If the xylem of a plant is blocked using a dye that clogs the vessels, which of the following will be directly affected first?
A. Phloem loading
B. Photosynthesis rate
C. Root pressure generation
D. Opening of stomata
Answer (2)
The blockage of the xylem in a plant directly affects root pressure generation first. This results in limited water transport from the roots to the leaves, impacting processes like photosynthesis. Thus, the correct answer is C.
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To understand which process will be directly affected first when the xylem of a plant is blocked, it's important to know the function of the xylem.
The xylem is responsible for transporting water and dissolved minerals from the roots to the rest of the plant, including the leaves. This process is crucial for several functions in the plant.
Root Pressure Generation (C) : Root pressure is generated when water is absorbed from the soil through the roots and moves into the xylem. If the xylem is blocked, the movement of water from the roots is directly impeded, affecting root pressure almost immediately.
Phloem Loading (A) : Phloem loading involves the transport of sugars. While it requires water from the xylem for the movement of sugars, it wouldn't be the first process affected as the xylem primarily transports water and minerals, not sugars.
Photosynthesis Rate (B) : Photosynthesis depends on water, which is transported through the xylem. However, the immediate restriction will more directly affect root-related processes before the overall water availability for photosynthesis declines.
Opening of Stomata (D) : The opening of stomata is influenced by water pressure within the leaf cells, which is affected by the water supply from the xylem. While it will eventually be impacted, it is not the first direct consequence of a blocked xylem.
Given this explanation, the process that will be directly affected first when the xylem is blocked is (C) Root pressure generation. The xylem's primary role is to move water from the roots, and a block will immediately impact this movement, leading to a reduction or loss in root pressure.
