Impact of heavy metals and biochemical parameters on specific leaf area of roadside trees in Kathmandu, Nepal

Abstract

Kathmandu is seriously facing the air pollution problembecause of the rapid increase in vehicular emissions.Most commonly grown roadside trees like Populuseuroamericana, Ficus religiosa, Jacaranda mimosifolia,Grevillearobusta, Callistemon lanceolatus and Cinnamomumcamphorafrom different sites of Kathmandu werecollectedduring the winter season to measure specific leaf area(SLA), biochemical parameters and heavy metals(Cu, Pb and Zn) content. The relations among them (SLA,biochemical parameters, heavy metals) were alsostudied. Specific leaf area (SLA) ranged from 24.48±0.87cm2 g-1 to 188.08±35 cm2 g-1 and the highest SLAwas observed in Jacaranda mimosifolia (188.08±35cm2g-1). The mean value of biochemical parameters suchas total chlorophyll (TCh) ranged from 0.64mg/g inCinnamomum camphora to 1.243 mg/g in Ficus reliogiosawhereas pH ranged from 5.28 in Callistemon lanceolatusto 6.75 in Grevillea robusta. Similarly Ascorbic acidrangedfrom 4.54 mg/g in Cinnamomum camphora to8.61mg/g in Populus euroamericana and relative watercontent (RWC) from 40.02 % in Jacaranda mimosifolia to86 % in Cinnamomum camphora. Mean value of Znaccumulation ranged from 14.83 mg/kg in Ficus religiosato 71.92 mg/kg in Populus euroamericana, Cuaccumulation from 4.14 mg/kg in Populous euroamericanato 14.56 mg/kg in Jacaranda mimosifolia and Pbaccumulation from 0.05 mg/kg in Populus euroamericanato 22.47 mg/kg in Callistemon lanceolatus. Pb andCu accumulation at phytotoxic concentrations in leavesshowed negative impact on SLA.