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Seed physiology of wild species has not been studied as deeply as that of domesticated crop species. Trichocline catharinensis (Asteraceae) is an endemic wildflower species from the high‐altitude fields of southern Brazil. This species is of interest as a source of genes to improve cultivated Asteraceae because of its ornamental features, disease resistance and ability to tolerate drought and poor soil conditions. We studied the effects of abscisic acid (ABA) and gibberellic acid (GA3) and their inhibitors, fluridone (FLU) and paclobutrazol (PAC), on seed germination. We individually assessed ultrastructural changes and differential protein accumulation. The principal component analysis explained 69.66% of differential accumulation for 32 proteins at phase II of seed germination in response to hormone and inhibitor treatment. GA3‐imbibed seed germination (98.75%) resulted in increased protein accumulation to meet energy demand, redox regulation, and reserve metabolism activation. FLU‐imbibed seeds showed a higher germination speed index as a consequence of metabolism activation. ABA‐imbibed seeds (58.75%) showed osmotolerance and flattened cells in the hypocotyl‐radicular axis, suggesting that ABA inhibits cell expansion. PAC‐imbibed seeds remained at phase II for 300 h, and germination was suppressed (7.5%) because of the increased signaling proteins and halted reserve mobilization. Therefore, our findings provide insight into the behavior of Asteraceae non‐dormant seed germination, which broadens our knowledge of seed germination in a wild and endemic plant species from a threatened ecosystem. [ABSTRACT FROM AUTHOR]

An improved understanding of seed quality and germination control can contribute effectively to the use and conservation of neglected native species with ecological and economic value, such as Trichocline catharinensis, an endemic Asteraceae species from southern Brazil. We investigated the effects of applying gibberellin (GA3), abscisic acid (ABA) and their biosynthesis inhibitors, paclobutrazol (PAC) and fluridone (FLU), respectively, on T. catharinensis seed germination, and on polyamine (PA) content and antioxidant enzyme activities in germinating seeds. FLU and GA3 increased seed germination speed compared to treatment with H2O only. ABA inhibited both germination speed index and percentage, while PAC severely inhibited seed germination. The stimulatory effect of GA3 and FLU was associated with increased contents of putrescine (PUT) and spermidine (SPD) relative to spermine (SPM). As a result, high ratio (PUT + SPD/SPM) as well as superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) enzyme activities were observed when seed germination occurs. In contrast, in low or no seed germination treatment (ABA and PAC), low ratio (PUT + SPD/SPM) was observed, while the antioxidant enzymes, mainly SOD activity, tended to increase. Application of PAs at 200 μM stimulated germination through improving the speed and uniformity, and this effect was associated with antioxidant enzyme activity. Our results suggest a relationship between PA and the antioxidant system with the physiological mechanism of seed germination. These results improve the physiological knowledge of seed germination control in Asteraceae and contribute to the biological groundwork for future studies on the use and conservation of native species. [ABSTRACT FROM AUTHOR]