VernalisationPhase

VernalisationPhase models the crop developmental phase that begins at a specified stage and ends once vernalisation is satisfied using CAMP model. It simulates the accumulation of vernalisation based on gene expression, delaying development in winter-type genotypes until cold exposure requirements are met.

Overview

This phase is essential for crops (like winter cereals or canola) that require exposure to cold temperatures to trigger flowering. In APSIM NG, VernalisationPhase represents a portion of phenological development that is controlled by vernalisation genes (e.g., VRN1, VRN2, VRN3). It starts at a named stage (e.g., emergence) and ends once vernalisation is deemed complete CAMP model.

This is a biological switch in the plant’s calendar: it won’t progress toward reproduction until it has experienced sufficient “cold memory” through vernalisation.

Inputs

• Start: Name of the phenological stage where this phase begins.
• End: Name of the phenological stage where this phase ends.
• IsEmerged: Logical flag indicating whether this phase assumes emergence has occurred (default is true).
• CAMP: A linked component that provides gene expression values required for vernalisation progress:
  • BaseVrn: Base vernalisation gene expression
  • Vrn1, Vrn2, Vrn3: Vernalisation gene activators/inhibitors
  • MaxVrn: Maximum possible vernalisation value
  • IsVernalised: Logical output indicating completion

Methodology

Vernalisation progress is computed using CAMP model, summing gene expression components and scaling by a saturation threshold:

Let
- \(B\) = BaseVrn
- \(V_1\) = Vrn1
- \(V_2\) = Vrn2
- \(V_3\) = Vrn3
- \(M\) = MaxVrn
- \(R_e\) = RelativeVernalisation at emergence

Then:

\[ \text{Target} = 1 + V_2 \]

\[ R = \min\left(\frac{B + V_1 + V_3}{\text{Target}},\ M \right) \]

At emergence, \(R_e\) is recorded. Progress through the phase is:

\[ f = \min\left(1,\ \frac{R - R_e}{1 - R_e} \right) \]

The phase ends when IsVernalised is true, indicating the crop has fulfilled its vernalisation requirement.

Events

Events Listened For

Event	Purpose
Commencing	Resets internal counters and state for simulation startup

Events Raised to

No events are raised by this function.

Properties

Configurable and Reportable Properties

Property	Type	Description
Start	string	Name of the crop stage that initiates this phase
End	string	Name of the crop stage that ends this phase
IsEmerged	bool	Whether the phase assumes the crop is emerged (default = true)

Read-Only Reportable Properties

Property	Type	Description
FractionComplete	double	Proportion (0–1) of progress through this phase
ProgressThroughPhase	double	Alias for FractionComplete (used internally)
Target	double	Target vernalisation saturation = \(1 + \text{Vrn2}\)

User Interface

VernalisationPhase is added as a child of a Phenology node to simulate development that depends on cold exposure.

1. Right-click the Phenology node.
2. Select “Add Model…”.
3. Search for and select “VernalisationPhase”.
4. Configure Start, End, and link the CAMP component that simulates gene activity.

Practical Example

No practical example available.