Physiological and Morphological Responses of Amaranthus hybridus L. (Green) to Simulated Nitric and Sulphuric Acid Rain

Abstract

Aims: To determine the physiological and morphological responses of Amaranthus hybridus leaf area, shoot height, stem girth, leaf number, petiole length, fresh weight (FW) and dry weight (DW) of leaf, shoot and root, relative growth rate (RGR) and chlorophyll (chl.) content to simulated nitric and sulphuric acid rain. Place and Duration of Study: Department of Botany, University of Calabar, Calabar, Nigeria, between February and April, 2016. Methodology: Thirty five poly bags were used. Simulated nitric and sulphuric acid rain (SNAR and SSAR) of pH 2.0, 3.0, 4.0 and a control pH of 6.0 were separately prepared and sprayed every two days. The research was carried out in a greenhouse under controlled conditions. Results: Results showed highest decreases at pH 2.0 and lowest decreases at pH 4.0 in all the physiological parameters studied. Highest decreases are depicted by lowest measured values while lowest decreases by highest values in all measured parameters as affected by SNAR and SSAR. Acid rain treated plants showed necrosis, chlorosis and leaf deformation. Chlorophyll a, b and total chlorophyll of acid rains treated plants revealed a trend of decrease in content with increasing period of development. Mean values for leaf area response to simulated HNO3 and H2SO4 acid rains of pH 2.0, pH 3.0 and pH 4.0 at 4 weeks period of development were 14.60±0.33d, 17.50±0.47d, 18.80±0.11d and 14.94±0.23d 17.70±0.20d, 17.92±0.28d as against control value of 22.62±0.26d cm2. Mean values for shoot height response to acid rains had values of 16.48±0.59d, 19.65±0.66d, 20.46±0.88d, 15.82±0.59d and 18.27±0.12d, 19.74±0.17d and 24.48±0.23d cm. Mean values for chl. a, b and total chl. at 28 days for SNAR and SSAR pH 2.0 and pH 6.0 were 18.9±0.12, 23.4±0.04 mg g-1 FW and 42.3, 20.0±0.3, 23.6±0.3 mg g-1 FW and 43.8 and 58.2 0.3, 71.2 0.3 mg g-1 FW and 129.4 respectively. Conclusion: Physiological and morphological parameters studied responded negatively to simulated nitric acid (HNO3) and sulphuric acid (H2SO4) rain with significant decrease at all acidity levels with respect to the control.