Evaluating Arabidopsis Primary Root Growth in Response to Osmotic Stress Using an In Vitro Osmotic Gradient Experimental System.

Abstract

The root meristem navigates the highly variable soil environment where water availability limits water absorption, slowing or halting growth. Traditional studies use uniform high osmotic potentials, poorly representing natural conditions where roots gradually encounter increasing osmotic potentials. Uniform high osmotic potentials reduce root growth by inhibiting cell division and shortening mature cell length. This protocol describes a simple and effective in vitro system using a gradient mixer that generates a vertical gradient in an agar gel based on the principle of communicating vessels, exploiting gravity to generate a continuous mannitol concentration gradient (from 0 to 400 mM mannitol) reaching osmotic potentials of -1,2 MPa. It enables long-term Arabidopsis root growth analysis under progressive water deficit, improving phenotyping and molecular studies in soil-like conditions. Key features • Novel approach: Unique method to evaluate primary root growth in Arabidopsis under increasing osmotic potentials. • Osmotic gradient system: Simulating a gradual osmotic gradient in the root growth zone while maintaining aerial tissues under control conditions. • Sustained growth: Arabidopsis Col-0 and ttl1 mutant seedlings maintain proper root growth for 25 days, even at osmotic potentials as low as -1.2 MPa. • Enhanced growth rates: Roots grown in the osmotic gradient exhibit higher growth rates than those in homogeneous high osmotic potential conditions. • Phenotypic observation: ttl1 seedlings grown in the osmotic gradient do not show the typical swelling phenotype observed at extreme osmotic potentials (-1.2 MPa).

Plant phenotyping relevance

根の成長表現型を測定するための浸透圧勾配培養システム自体を開発・提示したプロトコルであり、表現型取得法が中心である。

Code and data availability

The article's supplementary files contain the paper's own root growth rate datasets (osmotic gradient and osmotic shock) and RT-qPCR results, plus the corresponding R analysis code, but no public repository URL is provided; access requires obtaining the supplement via the journal/authors.

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