Nano silver treatment is effective in reducing bacterial contaminations of Araucaria excelsa R. Br. var. glauca explants

The downside of plant tissue culture techniques is an unwanted microbial contamination. Elimination of contaminants is the first step of any successful investigation on plant tissue culture. Preliminary experiments on Araucaria excelsa R. Br. var. glauca (Norfolk-Island pine) (syn.: A. heterophylla) showed that most common decontaminants could not successfully eliminate the contamination. Therefore, nano silver (NS) colloids were evaluated for controlling contamination. Treatments were included soaking the explants in NS solution or adding NS to the culture medium. Explants were cultured on MS medium supplemented with appropriate growth regulators for their establishment. Results showed that surface sterilization followed by treatment with 200 mg l-1 of NS with soaking time of 180 min reduced the bacterial contamination from 61.5% to 11.3% and adding 400 mg l-1 NS to the medium reduced the bacterial contamination from 81.25% to 18.75%. Nano silver could be applied without adverse effects on plant growth and development. This is the first report on in vitro establishment of A. excelsa R. Br. using NS to reduce bacterial infections.

Variations in photosynthetic rates of fourteen coleus cultivars

Fourteen cultivars of coleus (Coleus blumei Benth) were found to vary in chlorophyll content, photosynthetic rate, anthocyanin content and number of stomates.Cultivars ;Gaslight' and ;Velvet Rainbow' had 0.17 and 0.92 mg chlorophyll per g of leaves, fresh weight, respectively.Maximum photosynthetic rate (18.7 mg CO(2)/mg Chl.hr) was found in the leaves of ;Pastle Rainbow' and minimum (2.7) in the ;Velvet Rainbow.'