Agriculture

The status of the Mauritian forest is alarming with deforestation and invasive alien species deeply affecting the indigenous flora. Therefore, major conservation strategies are needed to save the remaining endemic tree species. Explants form three endemic tree species Elaeocarpus bojeri, Foetidia mauritiana and Sideroxylon grandiflorum were grown under in vitro conditions. These species are rareand Elaeocarpus bojeri has been classified as critically endangered. Thidiazuron (TDZ) and 6-Benzylaminopurine (BAP) were used as growth promoters in order to stimulate seed germination, callus induction. Half strength Murashige and Skoog's (MS) media supplemented with coconut water, activated charocoal and phytagel were used as growth media. Hormone levels of TDZ were 0.3mg/l and 0.6mg/l while BAP level was at 1mg/l. Germination rate for E.bojeri was low (5%) with TDZ 0.3mg/l. Sideroxylon grandiflorum seeds showed no response to in vitro culture, while F mauritiana showed successful callus induction with TDZ 0.6mg/l and 0.3mg/l.

Reutilization of P from Setaria sphacelata residues having C:P ratios of 704:1, 227:1, and 77:1 was studied using a reverse 32P-isotopic dilution technique in the greenhouse. Residues were incorporated into two highly weathered Malaysian soils (Ultisols and Oxisols) treated with five levels of inorganic P labeled with 32P and cropped with Panicum maximum (Jacq.). Yield of dry matter, total P, and 32P activity of Panicum was monitored through four cuttings spanning a period of approximately 13 weeks. Panicum yields and residue-P uptake were depressed by high and medium C:P ratio residues at the first cutting but recovered in subsequent cuttings. General adequacy of P concentrations in the affected tissue and its failure to respond to applied inorganic P among other factors suggest that the initial yield depression was not induced by P immobilization. The fractional percentage of P derived from residues increased with increasing P content of residues at all cuttings. Similarly, L-values were consistently greater on residue-treated soils. Residue P had greater effects on the soil with lower than on that with higher P-sorbing capacity. Changes in residue P uptake, L-values, and extractable P in soil between successive cuttings suggest a rapid release of a large amount of easily mineralizable residue P within the first 4 weeks, with the subsequent P release being much slower by comparison.

The present investigation aims to assess the phytochemical content, antioxidant and antimicrobial activities of the essential oils from five different Mentha species that are locally available. Standard quantitative and qualitative tests including UV, TLC were performed on the essential oils of Mentha sp.1, Mentha sp.2, Mentha arvensis, Mentha pulegium and Mentha sp.5, to screen for the presence of bioactive compounds. Antioxidant activity was evaluated in terms of total antioxidant activity, which was carried out by DPPH free radical scavenging assay with reference to quercetin. Total phenolic content content was evaluated using Folin-Ciocalteau method and the Aluminium chloride method was used to estimate the total flavonoid profile of the mint essential oils. Antimicrobial susceptibility tests including microdilution assays for minimum inhibitory concentration (MIC) were determined. Phytochemical screening of the essential oil of the five different Mentha species: Mentha sp.1, Mentha sp.2, Mentha arvensis, Mentha pulegium and Mentha sp.5, revealed the presence of alkaloids, phenols, terpenes, coumarins, tannins, leucoanthocyanins, flavonols and saponins. The amount of phenolics among each Mentha species varied, ranging from 0.242 to 1.84 mg GAE/g FW whereas the total flavonoid contents estimated in each sample varied from 0.017 to 0.384 mg QE/g FW. In the present study, there was a significant variation in the composition of essential oils of the different mint species (p<0.05).The most powerful antioxidant activity was observed in the extracts of Mentha sp.1 having an IC50 of 0.128 ±0.001 mg/mL while the lowest antioxidant activity was noted in Mentha sp.2. Most essential oils from Mentha species showed effectiveness against Staphylococcus aureus (ATCC 29213), except for Mentha sp.1. However, all Mentha extracts showed promising activity Escherichia coli (ATCC 25922) and Klebsiella oxytoca (ATCC 43086). Mentha pulegium was reported to have the highest antimicrobial activities, with a MIC value of 6.25 mg/mL against S. aureus and 3.13mg/mL against both K. oxytoca and E. coli when compared to the other four Mentha species. Simple correlations were found between total phenolics, total flavonoids, antioxidant activity and antimicrobial activity (-1 < r <1). To conclude, essential oils of Mentha species showed considerable antioxidant and antimicrobial activity against selected bacteria and can be further exploited for the validation of pharmacological studies of essential oils.

... Soil water content also affects the mobility of nutrients in the soil. ... However, in the model presented here, b and De are allowed to change with nutrient content of the soil. The buffer curve is being described by a Freundlich equation. ...