Alleviation of allelochemical stress-induced growth inhibition and oxidative damage in lettuce under closed hydroponics through electro-degradation

Successive lettuce cultivation in closed hydroponics using the same nutrient solution causes the excess production and accumulation of allelochemicals. The accumulated allelochemicals induce oxidative damage and lipid peroxidation in plants leading to growth inhibition. In this study, we investigated the allelochemicals that induced oxidative damage and lipid peroxidation in lettuce grown in a once used non-renewed nutrient solution (1NR) and a twice used non-renewed nutrient solution (2NR) obtained from the successive cultivation and the alleviation of these damages through electro-degradation (ED). The 1NR solution was used for six weeks for a one-time lettuce cultivation while the 2NR solution was used for twelve weeks for a two-times lettuce cultivation. The results showed that the allelochemical stress caused growth inhibition in the lettuce in both the 1NR and 2NR solutions. It was observed that there was a higher generation of H2O2 and O2.– as well as a lower activity of the antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (POD), and ascorbate peroxidase (APX) in the roots of the plants grown in both the 1NR and 2NR solutions compared to plants grown in the new nutrient solution. The higher level of lipid peroxidation due to the higher MDA (malondialdehyde) content and higher soluble protein content were also observed in the roots of those plants. It was evident that lettuce root damage occurred due to accumulation of the allelochemicals in the 1NR and 2NR solutions. These damaged roots could not function normally nor uptake water and minerals from the culture solution. As a result, retarded lettuce growth was observed in the 1NR and 2NR solutions. The oxidative damage, soluble protein content, lipid peroxidation and ultimately growth retardation were more pronounced in the plants grown in the 2NR solution compared to the plants grown in the 1NR solution. The application of ED to the 1NR and 2NR solutions maintained the plant growth through less oxidative damage, soluble protein production and lipid peroxidation as was observed in the plants grown with the new nutrient solution. Therefore, the ED of a non-renewed culture solution would alleviate the allelochemical stress in lettuce under recycled hydroponics.

Effects of growth regulators on seed germination, seedling growth and some aspects of metabolism of Wheat under allelochemical stress

Effects of growth regulators on seed germination, seedling growth and some aspects of metabolism of wheat under allelochemical stress due to oleander and walnut leaf (extract and powder) were investigated. All parameters e.g. seed germination, seedling growth, leaf pigments except the proline content reduced significantly under stress. On the contrary, GA3 and IBA showed alleviating activities. The alleviation effect of GA3 was higher than that of IBA . DOI: http://dx.doi.org/10.3329/bjb.v42i1.15865 Bangladesh J. Bot. 42(1): 65-71, 2013 (June)

Analysis of correlation structure in Lymantria dispar L. larvae from locally adapted populations

The influence of allelochemical stress and population origin on the patterns of phenotypic and genetic correlations among life history traits and digestive enzyme activities were investigated in larvae of the gypsy moth (Lymantria dispar L.; Lepidoptera: Lymantriidae). Thirty-two full-sib families from oak (suitable host plant, Quercus population), and twenty-six full-sib families from locust-tree (unsuitable host plant, Robinia population) forests were reared on an artificial diet, with or without a 5% tannic acid supplement. Comparison of correlation matrices revealed significant similarity between the two populations in the structure of phenotypic and genetic correlations of life history traits and of digestive enzyme activities. The patterns of correlations of the examined traits, within each of the two locally adapted populations and in the presence of allelochemical stress, remained stabile despite the different selection pressures that mold these traits.