Quantifying growth mechanics of living, growing plant cells in situ using microbotics

Plant cell growth is a fundamental process during plant development and the developmental biology society has studied cell growth from various aspects using physiological, biochemical, genetic, mathematical and modelling approaches. Recent advances in the field of biology demonstrate a need for investigation and quantification of the mechanics of growth at individual cellular levels. Here, we describe a microrobotic system capable of performing automated mechanical characterisation of living plant cells in situ as these cells proliferate and grow. The microrobotic measurement system employs a single-axis capacitive MEMS microforce sensor, a multi-axis positioning system with position feedback, a high-resolution optical microscope and a custom-user interface for the guiding of the automated measurement process. The system has been applied to measure mechanical properties of Lilium pollen tubes approximately 20--m wide. The measurements were performed in growth medium, and the observed growth rate of the pollen tubes is about 20--m per minute. For the mechanical characterisation of pollen tubes, nano-Newton level loads and nanometric indentations are applied. The force-deformation data obtained show a difference in stiffness from the tip to the apex demonstrating that the developed measurement system is a promising tool for better understanding the mechanics of plant cell growth.