Differential Response of Pure Lines of Avena fatua L. to Substituted Phthalimides: Germination and Endosperm-mobilization Studies

The germination and endosperm-mobilization responses of twogenetically pure lines (AN-51 and Mont 73) of Avena fatua (wildoat) to gibberellic acid (GA₃, ) and three substituted phthalimides(experimental compounds AC-92, 803, AC-94, 377 and AC-99, 524)were studied. The line AN-51 showed a much greater responseto GA₃, in terms of the percentage and the rate of stimulationof germination, than Mont 73. These lines also differed significantlyin their response to AC-94, 377 and AC-99, 524. The relativegermination response of the two lines to these phthalimideswas very similar to that for GA₃. The phthalimide AC-94, 377was more effective at stimulating germination than AC-99, 524,whereas AC-92, 803 had little or no effect. Salicylhydroxamate,an inhibitor of alternative respiration, did not inhibit theAC-94, 377-induced germination. Like GA₃, AC-94, 377 induced -amylase production and the releaseof reducing sugars by 3 mm endosperm segments. GA₃, was mosteffective at inducing endosperm mobilization, followed by AC-94,377, AC-99, 524 and AC-92, 803, respectively. The line AN-51showed a significantly greater response to both AC-94, 377 andGA₃, than Mont 73. It is concluded that: (1) genetically pure lines of wild oatsdiffer in their response to substituted phthalimides - the lineAN-51 being more responsive than Mont 73, (2) the phthalimideAC-94, 377 is the most effective at inducing germination andAC-92, 803 the least, (3) like GA₃, phthalimides induce endospermmobilization and pure lines differ in the degree of this response,and (4) salicylhydroxamate-sensitive respiration is not necessaryfor the stimulation of germination by AC-94-77. The similaritiesin the effects of AC-94, 377 and GA₂, (two structurally dissimilarcompounds), and in the relative response of the two lines tothese chemicals may provide a useful system for the investigationof wild oat seed physiology. The differential susceptibilityof pure lines to phthalimides also indicates that use of thesecompounds to deplete wild oat seed banks may increase the proportionof less responsive biotype(s) in field populations. Wild oats, weed seed bank, dormancy, germination, endosperm mobilization, -amylase, Avena fatua, phthalimides, gibberellic acid