diamond (shape), water chestnut, rhombus
菱 centers on the diamond or rhombus shape, which is the visual form of a water chestnut. The plant sense is a specific application of that same shape idea.
菱 combines 艹 (plant) with 夌, which likely contributes the sound. The character originally referred to the water chestnut plant, whose fruit has a distinctive diamond shape, later extending to the rhombus sense.
The plant radical 艹 sits above 夌, like a water chestnut plant with its diamond-shaped fruit visible below the leaves.
For リョウ, imagine a diamond-shaped water chestnut floating in a clear rill: rill -> リョウ, and the diamond shape catches the light.
Mitsubishi
Mitsubishi Electric
water caltrop (esp. Trapa japonica); water chestnut
Mitsubishi Heavy Industries
Mitsubishi Corporation
rhombus; rhomb; lozenge; diamond (shape)
Mitsubishi Materials Corporation
Mitsubishi Heavy Industries, Ltd.
rhombus-shaped mochi
flower-shaped family crest
Mitsubishi Rayon
Mitsubishi Pharma
Mitsubishi Trust And Banking Corporation
Mitsubishi Logistics Corporation
Mitsubishi Chemical Corporation
Mitsubishi Tokyo
Mitsubishi Motors Corporation
Mitsubishi Motor Corp. (abbr)
Mitsubishi Paper Mills Limited
Mitsubishi Securities