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Indonesian Journal of Agriculture 1(1), 2008: 34-43                                                                        A. Santi et al.


                                 A. Santia), M.S. Saenib), N.A. Mattjikb), T. Juneb), and H. Hardjomidjojob)
               Indonesian Ornamental Plants Research Institute, Jalan Raya Ciherang, PO Box 8 SDL, Segunung, Pacet, Cianjur 43252
                                         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
     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)

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                                                                           Dendrobium
Amount of S35 absorption

                                                                             Dendrobium                                                                      Oncidium
                           40.000                                                                                12


                                                                                             N content


                               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


                             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.

                                                                                   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


                           10                                                          Model of Acid Rain Effect on Growth and
                                                                                           Development of Orchid Plant
                                                                                   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

                                                                                   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

                           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
                                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

                                                                                       To develop a model, input suitable to proper process
                            8                                                      should be made, so the program could process and produce

                            6                                                      required output. Diagram of determination of critical point
                                                                                   (Figure 9) explained that input consisted of rain water pH,
                                                                                   stomata number, and leaf thickness. Limit of pH ≤ 3 was
                            2                                                      used because at that pH value oncidium orchid could not
                                                                                   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+
              • 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

                                                                 number                        Dead

                                                                thickness                      Dead

                                                       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

                                                                                  (mg/l)                 0.136


                                                                                                                     0            2           4            6        8

                                                                                                                                  Acidity of acid rain, pH

                                                  Figure 13. Relationship between acid rain acidity and H+ concentration on vanda

                                                         18                                                          y = -0.2593x2 + 54.385x - 128.01
                     Nitrogen ion concentration

                                                                                                                                                        N concentration
                                                                                                                                                        Standard deviation for N = 8.6 mg/l

                                                                                                                                                        Standard deviation for N = 12.15 mg/l
                                                             8                                                                                          Standard deviation for N = 10.5 mg/l




                                                                    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
                                                  H concentration

                                                                        0,10                                                                                       Oncidium

                                                                        0.08                                                                                       Poly. (Oncidium)
                                                                                                     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. McGraw Hill/Irwin Co.,
point at rain water pH of 3.0-6.0, while oncidium had critical        New York. 694 pp.
point of plant response to acid rain at pH 4.                     Fan, H.B. and Y.H. Wang. 2000. Effect of simulated acid rain on
                                                                      germination, foliar damage, chlorophyll contents and seedling
                                                                      growth of five hardwood species growing in China. Forest Ecol.
                                                                      Manag. 126: 321-329.
                                                                  Finley, S. 2001. Hujan Asam. Kumpulan Makalah Toksikologi
      CONCLUSION AND RECOMMENDATION                                   Lingkungan. Program Pascasarjana, Program Studi Ilmu
                                                                      Lingkungan, Universitas Indonesia. 21 hlm.
                                                                  Kohno, Y., R. Matsuki, S. Nomura, K. Mitsunari, and M. Nakao.
Condition of pollutant at research location in one year               2001. Neutralization of acid droplets on plant leaf surfaces.
                                                                      Water, Air, Soil Poll. 130: 977-982.
reached 32.69 ppb or 0.00327 ppm for SO2 and 193.63 ppb
                                                                  Mansfield, T.A. 1994. Some aspects of stomatal physiology relevant
or 0.1936 ppm for NO2. This condition caused rain                     to plants culture in vitro. In. P.J. Lumsden, J.R. Nicholas, and
occurrence with average pH 4.97 or categorized as acid                W.J. Davies (Eds.) Physiology Growth and Development of
                                                                      Plants in Culture. Kluwer Academic Publishers. p. 120-131.
rain, but still adequately suitable for growth of orchid plant.   Momen, B. and J.A. Helms. 1996. Effects of simulated acid rain
    Vanda and dendrobium had fewer stomata number and                 and ozone on foliar chemistry of field grown Pinus ponderosa
higher leaf thickness than oncidium, so both orchids had              seedlings and mature trees. Environ. Pollut. 91(1): 105-111.
                                                                  Momen, B., P.D. Anderson, J.A. Helms, and J.L.J. Houpis. 1997.
more resistance in controlling acid rain effect at pH ≤ 3.            Acid rain and ozone effects on gas exchange of Pinus
This showed that vanda and dendrobium were less                       ponderosa: A. Comparison beetwen trees and seedlings. Int. J.
sensitive, while oncidium was sensitive to acid rain.                 Plant Sci. 158(5): 617-621.
                                                                  Momen, B., P.D. Anderson, and J.A. Helms. 1999. Temperature
    Chlorophyll content increased with decline of rain water          dependency of acid rain effect on photosynthesis of Pinus
pH due to positive effect of N in leaves which were able to           ponderosa. Forest Ecol. Manag. 113: 232-230.
reduce negative effect of H+ of rain water, so chlorophyll        Munzuroglu, O., E. Obek, F. Karatas, and S.Y. Tatar. 2005. Effects
                                                                      of simulated acid rain on vitamin A, E, C in strawberry
formation can be generated.                                           (Fragrasia vesca). Pakistan J. Nutrition 4(6): 402-406.
    Using Visual Basic program version 6.0, it could be           Shan, Y., Z. Feng, T. Izuka, M. Aoki, and T. Totsuka. 1995. The
developed model of air pollution by acid rain on growth of            individual and combined effect of ozone and simulated acid
                                                                      rain on chlorophyll contents, carbon allocation and biomas
orchid plants. From data on relationship between rain water           accumulation of armand pine seedlings. Water, Air, Soil Poll.
pH and leaf N content, with relationship of rain water pH             85: 1399-1404.
                                                                  Shan, Y., Z. Feng, T. Izuka, M. Aoki, and T. Totsuka. 1996. The
and hydrogen content of rain water, it can be produced
                                                                      individual and combined effect of ozone and simulated acid
critical point of plant response to acid rain which occurred          rain on growth, gas exchange rate and water use efficiency of
at N content of 5.28 mg/l and H content of rain water 0.14            Pinus armandi Franch. Environ. Poll. 91(3); 355-361.
                                                                  Shan, Y. 1998. Effects of simulated acid rain on pinus densiflora:
mg/l.                                                                 Inhibition of net photosynthesis by pheophytization of
    This research should be further assessed for other                chlorophyll. Water, Air, Soil Poll. 103(1/4): 121-127.
orchid plants due to variation of leaf structures. If stomata     Sigh, S.K., D.N. Rao, M. Argawal, J. Pandey, and D. Narayan.
                                                                      1991. Air polution tolerance index of plant. J. Environ. Manag.
number and leaf thickness could be used to determine                  32: 45-55.
Impact and model of air pollution ...                                                                                            43

Singh, S.K. and M. Argawal. 1996. Response of two cultivars of        Treshow, M. 1984. Air Pollution and Plant Life. John Wiley and
    Triticum aestivum L. simulated acid rain. Environ. Poll. 91(2):       Sons, New York.
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Sukarsono. 1998. Dampak Pencemaran Udara terhadap Tumbuhan                Anggrek. Buku Komoditas Anggrek. Balai Penelitian Tanaman
    di Kebun Raya Bogor. Tesis. Program Pascasarjana Institut             Hias, Jakarta. hlm. 14-28
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