Chemotactic responses of sweet flag (Acorus calamus L.) root exudates and evaluation of inoculation effects on its growth

Saabunud / Received 04.11.2020 ; Aktsepteeritud / Accepted 20.04.2021 ; Avaldatud veebis / Published online 20.04.2021 ; Vastutav autor / Corresponding author: B. Karthikeyan [email protected] exudate is an important source of nutrients for microorganisms in the rhizosphere and it plays a major role in the early colonization including chemotactic responses and adsorption of rhizospheric bacteria. In this study, we characterized the root exudates from sweet flag under hydroponic conditions and assessed their effect on plant growth. In the present study, the crude root fractions of sweet flag recorded a maximum yield of 520.6 μg plant–1 followed by cationic, anionic and neutral fractions. Among the qualitative and quantitative analysis of different fractions, the cationic fraction recorded a maximum of 90 μg plant–1 for glutamic acid, followed by aspartic acid, glycine, serine and proline. In the anionic fraction, malic acid recorded a maximum of 78.0 μg plant–1 followed by oxalic, succinic, citric and glutamic acid fractions. The neutral fractions included different saccharides, among which, fructose recorded a maximum of 42.5 μg plant–1, followed by glucose, maltose, ribose and arabinose. The relative chemotactic response (RCR) of PGPB (plant growth-promoting bacteria) strains towards different root exudate fractions of Acorus calamus was recorded and it was observed that the combination of Anionic + Cationic + Neutral fraction recorded maximum chemotactic response for PGPR strains. The adsorption of PGPR strains in the root of the Acorus calamus was recorded in three different phases of growth and among these, Log phase bacterial cells exhibited maximum colonization of 7.65 × 10–6 cells g–1 with A.venilandii (ACAzt-2). Inoculation effect of PGPB strains on the root exudate of Acorus calamus and its growth was evaluated and it was observed that the treatment T5 – Consortium recorded maximum plant height and root growth of Acorus calamus, followed by T2. Our results indicate that sweet flag root exudates induce chemotactic responses of PGPR strains and promoted their growth

Efekt inokulacije korijena korijenovim bakterijama za poticanje rasta (PGPR) na rast biljke, sadržaj alkaloida i nutrijenata kod biljke Catharanthus roseus (L.) G. Don.

The effect of plant growth promoting rhizobacteria such as Azotobacter, Bacillus and Pseudomonas was tested separately or in combination in Catharanthus roseus for two consecutive years (2005 and 2006). The combinations of above mentioned PGPR strains significantly increased plant height, root length, root girth and alkaloid content in C. roseus in comparison to the control. In addition, all nutrient contents (N, P, K, Ca and Mg) were also significantly increased as compared to the control. The maximum N, P, K content was obtained from the combination of PGPR treatment. The results of this study suggest that PGPR applied in combination have the potential to increase the plant growth, alkaloid content and nutrient content of C. roseus.Testirani su učinci korijenovih bakterija za poticanje rasta, kao što su Azotobacter, Bacillus i Pseudomonas, zasebno ili u kombinaciji, na biljci Catharanthus roseus i to tijekom dviju godina (2005 i 2006). Kombinacije gorespomenutih PGPR sojeva značajno su povećale visinu biljaka, duljinu korijena, debljinu korijena i sadržaj alkaloida kod C. roseus u usporedbi s kontrolom. Uz to sadržaj svih nutrijenata (N, P, K, Ca i Mg) bio je značajno povišen u usporedbi s kontrolom. Maksimalni sadržaj N, P, K dobiven je kombiniranim tretmanom PGPR. Rezultati ovog rada sugeriraju da PGPR primjenjeni u kombinaciji imaju potencijal povećati rast biljke, sadržaj alkaloida i nutrijenata kod biljke C. roseus