Air Pollution Tolerance Index: Many fruit bearing trees falling to stress from industrial, automobile pollution

Syed Akbar
Hyderabad: Contrary to popular belief that trees fight
pollution, several species of plants including cashew, tamarind,
guava, mango, custard apple, gulmohar, banyan, sapota and Jack fruit,
are falling prey to heavy air pollution in the industrial city of
Visakhapatnam.

Researchers from the departments of chemistry, and environmental
studies, GITAM University, Visakhapatnam, have found that many plant
species have been experiencing “physiological changes” due to heavy
air pollutants before exhibiting visible damage to leaves. The content
of chlorophyll has come down in many trees affecting the delicate
process of converting carbondioxide into oxygen. It has also affected
food preparation by the trees, and thus reduction in their fruit yield
and growth.

Of the 29 trees studied, only six fell under the “moderately tolerant”
to air pollutants category. None of them is tolerant to chemicals
present in the air. Only those trees that are tolerant to heavy air
pollutants are capable of fighting pollution in industrial belts, and
reducing its impact on human beings, animals and other plants. The
research was conducted separately by N Srinivas and others from
department of environment studies, and A Sunil Dadhich and team from
the department of chemistry.

Peepal, jujube, amla, cassia, lemon and neem are moderately tolerant
to pollution. A majority of trees fall in the sensitive category. This
means growing these trees in industrial belts and highly polluted
areas will do more harm than good to the environment.

“Trees can be used as both passive biomonitors and bio-mitigators in
the urban industrial environment to indicate the environmental quality
and to ameliorate the pollution level in a locality. Air pollutants
can directly affect plants via leaves. The level of injury is high in
sensitive species and low in tolerant ones,” they pointed out.

The teams studied the content of chlorophyll and ascorbic acid,
relative humidity, pH and air pollution tolerance index (APTI) of
trees selected. The results were compared to those obtained from trees
growing in less polluted localities. They found that the total
chlorophyll and ascorbic content was higher in trees from less
polluted areas, as compared to the trees growing in industrial areas.