AP BIOLOGY

Detailed explanation-1: -As the sink cells pull the solute out of the phloem, water leaves the phloem by osmosis, passing to neighboring tissues that have higher solute concentrations. The retreating water reduces the pressure in this region of the sieve tubes and encourages fluid to continue to flow from regions of higher pressure.

Detailed explanation-2: -Within the phloem, sugars migrate to regions of low osmotic concentration and low water pressure, called sinks, from areas of high osmotic concentration and high water pressure, known as sources.

Detailed explanation-3: -The photosynthates from the source are usually translocated to the nearest sink through the phloem sieve tube elements. For example, the highest leaves will send sugars upward to the growing shoot tip, whereas lower leaves will direct sugars downward to the roots.

Detailed explanation-4: -The points of sugar delivery, such as roots, young shoots, and developing seeds, are called sinks. Seeds, tubers, and bulbs can be either a source or a sink, depending on the plant’s stage of development and the season. The products from the source are usually translocated to the nearest sink through the phloem.