The impact of heavy metals on the physiological responses in Chaemocostus cuspidatus

Abstract

Chamaecostus cuspidatus (insulin plant) is a medicinally important plant used in several medicines and as dietary supplements. Leaves of this plant have been used to treat diabetes since ancient times. Photosynthesis is a crucial aspect of plant physiology, ultimately affecting plant growth and metabolite production. In the current study, the plant was grown in controlled polyhouse conditions and treated with three heavy metals (Pb, Cr, and Cu). Five different concentrations (Pb and Cr- 50, 100, 150, 200, 250 ppm and for Cu- 25, 50, 75, 100, 125 ppm) of each metal were used for the treatment. Non-destructive methods were used for the study of physiological aspects of plants. CI-340 Handheld Photosynthesis System and CI-710s SpectraVue Leaf Spectrometer were used to measure approx 10 different parameters. Photosynthetic active radiation (PAR) was highest in Cu 100 (52.733 ± 0.466) treated plants. The highest Net photosynthetic rate (Pn) values were observed in Cr 200 (38.65 ± 0.384). The transpiration rate (E) was found to be highest in Cu 125 (0.846 ± 0.0202). Total chlorophyll content (CPHLT) and Chlorophyll Content Index (CCI) were also measured, and it was found to be highest in Cu 75 (30.344 ± 0.262) and Pb 150 (11.979 ± 0.231), respectively. Water Band Index (WBI), Normalized Difference Vegetation Index (NDVI), Anthocyanin Reflectance Index 2 (ARI 2), and Carotenoid Reflectance Index 2 (CRI 2) were also measured and analyzed for all the treatment groups along with control for each set. Statistical analysis represents significant differences among all the treated and control plants. These indices represent plant physiology, growth, and vegetative health of plants. Further biochemical and metabolite level studies can be done to further understand the effect of heavy metals on plant growth and metabolite production.