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Chromium (Cr), especially in hexavalent chromium [Cr(VI)] may contaminate water or soil and cause detrimental effects, as it is potentially carcinogenic and teratogenic. Phytoremediation using plants such as Typha angustifolia provides an alternative approach for handling Cr waste. The objective of this study was to determine the mechanism of Cr accumulation in T. angustifolia. Hydroponic media containing T. angustifolia was added with 0, 1, 5, 10 and 20 ppm of Cr (VI) (K 2 Cr 2 O 7 ). After 15 days of treatment, distribution and speciation of Cr in roots and shoots of T. angustifolia were analyzed using XAS and µ-XRF. Results showed that Cr was detected in almost all parts of root and shoot at different intensities. Intensities of Cr was higher in roots (especially in the vascular bundle) than in shoot. Cr speciation in the root and shoot was found as trivalent chromium [Cr(III)] which formed as a result of Cr(VI) reduction. Based on the patterns of Cr distribution and speciation, results of this study suggest that T. angustifolia in this study does not reduce Cr(VI) to become Cr(III) inside the plants.

Abstract. Putrie RFW, Aryantha INP, Iriawati, Antonius S. 2020. Diversity of endophytic and rhizosphere bacteria from pineapple (Ananas comosus) plant in semi-arid ecosystem. Biodiversitas 21: 3084-3093. The natural environment majorly influences plant microbiome diversity, in terms of endophytic and rhizobacteria. Pineapple (Ananas comosus L. Merr) has been identified as one of host plants with a capacity to grow in semiarid ecosystems. The intrinsic microbial symbiont composition is recognized in a specific ecological niche. The scientific information available is limited to the inoculants' ability to reduce plant stress, although the diversity in a semiarid ecosystem has not been studied. The aim of this research is to investigate the diversity of endophytic and rhizosphere bacteria obtained from pineapple in a semiarid ecosystem. A total of 117 culturable microbial isolates, dominated by Gram-positive bacteria were obtained from pineapple (88) and rhizosphere (29). The metagenomic analysis showed higher diversity and abundance in rhizospheres compared to the endophytes. Actinobacterium was identified as the most populated colony, while Proteobacterium was more prominent in the host plant. The Bacillus genera were recognized as the dominant symbiont genus. Therefore, the culturable isolates were further developed as candidate inoculants for microbe databases. This is expected to be useful in broadening theoretical knowledge.

Abstract. Selection and regeneration of specific hybrids of Phalaenopsis typically takes a long time since this plant usually reproduces through seeds. This study was conducted to examine the best medium and explants for regeneration of Phalaenopsis 'Join Angle x Sogo Musadian'. In vitro and in vivo roots and leaves were used as explants, which were cultured in half-strength Murashige and Skoog medium supplemented with various combinations of plant growth regulators (TDZ, 2,4-D, NAA, BAP and IAA). The results showed that the in vitro roots produced the highest number of PLBs (49.3 PLBs) when they were cultured in medium containing 0.5 ppm NAA, 5 ppm BAP, and 0.5 ppm IAA. The in vitro leaf explants also regenerated PLBs, however, only two PLBs developed, i.e. when they were cultured in medium containing 1 ppm TDZ and 2 ppm 2,4-D. PLB germination into plantlets was performed by culturing each PLB on MS medium without plant growth regulators. Based on the results of the present study, it can be concluded that in vitro roots and half-strength MS medium supplemented with 0.5 ppm NAA, 5 ppm BAP, and 0.5 ppm IAA are the best explant and best medium respectively for plant regeneration through PLBs.

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