Effect of Seed Priming Agents on Seed Germination and Seedling Growth of Ptilotus exaltatus

In order to solve the problems of the poor germination uniformity, low plug-seedling quality and poor seedling size uniformity of P. exaltatus, the effects of single priming agents, namely KCl (0.50%, 0.75%, 1%), KNO₃ (0.50%, 0.75%, 1%), PEG-6000 (5%, 10%, 15%), and GA₃ (100, 200, 300 mg·L⁻¹) on the seed germination were explored. Subsequently, the effects of different combinations of composite priming agent (PEG-6000 + KNO₃) were examined, and the effects of the screened composite priming agent on the seed germination and the seedling quality traits such as plant height and crown width of different P. exaltatus cultivars were explored. The results showed that among the single priming treatments, 10% PEG-6000 or 0.75% KNO₃ produced the best overall germination performance for the cultivar Joey. The composite priming treatment 10% PEG-6000 + 0.75% KNO₃ was significantly better than that of single initiator and control treatment, achieving the highest germination rate (96.13%) and germination potential (88.90%), which were 9.15% and 28.04% higher than those of the control treatment. When this composite priming agent was applied to two cultivars, Matilda and Joey, it not only improved the seed germination rate and the vigor of germination, but also markedly enhanced the seedling quality. The optimized composite priming agent identified in this study could provide the technical support for improving the quality of seed germination and seedling cultivation of Ptilotus exaltatus.