Table 1.
Summary of the meta-analyses to answer four research questions about plant reliance on phenolic compound induction following insect feeding or microorganism colonization.
| Research question | Phenolic class | Inducer/Plant type | K | N | t | P | % change | CI lower | CI upper |
|---|---|---|---|---|---|---|---|---|---|
| Do phenolic levels increase in response to insects or microorganisms? | Total phenolics | All | 111 | 51 | 5.71 | <0.0001 | 45.37 | 27.42 | 65.83 |
| Insects | 25 | 12 | 3.94 | 0.0002 | 34.78 | 15.89 | 56.75 | ||
| Bacteria | 38 | 25 | 6.48 | <0.0001 | 56.14 | 36.00 | 79.25 | ||
| Fungi | 43 | 21 | 5.14 | <0.0001 | 41.67 | 23.61 | 62.34 | ||
| Oomycetes | 5 | 3 | 1.50 | 0.1400 | 46.64 | −12.25 | 145.05 | ||
| Flavonoids | All | 82 | 31 | 3.69 | 0.0010 | 57.32 | 22.26 | 102.43 | |
| Insects | 27 | 9 | 1.43 | 0.1581 | 27.66 | −9.34 | 79.75 | ||
| Bacteria | 24 | 16 | 3.39 | 0.0018 | 61.98 | 21.30 | 116.30 | ||
| Fungi | 22 | 9 | 5.90 | <0.0001 | 159.97 | 87.87 | 259.74 | ||
| Other Microbes | 9 | 6 | −0.19 | 0.8480 | −3.27 | −31.50 | 36.59 | ||
| Hydroxycinnamic acids | All | 51 | 18 | 4.13 | 0.0020 | 125.62 | 45.41 | 250.08 | |
| Insects | 27 | 8 | 1.74 | 0.0883 | 138.14 | 43.92 | 294.01 | ||
| Bacteria | 11 | 9 | 1.31 | 0.2074 | 121.49 | −38.50 | 697.73 | ||
| Fungi | 9 | 7 | 2.17 | 0.0415 | 91.94 | 2.80 | 258.37 | ||
| Other Microbes | 4 | 2 | 1.43 | 0.1688 | 83.42 | 32.13 | 344.51 | ||
| Do phenolic level changes differ depending on whether plants were colonized with beneficial microorganisms or pathogens? | Total phenolics | Beneficial Bacteria | 24 | 16 | 4.84 | <0.001 | 73.78 | 21.84 | 147.86 |
| Pathogenic Bacteria | 14 | 7 | 3.24 | 0.0039 | 78.21 | 39.21 | 128.12 | ||
| Beneficial Fungi | 15 | 8 | 4.96 | <0.0001 | 63.44 | 33.54 | 100.07 | ||
| Pathogenic Fungi | 28 | 18 | 1.71 | 0.1006 | 16.91 | −3.65 | 41.79 | ||
| Do phenolic level changes differ depending on how insects feed on plants? | Total Phenolics | Chewing Insects | 11 | 5 | 2.72 | 0.0272 | 60.46 | 7.17 | 140.25 |
| Piercing–Sucking Insects | 9 | 5 | −0.09 | 0.9297 | −1.70 | −36.91 | 53.16 | ||
| Wood-Boring Insects | 5 | 2 | −1.01 | 0.3385 | −24.88 | −60.47 | 42.78 | ||
| Do phenolic level changes differ whether infested/inoculated plants are annuals or perennials? | Total Phenolics | Annuals | 68 | 35 | 5.81 | <0.0001 | 72.86 | 31.80 | 126.73 |
| Perennials | 43 | 16 | 1.88 | 0.0662 | 38.85 | 5.15 | 83.33 | ||
| Flavonoids | Annuals | 51 | 20 | 4.12 | 0.0003 | 78.53 | 35.50 | 135.23 | |
| Perennials | 31 | 11 | 2.40 | 0.0220 | 42.28 | 7.22 | 88.78 | ||
| Hydroxycinnamic Acids | Annuals | 38 | 12 | 3.54 | 0.0060 | 126.42 | 34.61 | 280.80 | |
| Perennials | 13 | 6 | 1.65 | 0.1371 | 122.55 | −27.13 | 579.64 |
Meta-analyses number of case studies used in each category (K), number of corresponding articles (N), t-statistics, and p-values (P) are provided, as well as the mean percent change in phenolic levels in induced plants compared to controls [with 95% confidence intervals (CI)].