Abstract The knowledge of cardinal temperatures is critical for understanding environmental tolerance limits for germinating plant species. However, this information is not readily available for Tylosema fassoglense [Family: Fabaceae]; despite its potential as a future crop to improve nutrition and enhance sustainable agriculture in Kenya. The objective of this study was to characterise seed germination responses to temperature and water potential of seed lots of T. fassoglenseseeds collected from three counties in Kenya; namely Busia, Migori and Siaya. Scarified seeds were germinated at a wide range of constant temperatures from 10 to 45 °C with intervals of 5 °C and water potentials from 0, -0.25, -0.5, -1.0, -1.5 Megepascal (MPa) at 25 °C. Seeds of T. fassoglense had a wide range of germination temperature of 20 °C (from 15 to 35 °C). Low (10 °C) and high (≥40 °C) temperatures significantly reduced germination in the three seed lots. Busia seed lot had the lowest final germination of 5% at 10 °C while germination was zero at 45 °C in all the seed lots tested. The calculated base, optimal and ceiling temperature (Tb, To and Tc) ranges were 4.05 - 8.0 °C; 33.61 - 35.75 °C; and 46.54 - 47.24 °C, respectively. Suboptimal and supraoptimal thermal time (θT(50)) ranged between 76.19 – 89.02 degree celcius days (°C d) and 30.3–41.89 °C d respectively. Water potential of -0.5 MPa significantly reduced final germination to less than 50% in all seed lots while germination was zero at both -1.0 and -1.5 MPa. The base water potential (Ψb) and hydro time (θH(20)) was between -0.92 to -0.97 MPa and 3.95–4.11 Megapascal days (MPad) respectively. The optimum temperature range for germination was 30–35 °C and seeds were tolerant to low water potential up to -0.5 MPa. However, further studies will need to be carried out on germination in the supraoptimal temperature range and water potential between 0 and -1.0 MPa. The findings in this study will be useful in future research contributing towards domestication of T. fassoglense.

中文翻译：

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蔓延的紫荆（Tylosema fassoglense）对温度和水势的萌发响应，这是肯尼亚的一种潜在作物

摘要 基本温度的知识对于理解萌发植物物种的环境耐受极限至关重要。然而，Tylosema fassoglense [科：豆科] 的信息并不容易获得；尽管它作为未来作物在肯尼亚改善营养和促进可持续农业的潜力。本研究的目的是表征从肯尼亚三个县收集的 T. fassoglenseseeds 种子批次对温度和水势的种子萌发响应；即Busia、Migori和Siaya。松土种子在 10 到 45°C 的广泛恒温下发芽，间隔为 5°C，水势从 0、-0.25、-0.5、-1.0、-1.5 兆帕 (MPa) 到 25°C。T. fassoglense 种子的发芽温度范围很广，为 20 °C（从 15 到 35 °C）。低温 (10 °C) 和高温 (≥40 °C) 显着降低了三个种子批次的发芽率。在所有测试的种子批次中，Busia 种子批次在 10 °C 时的最终发芽率最低，为 5%，而在 45 °C 时发芽率为零。计算的基准、最佳和最高温度（Tb、To 和 Tc）范围为 4.05 - 8.0 °C；33.61 - 35.75 °C；和 46.54 - 47.24 °C，分别。次优和超优热时间 (θT(50)) 分别介于 76.19 – 89.02 摄氏度天 (°C d) 和 30.3–41.89 °C d 之间。-0.5 MPa 的水势显着将所有种子批次的最终发芽率降低至 50% 以下，而在 -1.0 和 -1.5 MPa 时发芽率均为零。基础水势 (Ψb) 和水时间 (θH(20)) 分别介于 -0.92 至 -0.97 MPa 和 3.95-4.11 兆帕天 (MPad) 之间。发芽的最佳温度范围为 30-35°C，种子耐受低水势可达 -0.5 MPa。但是，需要对超最佳温度范围内的发芽和 0 到 -1.0 MPa 之间的水势进行进一步研究。本研究的发现将有助于未来有助于驯化 T. fassoglense 的研究。