DEGREE IN BIOLOGYA RESEARCH PROJECT SUBMITTED TO THE DEPARTMENT OF BIOLOGY, FACULTY OF CHEMICAL AND LIFE SCIENCES USMANU DANFODIYO UNIVERSITY, SOKOTOIN IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR AWARD OF THE BACHELOR OF SCIENCE (B.SC. HON)

Abstract

This study investigated the physiological and biochemical responses of maize (Zea mays L.) seedlings exposed to varying concentrations of lead nitrate [Pb(NO₃)₂]. Certified maize seeds were subjected to lead treatments of 0, 1, 3, 5, and 7 mM prepared from Pb(NO₃)₂ in a completely randomized design with three replicates. Seeds were surface-sterilized and germinated under controlled conditions for seven days, after which growth parameters including germination percentage, root and shoot lengths, and tolerance index were determined. Biochemical analyses were also conducted to quantify proline accumulation and lipid peroxidation (MDA content) using standard spectrophotometric procedures. The results showed that increasing Pb concentration induced significant physiological stress, reducing germination and seedling growth. Proline content increased with Pb exposure, indicating osmotic adjustment and stress tolerance, whereas MDA levels also increased, reflecting enhanced membrane lipid peroxidation due to oxidative stress. These findings demonstrate that lead toxicity negatively affects maize growth by disrupting physiological and biochemical processes, while the observed increase in proline suggests a protective stress response. The study highlights the need for monitoring heavy metal contamination in agricultural soils to ensure sustainable crop productivity.