Storage forms of organic molecules (example: starch, fats, proteins) are too large or insoluble for transport throughout the plant body. Cells break them down to smaller molecules for transport. Sucrose is the main carbohydrate transported. Carbohydrates are stored as starches.
Organic molecules travel from photosynthetic sites to organs that need them by translocation. Molecules move through phloem from sources (leaves) to sinks (flowers, fruits, seeds, roots). According to the pressure flow theory, translocation depends on pressure gradients. Solutes move into the phloem from a source , then water follows, pressure builds, and fluids move away to sink areas. At the sink, organic compounds move by active transport into sink cells where they are used.
This animation (Audio - Important) describes the pressure flow theory.
Movement of materials through the plant are interdependent processes.
This animation (Audio - Important) reviews vascular tissues.
REVIEW: The cells that function with the sieve tubes are the
REVIEW: The source region in the pressure flow explanation of phloem transport is most often the
REVIEW: The most common form of sugar transported to the roots is
REVIEW: In phloem, organic compounds flow through _____ .
REVIEW: _____ conducts water and ions; _____ conducts food.
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