JPA: default column name mapping for @ManyToOne relations

When we have a class:

@Entity
Order implements Serializable {
    @Id
    private Integer id;
    ...
}

and:

@Entity
OrderLine implements Serializable {
    @Id
    private Integer id;

    @ManyToOne
    Order order;
    ...
}

What row name will the property order map to?

order_id, ORDER_ID or Order_id?

(ommiting the @JoinColumn(name='order_id') is deliberate)