One hypothesis is that rootstock-induced vigour may be caused by signals such as water, nutrients, and especially hormones and nucleic acids that move through the graft union to affect scion growth. In support of this hypothesis, a significant number of mobile macromolecules can move through the vascular system。
Larger signalling molecules such as proteins or RNAs can also move through the graft union, and small differences in signal concentration or in their receptors/targets can alter gene expression and shoot growth
砧木当中的一些活性物质，蛋白质，RNA，等等会通过韧皮部从砧木运输到接穗从而影响接穗的生理生化等代谢活动，具体主要影响的方面如下：
| Primary metabolites | Amino acids |
| | Sugars |
| | Sugar Phosphates |
| | Organic acids |
| | Fatty acids |
| | Polyols |
| Secondary metabolites | Alkaloids |
| | Flavonoids |
| | Glucosinolates |
| | Isoprenes |
| | Oxylipins |
| | Phenylpropanoids |
| | Pigments |
| | Saponins |
| Phytohormones | Abscisic acid and derivatives |
| | Gibberellins (GA1, GA3, GA4) |
| | Cytokinins (tZ, ZR, iP) |
| | Auxins (IAA and other indoles) |
| | Jasmonic acid and methyl jasmonate |
| | Salicylic acid |
| | Ethylene precursor (ACC) |
| | Brassinosteroids |
| | Strigolactones |
Note：Biochemical groups of compounds in the primary and secondary metabolism, and phytohormones detected in the m/z range 85–900, susceptible to being transported in the xylem sapHigh-resolution mass spectrometry with Orbitrap technology was used to identify the metabolites by exact mass.
参考文献：
Unravelling rootstock×scion interactions to improve food security
