Types of systemic Fungicides and Definitions

Systemics (also called penetrants) are absorbed into plants. Some systemics move very short distances from the site of application, such as across a leaf blade from one surface to the other (local systemic or translaminar). Some fungicides are weakly systemic and can move further from the application site than local systemics. Most systemics move more extensively because they are mobile in xylem tissue. When applied to the root zone, these are absorbed by roots and then move upward through the plant with the transpiration stream (xylem-mobile systemic). Xylem-mobile systemics applied to leaves move throughout the leaf where deposited, but cannot be redistributed out of that leaf; however, any material deposited on stems can move upwards into leaves. Phloem-mobile systemics (also known as "true" or amphimobile systemics) have bi-directional mobility, some material moves in phloem out of the leaf where deposited upwards to other leaves and downwards to roots. Systemics cannot move again after translocation.
Phosphonates belongs to PMS ( Phloem-mobile systemics)have bi-directional mobility, when applied to leafe it can move to roots and if we applied to roots  it can move to leafe . ,SO IT is very effective for foliar spray aswell as rooting also 
source -- apsnet