3. Results
Ten bioactive phenolic acids or
flavonoids were detected in red
leaf lettuce during the experiment. Six compounds out of ten
changed in concentration significantly under blue light enhancement
(Table 2). Concentration of protocatechuic acid increased
during the
first 36 days (P < 0.05), but dropped then to the level of
plants under only the red-weighted treatment (i.e., zero days
under enhanced blue). There were no spectral responses in
chlorogenic acid, chlorogenic acid derivative and quercetin-
diglucoside concentrations. Quercetin-malonyldiglucoside concentrations
were highest in plants that experienced the longest
period of enhanced blue light (P < 0.05). Quercetin 3-malonyl-
glucoside increased as a function of extending the period under
enhanced blue light (P < 0.001). A similar response occurred in
concentrations of cichoric acid (P < 0.001). Cichoric acid derivative
remained stable for 24 days, but increased
finally when plants had
experienced enhanced blue light for 36 and 48 days (P < 0.01). The
response in quercetin rhamnoside was quite similar (P < 0.01).
Apigenin derivative was the only compound that displayed a
negative trend, although not statistically significant, for blue light
treatment.
Eight bioactive compounds in addition to two amino acids were
detected in the chromatograms of basil, where blue lightstimulated production of only two compounds (Table 3). Cichoric
acid and quercetin rhamnoside increased during the experiment
(P < 0.05). Many compounds showed a tendency, while nonsignificant,
to decrease from the second longest exposure (36 days)
to the longest exposure (48 day) of enhanced blue.
Measurements on chlorophyll
fluorescence ratio (Fv/Fm)
indicate that red leaf lettuce experienced no stress during the
experiment (Fig. 3). The ratio was generally slightly lower in basil,
although the difference was not statistically significant. Shoot
elongation of basil tended to decrease, while not significantly, as a
function of increased days under enhanced blue (Fig. 4).