Multicolor staining of root systems in pot culture

Abstract

We have developed a method for staining the root systems of neighboring plants distinguishably in pot culture to facilitate studies of the interactions between plants. Pot soil was desiccated until the plant wilted, and then the shoot was cut and a dye solution (Fantasy) was pressure-injected into the roots at 0.05 MPa (gauge). All the roots, including fine roots of double-planted tomato (Lycopersicon esculentum var. Momotaro), in a 10-cm-diameter pot were well stained, but the root hairs were not. The volume of dye and the time required for staining were 6.4 mL and 5 h, respectively (root length 179 m plant; root fresh weight 2.62 g plant −1 on average). The root distribution of double-planted tomato in a 40 L container was well determined. The volume of dye and the time required for staining were 100 mL and 40 h, respectively (root length 1,514 m plant; root dry weight 4.93 g plant −1 on average). Each plant's roots accounted for 37-52% of the total root weight at an intermediate position between the two plants, whereas at the other positions, the roots of either plant were dominant (82-99% of total root weight). In principle, the proposed method is applicable to whole plant species with vascular systems.

Improvement of root staining method for field applications

“…In the four blocks at the intermediate positions between two adjacent plants, the roots of both plants were well distributed. This trend agreed with that observed in the container experiment (Murakami et al 2006). In the 15-30 cm soil layer, most of the roots in the four blocks surrounding the hills came from the hills, although roots of other plants also existed.…”

“…Under the two dry conditions, staining was carried out using the previously proposed equipment (Murakami et al, 2006). Under the remaining two wet conditions, the modified system for high pressure injection, which consists of pressure-resistant tubes, two-way stopcocks, plastic pipettes, and a nitrogen gas tank, was employed (Fig.…”

“…Dye consumption was recorded every 60 min (15-30 min during the first 1 h) until 8-10 mL of the dye was consumed or 24 h had passed. The injection volume was decided on the basis of a previous report (Murakami et al 2006). After staining, the stained roots were washed and separated by the water floating method described in a previous report.…”

“…The pressure was maintained at 0.5 MPa until 150 mL of the dye was consumed or 96 h had passed. The volume of the dye used was determined as follows: average shoot weight  root/shoot ratio (8.6%, Jackson and Bloom 1990)  factor (2.4-3.8, Murakami et al 2006).…”

“…Previously, we developed a simple method of staining root systems in pot culture by dye injection and demonstrated its validity by performing a quantitative analysis of root distribution (Murakami et al 2006). Using this method, Ikenaga et al (2009) clarified the more rapid root growth of wheat and barely than soybean in mixed cropping in a small container 24-30 days after sowing (DAS), Miyazawa et al (2010) clarified the difference in root distribution between sole cropping and intercropping of green manure crops in a non-woven fabric bag 42 DAS.…”