In which form plants do absorb boron?

Absorption of Boron ($\mathrm{Br}$) by plants:

• Boron is taken mostly by plants as Boric acid (${\mathrm{H}}_3{\mathrm{BO}}_3$) and Borate ions (${{\mathrm{BO}}_3}^{3-}$).
• Boron is liberated during the withering of rock minerals.
• Boron absorption is a passive process that is affected by the concentration of Boron in soil solution.
• As a result, its concentration in seawater is higher than in freshwater.

Thus, plants absorb Boron as Boric acid and Borate ions.