High resolution analysis of plant organ growth using non-contact inkjet marking

To examine plant organ growth, lines of small dots (0.1–0.2 mm in diameter) were printed on the surfaces of plant organs using a non-contact inkjet printer, and time-lapse images of the dot-marked plants were obtained. Displacement of dots in the sequential images was traced using a motion-analysis program, and the distances between the dots were calculated to analyze plant organ growth. Using this method, the forms of elongation of each millimeter segment in the elongation zone of inflorescence stems of Arabidopsis thaliana could be examined. Elongation of these segments showed almost coordinated, but slightly different patterns of rhythmic oscillation. The elongation of the second leaf of rice seedlings was also examined. In contrast, their elongation took place in the elongation zone hidden by the leaf sheath of the first leaf, and was linear. We examined the change in their elongation rates in relation to temperature shift (30 °C → 20 °C → 10 °C → 30 °C). Where temperature shift was rapid, the elongation rate also changed without an observable time lag. After a rapid temperature shift from 10 °C to 30 °C, a temporal increase in growth rate was detected. This simple and rapid process could be a high throughput method for high resolution analysis of plant organ growth.