Effect of S02 on Growth and Development of
Dahlia rosea Cav.
Sulphur dioxide, being a by-product of fossil fuel consumption is
one of the major air pollutants prevailing in Indian environment.
The pernicious effects of SOı87 on plant growth and yield have been
well documented (Mudd and Kozlowski 1975, Linzon 1978). However,
it remained debatable for many years whether low concentrations
of SO 2 are adequate to induce injury to agricultural and horticultural
crops. In recent years, there has been a growing interest in the
study of the mechanism of SO~. phytotoxicity (Malhotra and Hocking
1976; 3ager 1977; Schlee 1977~. Takemoto and Noble (1982) and
Alscher (198t~) studied the effect of SO 2 on light and dark reactions
of photosynthesis and respiration. The break-clown of chlorophylls
was reported by Rao and LeBlanc (1966) and Syratt and Wanstall
(1969) in lower plants. Godzik and Linskens (1974) noted a remarkable
decrease in protein content of SO_-exposed Phaseolus vulgaris leaves
accompanied by an increase m free ammo-actds pool. Unsworth et al.
(1972) demonstrated that relative humidity modified the response
of stomata to SO9. Bonte (1982) reviewed the effects of air poilutants
on flowering – fruiting of plants.
In the light of above reports) the present study was undertaken to
investigate the eIfect of long-term fumigation with SO_ on plant
foliage, photosynthetic pigments, protein content, stomata~ response)
phytomass and flowering in Dahlia rosea Car. a popular ornamental
annual plant.
MATERIALS AND METHODS
Seedling~ of Dahlia rosea Cav. (30-day-old) were transplanted in
six 1 m plots at a distance of 20 cm from'plant to plant in rows,
25 cm apart. At age 60 days, the plants of two plots were fumigated
with 1 ppm SO~ and that of another tv~o plots with 2 ppm
SO9. The fumigation v~as carried out inside 1 m- polythene chambers
for-two hours on alternate days between the age of 30 and 75=days
as scheduled in Table 1 (Singh et al. 1955). The plants of remaining
two plots were not treated with SO 2 and they served as controls.
However) control plants were also covered with polythene chambers
during fumigation period in order to simulate the conditions of treated
