Table 6.

Linear regression analysis between SPAD values and NNI at different leaf positions.

Cultivars	1LFT		2LFT		3LFT		4LFT		5LFT		Average SPAD
	R2	RMSE	R2	RMSE	R2	RMSE	R2	RMSE	R2	RMSE	R2	RMSE
NG46_1	0.45(1)	0.18	0.66	0.14	0.77	0.12	0.74	0.13	0.77	0.12	0.77	0.12
NG46_2	0.68	0.11	0.79	0.08	0.79	0.09	0.74	0.09	0.80	0.09	0.83	0.08
NG46_3	0.57	0.11	0.61(a)	0.10	0.65(a)	0.09	0.61(1)	0.10	0.67	0.09	0.68	0.09
WYG35	0.29(1)	0.13	0.29(a)	0.13	0.35(a)	0.13	0.38(a)	0.12	0.43	0.12	0.43	0.12
NG5055	0.68	0.11	0.80	0.09	0.81	0.08	0.74	0.09	0.78	0.09	0.84	0.08
J67	0.76	0.09	0.90	0.06	0.88	0.06	0.85	0.07	0.79	0.08	0.91	0.06
XS14	0.31(1)	0.13	0.56(a)	0.10	0.58	0.10	0.37(1)	0.12	0.27(1)	0.14	0.47(1)	0.11
JH218	0.46	0.12	0.64	0.10	0.81	0.07	0.68	0.09	0.81	0.07	0.81	0.07
YG13	0.47	0.06	0.69	0.05	0.67	0.05	0.53(1)	0.05	0.67	0.05	0.68	0.05
CY5	0.54(1)	0.06	0.57(1)	0.06	0.61(1)	0.06	0.60(1)	0.06	0.71(a)	0.06	0.64(1)	0.05
CY6	0.48	0.14	0.78	0.10	0.80	0.09	0.63	0.12	0.77	0.10	0.79	0.09
JYZK6	0.56(1a)	0.19	0.54(1)	0.18	0.52(1)	0.19	0.52(1a)	0.19	0.56(1)	0.18	0.54(1)	0.19
HHZ	0.62	0.13	0.60	0.13	0.60	0.13	0.62	0.13	0.50(a)	0.15	0.62	0.13
MXXZ	0.77	0.10	0.80	0.09	0.87	0.07	0.61(a)	0.13	0.63	0.13	0.79	0.10
TY398	0.59(b)	0.10	0.67(a)	0.09	0.66	0.09	0.68	0.09	0.39(1)	0.14	0.68	0.09
TYXZ	0.60	0.13	0.78	0.10	0.91	0.06	0.83	0.09	0.90	0.07	0.90	0.07
TYHZ	0.59	0.10	0.59(a)	0.10	0.64(a)	0.09	0.65	0.09	0.37(1)	0.13	0.61	0.10
Mean	0.55	0.12	0.66	0.10	0.70	0.09	0.63	0.10	0.64	0.11	0.70	0.09

The R² and RMSE values for each cultivar represent the averages of regression analyses conducted separately across different growth stages. Numbers in parentheses indicate the number of growth stages where the regression coefficients for that cultivar are not statistically significant. The letters ‘a’ or ‘b’ indicate that the regression coefficients for one or two growth stages, respectively, are significant at the 0.1 level. All other unmarked regression models have coefficients that are significant at the 0.05 level.