After the sugar has been moved to the sink within a plant,

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1)First an energy-requiring proton pump establishes an electrochemical gradient-more H+ is outside than inside phloem.Sugar then travels across the membrane in conjunction with gradient.2)After sugar enters the sieve tubes,water follows passively by osmosis.3)The buildup of water within sieve tubes creates the positive pressure that starts the bulk flow of the phloem contents.4)The roots (and other growth areas)are a sink for sugar.After sugar is actively transported out of sieve tubes,water exits the phloem passively by osmosis.5)Water is taken up by xylem.6)Xylem transports water to the mesophyll of the leaf where it is used for photosynthesis.7)Although up to 90% of water is transpired,some is used for photosynthesis,and some reenters the phloem by osmosis.

After the Sugar Has Been Moved to the Sink Within