Sulphur is an essential element of life and important constituent of
protoplasm in plants and animals. Since coal and oils are derived from
living organisms, these fuels contain some sulphur, when these fuels burn
so does the sulphur, producing a mixture of oxides of sulphur. viz.
Sulphur dioxide (SO2). Sulphur trioxide (SO3), Sulphur tetra oxide (SO4),
Sulphur sesqueoxide (S2O3) and Sulphur heptoxide (S2O7). Of all these
oxides emission of SO2 is found to be most harmful to plants and animals,
hence it is of great significance.
Chief source of sulphur dioxide emission are several industrial
processes that include roasting of sulphidic copper, nickel, lead and zinc
ores, manufacture of sulphuric acid, paper and pulp and oil refining etc.
About 75% of total emission of sulphur dioxide is from burning of fossil
fuel in domestic sector, industrial furnace and power plants. Most of the
remaining 25% of SO2 emission is from non- ferrous smelters and
petroleum refineries.
Sulphur dioxide is a colorless gas with a penetrating and pungent
odor. It is 2.2 times as heavy as air and non- combustible it is highly
soluble in water and forms sulphurous acid. It easily liquefies at room
temperature under a pressure of 2 atm. It condenses at 10 ̊C to a colorless
liquid with freezing point - 75.5 ̊C.
The molecular formula of sulphur dioxide is SO2 with a molecular
weight of 64.06 in all its states. This gas is acidic in nature and acts as an
oxidizing agent, reducing agent and wet bleaching agent with temporary
effect.
Sulphur dioxide is a proven phytotoxicant. Plants absorb it mainly
by gaseous diffusion through stomata from where it reaches the
mesophyll tissue of leaf. The number of stomata and size of aperture play
important role in uptake of SO2. In mesophyll tissue sulphite (SO 3-2) and
bisulphite (HSO 3) are the main chemical species formed upon the
dissolution of SO2 in aqueous solutions. Both SO3-2 and HSO3 have been
shown to be phytotoxic in many biochemical and physiological processes
(Zeigler, 1975; Malhotra and Hocking, 1976). Plants can overcome these
phytotoxic effects by converting SO3-2 and HSO3– to less toxic forms.
Oxidation of SO3-2 to SO4-2 in plant cells can occur both by enzymic and
non enzymic mechanisms and SO4-2 accumulated is considerably less
toxic than SO 3-2 (Thomas et al. 1943).
The intensity of a plant’s response to SO2 is influenced not only by
the concentration, duration and frequency of exposure but also by its
resistance to the pollutant, which moreover depends on internal and
external factors.
REVIEW OF LITERATURE
Sulphur dioxide causes some effects in plants. The fact has been
established since long. Sulphur is an important plant nutrient. It is
essential for proper growth, full development and metabolism in plants.
Aggarwal and Aggarwal
(1990) reported in Oryza sativa and
Guinaphase (an organo phosphorus insecticide ) bring abnormality in
plant growth development that leads to decrease in various growth
parameters.
Singh and Rao (1990) reported impacts of sulphur di-oxide on
ascorbic acid and sulphuric acid and sulphur content in case of Vigna
radiata. These plants were subjected to 0.25 , 0.5, 1.0 and 2 ppm SO2 for
8,4,2 and 1 hour and noted that ascorbic acid content in plants was
directly proportional to concentration of SO2 excluding sulphur, which
increased with increasing exposure time.
Veeranjaneyulu et al. (1991) reported different concentration of
SO 2 have differential effect on photo chemical activities of sugar maple
leaves.
Qifu and Murray (1991) observed that in potato plant leaf, stem
and tuber growth were decreased in a significant amount when it was
subjected to 300ml per litre SO2.
Tomer et. al. (1993) reported foliar injury and reduction in growth
and yield characteristics when exposed Abelmoschus esculentus to higher
doses of SO2.
Gupta et al. (1993) treated the seeds of two cultivars Kalyanpur
and Pusa sumna of Lagenaria siceraria to 334, 667, 1334, 2001 and
2668 µgm-3 of SO 2 and noted a decrease in the germination percentage,
seedling survival and seed vigour. They also noted that growth and yield
characters were reduced in Lagenaria siceraria when it was fumigated
with higher concentration of SO2.
Chatopadhyay (1996) noted that decrease in stomatal frequency
and stomata abnormal when leaves of woody perennials were subjected to
air pollution.
Rath et.al. (1996) reported that 50% damage of leaves (in terms of
leaf number and leaf area affected) in Capsicum frutescens cv. California
wonder on exposure to 0.25, 0.50 and 1.00 ppm SO2.
Kumar and Dubey (1998) reported that when seedlings of Cassia
siamea and Delbergia sisso Rox. Of different ages (6 months, 1.2 and 4
years old) when subjected to SO2 treatment and on 45th day composite
leaf samples were analyzed for stomatal conductances, protein contents,
nitrate reductase activity, super oxide dis-mutase (SOD) activity,
peroxidase (POD) activity and ascorbic acid content . Stomatal
conductances , sulphate content, POD and SOD were increased, while
protein content was decreased both C. siamea and D. sisso. In both cases,
the plants with advancement of age develop the detoxifying mechanism
by the enhancement in antioxidant under SO2 stress and thus the SO2
toxicity decreased in the plants of higher age.
SO 2 caused injury and decrease the rate of photosynthesis, stomatal
conductance along with severe loss in quality and production of fruits
were observed in Mango (Mangifera indica).
Jeyakumar et.al. (2003) reported the effect of SO2 on maize (Zea
mays) seedlings at lethal doses.
Agarwal et.al. (2004) performed field experiment with three
cultivars of Triticum aestivum L. by treating them with ethylene di-urea
(EDU) and Ascorbic acid (AA) against air pollution stress in terms of
some selected growth, biochemical and yield characteristics and reported
that all cultivars showed a positive response for growth, biochemical and
yield parameters in EDU and AA-treated plants.
Renuga and Paliwal (2004) purified superoxide dismutase (SOD-1)
from Vigna unguiculata Chloroplast and Chromatography is done.
Studies indicate that SOD-1 differs significantly from SOD-2 and SOD-4,
other forms of SOD from Vigna unguiculata. Greater SOD levels in
Young leaves compared to older leaves were associated with lower SO2
sensitivities in these tissues.
Yasar Nuhoglu (2005) observed influence of air pollution on the
architecture of Calibrian pine (Pinus brutia Ten.) needles. It was reported
that air pollutants caused resin canal dilation and epidermis /hypodermis
layers slimming on the cross sections of calibrian pine needles and
endodermis was deformed.
PROPOSED WORK
During past few decades rapid industrialization and Urbanization ,
technological advancement, rising living standard and further more
proliferation of population intensified the magnitude of environmental
pollution. As we know Air pollution (SO 2 ) causes some adverse effects
on plants, animals or materials.
In the present study, the experiments will be performed to evaluate
the impacts of different concentration of SO2 on plant growth, yield and
certain biochemical components in selected varieties varieties of Solanum
tuberosum and observation will be recorded on the basis of various
morphological , Biochemical and stomatal analysis. In this way we can
measure degree of susceptibility or tolerance of these crops to various
levels of sulphur dioxide pollution and estimate its economic yield.
Parameters studied1.
Whole plant length
2.
Root length
3.
Shoot length
4.
Fresh weight of root
5.
Dry weight of root
6.
% Moisture content of root
7.
Fresh weight of shoot
8.
Dry weight of shoot
9.
% Moisture content of shoot
10.
Root weight ratio (RWR)
11.
Shoot weight ratio (SWR)
12.
Shoot weight ratio (SRR)
13.
Net primary Productivity (NPP)
14.
Phytotoxicity percentage
15.
Number of leaves
16.
Leaf area estimation
Biochemical attributes:
1.
Chlorophyll content
(a)
Chlorophyll a
(b)
Chlorophyll b
(c)
Total chlorophyll content
(2) Protein content estimation
(3) pH measurement
Stomatal Response
(1)
Stomatal density
(2)
Stomatal coverage area
(3)
Stomatal Index
Economic yield of plants will be measured in terms of1.
Number of tubers per plant
2.
Weight of tubers per plant
FUTURE ASPECTS
Present investigation is aimed for the characterization of relative
degree of susceptibility or tolerance of this experimental material to
various levels of sulphur dioxide pollution.
The plants exposed to SO 2 will be analyzed for visible changes,
morphological characters and biochemical characters. By measuring
changes in these parameters we can know about economic yield or Net
primary productivity of this plant in present time and also imagine about
beneficial and harmful effects of that environment in future.
METHODOLOGY OF STUDY
Certified seed tubers of Solanum tuberosum belonging to selected
varieties will be firstly treated with 0.1% of Hgcl2, a surface disinfectant,
for two minutes, to check the fungal growth. Same size of propagules will
be washed at least two times with distilled water. These propagules will
be soaked for 8 hours and then will be sown in earthen ware filled with
soil. Different concentration treatment of SO2 exposure will be given in
fumigation chamber.
PLANT ANALYSIS- 4 or 5 plants from every set will be choosed
at a regular interval and readings will be taken for various morphological
parameters.
Plant with intact root and shoot system will be taken carefully.
Roots will be washed with tap water and followed by air drying on
blotting paper. Then all parameters will be measured. For estimation of
dry weight, plant parts will be wrapped in sheets of news paper and then
kept in an oven at 80 ̊C for 30-40 hours and will be weighed.
CHLOROPHYLL CONTENT- Chlorophyll a, b and total
chlorophyll content will be measured according to Arnon (1949).
PROTEIN CONTENT- Protein content will be estimated
according to Lowery et al. (1951).
pH MEASUREMENT- 5 gm. Of fresh weighed leaves followed
by homogenization with 25 ml. of distilled water and centrifugation. Then
it will be filtered and pH of the extract will be measured with the help of a
digital pH meter.
STOMATAL STUDIES- Epidermis of leaves will be peeled off
manually, stained with saffrinin and mounted in glycerine. Slides will be
prepared and then will be analyzed for various stomatal parameters.
ECONOMIC YIELD ANALYSIS- By treating same sizes of
propagule with different concentration of SO2, toxicant magnification and
its effect on economic yield of the crop will be measured after successive
generations.
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