In Situ Study of Corn Seedling Root and Shoot Growth by Neutron Radiography1

Abstract

AbstractIn corn (Zea mays L.) root and shoot studies particular attention has been paid to environmental and soil influence on seedling root growth. Experimentation in this field has been limited by the difficulty in investigating root elongation, since no nondestructive in situ method was available other than glass‐sided boxes. The purpose of this study was to show that the neutron radiography is capable of supplying in situ root images permitting qualitative and quantitative interpretation so that comparative root and shoot growth may now be analyzed in a new way.The experiments consisted of shoot and root growth studies up to 21 days for two corn seeds sown at depths of 1 and 6 cm. The plants were grown in a growth chamber in a 2‐cm‐thick aluminum box containing coarse sand maintained at 8% volumetric water content. Daily neutron radiographs were made by the direct method using the 3.2° diverging thermal neutron beam of the MIRENE reactor at Valduc, France.The images obtained allowed a qualitative interpretation not only for seminal root but also for laterals. Root development was not harmed visibly by irradiation and repeated environmental changes due to neutron radiography experiments. The seminal root elongation rate was analysed vs. the plant age. Quantitative data show that the root growth was greater during the day than at night. Root and shoot lengths were related in a linear manner between 7 and 15 days after sowing.