Hong Kong shares rallied by 2.34 per cent Thursday, tracking overnight gains on Wall Street and spurred by optimism over plans to ease the debt crisis in Europe, dpa reported. The Hang Seng Index rose 428.35 points to close at 18,757.81. Turnover was a relatively robust 88.3 billion Hong Kong dollars (11.4 billion US dollars). Analysts said the upturn was triggered by plans to support European banks. However, they warned of more volatility to come and said the optimism would probably be short-lived. HSBC Holdings PLC rose 3.27 per cent to end the day at 64.65 Hong Kong dollars