<tree string="Sales Analysis">

<field name="product_id"/>

<field name="partner_id"/>

tree>

Above is the tree view I defined. I have added tree as one form of view_mode in the action as well. The titles of the tree(list) are displayed but the data for many2one fields is not there. 

FYI: many2one fields are being displayed in my pivot and graph views. The problem is with tree view only

Can anyone help fix this issue ?