Fusarium oxysporum is a fungus that attacks tomato plants, causing them to wilt and die. the fungus initially blocks the xylem and grows extensively within parenchyma. as the plant continues to wilt, the blockage of both xylem and phloem can be observed. the result is the suppression of both the xylem sap circulation in the plant and photosynthetic activity in the leaves. based on these observations, explain how the fungus affects the role of both the xylem and the phloem.