DYNAMICS OF LEAD TOLERANCE IN TOBACCO (NICOTIANA TABACUM L.) GENOTYPES

Abstract

Lead nitrate has reports of significantly inhibiting plant growth. Early exploration of the genotypic difference for lead nitrate stress in tobacco has started. The presented study had eight tobacco genotypes subjected to 200 μM lead nitrate (Pb [NO3]2) stress in a hydroponic culture. Lead stress treatment to plants for 14 days had data recording at three times intervals of stressed plants. Assessing photosynthetic and antioxidant enzymes’ activities was in a time series order of one day, seven days, and 14 days. One-day, seven-day, and fourteen-day-old seedlings gained treatment of 200 μM lead nitrate stress and control. Soil Plant Analysis Development (SPAD) values for most genotypes decreased, while oxidant and anti-oxidant enzymes increased activity. Chlorophyll-a, chlorophyll-b, and total chlorophyll evaluated after lead nitrate toxicity showed reduced activity in studied tobacco genotypes compared with control as time passed. All chlorophyll contents, i.e., chlorophyll a, b, and total chlorophyll, declined with a longer span in lead nitrate solution. Genotype QVA-20 could benefit lead-salt tolerance and susceptible genotype ‘long chang’ cigarette based on chlorophyll content and SPAD values. Chlorophyll a capacity decreased as lead exposure to plants increased, but chlorophyll b increased in all genotypes on the 15th day. The MDA (malondialdehyde) content increased in all tobacco genotypes with increased lead nitrate exposure. Meanwhile, SOD (superoxide dismutase) contents decreased in genotypes RG-8, E1, and X6 with increased time, but POD (peroxidase) contents increased in all genotypes on the 14th day. Genotypes RG-8, E1, and X6 proved considerably tolerant of lead toxicity at 200 µM.