Table II.

Comparison of monoterpene content and monoterpene volatilization rate of peppermint shoots

ParameterMeasurement
Shoot monoterpene content
 Monoterpene content of average leaf (n = 50)658 ± 115 μg
 Average number of leaves per plant (n = 6)185 ± 66.9 leaves
 Monoterpene content of average stem (n = 50)2.78 ± 0.47 mg m−1
 Average length of total stems per plant (n = 6)3.59 ± 0.77 m
 Total shoot monoterpene content per plant = (Ia × Ib) + (Ic × Id)132 mg
Rate of monoterpene loss
 Average daytime volatilization rate per plant (n = 18)1.22 ± 0.64 μg h−1
 Average nighttime volatilization rate per plant (n = 6)1.73 ± 0.60 μg h−1
 Average monoterpene loss over 24-h period per plant = (IIa × 16) + (IIb × 8)33.4 μg
Percentage
 Total shoot monoterpenes volatilized per day = (IIc)/(Ie)0.025%
 Total shoot monoterpenes volatilized per month = (IIc × 30)/(Ie)0.759%

Measurements were performed on a set of six plants that were 6 weeks old, 25 cm tall, and had not yet begun to flower. Stored monoterpenes were extracted by soaking in diethyl ether and analyzed by gas chromatography. Volatiles were collected by headspace sorption from intact plants at 24°C (see “Materials and Methods” for details). Each plant was measured three times during the light period and once during the dark period for a span of 3 to 6 h at a time. All values are given as mean ± sd.