Impact of dust accumulation on the physiological functioning of selected herbaceous plants of Delhi, India

Plants are now widely recognized for their potential role in improving the air quality by dispersion and deposition of atmospheric dust particles. However, suspended dust particles negatively affect plant growth and physiological development. The present study aims to assess the amount of dust accumulation on the leaf surface and to evaluate the effect of foliar dust on leaf gas exchange parameters, photosynthetic pigment, and metabolite content of five roadside herbaceous plant species (Amaranthus viridis, Achyranthes aspera, Acalypha indica, Parthenium hysterophorus, Trianthema portulacastrum). Two sites (site I and site II) were selected that differed in their surrounding anthropogenic activities and dust pollution levels. Results showed that the average amount of dust accumulated on the leaf surface was significantly greater in plants grown at the polluted site. Among the five species examined, the highest amount of foliar dust load was observed for A. aspera (0.49 mg cm(-2)). Dust accumulation caused substantial changes in plant physiology as indicated by the significant decline in chlorophyll content, photosynthetic rate, stomatal conductivity, and transpiration rate in plants grown at the polluted site. Moreover, an increase in antioxidant activity, total ascorbate, and metabolite content, responsible for maintaining plant defense, was higher in plants at polluted site. Biochemical response of the individual plants studied was variable, which suggests that different plants adopted different mechanisms to cope with the stress induced by dust particles.