Growth and Leaf Chlorophyll Content of Eucalyptus grandis W. Hill ex Maiden are Adversely Affected by Simulated Acid Rain

Abstract

The study assessed the effects of different pH values of simulated acid rain on growth and leaf chlorophyll content of Eucalyptus grandis.
 The treatments comprised of two simulated acid rain solutions of pH 4.0 and 3.5, and unacidified water at pH 6.5.
 Place and Duration of Study was the National Forestry Development Agency, Humid Savannah Zone, Bamenda I Sub-Division, North West Region, Cameroon, between June and September 2019, respectively.
 The experiment was conducted under field conditions. Thirty 3-month-old seedlings were exposed to each pH level at 7-day intervals using a spray bottle. While two sets of thirty seedlings were administered sulphuric acid calibrated tap water with pH values of 4.0 and 3.5, the third set that constituted the control was sprayed with normal tap water. Data were collected on morphology, biomass, and leaf chlorophyll content at the end of the study and subjected to analysis of variance and Scheffé’s test.
 Results: The pH 3.5 treatment resulted in significantly lower responses of height (12.95 cm), number of leaves (15.28), leaf area (23.96 cm2) and total biomass (0.61 g) than the other two pH levels that did not differ for any of the traits. Average values between pH 4.0 and control were 20.39 cm, 22.00, 45.66 cm2 and 1.77 g. Stem diameter and root collar diameter declined from 2.87 mm and 4.14 mm at the control to 2.54 mm and 3.78 mm at pH 3.5, respectively. Leaves at pH 3.5 showed signs of necrosis, drying and curling. Leaf chlorophyll content was significantly greater in the control (45.30 SPAD units) than in the pH 4.0 (40.01 SPAD units) and pH 3.5 (39.82 SPAD units) treatments that displayed similar responses.
 Conclusion: The study reveals that simulated acid rain at pH 3.5 can have a harmful effect on chlorophyll content and growth of Eucalyptus grandis.