Table 3.

Equations and R² of linear regression between plant fresh weight and total root surface area of root-flooded A. philoxeroides subjected to nutrient and dissolved oxygen treatments (n = 10).

Treatment		Regression equation	R2	Significance of difference between line slopes
Nutrient level	5%	Y = 0.033X + 1.89	0.61	a
	50%	Y = 0.078X + 1.62	0.87	b
	100%	Y = 0.090X + 1.23	0.89	b
Dissolved oxygen level	5%	Y = 0.162X + 1.28	0.94	a
	50%	Y = 0.142X + 1.32	0.65	a
	100%	Y = 0.115X + 1.23	0.87	b

The set-up of nutrient and dissolved oxygen levels was the same as that in Table 1. The difference between slopes of regression lines was investigated by stepwise regression, with plant fresh weight as dependent variable and total root surface area, treatment level, and the interaction between total root surface area and treatment level as independent variables. The significance of difference between line slopes is indicated by different lowercase letters (P < 0.05).