Complex sentence: The appearance of B deficiency symptoms coincides with the decrease of water-insoluble B, from which it is concluded that the insoluble B is the functional form while the soluble B represents the surplus.
Split into simpler sentences: The appearance of a boron deficiency coincides with the decrease of water-insoluble boron. It appears that the insoluble boron is the functional form while the soluble boron represents the surplus.