Effect of contrasting maternal nitrogen environments on Buglossoides arvensis seed germination response to gibberellic and abscisic acids

Abstract

Nitrogen availability in Buglossoides arvensis mother plants influences seed dormancy level. Abscisic acid (ABA) levels chiefly determine primary dormancy during embryo maturation and its maintenance depends on ABA/gibberellic acid (GA) balance. We hypothesised that soil nitrogen fertilisation of B. arvensis mother plants affects seed sensitivity to hormonal germination promotors and inhibitors. The purpose of the present work was therefore to investigate to what extent the changes that occur in seed germinability as a result of maternal nitrogen fertilisation (with -N(+)- and without -N(−)-)are paralleled by changes in ABA or GAs de novo synthesis and embryonic sensitivity to ABA or GAs. Seed germinability was assessed under a gradient of ABA and GA3 and their corresponding de novo synthesis inhibitors (fluridone -FLU- and paclobutrazol -PBZ-). B. arvensis seeds were incubated at suboptimal (7°C), optimal (15°C) and supraoptimal (20°C) temperatures. Results indicated a higher germination of N(+) seeds, irrespective of hormone type, dose or incubation temperature. N(−) seeds were more sensitive to FLU at 7°C and to GA3 at 15°C, whereas N(+) seeds were more sensitive to FLU at 15-20° C and to PBZ at 7°C. At 20°C, N(+) seed germinability was stimulated by GA3 counteracting the thermo-inhibitory effect. The higher seed germinability recorded from nitrogen-fertilised plants could be associated to a decrease in seed dormancy levels due to lower ABA levels during embryogenesis, thus requiring a lower amount of GAs to germinate. Further studies are required to confirm this hypothesis.