ColdVrnResponse
The ColdVrnResponse function models the upregulation of the Vrn1 gene in response to cold temperatures. This function is an extension of the base Vrn1 expression and represents how cold temperatures enhance vernalisation responses in cereal crops, as described in Brown et al. (2013). It is part of the vernalisation module used in the phenology model within APSIM NG.
Overview
The ColdVrnResponse function calculates an additional contribution to Vrn1 expression due to exposure to low temperatures, allowing plants to progress through their vernalisation requirement. It uses a temperature-dependent response, where expression increases exponentially with decreasing temperature. When temperatures exceed a threshold, the response is either reduced or suppressed, mimicking de-vernalisation effects. This function plays a crucial role in modeling development timing for cold-requiring cultivars.
It implements the IFunction and IIndexedFunction interfaces, and is used within the context of the CAMP model for phase progression in phenology.
Inputs
The following inputs are required by the function, supplied as child models or linked references:
CAMP: The parent model that contains the parameters and context for the CAMP model.k: The exponential shape factor controlling the temperature response curve.deVernalisationTemp: The temperature threshold above which vernalisation is reduced.deVernalisationRate: The rate of down-regulation of Vrn1 when temperature exceeds the de-vernalisation threshold.camp.Params: A parameter check from the CAMP model indicating whether computation is active.
Methodology
The function computes the indexed value of Vrn1 upregulation for a given temperature input \(dX\) (likely a sub-daily temperature).
The response follows the logic:
- If
camp.Paramsis null, return 0 (no response). - Compute upregulation:
\[ U_{dVrn1} = e^{k \cdot dX} \]
- If \(dX < \text{deVernalisationTemp}\):
\[ \text{Response} = \frac{U_{dVrn1}}{24} \]
- Else (temperature exceeds de-vernalisation threshold):
\[ \text{Response} = \frac{\text{deVernalisationRate}}{24} \]
This response is scaled to a sub-daily (hourly) timestep by dividing by 24.
Events
Events Listened For
No events are listened by this function.
Events Raised to
No events are raised by this function.
Properties
Configurable and Reportable Properties
| Property | Type | Description |
|---|---|---|
| k | IFunction | The exponential shape factor for cold temperature response. |
| deVernalisationTemp | IFunction | Temperature above which de-vernalisation occurs. |
| deVernalisationRate | IFunction | Rate of Vrn1 downregulation above the temperature threshold. |
Read-Only Reportable Properties
No read-only properties are available for this function.
User Interface
ColdVrnResponse can be added as a child of a Function node in the model tree. Right-click the parent node, select “Add Model…”, and search for ColdVrnResponse in the Filter Box.
Practical Example
No practical example is available for this function.
See Also
- Source code: ColdVrnResponse.cs on GitHub