“…The source of the NADPH for the respiratory burst comes mainly from the reduction of NADP + in the pentose-phosphate (P-P) pathway, which is very active during the respiratory burst. In plants, one substrate of the P-P pathway, 6-phosphogluconate, is known to complex with boron, which thereby inhibits 6-phosphogluconate dehydrogenase (PGD), a key enzyme in the P-P pathway [12]. Thus a serious problem in boron-deficient plants is an increase in the amount of substrate metabolized via the P-P pathway, which gives rise to overabundant synthesis of phenolic compounds and subsequent death of plants in the subclass Dicotyledoneae [12].…”