M. Gomathinayagam

Differential responses in water use efficiency in two varieties of Catharanthus roseus under drought stress

Two varieties, rosea and alba, of Catharanthus roseus (L.) G. Don. were screened for their water use efficiency under two watering regimes, viz. 60 and 100% filed capacity in the present study. Drought stress was imposed at 60% filed capacity from 30 to 70 days after sowing, while the control pots were maintained at 100% filed capacity throughout the entire growth period. Leaf area duration, cumulative water transpired, water use efficiency, net assimilation rate, mean transpiration rate, harvest index, biomass and yield under the water deficit level were measured from both stressed and well-watered control plants. Water use efficiency significantly increased in both varieties under water stress. Drought stress decreased leaf area duration, cumulative water transpired, net assimilation rate, mean transpiration rate, harvest index, and biomass yield in both varieties studied. Among the varieties, rosea variety showed the best results.

Soil applied cobalt alters the nodulation, leg-haemoglobin content and antioxidant status of Glycine max (L.) Merr.

The present investigation has been carried out to estimate the effect of cobalt on the nodulation leg-haemoglobin content and antioxidant enzyme activities of soybean plants. The experiments were conducted in earthen pots containing 3 kg of air dried soil. The inner surface of pots was lined with polythene sheet. Soybean plants were raised in soil amended with different concentration of cobalt (0, 50, 100, 150, 200 and 250 mg/kg). The root nodule formation, leg-haemoglobin contents and antioxidant enzyme activities were analysed at 15 days intervals, namely 15, 30, 45, 60 and 75 days after sowing (DAS). There found a significant increase in the total number of root nodules, leg-haemoglobin content and antioxidant enzyme activities at 50mg/kg cobalt application in the soil in all the sampling days when compared to control. Further increase in the cobalt level (100-250 mg/kg) in the soil decreased root nodules formation as well as leg-haemoglobin content antioxidant enzyme activities of soybean plants in all the sampling days.

Endogenous hormonal and enzymatic responses of Catharanthus roseus with triadimefon application under water deficits.

The effect of triadimefon was investigated in a medicinal plant, Catharanthus roseus subjected to water deficit stress. The abscisic acid (ABA) level, DNA and RNA contents and activities of ATPase and protease were found varying in different parts of the plants under treatment. Drought treatment increased the ABA level more than twofold in all parts of the plants. TDM treatment to the drought stressed plants showed highest contents. In roots, stem and leaves, drought stress caused a decrease in the DNA and RNA contents when compared with control and other treatments. TDM treatment with drought increased the nucleic acid contents to the level of the control roots. The activity of ATPase and protease were increased under drought treatment and lowered due to TDM applications. This information could be useful in the field of soil water deficits reclamation efforts by using plant growth regulators.

ABA and GA 3 affect the growth and pigment composition in Andrographis paniculata Wall.ex Nees., an important folk herb

In this study, 5 μmol·L−1 abscisic acid (ABA) and gibberellic acid (GA3) were used to study the effect of both growth regulators on the morphological parameters and pigment composition of Andrographis paniculata. The growth regulators were applied by means of foliar spray during morning hours. ABA treatment inhibited the growth of the stem and internodal length when compared with control, whereas GA3 treatment increased the plant height and internodal length. The total number of leaves per plant decreased in the ABA-treated plants, but GA3 treatment increased the total number of leaves when compared with the control. Both growth regulators (ABA and GA3) showed increased leaf area. ABA and GA3 treatments slightly decreased the total root growth at all the stages of growth. The growth regulator treatments increased the whole plant fresh and dry weight at all stages of growth. ABA enhanced the fresh and dry weight to a larger extent when compared with GA3. An increase in the total chlorophyll content was recorded in ABA and GA3 treatments. The chlorophyll-a, chlorophyll-b, and carotenoids were increased by ABA and GA3 treatments when compared with the control plants. The xanthophylls and anthocyanin content were increased with ABA and GA3 treatments in A. paniculata plants.

Preliminary study on the antimicrobial activity of Enicostemma littorale using different solvents.

OBJECTIVE To study the antimicrobial activity of Enicostemma littorale (E. littorale) using different solvents. METHODS Chloroform, methanol and acetone extracts of different parts of E. littorale (leaf, stem and root) were evaluated for antimicrobial activity using disc diffusion method against some gram-negative species such as Escherichia coli, Klebsiella pnemoniae, Pseudomonas aeruginosa, Salmonella typhi and gram-positive species Staphylococcus aureus, Bacillus cereus, Bacillus subtilis and two fugal species viz., Aspergillus fumigates and Aspergillus flavus. RESULTS The chloroform extracts showed the highest antibacterial activity. Among leaf, stem and root extracts, the stem extracts showed maximum antibacterial activity. All of the used extracts had no significant antifungal activity against Aspergillus fumigates and Aspergillus flavus. The chloroform stem extract showed highest activity (about 20 mm inhibition zone) against Bacillus subtilis (at 500 mg/mL) followed by the methanolic stem extract which showed highest activity against the same organism. The lowest antibacterial activity was observed by the acetone leaf extract (about 8 mm inhibition zone) against Escherichia coli. CONCLUSION The findings of the study indicate littorale could also be a new source for antibiotics discovery.

Alterations in sucrose metabolizing enzyme activities and total phenol content of Curcuma longa L. as affected by different triazole compounds

Changes in the sucrose metabolism of Curcuma longa L. plants were studied under treatment with different triazole compounds viz., triadimefon (TDM) and propiconazole (PCZ). Plants were treated with TDM at 15 mg/L and PCZ at 10 mg/L separately by soil drenching on 80, 110, and 140 days after planting (DAP). The plants were harvested randomly on 90, 120, and 150 DAP to determine the effect of both the triazoles on sucrose metabolizing enzymes and phenol content. The sucrose metabolism was studied by analyzing sucrose metabolizing enzymes like sucrose synthase and sucrose phosphate synthase. All the analyses were assayed in leaves and tubers of both control and treated plants. It was found that both of the triazole compounds had profound effects on these parameters.