disabling rendering of a particular column on rendering entire datatable - css

Question

In the code below there is datatable with id discoObject. This id is render on selecting a drop down which changes color of the column according to the selection hence AJAX call.
There is another field call freeText of type inputTextArea. As soon as i select a drop down value what ever text is written in freeText area it vanishes. This is because on ajax call i am rendering whole datatable. But if i don't render whole datatable and only render column id for drop down, it will not change color of drop down. I want the color of drop down to be changed retaining whatever value i have entered in freetext.
Please help me in this.
Thanks is advance.
<p:dataTable styleClass="ui-datatable-scrollable-body list" var="discoViewObject" rowIndexVar="index" id="discoObject" rowKey="#{discoViewObject.uniqueId}" style="height:500px"
rowStyleClass="#{(index % 2) eq 0? 'tablerow' : 'tablerowAlter'}" selection="#{staffMsgingHccDiscoHandler.hccDiscoBean.discoViewObjectSelectionList}"
value="#{staffMsgingHccDiscoHandler.hccDiscoBean.discoViewObjectList}" >
<p:column id="decisionColor" headerText="#{message['CNS.fltDisruption.oneFlightMessae.hccDecision']}"
styleClass="#{(discoViewObject.disruptedPaxGroupType.decision) eq 'MISSED CONNECTION'? 'decisionRed' : '' }
#{(discoViewObject.disruptedPaxGroupType.decision) eq 'WILL WAIT'? 'decisionGreen' : '' }
#{(discoViewObject.disruptedPaxGroupType.decision) eq 'PENDING'? 'decisionYellow' : '' }">
<h:selectOneMenu value="#{discoViewObject.disruptedPaxGroupType.decision}">
<f:selectItem itemLabel="CONNECTION OK" itemValue="CONNECTION OK"></f:selectItem>
<f:selectItem itemLabel="WILL WAIT" itemValue="WILL WAIT"></f:selectItem>
<f:selectItem itemLabel="PENDING" itemValue="PENDING"></f:selectItem>
<f:selectItem itemLabel="MISSED CONNECTION" itemValue="MISSED CONNECTION"></f:selectItem>
<f:selectItem itemLabel="TO BE ANNOUNCED" itemValue="TO BE ANNOUNCED"></f:selectItem>
<f:ajax event="change" render="discoObject"></f:ajax>
</h:selectOneMenu>
</p:column>
<p:column headerText="Free Text" >
<h:inputTextarea cols="6" rows="4" style="width: 192px; height: 63px;" value="#{discoViewObject.freeTextOutBoundFlt}" ></h:inputTextarea>
</p:column>