funny said:hollow stems, thats a sativa trait. if u grow a sativa and a indica, the sativa will ( 90%) of the time have hollow stems. and the indica will not.
A little info on the strain might help out with an answer. I had an AK47 fruit pheno and crossed it with a California Orange/Hash plant. Then the seeds from the cross were sprouted and two plants that most resembled the AK47 were selected (a male and a female) and then crossed, so that a brother and sister now made seeds. These seeds were the ones with the hollow stems and stock. The AK47 is an elite clone from around my town, and the CO/HP was from an unknown source.