stated that plant damage by acid rain was Variables observed were plant height increment, leaf worrying. length increment, number of stomata, leaf thickness, To find out the effect of acid rain on growth of orchid, chlorophyll content, N content, and number of flower stalk. model of plant response to acid rain has to be developed. The experiment was carried out in several stages, that This will help plant ecophysiologists to overcome plant are analysis of air pollutants (SO3 and NO2) at research damage caused by acid rain. location, leaf analysis (number of stomata, leaf thickness) The purpose of this research was to study response of before and after acid rain simulation, leaf analysis orchid plants to the simulated acid rain. The specific aims (chlorophyll content, total sugar, and N content) after were (1) to detect the SO3 and NO2 pollutants that generate treatment, and developing model of air pollution impact by acid rain in the research location, (2) to analyze plant acid rain on growth of orchid plant. damage through leaf analysis (total stomata, chlorophyll, To develop model, it was required several influencing nitrogen, and sugar), and (3) to develop the model of air variables on plant growth, such as rain water pH, number pollution by simulated acid rain on the growth of orchid of stomata, leaf thickness, chlorophyll, H+ content of rain plants. water, leaf N content, and total sugar (Table 1). The development of air pollution model by acid rain used Visual Basic program version 6.0. This program was chosen MATERIALS AND METHODS because it had attractive feature, relatively easy to be operated, and more flexible and dynamic. Data of Field trial was conducted in the shaded house at Agriculture observation result which were processed and written in and Forestry Provincial Office of DKI Jakarta from July Window program would be applied with Visual Basic 2003 to July 2005. Sample analysis was carried out at program version 6.0 (Bradley and Millspaugh 2002). laboratory of Study Center for Plant Breeding, Bogor Agricultural University. The plant materials used in this experiment were three RESULTS AND DISCUSSION orchid plant genera, namely Vanda Douglas, Dendrobium Hybrid, and Oncidium Golden Shower. Acid rain with Pollutant Condition Stimulating Acid Rain several acidity level (pH 4.3, 4.9, and 5.8) was prepared by Occurrence in Research Location SARPEDAL Puspitek Serpong. The experiment was arranged in a factorial randomized This study was initiated with reaction of SO2 and NO2 block design with three factors. The genera of orchid plant pollutants with O2 which would form SO3 and NO3. With (Vanda Douglas, Dendrobium Hybrid, and Oncidium the occurrence of water vapor in air, it would produce Golden Shower) were used as the first factor, while acidity H2SO4 and HNO3 compounds having acid properties and of acid rain (pH 4.3, 4.9, and 5.8) was as the second factor would fall with rain water forming acid rain. Acid rain would and frequency of acid rain (once a week and twice a week) enter to the plants and affect process occurred in plants. Table 1. Variable in modeling design of acid rain effect to orchid growth. Variable measured Purpose of measurement Effect to the plant Rain water pH To find out acidity of rain water Number of chlorophyll and photosynthesis process SO2, NO2 To find out SO2 and NO2 at research location Acid rain occurrence Number of stomata To determine leaf stomata number Amount of pollutant absorption into leaf Number of chlorophyll To find out leaf chlorophyll number Photosynthesis process Leaf nitrogen (N) To determine leaf nitrogen concentration Positive effect of nitrogen enables to suppress negative effect of hydrogen Leaf thickness To find out leaf thickness Leaf thickness affects plant sensitivity to acid rain Total sugar To determine leaf total sugar content Energy resulted in photosynthesis process and used to support growth 36 A. Santi et al. Continuous process in plants highly depended on N Table 2. Chemical compound in rain water with several value content in leaf which controlled acid effect from H+ from acidity. acid rain. If the plants were not tolerant to acid rain, the Chemical compound Concentration process of photosynthesis in the plant would inhibit and finally caused the plant died. But if the plants were tolerant CaCl2 (g/l) 0,2773 0.2774 0.2763 to acid rain, the process of photosynthesis in plant KCl (g/l) - - 0.1932 occurred and the plant would grow and develop. MgSO4.7H2O (g/l) 1.0284 1.0375 1.0271 Based on the result of chemical compound analysis in KNO3 (g/l) 0.5197 0.5198 - rain water, the compounds obtained were CaCl2, KCl, (NH4)2SO4 (g/l) 0.7333 0.7363 0.7380 MgSO4, 7H2O, KNO3, (NH4)2SO4, Na2SO4, NaOH, and Na2SO4 (g/l) 0.3092 0.3096 0.3113 CH3COOH (Table 2). Each acidity value (pH) of rain water CH 3COOH (ml/l) 10 4 - had different mineral contents. Concentration of each NaOH (ml/l) - - 2 mineral in rain water would determine the acidity of that rain water. Table 3. Effect of kind of orchid, acid rain acidity, and acid rain simulation frequency on plant height and leaft length increment of vanda, dendrobium, and oncidium. Damage Analysis by Conducting Leaf Analysis (Stomata Number, Total Chlorophyll, Total Plant Leaf length Nitrogen, and Total Sugar) Treatment height increment increment (cm) (cm) Group/replication Result of statistical analysis indicated that acid rain Group I 48.48b 30.30a simulation and treatment frequency did not significantly Group II 77.77ab 40.40a affect plant height and leaf length increment. Whereas plant Group III 95.95a 86.86a height increment of three orchid genera had significantly different. This was happened because the three orchid Kind of orchid plants had different growth character (Table 3). Vanda had Vanda Douglas 90.90a 4.04a monopodial growth character, while dendrobium and Dendrobium Hybrid 81.81b 86.86b Oncidium Golden Shower 3.2c 67.67b oncidium had sympodial growth character, so the growth of vanda was faster than that of other two orchids. Acid rain acidity (pH) The difference of acid rain effect on plant growth was 4.3 59.59a 54.54a caused by different leaf thickness and stomata number 4.9 37.37a 43.43a among the three orchids, so it affected rain water absorption. 5.8 23.23a 59.59a The average of leaf thickness and stomata number of three Frequency of acid rain simulation orchids can be seen at Table 4. Vanda had thicker leaf (5.35 1 x 44.44a 72.72a mm) and fewer stomata number (53) than dendrobium and 2 x 12.02a 4.32a oncidium which were more tolerant to acid rain. This was resulted in acid rain which entered to leaf tissue through Interaction not significant not significant fewer stomata, so the effect was also less. Stomata function might be influenced by several factors, such as mechanical disturbance between cell at epidermis tissue and turgor change of guard cell (Mansfield Table 4. Leaf width and stomata number of vanda, dendrobium, 1994). Entrance of acid rain into orchid plant could be and oncidium. detected by labelling method of S35 element. S35 was used because the element was predominant in rain water. In Leaf width Stomata number Kind of orchid addition sulphuric acid was more stable than chloride acid (mm) (stomata/10 -6 mm 2 ) and nitrate acid (Kohno et al. 2001). Vanda Douglas 5.35 53 Amount of acid rain absorption detected by absorption Dendrobium Hybrid 1.83 70 of S35 element was proved to enter in orchid at upper, center, Oncidium Golden Shower 0.55 293 and down parts (Figure 1). The difference of absorption Impact and model of air pollution ... 37 Vanda 50.000 Vanda Dendrobium 14 Amount of S35 absorption Dendrobium Oncidium 40.000 12 Oncidium 30.000 N content 8 (mg/l) 20.000 4 10.000 0 0 Top Middle Bottom pH 4.3 pH 4.9 pH 5.8 Part of orchid plant Acidity of acid rain, pH Figure 1. Absorption of S35 in plant part of vanda, dendrobium, Figure 2. Ntrogen content of vanda, dendrobium, and oncidium and oncidium. at several acid rain acidity treatments. Vanda Vanda Dendrobium Dendrobium 2.5 200 Oncidium Oncidium Chlorophyll content Total sugar content 2.0 160 (mg/g) (mg/g) 1.5 120 1.0 80 0.5 40 0 0 4.3 4.9 5.8 4.3 4.9 5.8 Acidity of acid rain, pH Acidity of acid rain, pH Figure 3. Chlorophyl content of vanda, dendrobium, and oncidium Figure 4. Total sugar content of vanda, dendrobium, and onci- orchid at several acid rain acidity treatments. dium orchid in several acid rain acidity treatments. amount of S35 element among orchid types was caused by though pH of simulated acid rain decreased. N content in different stomata number of each orchid type. Oncidium rain water was adequate to stimulate chlorophyll having the most stomata number (293/10-6 mm2) had highest production which might reduce the effect of H+ from rain S35 absorption, that was 44,264.13/minute, than dendrobium water as stated by Shan et al. (1995) that acid rain simulation and oncidium with stomatal number of 70 and 53/10 -6 mm2 increased chlorophyll content of Pinus armandi leaf. Shan and S35 absorption of 15,712.03 and 9,327.87/minute, et al. (1996) also stated that acid rain simulation at pH 3.0 respectively, at upper plant part. and 2.3 with frequency six times a week for 14 weeks on P. Nitrogen content of vanda and oncidium increased at armandi plant increased net photosynthesis rate per pH 4.9, but decreased at pH 5.8. Whereas N content at chlorophyll a+b content unit. dendrobium decreased at pH 4.9 and increased at pH 5.8 Total sugar content decreased with increase of rain (Figure 2). This was caused by acid rain simulation which water pH on vanda and oncidium, while on dendrobium affected specific N content for each kind of orchid. Singh total sugar content increased with raising of rain water pH and Agrawal (1996) reported that N content in Triticum (Figure 4). Momen and Helms (1996) revealed that effect of aestivum increased with the raising of rain water acidity. acid rain simulation at pH 5.1 and 3.0 combined with ozone Positive effect of leaf N content was more than negative to tiller and matured P. ponderosa increased C-N ratio. Acid effect of H+ generated from acid rain (Shan 1998). rain simultaneously increased chlorophyll content and Chlorophyll content of vanda, dendrobium, and reduced chlorophyll use efficiency in photosynthesis oncidium orchids was higher at pH 4.3 than pH 4.9 and 5.8 process. The reduction of chlorophyll use efficiency was (Figure 3). This result was similar to Shan (1998) that assumed correlated with increase in degradation rate of chlorophyll content (a+b) in leaf increased parallelly even chlorophyll into pheophytin (Shan 1998). Research result 38 A. Santi et al. 20 of Momen et al. (1999) on P. ponderosa showed that acid rain with pH 3.0 decreased net photosynthesis value of 11-25%, depended on temperature treatment. Plant height increment 15 (cm) 10 Model of Acid Rain Effect on Growth and Development of Orchid Plant 5 To find out the resistance of orchid plant to rain water acidity, additional research should be conducted by 0 broaden interval of rain water pH, that are from 2.0 to 5.6. 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Response of plant height increment of vanda, dendrobium, Acidity of acid rain, pH and oncidium to acid rain simulation with pH of 2.0-5.6 was presented in Figure 5, 6, and 7. According to Fan and Wang Figure 5. Plant height increment in vanda orchid at several acid (2000) leaf damage, decrease of chlorophyll content, growth rain acidity treatments. of seedling of all hardwood species tested occurred at acid rain simulation with pH 2.0. The simulated acid rain with pH 3.0 once a week for 14 months on P. ponderosa decreased water number use efficiency (Momen et al. 20 (1997). Plant height increment of vanda was raising with the increase of rain water pH from 2.0 to 3.5, then it slightly Plant height increment 15 decreased until pH 5.6. At extreme pH of 2.0 and 2.5, the plant could still survive even its growth was not good (cm) 10 (Figure 5). Plant height of dendrobium increased with raising of rain water acidity from 2.0 to 3.0, then it was relatively 5 stable. Eeven though its growth was inhibited at pH 2.0 and 2.5, the plant was still able to survive (Figure 6). Plant height increment of oncidium was inhibited at rain water 0 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 acidity of 2.0-4.0, even at pH 2.0-3.0 the plant could not Acidity of acid rain, pH grow or even dead (Figure 7). Input-output diagram of acid rain impact on orchid Figure 6. Plant height increment in dendrobium orchid at several growth required uncontrolled input in term of stomata acid rain acidity treatments. number and leaf thickness because it depended on each plant types and controlled input consisted of orchid plant genera and rain water acidity. Whereas required output was the occurrence of critical point of growth, and unrequired output was that plant did not response to H+ 14 concentration. Parameter measured for determining model 12 was relationship between H+ concentration in acid rain and H concentration in leaf (Figure 8). Plant height increment 10 To develop a model, input suitable to proper process 8 should be made, so the program could process and produce (cm) 6 required output. Diagram of determination of critical point (Figure 9) explained that input consisted of rain water pH, 4 stomata number, and leaf thickness. Limit of pH ≤ 3 was 2 used because at that pH value oncidium orchid could not 0 optimally grow. Other orchid plants (vanda and 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 dendrobium) could survive, because of different stomata Acidity of acid rain, pH number and leaf thickness. Stomata number of vanda and dendrobium was fewer than that of oncidium, so pollutant Figure 7. Plant height increment in oncidium orchid at several entering through stomata was fewer at vanda and acid rain acidity treatments. dendrobium than that of oncidium. Leaf thickness also Impact and model of air pollution ... 39 Environmental input Uncontrolled input Required output • Stomata number • Critical point of plant • Leaf thickness response to acid rain Model of acid rain impact on growth of orchid plant Controlled input Unrequired output • Kind of orchid plant • Plant did not response (vanda, dendrobium, to H+ oncidium) • Rain water pH Parameter of plant growth • H concentration of rain water • Leaf N concentration Control management Figure 8. Input-output diagram of acid rain impact on orchid plant. Input: Rain water pH Stomata number Leaf thickness pH 3 Stomata number Dead 150 Leaf thickness Dead 1.7 g(x) = function of pH to N f(x) = function of pH to H f(g(x)) = critical point function of N and H f H (N (pH)) Critical point Plant growth Figure 9. Flow diagram of critical point decision in nitrogen and hydrogen on orchid plant. 40 A. Santi et al. Figure 10. Model simulation results for oncidium orchid. Figure 11. Model simulation results for vanda orchid. Figure 12. Model simulation results for dendrobium orchid. affected pollutant entering the plants; the thicker the Correlation of rain water acidity (pH) and H+ content in leaves, the more difficult the pollutant penetrating plant rain water is presented at Figure 13. Regression quotient tissue. The limit of stomata number was ≤150, that was a produced was used to determine joint critical point with range between stomata number of oncidium and regression quotient derived from correlation of rain water dendrobium. The limit of leaf thickness was used a value acidity (pH) and leaf N content (Figure 14). Both quotient between leaf thickness of vanda and dendrobium (≥1.7 m). could be combined because they had same element, that is Composite function of pH function on N and H produced rain water acidity (pH), so they could form new quotient, a critical point of plant response to acid rain at N and H correlation of N and H content which produced critical concentration of 5.28 and 0.14 mg/l, respectively. point of plant response to acid rain (Figure 15). Result of model simulation is presented in Figure 10 for Regression quotient of relationship between rain water oncidium, Figure 11 for vanda, and Figure 12 for acidity and H+ was f(x) = Y= -0.0074x2 + 0.0781x - 0.0641, dendrobium. Critical point of N to H was (5.28, 0.14), that whereas regression quotient of relationship between rain was when leaf N content 5.28 mg/l, the H content would be water acidity and N ion was g(x) = Y = -5.5293 x2 + 54.385x 014 mg/l meaning that H decreased with N increased. - 128.01. From both regression quotient (f(x) = -0.0074x2 + Impact and model of air pollution ... 41 0.144 y = -0.0074x2 + 0.0781x - 0.0641 Hydrogen ion concentration 0.140 (mg/l) 0.136 0.132 0 2 4 6 8 Acidity of acid rain, pH Figure 13. Relationship between acid rain acidity and H+ concentration on vanda orchid. 18 y = -0.2593x2 + 54.385x - 128.01 16 Nitrogen ion concentration 14 N concentration 12 Standard deviation for N = 8.6 mg/l (mg/l) 10 Standard deviation for N = 12.15 mg/l 8 Standard deviation for N = 10.5 mg/l 6 4 2 3 4 5 6 Acidity of acid rain, pH Figure 14. Relationship between acid rain acidity and nitrogen ion concentration on oncidium orchid. 0.16 Critical point: (5.28; 0.14) 0,14 y = -0.0074x2 + 0.0781x - 0.0641 0,12 H concentration 0,10 Oncidium (mg/l) 0.08 Poly. (Oncidium) 0.06 0.04 0.02 0 0 2 4 6 8 10 N concentration (mg/l) Figure 15. Relationship between nitrogen and hydrogen concentration on oncidium orchid. 42 A. Santi et al. 0.0781x - 0.0641) and (g(x) = -5.5293 x2 + 54.385x - 128.01) critical point of plant response to rain water acidity, so it obtained from two graphics (Figure 13 and 14), a new could be purposed for other plants beside orchids. quotient was produced, i.e. f(g(x)) = -0.0074x2 + 0.0781x - Plant response to acid rain on other plant species having 0.0641, which was a combination of both quotient, and different growth cycle from orchid plants should be tested. from the estimation it could be determined critical point of Orchid plants had Crassulacean acid metabolism (CAM) plant response to acid rain occurred at N concentration of growth cycle which fixed CO2 at night and changed it into 5.28 mg/l and H of 0.14 mg/l (Figure 15). This phenomenon malic acid, then at daylight used CO2 for photosynthesis. showed that at the initial point positive effect of N could Therefore, study on other plants having C3 and C4 growth reduce negative effect of H (acid). Research conducted by cycle was required. Shan (1998) on P. densiflora plant showed that N content Model of acid rain impact should be tested on other in rain water was adequate to stimulate chlorophyll plants, because each plant had different stomata number production and control H+ degradation effect of acid rain. and leaf thickness. If the result was similar or had the same Acid rain simultaneously increased total chlorophyll trend, the model could be generally used. content and reduced chlorophyll use efficiency in photosynthesis process. Increase of H+ in simulated acid rain caused degradation of chlorophyll into pheophytin. H + could substitute Mg 2+ in chlorophyll molecule: REFERENCES chlorophyll + 2 H+ → pheophytin + Mg2+ (Shan 1998). Result of data processing with the system approach showed that vanda and dendrobium did not have critical Bradley, J.C. and A.C. Millspaugh. 2002. Programming in Visual Basic Version 6.0. Update Edition. 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"IMPACT AND MODEL OF AIR POLLUTION BY SIMULATED ACID RAIN ON THE "