Table 2 Effect of different concentrations of Put, CQDs and Put-CQD NPs on photosynthetic pigments and SPAD index ofVitis viniferacv. ‘Sultana’ under salinity stress (CQDs, carbon quantum dots; Put, putrescine, Put-CQD NPs, carbon quantum dots functionalized by putrescine nanoparticles). Different letters indicate significant differences based on Duncan’s post-hoc analysis at P ≤ 0.05

Treatments	Chla (mg g^− 1FW)	Chlb (mg g^− 1FW)	Carotenoids (mg g^− 1FW)	SPAD
NaCl (0 mM) + No Treatment	2.039 ± 0.05^ef	0.579 ± 0.002^cd	0.521 ± 0.003^e	26.86 ± 0.73^c
NaCl (0 mM) + Put 5 mg L^− 1	2.228 ± 0.02^c	0.657 ± 0.008^b	0.633 ± 0.012^bc	29.38 ± 0.83^ab
NaCl (0 mM) + Put 10 mg L^− 1	2.317 ± 0.12^bc	0.682 ± 0.011^ab	0.662 ± 0.009^b	29.91 ± 0.54^ab
NaCl (0 mM) + CQDs 5 mg L^− 1	1.797 ± 0.09^fg	0.538 ± 0.009^d	0.584±0.011^cd	28.13 ± 0.91^b
NaCl (0 mM) + CQDs 10 mg L^− 1	1.983 ± 0.01^ef	0.582 ± 0.023^cd	0.604 ± 0.013^c	25.83 ± 0.95^cd
NaCl (0 mM) + Put-CQD NPs 5 mg L^− 1	2.324 ± 0.08^b	0.697 ± 0.016^b	0.649 ± 0.008^bc	29.26 ± 0.38^ab
NaCl (0 mM) + Put-CQD NPs 10 mg L^− 1	2.426 ± 0.05^a	0.723 ± 0.008^a	0.721 ± 0.009^a	31.82 ± 0.77^a
NaCl (100 mM) + No Treatment	1.482 ± 0.12^h	0.357 ± 0.014^f	0.358 ± 0.007^f	19.63 ± 0.14^g
NaCl (100 mM) + Put 5 mg L^− 1	1.718 ± 0.07^fg	0.477 ± 0.021^e	0.597 ± 0.012^cd	21.7 ± 0.54^ef
NaCl (100 mM) + Put 10 mg L^− 1	1.891 ± 0.11^f	0.534 ± 0.016^d	0.612 ± 0.018^c	22.7 ± 1.12^e
NaCl (100 mM) + CQDs 5 mg L^− 1	1.686 ± 0.09^g	0.456 ± 0.009^e	0.523 ± 0.014^de	20.13 ± 0.82^fg
NaCl (100 mM) + CQDs 10 mg L^− 1	1.751 ± 0.08^fg	0.461 ± 0.015^e	0.542 ± 0.009^d	21.4 ± 0.61^f
NaCl (100 mM) + Put-CQD NPs 5 mg L^− 1	2.052 ± 0.01^e	0.596 ± 0.022^c	0.648 ± 0.019^bc	22.23 ± 1.24^ef
NaCl (100 mM) + Put-CQD NPs 10 mg L^− 1	2.141 ± 0.08^d	0.586 ± 0.008^cd	0.663 ± 0.008^b	24.2 ± 0.43^d