Earth Rotation Measured by Lunar Laser Ranging

A root penetration model of Arabidopsis thaliana in phytagel medium with different strength

Phytagel media were evaluated as systems to mechanically impede roots of A. thaliana. Studying mechanical properties of Phytagel and exploring the root response to mechanical stimulation can facilitate plant culture and plant development. Breaking strengths of 0.5-2.0% phytagel media were tested by uniaxial compression test. Different phytagel concentrations were set to alter the strength of layers in growth medium. Negative correlations were observed between root length, straightness and medium strength. When roots elongated through soft upper-layer (0.6%), penetration ratio decreased with the increase of lower-layer strength (0.6-1.2%) and all roots couldn't penetrate into lower-layer with concentration ≥1.2%. Roots could grow into soft lower-layer (0.6%) from hard upper-layer (0.6-1.2%), with decreased penetration ratio. When roots grew in soft lower-layer, the growth rate linked with upper-layer strength increased to peak. Roots penetration capability into 1.2% lower-layer was improved by growing plants through moderate layer inserted between soft and hard layer, and roots in 0.8% moderate medium have a significant higher penetration ratio than that in 1.0%. It was concluded that the Phytagel systems studied were suitable for studying the effect of mechanical impedance on the elongation of A. thaliana roots. The medium strength affected root penetration significantly and acclimation can improve root penetration capability.

Application of space technology to geodynamics

Measurements of the movement and deformation of tectonic plates are needed for many research areas in geodynamics, but observations with adequate accuracy and frequency of measurement are not feasible if classical geodetic methods are used. Long-baseline microwave interferometry and laser ranging to Earth satellites are among the new techniques that have been developed within the past decade to make the required measurements. Fixed and mobile stations using both these methods have been constructed in several countries and are now being used in an internationally coordinated research program. Baseline length accuracy better than 2 to 3 centimeters (1 standard deviation) is expected within the next 5 years.