The general pattern of morphological damage to plants caused by air pollution is now well known. Subsequent to the publication of a review (Thomas, 1951) a lot of Information has been added to the subject. Intercostal soft patches to leaf senescence caused by ambient SO2 have been variously described by different authors (Brandt & Heck , 1968 ; David , 1972 ; Pandey & Rao , 1978 ; Boralkar, 1979). Reduced rates of germination and adverse effect on root nodulation in beans were reported by Banerjee & Chaphekar (1978).

The seeds of Crotalaria junceawere soaked in distilled water and spread on filter paper in petridishes. A fifty seed lot was then exposed to 1.0, 0.5, 0.09 and 0.04 ppm of SO2 , separately in a fumigation chamber for 3h each (Banerjee et al., 1980), and then left for germination. Emergence of radical was taken as successful germination which was noted at every 24 h for five consecutive days and germination index ( Gl ) was calculated (Carley a Watson, 1968).

Root and shoot lengths of 500 seedlings from each treatment were measured and their means and standard deviations were calculated. A control without treatment was run simultaneously with the same number of seeds. SO 2 show a marginal decrease in germination percentage with increasing concentrations and seedling growth was significantly affected. The implications of these findings pose interesting possibilities. At the significant levels of pollution i.e. above 0.09 ppm along.

Table 1 : Effect of SO2 on C. juncea after 3 h of fumigations at different concentrations.

Conc.   (ppm)	Germination  (%)	Gl	Root length  in cm + s.d.	Shoot length in cm±s.d.	Root/shoot ratio
1.0	90	1400	2.5 ± 1.0	3.04± 2.5	0.67
0.5	92	1421	2.6 ± 1.3	4.51 ± 3.1	3.58
0.09	95	1444	2.8 ± 1.4	6.64 ± 2.1	0.43
0.04	86	1460	3.2 ± 1.8	8.70 ± 2.2	0.36
Control	98	1482	3.9 ± 1.2	9.39 ± 2.6	0.42

with marginal reduction in germination of the seeds the absorbing and photosynthesizing organs of the successfully germinated seeds were also reduced in size. This reduction in the size of a plant may affect its competitive ability, as such a plant does in effect correspond to one from a smaller seed giving rise to a weakling in a plant population. Lack of competitive ability of these plants is also brought out further by an increased root/shoot ratio, exposed to higher concentration of the pollutant forming less photosynthetic tissue.

The weak plant may as a result, produce less photosynthate as also smaller seeds from fewer flowers (Harper et al..1970). Thus not only the immediate net primary production is affected due to the pollutant but subsequent generations of plants also would be impoverished. The authors are thankful to U G. C. for financial help and Dr B. C. Haldar, and Dr. V. D. Tilak for resourceful encouragement.

REFERENCES

• Banerjee, A K., Boralkar, D. B. and Chaphekar, S. B. Indian J. Air Pollut. Contr., 1980, 3, 23-26.
• Banerjee. A. K. and Chaphekar. S. B. Proc. Int. Symp. Environ Agent & their Biol. Effect, Hyderabad, 1978, 126-132
• Boralkar, D. B. Ph. D. Thesis, University of Bombay. 1979.
• Brandt. C. C. and Heck. W. W. Air Pollution 2nd ed. Vol. I. A. C. Stern (ed.) Academic Press. New York 1968.
• Carley, E. H. and Watson. R. D. Bot. Gaz,1968, 129, 57-62.
• David, C.R. J. Air Pollut. Contr. Assoc, 1972. 22, 964-966.
• Harper. J. L., Lovell, P. H. and Moore, K. G, Ann. Rev. Ecol. & Syst ., 1970, 1. 327-335.
• Pandey, S. N. and Rao, D. N. Indian J. Air Pollut. Contr., 1978. 1, 9-16.
• Thomas. M D. Ann. Rev. PI. Physiol., 1951. 2, 293-321.