Simulated acid rain caused damage on leaf anatomy reduce growth and yield of Dioscorea alata (L.)

Most crops grown in the Southern part of Nigeria are exposed to acid rain owing to the release of sulphur and nitrogen oxides into the atmosphere. These gases emanate from man’s activities such as vehicular movements, electricity generation gas flaring and industrial activities. A mixture of sulphur oxides, nitrogen oxides and atmospheric water or water vapour gives rise to acid rain. This study was undertaken to determine the influence of simulated acid rain on the growth, yield and leaf anatomy of Dioscorea alata, water yam. The plants were exposed to simulated acid rain of pH 2.0, 3.0, 4.0 and 6.0 (control) respectively. Necrosis and chlorosis were observed on the yam leaves, after simulated acid precipitation. The impact of simulated acid rain became more noticeable with the increase in acidity. Vine length, leaf number, leaf area and chlorophyll content index were inhibited (p<0.05) at pH2.0 and pH3.0 as compared with the control. At pH2.0, 28% leaf surface area of D. alata was injured after simulated acid rain treatment while necrosis was absent at pH6.0. Acidic precipitation did not significantly (p>0.05) affect harvest index in D. alata, however, highest value was found at pH6.0. Anatomical sections of D. alata leaves revealed cuticle wax damage and breakage of the epidermis at lower pH2.0 and 3.0. Mesophyll tissue breakdown was also observed in the treated leaves.