Abstract Hypericum ericoides is a rock plant of potential ornamental use in sustainable gardening in Mediterranean urban environment. This study was carried out to investigate the effects of temperature, light, salinity and soil moisture at the stage of plant life most sensitive to abiotic stresses (seed germination). The results indicate that light is not a germination requirement, while temperature the main factor that regulates the germination process of this species. Seed germination was inhibited by warm temperatures of 25 and 30 °C. By contrast, intermediate temperatures of 10, 15 and 20 °C induced high germination percentages both in alternating light/darkness and continuous darkness. The alternating temperature of 12/20 °C led to germination percentages close to 100 % and the highest germination speed, making this the suggested optimal for germination. The germination values attained demonstrated the absence of dormancy in H. ericoides seeds. In general, salinity and drought stress (induced by NaCl and PEG solutes, respectively) caused similar effects, reducing and delaying seed germination as the osmotic potential decreased (from 0 to -1.68 MPa). However, while most non-germinated seeds remained viable during exposure to all the osmotic potentials induced by PEG and germinated when drought stress was alleviated, the highest levels of salt stress permanently inhibited germination, although not in all seeds. These results indicated that germination inhibition under both NaCl and PEG stress is mainly due to the low water potential caused by osmotic stress, while salt stress had the added toxic effect of specific ions at the highest concentrations of NaCl. So, H. ericoides seeds can germinate well under conditions of moderate salinity and high drought stress, making it a promising species for use in sustainable urban gardening, with a low input of irrigation water of low quality.

中文翻译：

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光、温、盐和干旱胁迫对具有观赏潜力的野生植物金丝桃种子萌发的影响

摘要 金丝桃是一种岩石植物，在地中海城市环境中的可持续园艺中具有潜在的观赏用途。本研究旨在研究温度、光照、盐度和土壤水分对非生物胁迫最敏感的植物生命阶段（种子萌发）的影响。结果表明，光不是发芽要求，而温度是调节该物种发芽过程的主要因素。25°C 和 30°C 的温暖温度会抑制种子发芽。相比之下，10、15 和 20 °C 的中间温度在交替的光/暗和连续黑暗中均能诱导高发芽率。12/20 °C 的交替温度导致发芽率接近 100% 和最高的发芽速度，使其成为发芽的最佳建议。所获得的发芽值证明了在 H. ericoides 种子中不存在休眠。一般来说，盐度和干旱胁迫（分别由 NaCl 和 PEG 溶质诱导）引起类似的影响，随着渗透势的降低（从 0 到 -1.68 MPa）降低和延迟种子萌发。然而，虽然大多数未发芽的种子在暴露于由 PEG 诱导的所有渗透势期间保持活力并在干旱胁迫减轻时发芽，但最高水平的盐胁迫会永久抑制发芽，尽管并非在所有种子中。这些结果表明 NaCl 和 PEG 胁迫下的萌发抑制主要是由于渗透胁迫引起的低水势，而盐胁迫在最高浓度的 NaCl 下会增加特定离子的毒性作用。因此，H. ericoides 种子可以在中等盐度和高干旱胁迫的条件下很好地发芽，使其成为用于可持续城市园艺、低质量灌溉水输入的有前途的物种。