Table 4.

Effect of nitrate deprivation at different days before harvest (DBH) on SPAD index and maximum quantum use efficiency of PSII (F_v/F_m) in dark-adapted state of cardoon plants (Cynara cardunculus L. var. altilis DC) harvested at different days after sowing (DAS); cardoon plants were grown in a floating system under greenhouse conditions (Experiment 2).

Nitrate deprivation	SPAD index			Fv/Fm
DBH	59 DAS	97 DAS	124 DAS	59 DAS	97 DAS	124 DAS
0	28.5	32.6	34.7	0.80	0.84	0.83
5	25.4	34.2	33.5	0.81	0.84	0.83
10	27.1	36.5	30.8	0.81	0.84	0.83
15	25.4	33.7	28.0	0.77	0.84	0.83
Significance	NS	NS	L***	NS	NS	NS

L, linear; NS, non-significant; ***P < 0.001.