# Rheological Flow Behavior of Six Gelling Agents and Their Relevance for In Vitro Culture Performance of Medicinal Plants

## TL;DR

This study compares six gelling agents for plant tissue culture, showing how their flow properties affect plant growth in lab conditions.

## Contribution

The study links gelling agents' rheological properties to in vitro plant performance across three species.

## Key findings

- Daishin agar had the highest viscosity, while Gelrite had the lowest.
- Gelrite supported the best shoot and root growth in Hypericum perforatum.
- Gelcarin and Plant agar showed superior performance in Mentha × piperita and Stevia rebaudiana.

## Abstract

Gelling agents are widely used to solidify plant tissue culture media, yet differences among commercial products may influence the medium’s physical properties and in vitro development of explants. The aim of this study was to characterize the rheological behavior of six gelling agents (Daishin agar, Gelcarin, Gelrite, Microagar, Phytoagar, and Plant agar) and to examine it in parallel with in vitro performance in Hypericum perforatum, Mentha × piperita, and Stevia rebaudiana. Rheological measurements were performed under steady shear by recording apparent viscosity and shear stress across 5–300 s−1. Daishin agar showed the highest apparent viscosity (49,028.95 ± 128 mPa·s), whereas Gelrite exhibited the lowest viscosity (7826.75 ± 98 mPa·s). Plant responses were evaluated after four weeks on PGR-free Driver and Kuniyuki Walnut (DKW) medium by assessing shoot growth, rooting parameters, and shoot water content. In H. perforatum, the longest shoots were obtained on Gelrite (3.92 ± 0.34 cm), accompanied by the highest rooting percentage (95%). In M. × piperita, Gelcarin produced the longest shoots (8.20 ± 0.55 cm) and the highest number of roots per explant (9.75). In S. rebaudiana, Gelcarin promoted superior root elongation (2.86 ± 0.16 cm) and enhanced shoot growth, while Plant agar also supported favorable shoot development. Shoot water content ranged between 74% and 90%, depending on species and gelling agent. These findings highlight the practical relevance of considering low-shear rheological properties when comparing gelling agents for improving the consistency of in vitro culture media.