Effect of 009 ppm, concentration of sulphur dioxide on Jowar, Sorghum vulgare Pers. Var. CSH—l were studied as indicated by seed germination, growth performance, dry matter production, chlorophyll contents, sugar and protein contents. The three hour treatment of sulphur dioxide affected germination of seeds and germinated seedlings had smaller roots and hypocotyls for the first five days.

Yields in terms of dry matter of the fumigated plants was less as compared to that of the controls. Seedlings and young plants suffered more due to the fumigation. 24 h after a 3 h fumigation treatment a drop in chlorophylls and proteins was observed.Sugars were however less affected at this concentration.

INTRODUCTION

Many responses of vegetation to air pollution are stable. Subsequent to the review published by Thomas (1951) lot of information has been added to this subject (Rao and Le Blanc, 1965; David, 1970; Roberts, 1976 and Pandey and Rao, 1978).

The reduced percentage germination, germination index, root-shoot lengths and their ratio, were observed to be affected considerably in crops, ornamental and kitchen garden plants in this laboratory by Bandyo-padhyaya (1976). The work presented here was carried out to study the effects of sulphur dioxide on growth and production of Jowar, a major cereal crop in Maharashtra State.

MATERIALS AND METHODS

The Jowar (Sorghum vulgare Pers. var. CSH—1) seeds were sown in earthen pots of 25 cm diameter, containing soil and farm-yard manure. Eight days after sowing, plants were thinned to five per pot. Further thinnings were done to three per pot at young plant stage (30 days old) and to one per pot at mature plant stage (45 days old). Plants were watered regularly.

The fumigations of these plants at 009 ppm concentration of S02 were carried out in a perspex chamber by mixing predetermined quantities of sulphuric acid and sodium sulphite. A fifty seed lot in duplicate was soaked in distilled water for 2 h and then exposed to SO2 for three hours at 009 ppm concentration. The seeds were left for germinatoin on moist filter paper in petri dishes. The emergence of radical was taken as a mark of germination which was noted every 24 h for five consecutive days. Germination Index (GI) values were calculated as per Carley and Watson (1968) method. Root and shoot lengths of seedlings were measured on the fifth day. A control without fumigation was run with the same number of seeds. 24 h after a three-hour fumigation of plants at seedling stage (15 days old), young plant stage (30 days old) and mature plant stage (45 days old), estimations of chlorophylls, total proteins, and sugars were done.

30 days after fumigation, yield in terms of dry matter production of fumigated plants and controls were determined by harvest method. Some of the plants fumigated at seedling stage (SS), young plant stage (YPS) and mature plant stage (MPS) were allowed to grow till ear formation (i.e. 100 days) and lengths of inflorescences, and yields as dry matter of shoots and roots were noted.

RESULTS AND DISCUSSION

Results of seed germination are presented in Table 1. Normally the seeds showed 83 per cent germination and at 0.09 ppm SO2 fumigation it was reduced to 77 per cent. The GI values were also correspondingly lower as against 1336 in control, it was 1304 in the fumigated ones.

Mean radical length was 2. 38 ± 1.16 cm in seedlings from the fumigated seeds as against 3.7 ± l.3 cm in the controls. Similarly, the shoot size was 3. 6 ± 1. 2 cm in fumigated and 4. 2 ± l. l cm in the control. Thus though the rate of seed germination was not found to be greatly affected, development of root and shoot systems showed acute adverse effects.

Table 1 : EFFECT OF A 3 HOUR 0. 09 ppm SO2FUMIGATION ON JOWAR SORGHUM VULGARE PERS. VAR. CSH—1, SEED GERMINATION.

Fumigation   stage	Percent  germination	Germination  index	Root length     (cm±S D)	Shoot length  (cm±S D)	Root / Shoot
Treated	77	1304	2.38 ± l.16	3.6 ± 1.2	0.63
Control	83	1336	3.7 ± 1.3	4.2 ± 1.1	0.88

Table 2 shows that the total chlorophyll content was reduced to 2.039 mg/g fresh weight in fumigated plants from 2.831 mg/g fresh weight of controls at seedling stage. At young plant stage and mature plant stage it was less affected. The damage at these stages was only 14.9 and 49 per cent, respectively.

The total chlorophyll a was affected by 29.3 per cent at seedling stage and 12.8 per cent at mature plant stage. At young plant stage however, the damage was 16 per cent. The control had 0.942 mg/g fresh weight of total chlorophyll a at young plant stage whereas the treated one contained only 0.792 mg/g fresh weight. Like the chlorophyll a , the total chlorophyll was lowest in seedling stage plants. Control had 1.53 mg /g fresh weight of total chlorophyll b at seedling stage whereas the treated one had 1.126 mg / g fresh weight. Thus the damage was 26.5 per cent at seedling stage. At young plant stage and mature plant stage the damage was 14.5 per cent and nil, respectively.

Table 2 : EFFECT OF A 3 h SO2 FUMIGATION OF 0 09 ppm CONCENTRATION ON DIFFERENT CONTENTS OF LEAVES AT DIFFERENT STAGES OF GROWTH OF JOWAR, SORGHUM VULGARE PERS. VAR. CSH-1.

	Chlorophylls (mg/g fresh weight)				Protein (Percent fresh weight basis)						Sugars (mg/g dry weight)
	Total		a	b							Total							Total reducing
Fumigat on stage	SS	YPS	MPS	SS	YPS	MPS	SS	YPS	MPS	SS	YPS	MPS	SS	YPS	MPS	SS	YPS	MPS
Treated	2.039	2.0	3.15	0.836	0.792	1.256	1.126	1.129	1.775	6.70	12.0	11.00	14.44	14.57	27.63	6.142	5.49	15.69
Control	2.831	2.35	3.31	1.191	0.942	1.439	1.53	1.32	1.759	11.25	15.0	12.75	16.77	22.7	31.62	6.874	7.58	19.41
Percent-age loss	28.0	14.9	4.9	29.8	16.0	12.8	26.5	14.5	—	40.5	20.0	13.8	13.9	36.2	12.7	10.7	27.6	19.20

Values are the mean of 3 replicates.
SS—Seedeing stage; YPS—Young plant stage; MPS—Mature plant stage.

The protein contents of plants as a result of S02 fumigation are shown in Table 2. Due to a 3 h fumigation at 0 09 ppm S02 concentration, the protein content after 24 h was found to have dropped by 40.5, 20, and 13.8 per cent at seedling stage, young plant stage and mature plant stage, respectively. With an increase of age from seedling onwards upto mature plant stage the protein content damage was progressively less.

The total sugars and total reducing sugars are affected at all the three stages, though the damage was more severe at the young plant stage. At this stage the control had 22.7mg / g oven dry weight of total sugars whereas the treated one had 14.57 mg / g oven dry weight. Thus the reduction was 36.2 per cent at young plant stage while at seedling stage and mature plant stage it was 13.9 and 12.7 per cent respectively. Similarly, the drop in total reducing sugars was 10.7, 27.6 and 19.2 per cent at seedling stage, young plant stage and mature plant stage, respectively.