Plug Power (NASDAQ: PLUG), backed by asset management giant BlackRock (NYSE: BLK), has seen growing bullish sentiment from investors following a series of positive developments.As of March 31, BlackRock disclosed a stake in the company, holding just under 80 million shares valued at $107.5 million. While that represents a small portion of its overall portfolio, it signals confidence in Plug Power’s longer-term potential.On Tuesday, PLUG shares closed at$1.28, up 4.9% on the day. Over the past month, the st ...