You are not sending a cr/lf with those. Use client.println() instead of .print().
when i use : client.print(F("GET /1.1/statuses/user_timeline.json?screen_name=plantaexpre&count=1 HTTP/1.1"));
This is how the server sees your request, and this would be bad.
GET /1.1/statuses/user_timeline.json?screen_name=plantaexpre&count=1 HTTP/1.1Host:api.twitter.comAuthorization: OAuth oauth_consumer_key="j3UCRhGsBZSfRltac4zEXg", oauth_nonce="XXXXXXXXXXXXXXXXXXXXXXX", oauth_signature="XXXXXXXXXXXXXXXXXXXXXX", oauth_signature_method="HMAC-SHA1", oauth_timestamp="1364306703", oauth_token="*********************************************", oauth_version="1.0"