## 4 Results
### Testing Synthetic Volatile Compounds  
To test the effect of the identified VCs by HS-SPME-GC-TOF-MS on rice seedling growth, rice seedlings were cultivated in non-contact exposure manners on filter paper that was stained with various volume of the four key compounds: 1-Octen-3-one, 3-octanone, 1-octen-3-ol, and 3-octanol (Supplementary Figure S2). The optimal dose rates of synthetic VCs were initially determined based on the protocol described by [PERSON] et al. (2022) [PERSON] et al. (2022), with minor modifications. Rice seedlings were cultivated in Magenta boxes filled with sterile culture soil, ensuring no direct contact with the synthetic compounds. The organic compound solutions were administered at varying doses (0 \(\upmu\)L [control], 0.1 \(\upmu\)L, 1 \(\upmu\)L, 5 \(\upmu\)L, and 10 \(\upmu\)L) by pipetting onto filter papers (1.2 \(\upmu\)m pore size, type RA; Nihon Millipore Kogyo K.K., Tokyo, Japan) placed on Petri dishes. The cultivation setup was housed in 3 L covered containers, and the seedlings were grown under a 27 \({}^{\circ}\)C 13 h light/23 \({}^{\circ}\)C 11 h dark cycle condition for 14 days. The organic compound solutions were resupplied 7 days after treatment started. For 3-octanone, the dry weight peaked at 1 \(\upmu\)L (46.2 \(\pm\) 5.89 mg), reflecting a 30.5% increase compared to the control (35.4 \(\pm\) 3.13 mg) (Figure 7A). The second highest dry weight occurred at 5 \(\upmu\)L (41.6 \(\pm\) 3.65 mg, +17.5%), while a decline was observed at 10 \(\upmu\)L (34.4 \(\pm\) 8.20 mg, \(-\)2.8%) (Figure 7A). The tallest plants were recorded at 1 \(\upmu\)L (37.0 \(\pm\) 3.25 cm, +10.1%) followed by 5 \(\upmu\)L (35.3 \(\pm\) 1.78 cm, +5.1%), whereas at 10 \(\upmu\)L, the height decreased slightly (33.4 \(\pm\) 2.90 cm, \(-\)0.8%) (Figure 7B). For root length, both 5 \(\upmu\)L and 10 \(\upmu\)L produced the longest roots (6.9 \(\pm\) 0.86 cm and 6.9 \(\pm\) 1.93 cm, +5.5%), with the control showing slightly shorter roots (6.5 \(\pm\) 2.02 cm) (Figure 7C). However, despite these numerical differences, none of these changes were statistically significant (\(p\) > 0.05), indicating that 3-octanone did not produce a statistically confirmed effect on the measured variables at the evaluated doses. For 3-octanol, the highest dry weight was observed at 0.1 \(\upmu\)L (39.8 \(\pm\) 8.04 mg, +48.5%), followed by 1 \(\upmu\)L (38.6 \(\pm\) 2.19 mg, +44.0%) (Figure 7D). At 10 \(\upmu\)L, the dry weight declined to 34.6 \(\pm\) 5.86 mg (+29.1%) (Figure 7D). Plant height was greatest at 1 \(\upmu\)L (30.7 \(\pm\) 0.88 cm, +17.1%), followed by 5 \(\upmu\)L (29.9 \(\pm\) 1.29 cm, +14.4%), but decreased at 10 \(\upmu\)L (29.8 \(\pm\) 2.71 cm, +13.8%) (Figure 7E). The longest root length was achieved at 1 \(\upmu\)L (9.1 \(\pm\) 0.68 cm, +15.4%), while the shortest occurred at 10 \(\upmu\)L (6.6 \(\pm\) 0.47 cm, \(-\)16.7%) compared to the control (7.9 \(\pm\) 1.54 cm) (Figure 7F). For 1-octen-3-one, the highest dry weight was at 1 \(\upmu\)L (45.8 \(\pm\) 9.76 mg, +97.4%), followed by 0.1 \(\upmu\)L (25.4 \(\pm\) 2.51 mg, +9.5%), while 10 \(\upmu\)L resulted in the lowest dry weight (20.4 \(\pm\) 2.51 mg, \(-\)12.1%) (Figure 7G). The tallest plants were recorded at 1 \(\upmu\)L (32.6 \(\pm\) 1.25 cm, +4.1%), with a sharp reduction at 10 \(\upmu\)L (18.3 \(\pm\) 1.96 cm, \(-\)41.5%) (Figure 7H). Root length showed minimal variation between the control and 0.1 \(\upmu\)L (both at 7.7 cm), but the shortest roots were at 10 \(\upmu\)L (7.0 \(\pm\) 0.78 cm, \(-\)9.1%) (Figure 7I). For 1-octen-3-ol, all treatments significantly inhibited growth and biomass (Figure 7I). The lowest dry weight was observed at 1 \(\upmu\)L (10.8 \(\pm\) 2.59 mg, \(-\)60.9%) compared to the control (27.6 \(\pm\) 2.51 mg) (Figure 7I). Similarly, plant height was severely reduced at 1 \(\upmu\)L (11.6 \(\pm\) 0.99 cm, \(-\)61.3%) relative to the control (30.0 \(\pm\) 2.15 cm) (Figure 7I).