ABSTRACT
The present study was conducted to assess quantitative information about lead (Pb) contamination in soil on the growth and physiology of wheat. Solutions with three different concentrations of Pb as [Pb(NO3)2 at 500, 1000 and 2500 >M] were incorporated into the soil to achieve Pb-stressed conditions in comparison to unstressed, water treated, control variant. Wheat growth measured in terms of root length, shoot length and dry weight exhibited a significant decline with increasing Pb concentrations in the soil. Root and shoot length and seedling weight declined in the range of ~23–51, ~17–44, and ~21–44% in response to 500 to 2500 >M Pb. In addition, there was a significant reduction in the levels of photosynthetic pigments-chlorophyll a (16-66%) and b (10-24%) and total chlorophyll content (by 14-39%) in plants growing in Pb-contaminated soil. It indicated a negative effect on photosynthetic activity in wheat and was confirmed by reduced photochemical efficiency of PSII (Fv/Fm) in the range of ~ 3-37% in response to 500 to 2500 >M Pb. The reduction in wheat growth in Pb-contaminated soil was accompanied by induction of oxidative stress as indicated by enhanced lipid peroxidation in terms of malondialdehyde (MDA) content (by 18-40%) and hydrogen peroxide (H2O2) content (by 34-123%) and alterations in the activity of enzymes, superoxide dismutases (SOD) and guaiacol peroxidases (GPX) in wheat roots. The study concludes that Pb in soil inhibits growth and phototsynthetic activity in wheat through induction of oxidative stress.
ABSTRACT
Benzoxazolin-2(3H)-one (BOA) is a well known allelochemical that is being explored for its herbicidal activity. However, not much is known about its effect on crop plants. The present study investigated the effect of BOA on germination and early growth of four vegetable crops viz. Pisum sativum L., Raphanus sativus L., Brassica oleracea L. var. botrytis and Brassica oleracea L. var. capitata. At 1000 <M, germination of P. sativum, R. sativus and B. oleracea var. botrytis was reduced by more than 50%, whereas that of B. oleracea var. capitata was completely suppressed. Further, BOA reduced the root and shoot length of the test plants by ~ 40-82% and ~55-85%, respectively. In general, the effect was more pronounced on the root (~82% in B. oleracea var. botrytis) than on the shoot growth (~73% B. oleracea var. botrytis). 2- Benzoxazolinone significantly enhanced the contents of proteins (by 6-28%) and carbohydrates (by 61- 189%) in B. oleracea var. capitata and decreased the activities of related enzymes like proteases (by 13- 36%), a-amylases (19-60%) and b-amylase (25-70%). The observed decline in the activities of hydrolytic enzymes amylases suggest that BOA interferes with the vital metabolic processes in the germinating seedlings leading to growth reduction. The study reveals that BOA interferes with the germination and early seedling growth of vegetable crops and induces biochemical alterations.