Converting observe_field to UJS in Rails 3

I am trying to rewrite my website in Rails 3 and Ruby 1.9.2.
Can some one help me convert my observe_field which is working under
Rails 2.3.5 to Rails 3. I would like to avoid using JQuery as over the
last year everything I have tried in JQuery has failed, including this
one. Perhaps due to my lack of knowledge. I would not like to install
the legacy upgrade.
What I have in my website is several pages(models) which use the same
search text field. Each controller has an action "search" which
renders a partial "_searchresults" on the page with the text field.
The code which works well in Rails 2.3.5 along with one typical
example search action from a controller and the "_searchresults" is
shown below:-

In the searches index.heml.erb:-

   <p align="center"><font color="blue"><b>Just type the word or part
of the word and wait two seconds</b></font></p><br/>
   <% if params[:area] != nil%>

<% form_tag({:action => "foo"},{:id => "search"}) do %>
     <%= label_tag(:query, "Search for:") %>
     <%= text_field_tag("query", params[:query], :autocomplete =>
"off" , :onKeyPress=>"return disableEnterKey(event)") %>
<% end %>

    <%= observe_field 'query', :frequency => 2,
                :update => "search_results",
                :url => {:controller => params[:area], :action =>
"search",:area => params[:area]},
                :with => "query" %>

<div id="search_results">
<p class="plantname2">(Search results will be listed here)</p>

<%= set_focus_to_id 'query' %>

In one of the controller:-
def search
  session[:query] = params[:query].strip if params[:query]

  if session[:query] and request.xhr?
    @plants_sn = Plant.find(:all, :conditions => ["scientificname
LIKE ?", "%#{session[:query]}%"], :order => "commonname ASC")
    @plants_cm =Plant.find(:all, :conditions => ["commonname LIKE ?",
"%#{session[:query]}%"], :order => "commonname ASC")
    @plants_desc =Plant.find(:all, :conditions => ["description
LIKE ?", "%#{session[:query]}%"], :order => "commonname ASC")

    @plants = (@plants_cm + @plants_sn + @plants_desc).uniq
    render :partial => "shared/searchresults", :layout =>
false, :locals => {:searchresults => @plants}

In Views/Shared/_searchresults:-
<% if searchresults.length == 0 %>

  <p>Sorry! No articles found...</p>

  <% elsif params[:query] == "" %>

    <p>You must enter a search term.</p>

  <% else %>

    <% if params[:area] == "plants" %>
      <tr>**************.............elseif,elsfif etc,etc.