What is an alternative to hook_node_view()? When a node is rendered in a panel pane, hook_node_view() is not invoked. (I use Panels 7.x-3.4.) Is there any alternative to change rendered node content in any other hook? 

I have tried  with hook_ctools_render_alter(), but the HTML output of the node is presented as one large string. I need to change node content in one particular field, so I need to access a $node variable as an array, as it happens with hook_node_view(). I need to execute custom PHP for changing the output of one of the fields.
If you are just editing one field you can use template_preprocess_field(), hook_field_display_alter(), or hook_field_display_ENTITY_TYPE_alter(). Those should also fire in other contexts if you use that field outside the panel pane in the future (which may be a good or bad side-effect depending on your context).