Physiological Responses to Nutrient Accumulation in Trees Seedlings Irrigated with Municipal Effluent in Indian Desert

Table 4

Regression equations^∗ between mineral element concentrations and net photosynthesis rate, transpiration rate, stomatal conductance, and instantaneous water use efficiency as the dependent variables and mineral concentrations as independent variables.

Variable	Equation	𝑎0	𝑏1	𝑏2	𝑏3	𝑅^2	SE	𝐹 value	𝑃 value
Rate of photosynthesis (𝑃𝑁)
N	Logarithm	−8.62930	3.97209	—	—	0.5319	0.7837	28.40	0.000
P	Sigmoid	1.69905	−0.23188	—	—	0.3166	0.2094	11.58	0.002
Ca	Cubic	12.29345	−2.00749	0.14362	−0.0031	0.3759	0.9434	4.62	0.011
Mg	Sigmoid	1.75381	−1.10272	—	—	0.1790	0.2295	5.45	0.027
Na	Quadratic	−8.92904	12.89990	−2.77332	—	0.7060	0.6338	28.82	0.000
Fe	Quadratic	−5.02941	0.01869	−0.00001	—	0.5924	0.7464	17.43	0.000
Mn	Inverse	5.97239	−1.44654	—	—	0.4325	0.8629	19.05	0.000
Zn	Power	1.25817	0.33138	—	—	0.1712	0.2306	5.16	0.031
K/N	Compound	6.71215	0.50522	—	—	0.1710	0.2306	5.16	0.032
Fe/Mn	Inverse	4.07304	2.71389	—	—	0.1638	1.0474	4.90	0.036
Rate of transpiration (E)
N	Linear	0.16705	0.09866	—	—	0.5111	0.5815	26.13	0.000
P	Cubic	0.85675	3.25457	−1.13713	0.1113	0.3623	0.6823	4.36	0.014
K	Sigmoid	1.45824	−6.13854	—	—	0.1242	0.2677	3.55	0.071
Ca	Cubic	12.73548	−2.24278	0.14900	0.002986	0.5185	0.6016	8.25	0.000
Mg	Sigmoid	1.45201	−1.17157	—	—	0.3397	0.2325	12.86	0.001
Na	Quadratic	−5.60495	7.83469	−1.57456	—	0.7883	0.3901	44.80	0.000
Fe	Sigmoid	1.96642	−729.363	—	—	0.6725	0.1637	51.33	0.000
Cu	Cubic	13.22883	−0.68615	0.01381	−0.000084	0.2865	0.7323	3.08	0.047
Mn	Inverse	4.01221	−108.593	—	—	0.4637	0.6090	21.61	0.000
Zn	Compound	1.86315	1.00904	—	—	0.2454	0.2485	8.13	0.008
Fe/Mn	Inverse	2.58987	2.01328	—	—	0.1711	0.7571	5.16	0.032
Zn/Mn	Inverse	2.68570	0.07460	—	—	0.1564	0.7638	4.63	0.041
Stomatal conductance (𝑔s)
N	Compound	28.39680	1.01473	—	—	0.1622	0.2003	4.83	0.037
Na	Sigmoid	4.24489	−0.79956	—	—	0.2381	0.1910	7.81	0.009
Fe	Sigmoid	4.08435	−256.357	—	—	0.1420	0.2027	4.14	0.052
Mn	Sigmoid	3.9789	−22.8573	—	—	0.2967	0.1835	10.55	0.003
Instantaneous water use efficiency (WUE)
P	Linear	1.43590	0.04460	—	—	0.4673	0.0869	21.93	0.000
K	Compound	1.81403	0.98970	—	—	0.3293	0.0655	12.27	0.001
Ca	Compound	1.8993	0.98773	—	—	0.3669	0.0636	14.49	0.000
Mg	Compound	1.76437	0.97289	—	—	0.6349	0.0483	43.48	0.000
Na	Compound	1.86695	0.89376	—	—	0.4765	0.0579	22.75	0.000
Fe	Compound	1.83373	0.99979	—	—	0.5011	0.0565	25.10	0.000
Cu	Compound	1.71655	0.99728	—	—	0.3036	0.0667	10.90	0.002
Zn	Compound	1.71518	0.99764	—	—	0.2151	0.0708	6.85	0.014
K/N	Inverse	1.28251	0.13853	—	—	0.2370	0.1039	7.76	0.010
Mg/Na	Cubic	0.41192	1.46011	−0.54740	0.0606	0.4673	0.0905	6.72	0.002
Fe/Mn	Quadratic	1.34984	0.09269	−0.00715	—	0.7007	0.0665	28.10	0.000
Zn/Mn	Cubic	1.30110	2.78703	−6.07910	3.5243	0.2924	0.1044	3.17	0.043
Mg/Mn	Cubic	1.30661	0.02323	−0.00047	0.000003	0.6924	0.0688	17.26	0.000

∗Nonsignificant (𝑃>0.05) relations have not been shown. 𝑎₀, 𝑏₁, 𝑏₂, and 𝑏₃ are regression constants. R ²: coefficient of determination and SE: standard error.