Amendment of hydroponic nutrient solution with humic acid and glutamic acid in tomato (Lycopersicon esculentum Mill.) culture

Figures & data

Table 1  Nutrient solution* for tomato (Lycopersicon esculentum Mill.) planted in soilless media

Component	Dosage (g 1000 L^−1)
Ca(NO3)2·4H2O	978.6
KNO3	525
KH2PO4	200
MgSO4·7H2O	250
EDTA NaFe	9.83
MnSO4·H2O	1.99
H3BO3·H2O	2.43
ZnSO4·7H2O	0.498
CuSO4·5H2O	0.187
Na2MOO4·2H2O	0.09
*Recipe used by Chinese scientists in Zheijang University. Ca(NO3)2·4H2O, calcium nitrate; KNO3, potassium nitrate; KH2PO4, monopotassium phosphate; MgSO4·7H2O, magnesium sulphate; EDTA NaFe, sodium iron ethylenediaminetetraacetic acid; MnSO4·H2O, manganese sulphate; H3BO3·H2O, boric acid; ZnSO4·7H2O, zinc sulphate; CuSO4·5H2O, copper sulphate; Na2MOO4·2H2O, sodium molybdate.

Table 2  The composition of humic acid (HA) extracted from a humified forest soil (measured per 100 g)

Composition	Dosage
N% (dry matter)	0.571
P% (dry matter)	0.034
Water content (%)	16.043
pH	4.5 ± 0.5
N, nitrogen; P, phosphorus.

Table 3  Effect of glutamic acid (GA) and humic acid (HA) on protein, nitrate (NO₃), sugar content and titratable acidity of tomato (Lycopersicon esculentum Mill.)

Treatments	Yield (g plant^−1)	Protein (µg g^−1)	NO3 (nmol NO3 g^−1 FW min^−1)	Sugar content (°Brix)	Titratable acidity (%)
NS	2019.12 ± 56.05 c	1.37 × 10^−3 ± 4 × 10^−4 c	2.98 ± 0.11 a	2.36 ± 0.50 b	0.049 ± 0.001 a
HA1	2013.64 ± 8.78 c	1.52 × 10^−3 ± 1 × 10^−4 bc	2.94 ± 0.90 a	2.53 ± 0.04 b	0.050 ± 0.017 a
HA2	2412.48 ± 39.11 bc	1.77 × 10^−3 ± 4 × 10^−4 bc	2.02 ± 0.10 a	2.68 ± 0.50 b	0.048 ± 0.017 a
GA	2522.81 ± 28.31 bc	7.15 × 10^−3 ± 4 × 10^−3 a	2.99 ± 0.10 a	3.48 ± 0.10 a	0.042 ± 0.002 a
HA1 + GA	2939.69 ± 84.90 ab	6.77 × 10^−3 ± 5 × 10^−3 ab	2.03 ± 0.90 a	3.40 ± 0.20 a	0.044 ± 0.006 a
HA2 + GA	3311.08 ± 40.47 a	9.26 × 10^−3 ± 4 × 10^−3 a	2.06 ± 0.10 a	3.53 ± 0.10 a	0.051 ± 0.005 a
Within each column, means ± standard deviation followed by the same letter are not significantly different at P < 0.05 according to the Least Significant Difference test. NS, nutrient solution.

Table 4  Effect of glutamic acid (GA) and humic acid (HA) on superoxide dismutase (SOD) and peroxidases (POD) activity and amount of malondialdehyde (MDA) in tomato (Lycopersicon esculentum Mill.)

Treatments	SOD activity (U/mg FW)	MDA content (nmol/g)	POD activity (U/g FW/min)
NS	137.40 ± 14.9 a	8.36 × 10^−4 ± 1.5 × 10^−4 ab	0.37 ± 0.3 a
HA1	119.02 ± 34.26 a	7.76 × 10^−4 ± 1.3 × 10^−4 ab	0.34 ± 0.8 a
HA2	137.23 ± 26.29 a	6.55 × 10^−4 ± 4.6 × 10^−4 ab	0.41 ± 0.4 a
GA	129.22 ± 42.80 a	3.85 × 10^−4 ± 4.8 × 10^−4 b	0.46 ± 0.4 a
HA1 + GA	103.29 ± 23.94 a	5.97 × 10^−4 ± 1.8 × 10^−4 ab	0.40 ± 0.5 a
HA2 + GA	128.41 ± 24.90 a	1.08 × 10^−4 ± 4.0 × 10^−4 a	0.51 ± 0.5 a
Within each column, means ± standard deviation followed by the same letter are not significantly different at P < 0.05 according to the Least Significant Difference test. NS, nutrient solution; FW, fresh weight.

Table 5  Effect of glutamic acid (GA) and humic acid (HA) on photosynthesis rate and chlorophyll content of tomato (Lycopersicon esculentum Mill.)

Treatments	Photosynthesis 1* (µmol CO2 m^−2 s^−1)	Photosynthesis 2** (µmol CO2 m^−2 s^−1)	Chlorophyll (SPAD value)
NS	2.2 ± 1.15 c	9.9 ± 0.86 c	36.3 ± 2.23 c
HA1	8.1 ± 1.02 b	11.6 ± 1.0 b	36.4 ± 2.45 c
HA2	11.8 ± 0.93 ab	13.3 ± 1.13 ab	37.9 ± 1.98 c
GA	9.6 ± 2.01 b	11.0 ± 0.7 bc	35.5 ± 2.00 c
HA1 + GA	12.2 ± 1.02 a	11.9 ± 0.65 b	49.1± 1.81 b
HA2 + GA	12.7 ± 1.10 a	14.6 ± 1.06 a	64.1 ± 2.08 a
Within each column, means ± standard deviation followed by the same letter are not significantly different at P < 0.05 according to the Least Significant Difference test. *Photosynthesis 1 = photosynthesis during the vegetative stage. **Photosynthesis 2 = photosynthesis during the reproductive stage. NS, nutrient solution; CO2, carbon dioxide.

Table 6  Effect of glutamic acid (GA) and humic acid (HA) on stomatal and mesophyll conductance, transpiration and photosynthetic water use efficiency (PWUE) of tomato (Lycopersicon esculentum Mill.)

Treatments	Stomatal conductance (mmol CO2 m^−2 s^−1)	Transpiration (mmol m^−2 s^−1)	Mesophyll conductance (mmol CO2 m^−2 s^−1)	PWUE (µmol CO2 m^−2 s^−1)
NS	0.56 ± 0.13 a	31.62 ± 0.71 a	25 × 10^−3 ± 1.0 × 10^−4 c	18.24 ± 4.32 a
HA1	0.71 ± 0.30 a	31.67 ± 0.61 a	29 × 10^−3 ± 2.0 × 10^−3 b	17.72 ± 3.68 a
HA2	0.64 ± 0.29 a	31.73 ± 0.56 a	28 × 10^−3 ± 1.0 × 10^−4 bc	18.68 ± 4.02 a
GA	0.58 ± 0.13 a	31.77 ± 0.68 a	28 × 10^−3 ± 1.0 × 10^−4 bc	18.92 ± 3.97 a
HA1 + GA	0.58 ± 0.19 a	31.82 ± 0.58 a	30 × 10^−3 ± 1.0 × 10^−4 b	18.21 ± 3.75 a
HA2 + GA	0.70 ± 0.12 a	31.87 ± 0.60 a	37 × 10^−3 ± 1.0 × 10^−4 a	19.71 ± 3.78 a
Within each column, means ± standard deviation followed by the same letter are not significantly different at P < 0.05 according to the Least Significant Difference test. NS, nutrient solution; CO2, carbon dioxide.