Tubers are the main means of propagation in purple nutsedge (Cyperus rotundus L.), one of the most troublesome weeds competing in crop and pasture systems throughout the world. Tuber sprouting is highly linked to temperature, the main environmental factor limiting the growth of purple nutsedge. In the present study, a new thermal time model was developed for describing the temperature-dependent tuber sprouting of purple nutsedge. This model was validated based on results from a laboratory tuber sprouting experiment performed under different temperature regimes. The proposed model is an integration of three equations comprising those of Gompertz, Dent like, and Segmented (GDS) functions, developed for describing cumulative sprouting, final sprouting and sprouting rate of purple nutsedge tubers respectively. The Gompertz-based model fitted the data well (R² = 0.94, RMSE %< 10). This model was also able to predict lag time (time up to start of sprouting), final sprouting and sprouting rate. A Weibull-based model was only able to estimate temperature thresholds based on the final sprouting. Whereas, the GDS model predicted related temperature thresholds according to both final sprouting (optimal in the range of 20.31–29.72°C) and the absolute sprouting rate (optimum at 29.96°C). In conclusion, the proposed model is simple and includes parameters of a biological significance, simultaneously generating estimates of useful temperature thresholds and fitting cumulative tuber sprouting of purple nutsedge. Our study has also proved the superiority of the absolute sprouting rate index when calculating the temperature thresholds.

中文翻译：

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开发一种新的热时间模型，用于描述紫色核仁 (Cyperus rotundus L.) 块茎发芽

块茎是紫核仁（Cyperus rotundus ）的主要繁殖手段L.)，是全世界作物和牧场系统中最麻烦的杂草之一。块茎发芽与温度密切相关，温度是限制紫色坚果生长的主要环境因素。在本研究中，开发了一种新的热时间模型来描述紫色坚果的温度依赖性块茎发芽。该模型基于在不同温度条件下进行的实验室块茎发芽实验的结果进行了验证。所提出的模型是三个方程的集成，包括 Gompertz、Dent 类和分段 (GDS) 函数，开发用于分别描述紫色坚果块茎的累积发芽、最终发芽和发芽率。基于 Gompertz 的模型很好地拟合了数据 ( R ² = 0.94，RMSE %< 10)。该模型还能够预测滞后时间（到发芽开始的时间）、最终发芽和发芽率。基于 Weibull 的模型只能根据最终发芽来估计温度阈值。而 GDS 模型根据最终发芽（最佳范围为 20.31–29.72°C）和绝对发芽率（最佳为 29.96°C）预测相关温度阈值。总之，所提出的模型很简单，包括具有生物学意义的参数，同时生成有用温度阈值的估计值并拟合紫色坚果的累积块茎发芽。我们的研究也证明了绝对发芽率指数在计算温度阈值时的优越性。