STUDIES ON THE GROWTH AND DEVELOPMENT OF THE RHIZOME AND LATERAL RHIZOME BUDS IN ELYTRIGIA-REPENS - SOME EFFECTS OF PARENT SHOOT EXCISION

In experiments conducted under controlled conditions, excision of the shoot of Elytrigia repens (L.) Nevski increased the rate of rhizome el ongation and promoted the growth of the lateral rhizome buds. Measurem ents with a transducer showed that the long-term growth response of th e rhizome to shoot excision (4-6 days) was preceded by an immediate bu t transient (10 min) increase in growth rate. These various responses were associated with the occurrence of guttation from the rhizome apex , increases in the water content of the rhizome apex and lateral buds, and a 62% increase in rhizome water (pressure) potential. Parent shoo t excision also induced a transition from rhizome to shoot development at the rhizome apex and caused lateral buds to develop as shoots inst ead of rhizomes when released from apical dominance. These development al responses were associated with reductions in the dry weight of the rhizome apex and lateral buds and increases in the total N, amino-N, a nd nitrate content of the rhizome apex when expressed on a dry weight basis. These results provide evidence that, in E, repens, competition for water by the parent shoot may limit rhizome growth and contribute to the correlative inhibition of the lateral buds. They are also consi stent with previous evidence that the C:N ratio may be an important mo rphogenetic factor in the mechanism controlling the path of bud and rh izome development.