IVrnExpression

The IVrnExpression interface defines the contract for models that track vernalisation gene expression in cereal crops. It provides a standardised way to access vernalisation state variables and developmental progression indicators used in phenology models like CAMP.

Overview

IVrnExpression is a core interface in APSIM Next Generation’s Plant Modelling Framework that establishes a standard protocol for monitoring and reporting vernalisation-related gene expression dynamics. Models implementing this interface expose key developmental state variables that track the molecular and physiological progress of cereal crops through vernalisation and reproductive transition phases.

This interface is primarily implemented by the CAMP (Cereal Apical Meristem Phenology) model, which uses molecular-level gene expression to simulate developmental transitions in temperate cereals. The interface allows other components within APSIM to query vernalisation status without needing to understand the internal mechanics of gene expression calculations.

The interface supports mechanistic modelling of genotype × environment interactions by providing access to:

  • Individual vernalisation gene expression levels (Vrn1, Vrn2, Vrn3)
  • Baseline and maximum expression rates
  • Boolean flags indicating completion of key developmental phases

This abstraction enables flexible coupling between phenology models and other plant components, supporting both detailed mechanistic models and simpler empirical approaches within the same framework.

Model Structure

This section describes how this model is positioned within the APSIM framework. It outlines the broader structural and computational components that define its role and interactions in the simulation system.

This model inherits structural and functional behaviour from the following core APSIM components:

As an interface, IVrnExpression does not inherit from other classes but defines a contract that implementing classes must fulfil. The primary implementation is:

  • CAMP - Cereal Apical Meristem Phenology model

Connections to Other Components

This section describes how the model interacts with other components in the APSIM Next Generation framework.
These connections allow the model to exchange information—such as environmental conditions, developmental stage, or physiological responses—with other parts of the simulation system. For a general overview of how model components are connected in APSIM, see the Connections Overview.

This interface enables connections between phenology models and other components that need to access vernalisation status:

Component Model Connection Type Description
CAMP CAMP Implementation Primary implementation tracking vernalisation gene expression.
Phenology Phenology Consumer Uses vernalisation status to coordinate developmental phases.

Model Variables

This section lists the key variables that describe or control the behaviour of this component. Some variables can be adjusted by the user to modify how the model behaves (configurable), while others are calculated internally and can be viewed as model outputs (reportable). For a general explanation of variable types and how they are used within the APSIM Next Generation framework, see the Model Variables Overview.

Configurable and Reportable Properties

No configurable properties are available for this interface.

Read-Only Reportable Properties

The following properties must be implemented by any class adopting the IVrnExpression interface:

Property Type Description
Name string The name identifier for the implementing model
Vrn1 double Expression level of Vrn1 gene (vernalisation promoter)
Vrn2 double Expression level of Vrn2 gene (flowering repressor under long days)
Vrn3 double Expression level of Vrn3 gene (photoperiod-dependent flowering promoter)
BaseVrn double Baseline vernalisation expression accumulating at genotype-specific rate
MaxVrn double Maximum potential vernalisation expression achievable
IsVernalised bool Indicates whether vernalisation saturation has been reached

Biological Interpretation

Vrn1: The Vrn1 gene is the primary coordinator of vernalisation response in cereals. It is upregulated by cold temperatures and, once methalated, provides a persistent “memory” of vernalisation. In the CAMP model, Vrn1 expression must reach a threshold (typically 1.0) for the plant to complete the vernalisation phase. Base expression occurs at warm temperatures, but cold exposure accelerates this process significantly.

Vrn2: This gene acts as a flowering repressor that is upregulated under long photoperiods. It effectively raises the threshold that Vrn1 must overcome before vernalisation is complete. Short photoperiods suppress Vrn2 expression, allowing “short-day vernalisation” where plants can complete vernalisation requirements more quickly under short days.

Vrn3: A photoperiod-responsive gene that promotes flowering. It is upregulated under long photoperiods and accelerates progress toward reproductive transition. Vrn3 expression increases after Vrn1 has sufficiently suppressed Vrn2, representing the plant’s readiness to initiate reproductive development.

BaseVrn: Represents the baseline accumulation of vernalisation signal that occurs even under warm temperatures. This parameter varies by genotype - vernalisation-insensitive varieties have higher base rates and can complete development quickly without cold exposure, while vernalisation-sensitive varieties have lower base rates and require cold to accelerate development.

MaxVrn: The maximum rate at which vernalisation can accumulate, typically achieved under optimal conditions (cold temperatures during vernalisation, long photoperiods during reproductive transition). This provides an upper bound on developmental rate.

IsVernalised: A boolean flag indicating whether the plant has completed vernalisation requirements. This transition occurs when total vernalisation signal (typically \(BaseVrn + Vrn1 + Vrn3 - Vrn2\)) exceeds a threshold value (typically 1.0). This flag triggers important developmental transitions in phenology models.

See Also