ABSTRACT In New Zealand, a commonly sown pasture combination is perennial ryegrass with white clover. The hydrothermal time model (HTT) was used to quantify germination under different temperature (T) and water potential (WP) conditions for white clover ‘Nomad’ and perennial ryegrass ‘Stellar AR1’. Seeds were germinated in vitro under a range of T × WP combinations, and HTT models were fitted to germination time course data. Rapid germination of white clover under optimum T and WP was reflected by a much lower value for its HTT constant compared with perennial ryegrass (10.8 vs 80.7 MPa °C d). However, the lower base water potential for perennial ryegrass (−1.29 vs −0.495 MPa) and a higher threshold temperature for thermoinhibition (21.8 vs 18.3°C), meant that predicted perennial ryegrass germination was more resilient in warm dry conditions. HTT models can be used to assist decisions about the timing of perennial ryegrass and white clover sowing.

中文翻译：

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用热液时间模型量化多年生黑麦草 (Lolium perenne L.) 和白三叶草 (Trifolium repens L.) 种子萌发对水势和温度的响应

摘要 在新西兰，一种常见的牧草组合是多年生黑麦草和白三叶草。水热时间模型 (HTT) 用于量化白三叶草“Nomad”和多年生黑麦草“Stellar AR1”在不同温度 (T) 和水势 (WP) 条件下的发芽情况。种子在一系列 T × WP 组合下在体外发芽，HTT 模型适合发芽时间过程数据。与多年生黑麦草（10.8 vs 80.7 MPa °C d）相比，白三叶草在最佳 T 和 WP 下的快速发芽表现为其 HTT 常数值低得多。然而，多年生黑麦草的较低基础水势（-1.29 对 -0.495 MPa）和较高的热抑制阈值温度（21.8 对 18.3°C）意味着预测的多年生黑麦草发芽在温暖干燥的条件下更具弹性。