VernalisationPhase

The VernalisationPhase defines a phenological development phase that is completed when vernalisation requirements are fulfilled. It integrates gene expression signals into crop phenology progression, making it essential for modeling genotypic and environmental responses affecting vernalisation.

Overview

The VernalisationPhase utilises Cereal Anthesis Molecular Phenology (CAMP) model (Brown et al. 2013) to proceed the phase development. The phase completes when vernalisation saturation is achieved. This function is crucial in modeling winter crops, such as wheat and barley, that require cold exposure to proceed in development. It translates gene expression signals (via the CAMP interface) into phenological progress.

Inputs

Input Name Type Description
Start string Name of the phenological stage that starts this phase
End string Name of the phenological stage that ends this phase
IsEmerged bool Boolean flag indicating whether the crop has emerged above the soil surface (i.e. this phase is happening above ground).
CAMP IVrnExpression Link to CAMP gene expression interface providing vernalisation signals

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:

The \(\text{target}\) of this phase is defined as: \[ \text{Target} = 1 + Vrn2 \]

Where:

  • \(Vrn2\) is the photoperiod-induced repressor of flowering.

The relative vernalisation expression \(R_{\text{Vrn}}\) is calculated as:

\[ R_{\text{Vrn}} = \min\left(\frac{Vrn_{\text{base}} + Vrn1 + Vrn3}{\text{Target}},\ Vrn_{\text{max}} \right) \]

Where:

  • \(Vrn_{\text{base}}\) is the baseline vernalisation expression,
  • \(Vrn1\) is the cold-induced vernalisation expression,
  • \(Vrn3\) is the photoperiod-dependent promoter of flowering,
  • \(Vrn_{\text{max}}\) is the maximum vernalisation expression.

At emergence, \(R_{\text{Vrn},\ emergence}\) is recorded which assumes as the first day of this phase. Progress through the phase (\(F_{\text{complete}}\)) is:

\[ F_{\text{complete}} = \min\left(1,\ \frac{R_{\text{Vrn}} - R_{\text{Vrn},\ emergence}}{1 - R_{\text{Vrn},\ emergence}} \right) \]

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

Events

Events Listened For

These are signals or notifications that the function listens for from other parts of the simulation:

Event Purpose
Commencing Resets internal counters and state for simulation startup

Events Raised to

No events are raised by this function.

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.

See Also

References

Brown, Hamish E., Peter D. Jamieson, Ian R. Brooking, Derrick J. Moot, and Neil I. Huth. 2013. “Integration of Molecular and Physiological Models to Explain Time of Anthesis in Wheat.” Annals of Botany 112 (9): 1683–703. https://doi.org/10.1093/aob/mct224.