AP BIOLOGY

Detailed explanation-1: -Amino acids are transported between different organs through both xylem and phloem. This redistribution of nitrogen and carbon requires the activity of amino acid transporters in the plasma membrane. In addition, amino acids can be taken up directly by the roots.

Detailed explanation-2: -Pollen is not transferred within the plant.

Detailed explanation-3: -Amino acids in roots are transported mainly to source leaves in the xylem transpiration stream [2]. As the main transport form of organic N in most plant species, amino acids synthesized in leaves or derived from roots are transported via phloem to developing sink organs to meet their N requirement [3].

Detailed explanation-4: -Transport of amino acids to sinks happens mainly via the phloem, and to achieve this, the leaf-synthesized N compounds are loaded into the phloem of the minor veins. In cases where amino acid synthesis occurs in roots, they are transported via the xylem with the transpiration stream, mainly to mature leaves.