Table 1.
Summary of PPO activity and substrate concentration in the major forage species.
| Species | PPO activity1 | Substrate content2 | Typical substrate3 | References |
|---|---|---|---|---|
| Grasses | ||||
| Cocksfoot (Dactylis glomerata) | +++ | +/+++ | Hydroxycinnamates | Jones et al. (1995), Lee et al. (2006a), Marita et al. (2010), Parveen et al. (2010) |
| Hybrid ryegrass (L. pratensis × L. multiflorum) | ++ | + | Hydroxycinnamates | Lee et al. (2006a), Parveen et al. (2010) |
| Italian Ryegrass (Lolium multiflorum) | ++ | + | Hydroxycinnamates | Lee et al. (2006a), Parveen et al. (2010) |
| Maize (Zea mays) | ++ | + | Hydroxycinnamates | Harpaz and Klein (1964), Parveen et al. (2010) |
| Meadow fescue (Festuca pratensis) | + | + | Hydroxycinnamates | Jones et al. (1995), Marita et al. (2010), Parveen et al. (2010) |
| Perennial ryegrass (Lolium perenne) | ++ | + | Hydroxycinnamates | Jones et al. (1995), Lee et al. (2006a), Marita et al. (2010), Parveen et al. (2010) |
| Reed Canarygrass (Phalaris arundinacea L.) | + | + | Hydroxycinnamates | Jones et al. (1995), Marita et al. (2010) |
| Smooth bromegrass (Bromus inermis L.) | ++ | + | Hydroxycinnamates | Jones et al. (1995), Marita et al. (2010) |
| Tall Fescue (Festuca arundinacea) | + | + | Hydroxycinnamates | Jones et al. (1995), Lee et al. (2006a), Marita et al. (2010), Parveen et al. (2010) |
| Timothy (Phelum pratense) | + | + | Hydroxycinnamates | Lee et al. (2006a), Marita et al. (2010), Parveen et al. (2010) |
| Legumes | ||||
| Alfalfa (Medicago sativa) | – | – | – | Jones et al. (1995) |
| Birdsfoot trefoil (Lotus corniculatus) | – | + | NI | Jones et al. (1995) |
| Cicer milk vetch (Astagalus cicer) | – | + | NI | Jones et al. (1995) |
| Crown vetch (Coronilla varia) | – | + | NI | Jones et al. (1995) |
| Kura clover (Trifolium ambiguum) | – | + | NI | Jones et al. (1995) |
| Lespedeza (Lespedeza cuneata) | – | ++ | NI | Jones et al. (1995) |
| Red clover (Trifolium pratense) | +++ | +++ | Hydroxycinnamates, flavonols, flavones, isoflavones | Jones et al. (1995), Parveen et al. (2010), Lee et al. (2013) |
| Sainfoin (Onobrychis viciifolia) | – | + | NI | Jones et al. (1995) |
| White clover (Trifolium repens) | – | –/++ | Flavonols, flavones, isoflavones | Jones et al. (1995), Marita et al. (2010) |
1PPO activities are reported as a range of units across studies [ukatal/g DM, abs/g fresh weight (FW), U/g FW] so to compare here, activities are reported relative to the species with the lowest activity in each respective study (e.g., Alfalfa): +++ = High (×100+), ++ = Medium (×10), + = Low (higher than absence), – = absence of PPO (no difference to alfalfa).
2Substrate content are reported as a range of units across the studies (abs/g fresh weight, umol/g FW) so to compare here, substrates are reported relative to the species with the lowest level in each respective study (e.g., Alfalfa): +++ = High (×2+), ++ = Medium (×1.5), + = Low (above alfalfa), – = absence of PPO (no difference to alfalfa).
3Marita et al. (2010) and Parveen et al. (2010); NI, not identified; Hydoxycinnamates in grasses tend to be chlorogenic acid whereas in red clover phaselic acid and clovamide predominate.