The general pattern of morphological and physiological damage caused by SO2 is well known. Subsequent to the publication of a review by Thomas (1951), much information has been added on the subject (Brandt & Heck, 1968; Boralkar, 1979; Raza et al., 1986 and many more).

The seeds of Spinacea oleracea L, Abelmoschus esculentus Moench var. Pusa Savni; Amaranthus viridis L. and Phaseolus aureus Roxb. var. Vaishakhee were obtained from the Agriculture College, Pune and were sown in the plastic pots filled with 90% red loam+10% farmyard manure mixture. Regular thinning was done to avoid compitition for space. Plants were fumigated under static conditions at 0.09 parts per million or 257 ug/cu.m of S02 for 4 h at the ages of 10, 20 and 30 days from sowing as per the method described elsewhere (Banerjee et al., 1980). All of them were analysed on the 45th day from sowing. The growth performance was noted in terms of the aboveground phytomass (dried at 80°C).

Table 1 : Effect of a 4-h fumigation by 0.09 ppm concentration of S02 at different ages on aboveground phytomass (g) production of plant species.

Species	Age at fumigation (days)			Control
	10	20	30
Spinacea	0.233	0.320	0.376	0.530
oleracea
Abelmoschus	0.294	0.417	0.468	0.589
esculentus
Amaranthus	0.398	0.357	0.651	0.982
viridis
Phaseolus	0.137	0.150	0.155	0.187
aureus

The amounts of damage caused to the tested species as a result of fumigation at different ages are presented in Table 1. It is seen from the results that 10-day old age of plant is more susceptible to S02 and the susceptibility decreases with an increase in the age of the plants at fumigation time; at least upto 30 days. The reduction in phytomass due to exposure of S02 may adversely affect the competitive ability and give rise to weakling of the plant species population. The weak plant may as result, produce less photosynthate as also smaller number, of seeds from fewer flowers (Harper et al., 1970). The relative sensitivity of species tested was as follows, on the basis of above-ground phytomass production.

Amaranthus >Spinacea > Abelmoschus > Phaseolus

Authors are thankful to Prof. B. C. Haldar, Director and Dr. V. D. Tilak, the then Head of the Botany Department, The Institute of Science, Bombay for encouragement and UGC, New Delhi for financial assistance.

REFERENCES

• Banerjee, A. K., Boralkar, D. B. and Chaphekar, S. B. Indian J. Air Pollut. Cont., 1980,3,23-26.
• Boralkar, D. B. Ph.D. Thesis, University of Bombay, 1979.
• Brandt, C. C. and Heck, W. W. Air Pollution, 2nd ed. Vol. 1. A. C. Stern (ed.),Academic Press, New York, 1968.
• Harper, J. L, Lovell, P. H. and Moore, K. G. Ann. Rev. Ecol. & Syst, 1970, 1, 327-335.
• Raza, S. H., Rao, N. B. and Murthy, M. S. R. Proc. Clean Air Congress. Clean Air Society of Australia & New Zealand, Eastwood, Australia, 1986, 3, 133-139.
• Thomas, M. D. Ann. Rev. PI. Physiol, 1951, 2, 293-321.