Seeds and 15 days old plants of Abelmoschus esculentus Moench var. Pusa Savni were fumigated by SO2 (50 pphm) and O3(10 pphm), singly and in combination, for 4 h in a fumigation chamber. While seed germination and lengths of plumule and radicle were reduced due to the pollutant gases fumigation, singly and in combination, the net primary production was reduced more due to the treatment of mixture of SO2 and O3 than the individual gases. Similar effects were observed on the chlorophyll contents also.

INTRODUCTION

It is becoming increasingly essential to understand the synergistic impact of air pollutants on organisms. Plants are invariably exposed to the mixtures of air pollutants in the atmosphere. Many workers have described the effects of mixtures of air pollutants on plants in field and laboratory conditions(Grosso et al., 1971; Singh and Rao, 1981; Banfield, 1971; Applegate and Durant, 1969; Chaphekar et al., 1979). The work presented here reports the effect of sulphurdioxide and ozone, singly and in combination, on the seed germination and chlorophylls.

MATERIALS AND METHODS

The seeds of Abelmoschus esculentus Moench var. Pusa Savni were soaked in distilled water for 2 h and spread on filter paper in petridishes. Both filter papers and petridishes were sterilised to avoid microbial interferences. A 50 seed lot was then exposed, in duplicate, to sulphurdioxide (50 pphm), and ozone (10 pphm), singly and in combination, in a fumigation chamber for 4 h separately (Banerjee et al; 1980; Rao and Pal, 1975) and then left for germination. Percentage germination was noted only 24 h after the treatment. Emergence of radicle was taken as successful germination which was noted at every 24 h for 5 consecutive days and germination index(Gl) was calculated (Carley and Watson, 1968). When the percentage germination 24h after the treatment of S02 alone was nil, the rate of seed germination was observed for the following 5 days as indicated by the number of seed germinated per day for calculation of GI. Root and shoot lengths on oven dry weights of 100 seedlings were determined after 5 days. A control with the same number of seeds was raised simultaneously without the treatment of gases. In an another experiment 15-day old plants of A. esculentus war. Pusa Savni were fumigated in a similar manner, as stated above and total chlorophyll a and chlorophyll b were determined 24 h after the fumigation (Arnon, 1949; Maclachlan and Zalik, 1963). A control was raised simultaneously except the treatment by gases.

RESULTS AND DISCUSSION

Results obtained are presented in Table. The percentage germination studied 24 h after the fumigation was affected due to the pollutant gases.lt was observed that S02 alone delayed the germination which was nil 24 h after the treatment whiie percentage germination was considerably reduced by the treatment of sulphurdioxide and ozone mixture and ozone alone.The rate of seed germination was also affected in a way similar to that of percentage germination.

Table 1 : Effect of a 4-hour fumigation by SO2 (50 pphm) and O3 (10 pphm), singly and in combination, on Abelmoschus esculentus var. Puro Savrn seed germination and chlorophylls.

Treatment		Germination		Length in cm*		Over dry wt. of seedling (mg)*	Total Chlorophyll
		(%)	Index	Shoot	Root		a**	b**
1.	Control	75	1255	6.9	3.0	306	0.167	0.448
2.	SO2***	Nil	715	5.3	1.7	292	0.144	0.369
3.	O3****	42	1070	6.3	2.2	329	0.148	0.682
4.	SO2***+O3***	66	1120	6.5	2.2	285	0.128	0.644

*Mean of 100 observations **of 15-day old plants in mg/g fresh weight (mean of 5 estimations) **(50pphm) ****(10 pphm)

The root-shoot length were considerably reduced due to the pollutant gasesas compared with that of controls and maximum reduction was in the case of S02. However, the net primary production was affected maximum in the seeds fumigated by the mixture of SO2 and O3. The observations reveal the fact that though the rate of seed germination and lengths of plumule and radicle was adversely affected by S02 and 03, singly and in combination, the net primarily production was reduced more due to the treatment of mixture of S02 and 03 as compared with that of S02 and 03 alone.

The total chlorophyll a was reduced due to the fumigation by sulphurdioxide and ozone alone but the adverse effect was more due to the mixture of both the gases. The total chlorophyll b was slightly affected due to the fumigation by sulphurdioxide alone but considerable increase in the chlorophyll b content in the plants fumigated by ozone and mixture of SO2 and O3 was observed. Similar increase in the total chlorophyll b contents was observed by Pandey and Rao (1977) in wheat plants and by Boralkar (1979) in Sorghum, Field beans and Sunhemp plants, fumigated by sulphurdioxide. The increase in the chlorophyll b contents in the plants fumigated by S02 alone and in combination with 03 deserves attention.

In conclusion it can be said that A.esculentus var. Pusa Savni plants was sensitive to sulphurdioxide and ozone, singly and in combination, and the adverse effect on the seed germination and chlorophyll contents was more due to the mixture of gases than the individual. The reduction in the formation of less photosynthetic tissue would result in the weakening of the plant which may produce smaller seeds from fewer flowers (Boralkar, 1979; Pandey and Rao,1977).

ACKNOWLEDGEMENTS

Authors are thankful to Principal R. M. Raverkar for encouragement and University Grants Commission for financial help through the Scheme of Restructured Courses sanctioned to the Science College, Karad.

REFERENCES

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