How to process purchase order with decreasing weight as ordered.

Dear All,

actually scenario is that i have built a purchase order of a tree weighted with 90 kg but as i have received that tree its weight reduced to 50 can we process such type of scenerio bcoz order was of 90 kg and received is can i be able to use in my production order that i have already planned for 90kgs.

Receipt the PO with receive now of 40kg and close the line. Run planning to get a new suggested purchase order to fulfill the shortfall in produciton.