CHAPTER 1 INTROD,UC TION . ~ ~.;..:; .

Sulphur is an important element· in the blosph~re

antl' occu,rs abundantly throughou't the earth's crust at aft ,

a:v;~rage concentration o.f about 0.1 per cent and as S02

in ~4~ atmosphere. at an average concentration ~f 0.003 pp~~

In recel]~ years on account of indus~tialization and increas ...

ing consumption of fossil fuels, emission of /SOZ 'has

steadily increased in India (Parikh,1977; Varshney and '

Garg, 1978).

The problem of S02 p01~V~ton has created

s.,er~ous concern in many countries lt~r, Canada, France, U.K. t

and U. S .A,., where complete lan'dscapes h~ve been destroyed , : (. ~:. ~ ! :t

by S02 pollution. The current ambien~, S02 levels in some

of the iinport,~pt ci ties of the world (Table 1) range from , • j i

60 - 600 llg m- 3·whichhave been shown to cause extensive •

losses to plan'ts (Hawksworth and Rose, 197Qi; Grodzinski. and' / .. ';. :. '

Yorks, 1981). 'Relatively susceptible specie~. are eliminated

in chronically polluted areas wi th the conseq~~n,t. changes 'in

the species compO,sition (Kozlowski, 1979, 1980) .•

fo~m of acidic def:,Q$.i tion interferes wi th the h;iR~i~~qf,~~'J1li'cal

cycling in the ec?.sy~stem and brings out irreversi~~~:., ~~l1g~s ,"

in the structure of,.'~,cosystem (Holdgate, 1979). ' De~S'~jr~~it;ipn ..

of copper basin area·.! of Tennessee (USA) whe're about :J09,~1t

acres of ri,ch decid.8.11 s,,- forest was completely destroyed

another 17 000 acf~s Qf'natural forest was replaced with , , " ;'" . grassl~~4 speFt~;; "dreqgecock, 1912) and disap~~aran:ce' of i

2

Table 1. Ambient S02 concentration of some importa~t.

cities of the world

Clty Year

Athens 1979 ISO··

Copenhagen 1976' 60*

London City 1976 260*

London greater 1976 150·

Milan 1976 600·

Paris 1976 110·

Stockholm 1976 ·70* .

To.ronto 1976 170·

2610 lJgm-3 =' 1 ppm

Source: It STIC'UUNG CONCAVE - THE HAGUE Report4/76 ,

** Lalas~, et a1., 1982 --

3

conifer trees along a narrow valley in Connecticut, USA (TOUIey,

1921) are some of the exampl~s of S02phytotoxic~ty.

The cost of S02 damages to crops'oofruits etc.ohavenot

been worked out for many developed or developingcotmtriesbut

they are escalating with the increasing in~trialization and i ..

. urbanization. A recent estimate shows that the cost of air

pollution damage in USA varies between US$ 2 billion to 5 billion

per year (El Hinawi, 1981).' .' i

The problem of S02 pollution is increasing 'in

India, but data on the cost of air pollution damage are

not availab Ie. A prel iminary survey of the S02 level5,

in the ambient air of seven cities of IndiaCfable' 21 . shows that average S02 levels vary between 0 .• 0.02 to O.~l

ppm i' (National Committee on Air Pollution, ~9 72). Since

thEm, S02 levels have increased due to our rapidly growing

consumption of coal and other fossil fuels (Varshney and Garg,

,1978). Relatively high concentrations of S02 are c<?mmon

in highly industrialized pockets, but the long range tfcmsportation '

of pollutants does not leave unindustr!alized fUrAI .reas

and countrys ide free from pollution problems ~ A policy

,of decentrali zed industrial growth persuaded by the Indian

.Government has promoted i!lcreasing industrialization ,of

small townships and extension of heavy industry tell back-

ward regions. The policy of diffused industrial growth •

Table, 2. Atmospheric concentrat1onsof SOZ 1n

, maj or Indian cities (in ppm)

4

- __ ' .. - ................... _._ ... _._'; ...... _'_ .... _~ ... _. __ ._ ... _-____ • __ ....... _-... ·_ ... ---. • .: ... __ • ____ T __ ~ ...

City Average Maximtun .-...... -= ... -.-:-,:-............. -.-.~-.-.-.-=-.-.-.-.-.... -............ -- ... -.-.-.-.-.--.--... -.-.... -~

Ahlnedabad 0.004 0.010

Calcutta 0.015 0.066

Delhi (1972) 0.022 ,0.130

Delhi (1981) * 0.010 0.030

Jaipur 0.002 0.005

Kanpur 0.030 0.060

Madras . 0.011 0.018

Nagpur 0.004 . Q.013

JNU (New Delhi)* 0.002 0.003

JNU (New Delhi) ** 0.003 Q.003

------------.. ~--~-.--:---.-=-.. ,---.--... --~-; .. -................... -... -_ ..... _-Source: Mehta, 1978 (Based on the report of

National Committee <?n Air Pollution, 1972) * From mid-term report of air pollution in Delhi

area (Dave, 1981) using TCM method.

** During present investigation using Thermoelectron S02 Analyser.

"

·5

adds to. the problem of S02 pollution due to local emissions

from industries established in rural/backward areas. On actount of these reasons the ambient S02 levels are going

to increase dramaticalJy in the foreseeable future"

S02 affects plants both at acute and chronic

leve Is of exposure. In general, chronic injury results

in chlorosis· which is usually lnter-coastal in distributio.n.

In the chlorotic areas the cells are. not ·1<:illed but the

chlorophyll is bleached. The chlorotic areas become

browni.sh red in colour. Leaves n:,~main turgid but function

at a reduced leve Is of efficiency. Acute injury is .. signalled by a cell plasmolysis leading to necrotic collapse

of leaf tissue (Thomas, 1961). Initially, the affected

leaf areas appear water-soaked, the metabolic processes

cease~ resulting in the drying up of the affected areas, i.e.

Recl'osis (Thomas, 1961; Brandt and Heck, 1968).

The symptomology.of S02 injury has bee~

ex.tensively studied "and documented by Barrett and

Benedict (1970), Baut and Stratmann (1970), Hawksworith

(J911, 1914), LeBlanc and Rao (1973), Mudd (1975),

Ziegler (1975.1, Davis and Wilhour (1976), Varshney and

Gar~ (1979 ).and Manning and Feder {19BO). Most of the

studies on plant'responses to S02 have use.d relat:jv~iy

high leve Is of S02 and thus do not re'flect the 'real

5ituation. Whereas, low levels of SOZ:have been found

6

to affect plants hoth at individual and community levels~

Low l.evels of S02 have been shown to ~reduce feaf area,"

biomass, growth, fruit and seed deve lopmen t" and yield "

(T~omas, 1961} Brandt and Beck, 1968; Heagle""~ "a}.:,"'19~4::

Sprugel ~al., 1980). Various plant processes such as:

photosynthesis, respiration, transpiration, nitrogen

fixation, reproduction etc. are adversely affected by 502

, (Malhotra, 1977; Ma ""~a1., 1973; Bull and Mansfield, 1974;""

Hallgren and Huss, 1975; Ma and Khan, 1976; Murdy and

Ragsdale, 1980; Varshneyand Varshn~y, 1981).

At biochelIlical level plant ,responses t~502

have been eVqluated in terms· of carbohydrate, protein" and

chlorophyll C·(i)J);tent .. and enzyme activity' CRabe and Kreeb,

1979; Pahlich, 1972, 1973; Malhotra and Hocking, 1976;

Wallace and Spedding, 1976; Varshney and Varshney, 1979.;

Pierre and Queiroz, 1981}.

.. - It is widely believed that ecophysiological

and bi!Jchemic~l changes are likely to occur much before·

the appearance of any visible change at sub~chronic.

levels of sg2'- Plants exposed tosllblethal'\c,9n~ent.ration

of S02 may a~Rear green and normal but· their. bioch~mical",

and physio19.gica1" processes are subdued and they genera~ly" , ..

funct:iona1;.,~ a;"reduced efficiency. The invisible changes' . ..' .:.~-:'" ~'II .'

c~used~··b'¥ .. {non-necrotit S02. exposure, can, however, be ,1. ," .. "

de,tec'~ed,(a t me tabo1ic 1eve 1 by examining certain , ~,;' , ; .. ', ,~. ';

P)hY;~~~'logica1 and biochemical parameters. ~ ... ", .

7

, Most of the studies (Table 3) conducted to

evaluate the response of plpnts to S02 at biochemical

level reveal that relatively high concentrations of SOz'

1.e. ,more than 2S pphm~ have been employed. Furthennore II

these studies provide lit'tIe guidance in terms of real

life situation where S02 concentrations are seidom as high

as have been used by earlier workers (Table 3). Therefore;

it has been suggested that S02 leve 1s less than 2S pp~

should be regarded as the upper limi tl£or ob~aining meaning-

ful results' on the plant response tc S02 (Bell and Clough.

1973; Bleasdale, 1973; Bull and Mansfield, 1974; Ashenden,

1978; Ashenden and Mansfield, 1978; Wellbum 'et al. J 1981). -- '

The criteria for selecting S02 copcentr~tions

uSed by various workers have not been properly discussed.

Moreover. the dividing line between the injurious and

non-injurious concentrations is not well defined because

plants vary in their susceptibility to S02 according to

the species, sub-species J stage of growth, and othar

environmental factors. f\-loreover,at present, the permissi ... , ' '

bIe levels of S02 for air quality criteria are based on

the ~ppearance of visible injury though plants often get

severely affected at concentrations much lower than the

Lrescri,bed limit Crable 4). "

Table 3. Effects of low levels of S02 on plants -- ..... -....... ~--.. -~ ............. -.... ~ ... ..,.. ......... ~ ............. ~ ................. .....:~ ................. ~ .. -. ............. .,:~ .. ...-.. ..... ~.~ ......... --........ ..: ...................... ~ ..... ... .. _.., .~ ........... ,.

S. Genus No •

/ Experimental Condi tfons EIlz:yme ,me taboli tes, Effects and others

Re,ference

... -....... ---... -~ ....................... -....... -... ----.... --.. .... -.... -....-... ... ..,;, ......... ~~ ........ -: ........ --.:, .. ,...-.: .... ~~ ............... --... -...... -~---~ .......... --.. -.: ... ..-..... -~- ... .... . ,.,. ,--'.

1. Pistml sa t ivum

Z. Lolium perenne.

SO 2 - 0.2, 1.\), 1.5, Z.O ppm

NO Z - 0.1, 1.0 ppm

for 6 days

502 - 0, 50, 100, 200, 400 usm" 3

for 77 days

Activities of RuDPC, Increased GPT,GOTjperoxidase

Horsman and We 1 Ibu.rn, 1975

Sulphur iri leaf, plant yield

Yield in- Lockyer et a1.,. --creased in .1976 sulphur de .. ficient soil but at higher con-centration

. yie ld redu .. . ced

3. Lolium S02 - 0.1 ppm for Leaf. area, root. Decreased Ashcnden and peren~7 4. weeks shoot ratio, dry Mansfield,

weight 1971. . ~ ~~ ............. ~ ......... -........................ ~ ........................ -~ .... -........ -................ -.,....-...... ----.... -.. -.------.-........... --..... ....

(~ntd.)

TableS (contd) ............. ----.,.......~~ ....... ~ ...... :-..~ ................ ~ ................ ----............ - .... ----.... - .. - ...... -.~--- ... ~.~.-..: .. - .... ~.-: .... --.--.-- ..... - ................ ,t.!:t • ...", ...

S.Genus· E.,Xpermental Conditions Enzymes. metaboli teSt Effects,,·, Reference ,~2.:. ___ ;;,,_:, ____ ... _. __ .... ___ . __ .. _____ ...... __ ......!!:2 .. 2!h~r! ____ ._ ... __ -.. ------.. ':..-.------.. -- ..... ---____ ..

4;, Bean

5. Rumex

6.

7.

ob tusi £0 li tl.11l

~ mays" Triticum aestivum

Pieea, Pinus, Lar"ix, Betula

S02 .. Q .. l to l .. l ppm for 8 days

S02 - 0.2 ppm for 11 days

S02 - O.lto 0.6 ppm fOT 100 hrl

-3 S02 - 1.17 ~gm fOT

20 _hI' per day for 20 days

8.. Populus eurame--:..50Z -0.1, 2.0 ppm orlcan a ~ 5 p iIl.a ~. .

G6PlE, Glli, Gly DH, PEP carboxylase, MDH,_ IDK t AST, NADP decar-boxymalat.e, Phospho-fructokinase ,RuDP carboxylase

RuDPC*,GPT, GOT, Peroxidase

Dry mass t foliar . . ., l.nJ ury , tota ... sulphur

GlutathioneCSH compoun4)

SOD and chlorophyll

, Increased

Incraased -Decreased

Decreased.

Increased

Pierre ~ 1977

Horsman and We I1bID't\ 19 77

.. Laurence, 19 79

Grill,~ al., 1979

SOD .. Increa- Tanaka and sed Sugahara,

ChI-Decreased 1980 .................. ~ _.-----.........,-------------------------~--.-~ ................ .., ....... --.; .... --.:- ... .......,. .. :-.. -.......... - ....... .,.' ....... -.-=-~ .. _-.:_: ........ .. . , .... u"" ,,', ." ..' •

(contd.)

c..o

~~1~,:,3 (1:on t.G!) •. ~ ... "._ 4' - .. _ ..... _-.. __ ~ .................... -..... ,....,; ............ ~._ ....... ~~ .......... 'tIa:' ... _-.:;_._ ......... .",.~* ..... _~~._: .. .-r~ ... _ ... ~ ... ~ ... ..: .... ' .. y-

~~. Genus ExperUliIultnl condi tions:~r:;~~~~~taboli tes" EffectsRefeTenc~ .... -.: ............ "..---.................... --- ...... -,-~ .... 4IV'~.-'.~ .. -.~~ .. -.................... -..... -.. -.--.., .... --..... -•.• --........... .;;.. .. --... --.;--............ ,~ ........ .... , ", .'

9.. Lolium S02 • 6.8 ppnm for 11 weeks - 2S ppbm fot' 11 days

10.

perenne, Dactylis gJ,9)rierulata, N02 .. 6 .. ~ ppbtn for 11 phleum -- wee.ks pra te.nse. Poa praten-sis

Betula pendula Betula pube-scense ~ pseudo-platanus Quercus rober

-3 SO~ - 150 ~gm for

~

15 to 24 weeks

Ratio of GOO and CS t j\'l'P formation

Sulphur content of leaves

Increased

Increased

Wellburn,et. ' .-;~. " -----

&1., 1981. -.

Garsed ~ aL, 1979 .

_--:, ___ ~_.~, ............. ~~-= .... __ -..: ...... '_ ....... ~ .... _ ...... ,.,: __ ...... -= ...... .-: .. ~ .... _'~ ... , ....... ~ .. _:-.r .. _ . ., .... <~ ........ ~~_..:;~~' .. -.,; ...... -~ ... .,:-~ .. .:----.. ..:...... ~

(~ontd.) ,0

~;labj(> 31:;::o:n1(',1 . . . _. . '''''-~'''.':'i'''''''''''''''''.·.'''_7I'Io~1'''·~'''''''''''"''-'-'''''-~''''''''''''''''''-'- __ '_''''''''''''''''<''''fIIp,-"""""'~""""._"""""""""'_:'Wo. .. _ ...... .., __ , .. _. _____ .. ~·ft_"""""", ___ """-"_,,,,,~ •• _~,=:-,, ....... ~.~'~.~

~~ Genvs txp~ rimen. tal condi - .f.n :r:ne s, m~tabcli test Eff~cts Reference' i·",. ti'CIlS ar,d c't heys ..... _, ..... "'"'.-.:-........... __ .... ~4IIIIO' ............................................ _~ ........... _ .... MP>.,;. .... 14IIfi .... _ ...... -........... _ ........ _~_ ..................... _ ... ~~; ........................ _ .... .,._.~ ...... _ .... _. __ ..... _....,..

,.11,. Srj'i~ci,es

12. Alianthus '!1 tissima

13. Agropyron

SO~ - 0.1 tc 1.5 ~

p;:n: for 8 hr

S02 - 0.1, 0.2 ppm for 1 and 2-weeks

Monthly median SO? 2

'"'", .. :3 ..... cone. ~ l-lgm' . to ,175 ;Jgm-3 fOT 4

years (1975-1978)

14. Phaseolus ,S02 - 0.1 ppm for

15.

vulgaris three weeks

.. 3 Agropyron .502 - 200 }Jgtn .

Photosynthetic process, openins of "6tomsta and conduc~ance in C3 and C,t plants

~rovth and biomass acc:umul,e't oi on ,

Total chlorophyl1~ Chloropb)'ll a and 011oTo.phy 11 b

Orga-nic aCids, amino acids,proteins, poly"

. mines,I.DH.GDH,AAT. malic enzyme peroxidase

14c t~ons1ocation'and

C3 i3 more- se.nSl tl ve tJ-,a.n C 4 b~cau!;~ o,f higher conductance and gTca tel' s timula.-tion ofs tcmatal ope,ning

Decreased

Decreased. chl-a m~re sensi ti ve than chI b

Increased

Increased

Winner ~nd Mooney, 1980

Marshall and Fumier, 1981

Lauenroth and Dodd, 1981

Pierre and ~roz.;

1981 .

Milchunas-!!. ~ .. , 1982

..... ..... smi thii ' for 30 days li:af growth

-----............................ ~ .. -........ -.-..... -; ........... -........... ~ ........ ......,. ...... -:---.... ~ ............... --,..:-.; .... '.,; .............. -.~ ................ ~ ............. ~, .... -.... -.: .... -~ ... ~~-...... --..: ............ .

I \ Table 4 S02 concentration,s causing visible

injury to various sensitivity groupings of vegetation (ppm S02)

12

........... -.~-.--:-.-.-..... -.. --........... --' ...... -.. ---- ........ --'-.--_....-..... _._ .... .; ......... .. Maximum average concen-tration

Sensitive Interuediate Resistant _ ...... __ .. :.,.:..,;_ ......... .,.. •. ..r ..... ...... _ .... ~._ ....... _ .................. _ .......... _ ...... -._._ ....... __ ... _ ...

Peak 1.0-1.5 1.5-2.0 >. 2.U

1 hour O.S-1.0 1.0-2.0 '> 2.0

3 hour 0.3-0.6 0.6-0.8' > 0.8 ,

............................ __ ... ;--=-= ........ -..: .. ' ... .-.:-=-: .... -.,--;-_ ........ --- ............ ,:----_ ... ---' ...

Source: Jones :~t a1., 1974

Therefore, the low levels of S02 should

be consid~red as the levels' equivalent or near t,o

ambient levels at which no visible symptom is likely ,

to produce even if the fumigation is extended throughout ,

their life. In view of these considerations the present

investigation w·as undertaken to study the plant ,I .

respons'es to low. levels of S02 which are relatively

more realist~.c. S02 levels at JNU (New Delhi) were

observed to b~ averaged at 0.3 pphm and taken a~ ,

background l~vel.

.. S~2 mostly enters plants through the

stomata (M~sfieldt 1973). tn fact, stomata are one of

13

the important controlling factor, of S02 injury to plants

(Mansfield, 1973; Mansfield and Majernik, 1970)~ 502 has ,

been observed to affect the opening and closing of the

stomata (Mansfield, 1973; Kondo and Sugahara, 1978; 01s%y~

and Tibbi ts J 1981J.' The plant injury due to 'S02 depends. on ,

the rate of absorptinn of S02 through stomata. It has been

debated that the sensitivity of differen.tspecies or different

cuI ti val's. of the same species deplUlds on, the uptake 'Of 502 , (Bennet and Hill, 1973; Craker and Starbuck, .1972; Roberts,

1974 ; Elkiey and Ormrod, 1981) •

S02 is converted into different ionic forms, i.e.

HS0 3 - S03 -~ J J

SO -2 4 and part of it remain as hydrated

form SOZ.H20 when it ccimes in contact with the cell. Some

amount of sulphite is metabolised and incorporated into

newly synthesized protein. The 'remaining sulphite is

accumulated in the form of sulphate. In some s\udies

fumigation of plants to low leve~s of S02 have been observed

t~ have beneficiary effect on the plant growth especially

in the sulphur deficient soils (Cowling ~!l., 1973).

Fumigations ,wloth low levels of S02 (13 pgm-3)' increased

the yield ofry~~~ass, growing in sulphur deficient soia

through the c,or~~<;:tion of soil deficiency (Cowlin:B £!.:!!. •• 1973). The yi~~d of dry matter of several ,speci~s growing

il.\: solution cul;ture were enhanced when t:h.e shoots were

exposed 'fo'1' 9 to 20 days in air containing S02 labelled

14

. 35 :). witll S J at 200 and 500 )Jg m- {F811~r"!.! "!!. •• ' 1970}"

, Milchunas ~ a!. J (1982) observe"d stimulation in leaf growth

·when Agropyron smithii Rydb. was fumigated during April to

9:~tober a.t 30 day median s02 concentration of" 200 'Jlg m .. 3• ' "

0,1\ tl1e \:>'8s15 of experi.mental exposures, a concentration Qf

"b t 429 m-3 S02 ( a ou "pg 0.15 ppm) has been widely accepted as

a thresh~ld below which a range of higher plants would not

be injured::even after a prolonged eXposure (Zahn ,1961) to

50Z-

Whenth~: capacity of the plant to m~tabolize

sulphite decreases,' the extra amount of sulphite •

accumulated in the cell becomes toxic and causes the

acidification of the cell fluid~ The first thing to be

affected by the toxicity of S02 is the ce 11 membrane as

S02 'interferes with the. structure and permeability of the

cell membt)ane. The change in the permeabili ty of mem ...

b.rane following the S02 fumigation has caused the leak.age

in the potassium 'ionsand other electrolytes from the

cell (Nieboer, &t 1 a1., 1976; Puckett et 81. t 1917; .. - - ---- ...-.-.

Tomassinl et !!.!.., 1977; Elkiey and,Ormrod, 1919). The

alteration of cell membrane permeability- will affect the

functioning of various enzymes attached to it which would

resul t into the' eco-physj ologi.cal chcuiges by disrupting

various hiochemical proc.ess es (Thomas ~ !l .. :1950;

Welburn !:.! E..!., 1972). After- disrupting the structure of

15

the cell membrane S02 affects various organelles and the

biochemical processes associated with them. 'Malhotra

and Hoe-king (1976) reported that S02 .a1tered the ultra-

structure of chloroplast and other photosynthetic pigments.

The conversion of chlorophyll to phaeophytin following the

fumigation wi th S02 has been observed by Rao and LeBlanc

(1966). The diminution in chlorophyll content was

'observed by several workers int;luding Gilbert (1968), 11~e

(1970)}and Steubing' 'et a1., (1974).

S02 was observed to suppress the ,glycolic acid

pa thway as a result of which glycine and setiire synthesis'

was adversely affected (Tanaka ~ !l., 1972), The dimi-

nution is soluble protein content after exposing to 502 is,

due on the one hand to a reduced de ~ synthesis (Barnett, t

and Taylor, 1966), and on the other hand to an iJncreased'

, clecomposi tion to amino acids (Dugger and Ting, 1,9,70; Ting

a~d M~erj+, 1971; Godzik and Linskens, 1974).

J~pth 502 and H.2S0 3 are capable, of converting

enzymes or pro'teil1s having disulphide bonds to thio-

sulphonates and thiols. The S-S b mds in the polypeptide

c~ains are cle~ved by' HZS03 (Bailey and Cole, 1959; Cecil - -2 i and Wake J 1962~:. The accumulation of HSO:s - 8.1\,41 .. 503 ons

disrup~ the IiaJural balance between incomple,te~y oxidlzed • • .' 0"-'';

S-compounds a.n9 SH:groups present in glutathio,~~ ~~d, ., " .. , .

cysteine that are essential for structural in~~gr~ty of : ;;: ~ ~:' ',,"!:.'

proteins (McMullen, 1~60 i Loughman. 19~4).

16

The change in the activity 0.£ various enzymes

and in the pools of metaboli tes due to S02 f~igation has

been observed.' It lias reporte<:i ~hat 400 ~ m~~ of SOZ'

increased the sugar content in bean leaves and enhanced 'Ii. ~ ;.' ;,

the incorporation of· 14C02 into sucrose and fructose in

ryegrass (Koziol and Jordan, 1978; Koziol and Cowling,

1978). Increase in the pool of polyamines in pea lDlder

0 •. 3 ppm S02 was observed by Priebe ~ a1. (1978). Godzik

and Linskens (1974) when fumigatedPryaseolus vulgaris

to 0.7 ~ 0.1 ppm S02 for 6, I2,or 24 hr day-l for 3 days

observed a gene:r;al; increase in the ~~.ol of fref:} ami.no acids.'

except for ~,spartic and glutamic acids .• ; which,. were found

to decre~se. Jager and Pahlich '(1972) anp Jager ~ .ak (1972} observed incE~ase in the cysteine, glutami~e,and

glutamate levels, in Pisum sativum when furnigat.ed for 7 . '.

to 2.1 days wi th 0.3 to 1. 3 ppm of S02. However, the leve Is

of glutamate started decreasing ~ith an initial increase.

Tpe levels of glut.~Fhione (Sa compound) was found to

increase in Picea, Pinus, Larix,and Betula species w~en

fumigated for 21 days with 1.17 mg m- 3 S02 for 20 hr day·! ; ~." ~ .

. (G:r~ ~1 ~ al., 1979).

Low levels of 502' have been report~d t:Ci, i~f\:crease

the activity of certain enzymes. Pierre (19:7,1.) 'studied , .. ~ .' - '. .

tht.1.:respon se of various enzymes _ in bean Q.!!!.~cot species)

fumigated for 8, days at 0.1 ppm - 1.1 ppm S02. He

17

observed increase in the activity of glucose b-phosphate

dehydrogenase, glutamate dehydrogena'se. glycerol phosphate

dehydrogen~se, 'phosphofructokinase, malate dehydrogenase.

NADP- carboxylase, 'isoci trate dehydrogenase, aspartate

amino tra~sferase and ribulose 1-5 diphosphate carboxylase.

f Increase in the activity of various enzymes such

as isoci t'~ate de,hydrogenase. organic acid'synthesis . /

(malic enzyme), amino acid synthesis (aspartate amino-

transferase)) and glutamate dehydrogenase was observed in

Phaseolus Vulgaris when exposed continuously t:J't 0.1 ppm S02'

(Pierre and Queiroz, 1981). Horsman and Wellburn (1977)

compared the activities of ribulose diphosphate carboxylase

(RuDPC), glutamate pyruvate transwninase (Gl'T) and glutamate • J '

oxaloacetate transaminase (GOT) from extract of seedli~8s of

Rumex obtusifolium fumigated with 0.2 ppm S02 for 11 days.

They observed increased activities of GPT and GOT but RuDPC

behaved di£..f.~ren tly~" in fumigated see lings. Synergis tic • 'r J ~ .' ~;' ';~: I

effects were.o~se;r.ved' when seedlings were fumigated with .• !,'

0 .. 1, ppm NO Z ~lo.ltg w~th 0.2 ppm S02'" Tanaka:'~!l. (1974) !

reported inhibi;,tion,,}tf the activity of enzyme ribulose, 1-5 ;;, h d' . h 3 10-5 ,3 X' 10-4 • diphosophate in.alf~lfa w en treate Wlt x •

'3~ x 10- 3 and :3 x 10- 2 M soluti.ons of sulphite or sulphate

ions.

18

Acid phosphatase activity in mosses'Wls found,

to increase initially when fumigated for 48 ~ours at 5 and -

5.5 llg m-3 S02 but later decreased and visible injury - J

appeared when funligation was. extended upto 14 days .

(Hackeme,sser,. 1981). Rabe and Kreeh (1979) also observed

increased activities of ~nzymes glucose-'6-phosphate

dehydrogenase (G6.PDH), isocitrate dehydrogenase· (leDH),

alanine amino transferase'CALT), aspargine amino trans-,

ferase· (AST)" and glutamat~ dehydrogenase (GDH), in various ,

pl~nt species a~' Medicago sativa, Vicia' faba,- -TuliEa

gesnerana,- Be'ta. vulgaris, Nicotiana tahacum,.. Hordeum

d:i,..stichon and Lycopersicon e'sculentum 'when these plants

we~e grown in the vicinity of the l'WS power station

StUttgart-MUnster. They have also suggested th.at on

increased enzyme activity may be use,d as i,ndicators of ,

low levels pollution which do not pro~uce any vi~ible

damage to plants. Wellburn -~!!. (1981) while working

on three clones of ,!,olium perenne of different sensiti-

vity to S02 togethe r with other grasses 'Dactyli,s -

glomerata, ~hleum l?ratense and ~,pratensis, obsented

significant rise in t~e ratio of glutamate dehydrogenas~ i

activity and glutamine synthetase at; 6.8 pphm S02 for 11

weeks. The effect was more ,than additive in the ,

presence qf N0 2 •

19

Out of rhese studies, 'GDH was one of the common

enzyme s tudie d by various' lV'orkers • However , the'

behaviour of GDH and its suitability as indi.cator of low

,levels of S02 is relatively unknown.

The activities of oxidative enzymes like'

peroxidase , catalase .. and superoxidedismutase (SOD) were

also observed to be enhanced following the. fumigatiDn wi 1lh

S02 (Nikolaevskiy, 1966; Keller, 1974; Horsman and Wellburn,

1975;, Tanaka and Sugahara, 1980; Pierre and Queiroz, 1981) ~. ,

The levels of peroxidase have"been reported to be

incre asing with the exposure to other pollutants such as

NO z' HF; OzoneJand HCI. The increase in peroxidase'

, activity has been often suggested to have' an indicator as

we 11 as protecti ve ,value against the stress situation.

Horsman and Wellburn (1975) observed synergistic

effect of 0.1 ppm N02 on the increase of peroxidase

act,ivity, in Pisum sativum :"fHmigated with 0.2 ppm S02·

,1 ncre ase ~n:tJt!l,e peroxidase acti vi ty has also. been reported , "

in the two cuitivars. of Glycine '~Merr., 'York' and

'Wye': grown iIi the fi~tered air f(n' 14 days and then , f

exposed to 35 pphm ozone for 2 hr (Curtis'~!l •• 19?6).', , ! i',

Increased acti vi ty Of perox~dases was observed by Das~

and Weaver ,( 196 8) in these'nsi ti ve cu1 ti vars ofs6yb'e'an

" h 0 f ~o foIl owi ng the ir fumi ga tion \~i th 13 ... 50 pp m 3 0r oJ

min. Endress et a1. (1980) exposed -"phase 0 Ius -:-

20

vulgaris and Lycopersicon esculentum plants to either

gaseous hydrogen chloride (4.08 - '12.52 mg m-3) for 20

min or ozo~e (196-:392 pg m- 3) for 1 hour. They concluded

that total peroxidase activity, associated with non~

necrotic injury increased fol~owing pollutant stress, and

that it is sensitive to the internal physiological

conditions of the plants. 1$s ,extreme sensitivity, however.

prec:ludes its use as a reliable indicator of pollution

s·t ress.

Keller (1974) found thnt peroxidase activity

increased with the increasing levels of pollution caused i

l,ly fluoride containing exhaolates emanating from an

alijminium smelter near Zurich. He used the peroxidase

activity of white ash plants for monitoring air polluti.on

in the vicinity of the aluminium smelter, and also to

determine the effect of exhaust of automotive traffic on

vegetation in the city ~f Zuric~. A significant increase.

of peroxid~s·e activity was found in the city, although the

. white ash did not show any injury symptoms. On the basis

of t.he studii:e;.$.'t' it was suggested that .the peroxidase

activity is a ve·ry sensitive indicator of pl.ant reac~ion

to air poilutio;n and reflects the so called "hid~en",

injury (Keller~nd Schwager, 1971; Keller e~ ~l.~ 1916)~ { ---~ ...

The .. isoenzyme pattern of plants can also be

used to detect the effect of lo~.~evel~ pf S02. Pahlic~ t

-'.-'

21

(1972, 1973) reported that S02 altered tlle jsoenzyme ~~1t~1 • '< .. ,;

of GDB .in Pis'lun satl vum. Endress et'.!!.. (19~O} re:poi·te,q

that the isoenzyme pattern of peroxidases in' ;Lycopersicc)n'-- , .. ~

~culentum changed by He! and/or ozone ,exposure. 'CuTt);'

!..f~. (1976) while. 'working on the response of soybean' ,: . ,p~!oxidase to ozone found that certain pe,roxi.das~s of"

ozone-tolerant 'X'crktwere relatively less affected thWl

the peroxidases of ozone sensitive 'Wye', and CJll the b~nd~

showed inc:reased' acti vi ty. The available information a,n

the effect of S02 on isoenzyme pattern .of GDH and, , ,. , ..........

peroxidase 1sfragmentaty and nc: t' sufficient to assess , .,:

the nature of the injury. Moreover" the informatiOn

related to the response to peroxidases~o low ,l~vels ~f : ~I

S02 in sensitive' and:"Trsistant specie.'s is comp~etely

lacking.

The causes of significance of ~l,W in,creased

activity of enzymes following S02 s tre,sshas not been

sati.sfactorily understood. However, some spe~::ulations

have been ma,de to suggest that',the enhanced enzyme

activity helps plant to.resisi against gaseous pollutants

and thus enables the plant, t6 wi~hst~nd such stre~s by a

quanti t ati ve readj us tmentof the intermediary metabol i.sm

(Pierre 'and Queiroz, 1981).;' It is further argl,led that

theillcrease 'in metabo'licpot~ntiality of the cell is

to resist pollutit5n by faster metabolizatiqn of S02~and

TH -lol-{4

- a stabilization of internal pH. The readjustment is

, transitory and possibly starts diminishing after couple

of'weeks of continuous fumigation (Pierre and Queirot, !

. 1981). Other workers have also suggested that an increase

in the activity of enzymes, especially peroxidase and

superoxide dismuta&e is benefiCial for, the plant (Hersman

andWellburn, 1975;. Curtis et ~., 1976;'Endress!! !!., ,1980; Keller 1977; Tanakaand.Sugahara, 1980; Asada, 1980).

Peroxidase has been sugges te dto play apro~ec-

tive role in plants against S02 stress. . It has been ( .

-2 postulated that peroxidase ehnances the oxidation of SOa . -z -to ~04 thereby reduces the toxicity of S02 (Tanaka and

Sugahara, 1980; As ada , 1980). The mechanism and rate of

conversinnof sulphite to sulphate (sulphite turnover rate)

under the influence of enhanced level of perojidase is not·

known. Information about the sulphite turnover rate in .the

SOZ sensitive and resistant plant species is lacking. I

The detoxification o~ S03-2 in the plant cell

generally takes'place by the oxidation of sulphite to

sulph~te, as describe d above, and also by the reduction

df S02' In -S02~,;reduction ascorbic acid has been;.,f(l1Jrid to - -'

play an imp.-Q~t~·n,t role. Keller and Sch~ager'.f19i7) ) -~.~ :-

reported th~t. ascorbic acid may also influence detoxifica· , ",-

ti,<;m of pollutants in plants by reducing S02" Continued

23

SOz fumigation decreases ascorbic acid content long

before visible injury symptoms appear. A spray of

ascorbic acid to gr~en house crops increased their

tolerance to exidants (Fr~ebairn, 1960; Freebairn and

Taylor, 1960). Rao et Q. (1981) reported that the spray

,of ascorbic aCid, in the form of potassium ascorbate.

over S02 fumigated Vicia faba reduced the S02 toxicity

and suggested that potassiUm ascorbate acts as an

antidote of S02 pollution.

Plants have been fOlWd to have some inbuilt

eapaci ty to r~C?X~ f from various s t~~s~s including S02

when the nor~a.l conditions are restored. In bean plants, t

'it wasobserveq Fr~-t after the termination of f~!,!}gation

to 0.7 ppm SOZ' th.~- total protein increased wh~rr~s, ~lle

to tal amino aci ds de ere ased (Godzik and Linskens, t~? 4).

The level of protein in fumigated be~n Pfqn.ts. increased to that of control, while tneconcen-tratioq. of

~ ~. 1 - .... . ~! : ~ 1 ! •

total ami~C? aFi~s was still slight'ly h,tgher 'than t~~

control plan,t,s. after 72 hr of termination of fumigation

thereby indicatf~g the recov~ry (Godzik and Linskens,

1974). The rat,e of 14coz uptake or photosynthesis ~as

been observed tp recover when S02 exposure was discon,ti-

nued (Tanaka et a.1. 1974). The activity o~ enzy,me n~i,tro" --genase and photosynthesis show good fecovery after the

: 1 . . ... <: removal of b llJ.e green alga Anabaena cylindrica from sodium

94 . .."

bisulphite solution (Hallgren and Huss, 1975). Though

plants have shown a capacity to recover, but it is still

an open question because it iS,not known as to how long a

plant can withstand fumigation and whether the plants ,can

recover irrespective of the preceeding period of fumigation.

The effect of plant age on the recovery process is also not

known.

The review of the literature on S02 phytotoxicity,

shows that the information regarding the ecological, conse-. ,

quences of low levels ofS02 on plants and their eco-

physiological behaviour under S02 stress is lacking.

F

The present sutdy is aimed to assess plant

response- to low levels of S02 (3,5 ,and 10 pphm) by evalua-

ting a range of parameters such as leaf biomass t chloro-

phylls, sulphite turnover rate, total sulphate and sulphur \

content, total protein, activity of enzymes, peroxidase

and GDH and their isoenzyme pattern, ascorbic acid. content.

total electrolyte} and potassium leakage. This study also

suggests the suitability of some of the above parameters'

fOT employing them as reliable bioindicator of S02

stress.