3 9   K . ▁M g B 2 ▁w ires ▁are ▁produced ▁with ▁the ▁pow der - in - t ube ▁process ▁and ▁applied ▁in ▁super con duct ing ▁magnet s . ▁ ▁Am orph ous ▁bor on ▁is ▁used ▁as ▁a ▁mel ting ▁point ▁de press ant ▁in ▁nick el - chrom ium ▁bra ze ▁allo ys . ▁ ▁H ex ag onal ▁bor on ▁nit ride ▁forms ▁atom ically ▁thin ▁layers , ▁which ▁have ▁been ▁used ▁to ▁enh ance ▁the ▁electron ▁mob ility ▁in ▁graph ene ▁devices . ▁It ▁also ▁forms ▁nan ot ub ular ▁structures ▁( B NN T s ), ▁which ▁have ▁high ▁strength , ▁high ▁chemical ▁stability , ▁and ▁high ▁thermal ▁conduct ivity , ▁among ▁its ▁list ▁of ▁des irable ▁properties . ▁ ▁Bi ological ▁role ▁ ▁Bor on ▁is ▁an ▁essential ▁plant ▁nut ri ent , ▁required ▁primarily ▁for ▁maintain ing ▁the ▁integrity ▁of ▁cell ▁walls . ▁However , ▁high ▁soil ▁concentr ations ▁of ▁greater ▁than ▁ 1 . 0   pp m ▁lead ▁to ▁marg inal ▁and ▁tip ▁ne c ros is ▁in ▁leaves ▁as ▁well ▁as ▁poor ▁overall ▁growth ▁performance . ▁Level s ▁as ▁low ▁as ▁ 0 . 8   pp m ▁produce ▁these ▁same ▁sympt oms ▁in ▁plants ▁that ▁are ▁particularly ▁sensitive ▁to ▁bor on ▁in ▁the ▁soil . ▁Near ly ▁all ▁plants , ▁even ▁those ▁somewhat ▁toler ant ▁of ▁soil ▁bor on , ▁will ▁show ▁at ▁least ▁some ▁sympt oms ▁of ▁bor on ▁to x icity ▁when ▁soil ▁bor on ▁content