To capture biogenic volatile organic compounds, BVOCs, emitted from plants, the original analyzer for total ozone reactivity R_O3 was combined with the branch enclosure, BE, to establish the BE/R_O3 measurement system. The detection limit of the R_O3 emission factor E_RO3 was 3.6×10⁻⁷ s⁻² (300 s average, S/N=3). The BE/R_O3 was utilized to quantify R_O3 in the BVOC samples emitted from outside nursery plants for 50 consecutive 50 days. When Q.Serrata was analyzed, diurnal variation patterns with daytime peaks were observed during hot days. Especially, in extremely hot days, the R_O3 started to increase in the midmorning due to the high temperature. Relative variations of R_O3 roughly agreed with the G93-model prediction. Individual compounds of the BVOCs were also monitored several times and their fractions in R_O3 were evaluated. The total contributions of the unmeasured BVOCs to R_O3 were found to be significant. The temperature dependence of R_O3 in the Q.Serrata samples was evaluated and the temperature factor β was determined to be 0.12 K⁻¹. It was experimentally confirmed that β of the ambient R_O3 previously observed in the neighboring forest (0.23 K⁻¹) could be explained as a combination of the BVOCs from isoprene-emitting plants and those from large-β monoterpene-emitting plants.