Table 2.

Effect of short-term nighttime supplemental LEDs to HPS lighting on phenolic compounds content in lettuce cultivated in a greenhouse during different seasons.

Phenolic Compounds	Lighting												Source of Variance
	HPS		400 nm		455 nm		455 + 530 nm		530 nm		660 nm		L	S	L ×S
	Spring	Autumn	Spring	Autumn	Spring	Autumn	Spring	Autumn	Spring	Autumn	Spring	Autumn
Caffeic a.	0.222 b	0.036 ef	0.217 b	0.043 e	0.269 a	0.018 ef	0.116 d	0.039 e	0.181 c	0.098 d	0.180 c	0.009 f		*	*
Chicoric a.	4.47 b	0.28 e	2.40 d	0.40 e	3.65 c	0.08 e	5.42 a	0.37 e	1.78 d	0.29 e	1.89 d	0.13 e		*	*
Chlorogenic a.	2.59 b	1.11 de	1.39 d	2.15 c	2.04 c	0.33 f	5.08 a	1.44 d	1.25 d	1.12 de	2.01 c	0.80 e	*	*	*
Gallic a.	0.059 a	0.012 f	0.030 cd	0.036 bc	0.026 cde	0.016 def	0.049 ab	0.013 ef	0.044 b	0.009 f	0.027 cd	0.017 def		*	*
o-coumaric a.	0.303 ab	0.190 bc	0.043 c	0.382 a	0.070 bc	0.035 c	0.087 bc	0.047 c	0.035 c	0.115 bc	0.036 c	0.067 bc	*		*
p-coumaric a	0.021 ab	0.005 ab	0.021 ab	0.027 ab	0.025 ab	0.005 ab	0.052 a	0.003 b	0.024 ab	0.003 b	0.038 ab	0.004 ab		*	*
Protocatechuic a.	0.210 a	0.012 d	0.122 bc	0.022 d	0.101 c	0.013 d	0.148 b	0.019 d	0.098 c	0.022 d	0.156 b	0.029 d		*	*
Rosmarinic a.	0.098 de	0.006 e	0.723 c	0.015 e	1.153 b	0.007 e	2.318 a	0.005 e	0.453 cd	0.006 e	0.771 c	0.006 e		*	*
Apigenin	0.390 b	0.010 e	0.428 b	0.051 e	0.255 cd	0.044 e	0.597 a	0.010 e	0.298 c	0.009 e	0.196 d	0.061 e		*	*
Epicatechin	0.493 a	0.095 bcd	0.088 cd	0.056 d	0.132 bc	0.050 d	0.146 b	0.067 d	0.480 a	0.078 d	0.143 b	0.050 d	*	*	*
Kaempferol	0.012 bc	0.002 de	0.012 bcd	0.005 cde	0.014 b	0.003 cde	0.016 b	0.004 cde	0.012 bc	0.001 e	0.031 a	0.002 e		*	*
Myricetin	0.031 abcd	0.027 bcd	0.027 bcd	0.052 a	0.029 bcd	0.017 cd	0.036 abc	0.014 d	0.045 ab	0.011 d	0.020 cd	0.015 d			*
Quercetin	0.025 ab	0.005 d	0.018 c	0.005 d	0.017 c	0.005 d	0.019 bc	0.006 d	0.029 a	0.005 d	0.023 abc	0.005 d		*	*
Rutin	0.179 f	2.809 c	0.041 f	5.101 a	0.062 f	1.299 e	0.091 f	3.390 b	0.053 f	2.478 cd	0.027 f	2.187 d		*	*
Total	9.11 b	4.59 ef	5.56 d	8.35 bc	7.85 c	1.92 g	14.17 a	5.43 d	4.78 de	4.24 ef	5.55 d	3.38 f	*	*	*

L—lighting; S—seasons; a.—acid. Individual phenolic compound content is presented as mg g⁻¹ in dry plant matter. Means with different letters (based on heatmapvalues with the same letters on a separate line are marked with the same color) are significantly different at the p < 0.05 level by Tukey’s honestly significant difference test (*).