Metabolic responses of tomato plants to metribuzin herbicide by in vivo and in vitro techniques

The effect of metribuzin at different doses [0.25, 0.5, 0.75 and 1.0kg ha-1] was studied on intact pot normally-grown seedlings of two tomato genotypes [Lycopersicon esculentum Mill, cv. Karnak vfnt F-1 and Castle rock]. The herbicide caused significant inhibitions in dry weight and protein contents of shoots and roots of both tomato genotypes. Significant reductions in chlorophyll, carotenoids, glucose, sucrose and starch were observed. The reduction was more pronounced at higher metribuzin doses. Possible tolerance to the herbicide in both genotypes was checked using tissue culture methods. Cotyledons and leaf discs from shoots regenerated on media containing different concentrations of metribuzin [0, 0.63, 1.25, 2.5, 5 and 10 mgM]were used to initiate three successive cycles of selection. Similar to potted plants, significant reductions in dry weight and protein content in shoots and roots of the in vitro selected plants were observed as well as in contents of chlorophylls, carotenoids, glucose, sucrose and starch of both tomato genotypes. The inhibition was remarkable at the high concentrations of metribuzin throughout the three cycles of selection. The magnitude of inhibition was relatively lesser in the 3rd cycle compared to the 1st or the 2nd cycles. Therefore, the effects of metribuzin on tomato appeared as declined after three cycles of the in vitro selection. Such decline could be regarded as a partial recovery response. This recovery response after three cycles of in vitro selection could point to a possibility of some developed resistance to the herbicide throughout the successive cycles

In-vitro induction of tomato resistance to metribuzin herbicide. Secondary metabolism indices

The effect of metribuzin at different doses [0.25, 0.5, 0.75 and 1.0 kg ai ha-1] was studied on original intact seedlings of two tomato variants [Lycopersicon esculentum Mill, cv. Karnak vfnt F-1 and Castle rock]. Metribuzin significantly reduced the growth parameters [shoot and root length, fresh and dry weight] of shoots and roots of both variants. Low doses of the herbicide significantly increased anthocyanin content and activities of phenylalanine ammonia lyase [PAL EC 4.3.1.5], tyrosine ammonia lyase [TAL EC 4.3.1] and chalcone isomerase [CI; EC 5.5 1.5] in both tomato variants. While, high doses seemed [if any] to have no effect. An attempt was conducted to check the effectiveness of cyclical in vitro selection for increasing resistance to metribuzin. Cotyledons and leaf explants from shoots regenerated on media containing different concentrations of metribuzin [0, 0.63, 1.25, 2.5, 5 and 10 muM] were used to initiate three successive cycles of selection. Throughout the three cycles of selection, metribuzin resulted in significant reductions in growth parameters of shoots of both variants. The reduction was more greater with the high concentrations of metribuzin. The reduction was relatively lesser in the 3rd cycle than the 1st cycle or the 2nd cycle. There were increases in anthocyanin contents of shoots and roots of both variants at all concentrations of metribuzin; high concentrations seemed to level off these increases. Only low metribuzin concentrations increased activities of PAL, TAL and CI of both variants. The response of secondary metabolism activities to the herbicide was lesser in plantlets selected from the 3rd cycle than in the 1st cycle

Correlation between endotoxin level in various forms of periodontal diseases with the disease activity

Periodontal disease follow a course with periods of quiescence and exacerbation [disease activity]. This study investigated the correlation between endotoxin level and the disease activity in various forms of periodontal disease, namely, rapidly progressive periodontitis, juvenile periodontitis and advanced adult periodontitis. The disease activity diagnosed on the basis of bleeding upon probing and amount of the attachment loss present [7-9 mm]. In addition, subgingival plaque collected to test the ability of these plaque sample to hydrolyze synthetic substrate benzoyl-DL-arginine naphthylamide [BANA]. This test is indicative to presence or absence of Gram-negative bacteria, especially Trepomena denticola, Porphyromonas gingivals and Bacteriodes forsythus. Fifteen subjects participated in this study, each subject provided 4 plaque samples, two samples from active lesions and two samples from comparable inactive control lesions. Then teeth associated with these sites were extracted to determine the amount of cementum bound of endotoxin during activity and inactivity stage. Therefore, no attempt was made to remove the cementum during scaling procedure. Ten impacted third molar teeth were extracted to serve as a control group. The results of the present study revealed that majority positive BANA test was associated with clinical diagnosis of active lesion. Also, correlation between endotoxin levles and disease activity were demonstrated. These findings suggest that, with additional studies, determination of site specific endotoxin levels may have potential application in predicting disease activity

effect of minimal dose of Nd: YAG laser on retained plaque and calculus

A scanning electron microscopic [SEM] study was conducted to evaluate the effects of pulsed Nd: YAG laser on retained plaque and calculus on diseased and scaled root surfaces. The experimental materials were 18 human teeth affected by severe periodontal disease, which were extracted because of a hopeless prognosis. Nine of these teeth were scaled with sharp scalers without attempting for removing necrotic cementum. The specimens were cut from the root proximal surfaces starting from CEJ and extending approximately 5 mm apically. All specimens were classified into 4 groups. The results showed that, untreated control specimens revealed a complex subgingival microflora of cocci, rods short, long filamentous and spirochetes. All treated specimens, regardless of treatment sequence, exhibited some degree of laser-induced root surface alteration. Notably, laser-treated calculus deposits were free of their characteristic surface layer of microbial plaque. However, SEM examination revealed residual deposits of plaque and calculus and presence of the smear layer in all treated groups except the group treated with scaling and laser radiation at 150 mj. The present results indicated that Nd: YAG radiation was effective in evaporation of the residual calculus and plaque of scaled root surface and removes the smear layer, uncovers dentinal tubules on the root surface with slight widening of its orifices