Histological characteristics, hydrolytic enzyme activity, and changes in plant hormones during the seed-shedding process in two Bromus catharticus Vahl

Seed dropping is an adaptive mechanism that enables plants to effectively reproduce and expand their populations during long-term survival competitions in harsh environments. However, the physiological mechanisms underlying seed drop in rescue grass remain unclear. In this study, we investigated the histological characteristics, hydrolytic enzyme activities, and plant hormone content of two varieties: Jiang-xia (JX) and Qian-nan (QN). The results showed that seeds began to drop 28 days after flowering (DAF), with the seed shattering rate (SSR) increasing as seed development progressed. Seed shattering was associated with the formation and degradation of the abscission zone. Cross-sections of the stalk became smooth at 18 DAF, and the abscission zone surfaces were degraded by 33 DAF. Cellulase activity did not differ between JX and QN, whereas polygalacturonase activity showed significant differences between 8 and 23 DAF. In addition, SSR and abscisic acid content were positively correlated in both JX and QN varieties. In conclusion, this study on seed dropping offers a theoretical basis into increasing forage seed yield. Seed shattering is associated with the formation and subsequent degradation of the abscission zone. The stalk cross-sections became smooth at 18 days after flowering (DAF), and the abscission zone surfaces began degrading at 33 DAF. The correlation between the seed shattering rate and abscisic acid and methyl jasmonate content varied among the two varieties.