Aims: The purpose of this experiment was to determine the artificial symbiosis interaction of Herbaspirillum seropedicae (Z78) on oil palm embryogenic calli. Methodology and results: For this purpose, symbiotic associations were established between Z78 and embryogenic calli of oil palm tissue cultured. A total of five treatments involved, in particular: i) + 3.0 mg/L 2,4-D + 100% N MS medium (control), ii) + Z78 pellet cells (1 mL) + 25% N MS medium, iii) + Z78 supernatant (1 mL) + 25% N MS medium, iv) + Z78 broth culture (1 mL) + 25% N MS medium, and v) + Z78 sonicated cells (1 mL) + 25% N MS medium. All treatments were supplied with minimal N sources (25% N), ammonium nitrate and potassium nitrate, while the control was treated with 100% N sources. Treated samples were harvested on D80 and observed for biomass and diameter increment (%), formation of embryoids, and Z78 colonization. The results showed embryogenic calli in the inoculated treatments that contained depleted N produced similar result to the control treatment which contained 100% N nutrients. Positive interactions occurred between the diazotroph and host plant tissues as viewed under FESEM and EFTEM. Among the treatments, Z78 sonicated cell showed better growth of embryogenic calli compared to others. Conclusion, significance and impact study: The in vitro nitrogen-depleted artificial symbiosis environment allowed the diazotroph (Z78) to be expressed and provide the nitrogen sources and indole-3-acetic acid for cell growth. This study represents beneficial co-culture interaction effects of different inocula of diazotrophic bacterial cells with in vitro embryogenic calli of oil palm.

Aims: The use of microalgae as source of natural antioxidants is under explored in Malaysia. Previous studies haveshown that microalgae contain minerals, polysaccharides, amino derivatives, carotenoids and phenolic compounds. Thisstudy aimed to determine total phenolic and flavonoid compounds and antioxidant activity when microalgae(Nannochloropsis oculata and Tetraselmis sp.) and cyanobacterium (Anabaena sp.) were subjected to abiotic stresses.Methodology and results: Treatment of sodium chloride (NaCI), sodium hypochlorite (NaOCI) and copper (Cu2+) weregiven when the cultures reached the exponential phase of growth and were collected at three different time points. Nontreatedcultures were used as controls. Total phenolic and flavonoid contents were determined using Folin-Ciocalteauphenol reagent and aluminium chloride colorimetric assays. Antioxidant activities were measured using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity assay. Tetraselmis sp. exhibited the highest phenolic contentunder copper stress (10.35 ± 0.33 μg GAE/mg extract). Nannochloropsis oculata showed the highest total flavonoidcontent under copper stress (33.85±3.16 μg QE/mg extract). Anabaena sp. showed the highest radical scavengingactivity under NaOCI stress (96.42 ± 0.26%).Conclusion, significance and impact of study: This study showed that total phenolic, flavonoid and antioxidantactivities in treated cultures were high compared to non-treated cultures. These microorganisms could be utilized as asource of useful bioactive compounds while exploiting its abund