COMMENTS

T. Maneewarn : How did you collect dust from mango leaves.?
S.B. Chaphekar : With a jet of distilled water, dust was washed from the leaf surfaces into a beaker.

T. Maneewarn : What age Commelina were used as test plants?
S.B. Chaphekar: 15 cm. shoots of Commelina were vegetatively propagated,and they were used when they were 10-12 days old.

R. Wohlfarth : Can you explain whether damage to leaves starts at a concentration of 0.9 ppm so2 ?
B. Chaphekar: 0.9 ppm SO2 is fairly high and damages the leaves of an average plant) a 5-hour exposure to 5 ppm SO2 causes damage to many plants.

R. Wohlfarth : What is the time duration for the dustfall study?
S.B. Chaphekar : Dustfall was measured only for the dry season, from October to April (7 months).

Wohlfarth : Why are factories not established in the main wind direction?
B. Chaphekar : Urbanization and industrialization have proceeded in Bombay for more than 100 years. Social and economic constraintsprevent the shifting of established factories. However, since 1956, new factories have been established in the main wind direction.

M. Numata : How would you monitor CO, N0X and O3 with plants?
S. B. Chaphekar : Monitoring of individual gases with plants is difficult in a city, because of synergistic or antagonistic reactions between gases. Nevertheless, some plants appear sensitive to specific gases (e.g. Alfalfa to SO2, Gladiolus to HI', Tobacco to Pb) , and we need to search for such indicators.

A. Santiago : Would SO2 and N0X emissions be harmful to plants in the humid tropics when some of them may be converted to fertilizers?
S. B. Chaphekar: At low concentrations these gases serve as fertilizers for plants. At high concentrations, as in cities, they are damaging to plant.

Table 1: Dust-fall on Mangifera indica L. leaves at different localities in the city of Bombay.

Locality Dust-fall/m2
Month	TIFR	Wilson College  ( RS - LV)	Sion ( RS - IIV)	Masjid ( RS - IIV )	Shivaji Park ( RS - LV )	Mahul ( I - C)	BARC ( I - C )
Dry season I
Sept.1976	0.4	1.4	10.8	2.7	1.0	1.2	0.7
April 1977	7.3	58.6	64.2	39.1	18.4	20.0	18.7
Dry season II
Oct.1977	1.5	1.6	2.6	6.9	1.8	1.6	1.2
Dec.1977	4.7	7.4	11.2	22.5	9.2	1.9	0.8
Jan.1978	6.3	16.3	36.2	41.4	9.6	9.2	2.9
Feb.1970	7.4	18.8	46.2	53.6	9.9	15.5	4.7
Mar.1970	8.2	53.1	89.6	79.9	13.1	22.9	6.2
Apr.1978	10.2	69.6	119.2	97.2	24.2	25.4	23.1

Table 2 : % reduction in different characters of Comme1ina benghalensis L. after four exposure to the ambient air at different localities in Bombay city, in April - May 1978

Characters	Shoot length	Nodes/ Plant	Length of IV Internode from top	Area of III leaf  from top	Shoot Dry wt.	Total Chloro- phylls	Total proteins	API = A+B+C+D+E+F+G  7
Locality	(A)	(B)	(C)	(D)	(E)	(F)	(G)
HolidayCamp (C1)	0 loss	0 loss	0 loss	0 loss	0 loss	0 loss	0 loss	-
Inst, of Sci (partly CI)	29"	13"	-3"	-6"	46"	-19"	-12"	7
Aquarium (RS)	70"	43"	40"	-25"	67"	-8"	77"	38
Loha Bhavan (RS)	44"	11"	37"	43"	49"	84"	39"	44
Bombay Gas Co.(A)(RS-I)	80"	46"	55"	12"	85"	18"	42"	48
Bombay Gas Co.(B)(RS-I)	57"	4"	54"	34"	2"	35"	68"	36
Dadar TT (RS-IIV)	33"	17"	11"	33 "	0.1"	24"	35"	22
Collector's Colony (I-C)	27"	9"	17"	53"	14"	-5"	51"	24
SOCLEEN Lab  (I-C)	47"	24"	29"	43"	20"	35"	39"	34