Arabidopsis thaliana (image) Penn State Share Print E-Mail Caption A new study by Penn State researchers using the model species thale cress, Arabidopsis thaliana, reveals that plant cells tend to grow longer instead of wider due to the alignment of the many layers that make up their cell walls. Credit NASA Usage Restrictions Credit must be provided alongside image. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.