Abstract: Some results from determining the content of B, Ca, S, CI, K, Phenol, IAA, ABA, ethylene and the activities of glacose -6-phosphate dehydrogenase and peroxidase of both deficient ard normal cotton petiole with 10B tracd etching, X-ray spetrum, chemical and biochemical analysis showed that, in boron deficient cotton petiole, the transportation of boron was blocked, the distribution of Ca, S, Cl and K in sieve tubes, vessels as well as pith cells was changed and the balance state among these elements was destroyed. The content of phenol, ABA, ethylene and the activites of psroxidase and glucose-6-phosphate dahydrogenase were significantly increased but IAA content was significantly decreased.