Table 4 Interaction of light spectra and stress (salinity and alkalinity) on leaf color parameters [a* indicates the position on the green–red axis (− greenness to + redness), and b* represents the position on the blue–yellow axis (− blueness to + yellowness)] and pigments of two lettuce cultivars.

0.94 ± 0.042^a

0.56 ± 0.02^a

1.51 ± 0.06^a

0.59 ± 0.011^b

222.6 ± 4.1^c

225.6 ± 9.9^k

16.3 ± 1.2^gh

0.82 ± 0.045^b

0.50 ± 0.01^bc

1.33 ± 0.10^b

0.51 ± 0.075^d

173.6 ± 0.6^c

618.6 ± 8.5^d

29.3 ± 1.5^bc

0.70 ± 0.038^c

0.47 ± 0.03^c

1.15 ± 0.09^c

0.51 ± 0.016^c

121.6 ± 2.9^g

675.0 ± 8.0^c

27.6 ± 1.2^cd

0.88 ± 0.041^b

0.54 ± 0.02^ab

1.42 ± 0.06^ab

0.66 ± 0.057^a

275.3 ± 5.1^a

212.3 ± 6.4^kl

17.3 ± 1.1^fgh

0.53 ± 0.035^e

0.33 ± 0.06^ef

0.87 ± 0.07^ef

0.35 ± 0.005^de

136.6 ± 2.1^f

302.6 ± 3.5^h

31.6 ± 1.5^a

0.62 ± 0.039^d

0.35 ± 0.06^ef

0.98 ± 0.05^d

0.37 ± 0.20^de

105.6 ± 9.2^h

769.0 ± 7.4^a

19.0 ± 0.1^f

0.45 ± 0.033^f

0.25 ± 0.04^h

0.71 ± 0.03^g

0.20 ± 0.109^fg

98.6 ± 2.4^h

202.6 ± 6.5^l

16.6 ± 0.6^gh

0.37 ± 0.031^g

0.19 ± 0.03^ij

0.56 ± 0.02^hi

0.22 ± 0.006^fg

80.0 ± 3.5^ij

204.0 ± 4.6^l

19.0 ± 1.0^f

0.25 ± 0.030^h

0.15 ± 0.02^jk

0.40 ± 0.06^j

0.15 ± 0.005^h

71.2 ± 7.7^jk

275.3 ± 6.1ⁱ

17.3 ± 1.1^fgh

0.57 ± 0.037^de

0.39 ± 0.02^d

0.97 ± 0.05^de

0.41 ± 0.004^d

265.3 ± 8.5^a

349.6 ± 8.1^g

22.0 ± 1.0^e

0.63 ± 0.028^d

0.37 ± 0.05^de

0.90 ± 0.06^def

0.37 ± 0.027^de

165.6 ± 5.3^e

594.3 ± 7.9^e

30.3 ± 0.6^ab

0.55 ± 0.036^e

0.26 ± 0.03^gh

0.92 ± 0.11^def

0.36 ± 0.039^de

249.3 ± 7.7^b

699.3 ± 8.5^b

27.4 ± 1.8^cd

0.53 ± 0.035^e

0.30 ± 0.04^fg

0.84 ± 0.03^f

0.33 ± 0.022^e

197.3 ± 4.6^d

250.6 ± 5.5^j

18.0 ± 1.2^g

0.36 ± 0.032^g

0.23 ± 0.02^hi

0.60 ± 0.06^h

0.23 ± 0.024^f

131.6 ± 2.9^fg

560.3 ± 9.9^f

27.6 ± 0.6^cd

0.28 ± 0.030^h

0.19 ± 0.01^ij

0.48 ± 0.02^ij

0.18 ± 0.005^fg

92.6 ± 1.5^hi

597.6 ± 8.3^e

26.1 ± 0.2^d

0.26 ± 0.029^h

0.16 ± 0.01^h

0.43 ± 0.03^j

0.16 ± 0.012^fgh

73.3 ± 2.1^jk

141.0 ± 3.0^m

13.0 ± 0.1ⁱ

0.28 ± 0.031^h

0.16 ± 0.02^j

0.44 ± 0.01^j

0.17 ± 0.019^fgh

33.0 ± 2.6^l

143.0 ± 1.0^m

21.3 ± 1.5^e

0.18 ± 0.028ⁱ

0.11 ± 0.02^k

0.29 ± 0.03^k

0.11 ± 0.003^h

58.6 ± 2.3^k

289.0 ± 6.9^hi

13.3 ± 0.5ⁱ