Effect of ammonium: nitrate nutrient ratio on nitrate and glucosinolate contents of hydroponically-grown rocket salad (Eruca sativa Mill.)

Figures & data

Table 1 Composition of nutrient solutions for different NH4 : NO3 percent molar ratios (PMR-N) in a 10 mmol L−1 total hydroponic nutrition solution (mmol L−1)

Compound	PMR-N
	0	25	50	75	100
KCI	−	3	5	6	6
(NH4)2SO4	−	−	I	1	1
Ca(NO3)2	2	2	2	−	–
NaNO3	2	−	−	−	–
KNO3	4	1	1	−	−
NH4NO3	−	2.5	−	2.5	−
(NH4)3PO4·3H2O	−	−	1	I	1
CaCl2	−	−	−	2	2
MgSO4	1	1	−	−	−
MgCl2	−	−	1	1	1
K2HPO4	1	1	−	−	−
NH4Cl	−	−	−	−	5
Micronutrients^†	+	+	+	+	+
^†Micronutrients were the same for all treatments applied according to Hoagland type solutions (Hoagland and Arnon 1938).

Table 2 Effect of NH4 : NO3 percent molar ratios (PMR-N) on the growth of rocket salad

PMR-N	Height (cm)	Dry weight (g)
		Leaf	Root
0	25.5 ± 3.59ab^†	2.44 ± 0.30ab	0.22 ± 0.06ab
25	28.3 ± 2.04a	2.92 ± 1.04a	0.28 ± 0.08a
50	28.7 ± 0.77a	2.48 ± 0.29ab	0.22 ± 0.04ab
75	27.1 ± 2.63ab	2.58 ± 0.49ab	0.29 ± 0.08a
100	23.8 ± 1.71b	1.66 ± 0.13b	0.15 ± 0.02b
^†Within each column values followed by the same letters are not significantly different at P < 0.05 using Tukey's multiple range test. Values are mean ± standard deviation (n = 5).

Table 3 Effect of NH4 : NO3 percent molar ratios (PMR-N) on the nitrate and sulfate content (g kg−1 fresh weight) of rocket salad leaves and roots

PMR-N	Leaf		Root
	NO3	SO4	NO3	SO4
0	7.2 ± 0.66a^†	3.6 ± 0.27a	3.1 ± 0.05a	1.6 ± 0.15a
25	6.4 ± 0.47ab	3.5 ± 0.21a	2.2 ± 0.09b	1.4 ± 0.13a
50	6.1 ± 0.55b	3.1 ± 0.19b	1.8 ± 0.14b	1.1 ± 0.09b
75	2.9 ± 0.26c	2.6 ± 0.27c	1.0 ± 0.09c	0.9 ± 0.06b
100	0.5 ± 0.04d	1.7 ± 0.13d	0.5 ± 0.05d	0.7 ± 0.03c
^†Within each columm values followed by the same letters are not significantly different at P < 0.05 using Tukey's multiple range test. Values are mean ± standard deviation (n = 5).

Table 4 Structures and names of glucosinolates (GSLs) isolated from rocket salad

No.^†	Structure of side chain (R)-groups	Semisystematic name	Trivial name	Response factor^‡
1	Unknown^§	−	−	1.00^¶
2	CH3-SO-CH2-CH2-CH2-CH2-	Dimeric 4-metbylsulfinylbutyl GSL	Glucoraphanin	1.07
3	C6H11O5-S-S-(CH2)4-	4-(β-D-glucopyranosyldisulfanyl)butyl GSL	−	1.00^¶
4	CH3-S-CH2-CH2-CH2-CH2-	4-Methylthiobutyl GSL	Glucoerucin	1.00^¶
5	Indole-3-CH2-	Indolyl-3-methyl GSL	Glucobrassicin	0.29
6	{-(CH2)4-S-S-(CH2)4-}	dimeric 4-mercaptobutyl GSL	−	1.00^¶
7	Indole-4-OCH3-	4-Metboxyindolyl-3-methyl GSL	4-Methoxyglucobrassicin	0.25
^†Elation order of GSL from high-pressure liquid chromatography profiles.
^‡The International Organization for Standardization (ISO 9167-1, 1992).
^§Unknown has not yet been identified, but showed an electrospray ionization mass spectrometry-based molecular weight of m/z 414 as desulfo-GSL.
^¶Not yet decided by the ISO.

Table 5 Effect of NH4 : NO3 percent molar ratios (PMR-N) on individual and total glucosinolate (GSL) content (g kg−1 dry weight) in the leaves and roots of rocket salad

Plant part	PMR-N	GSL							Total GSL
		Unknown A	GRA	4GPdB	GER	GBS	d4MCB	4MGB
Leaf	0	ND	2.96 ± 0.18b^†	1.84 ± 0.20ab	3.75 ± 0.18b	0.04 ± 0.00c	2.24 ± 0.14b	0.12 ± 0.02b	11.0 ± 0.28b
	25	ND	3.36 ± 0.11b	1.39 ± 0.20cd	3.99 ± 0.53ab	0.03 ± 0.00d	2.36 ± 0.43b	0.09 ± 0.00c	11.2 ± 1.14b
	50	ND	4.38 ± 0.42a	1.63 ± 0.131bc	4.38 ± 0.23ab	0.04 ± 0.00c	2.23 ± 0.09b	0.11 ± 0.01bc	12.8 ± 0.54a
	75	ND	2.46 ± 0.08c	1.94 ± 0.07a	4.58 ± 0.55a	0.05 ± 0.00b	3.10 ± 0.36a	0.11 ± 0.0lbc	12.2 ± 0.7ab
	100	0.74 ± 0.01	2.18 ± 0.21c	1.24 ± 0.11d	2.21 ± 0.15c	0.12 ± 0.01a	2.00 ± 0.17b	0.19 ± 0.02a	8.7 ± 0.38c
Root	0	ND	6.19 ± 0.58a	0.46 ± 0.04c	36.3 ± 4.88a	0.06 ± 0.01b	5.12 ± 0.56c	ND	48.1 ± 5.76a
	25	ND	5.43 ± 0.70ab	0.50 ± 0.051bc	36.7 ± 4.06a	0.05 ± 0.00bc	5.60 ± 0.43bc	ND	48.3 ± 4.76a
	50	ND	4.62 ± 0.50b	0.41 ± 0.04c	22.6 ± 3.52b	0.03 ± 0.00c	3.42 ± 0.32d	ND	31.1 ± 3.99b
	75	ND	4.96 ± 0.68b	0.67 ± 0.09a	34.9 ± 3.01a	0.08 ± 0.01a	7.75 ± 1.17a	ND	48.4 ± 4.61a
	100	0.73 ± 0.10	2.93 ± 0.42c	0.63 ± 0.13ab	20.4 ± 5.75b	0.09 ± 0.02a	7.15 ± 1.22ab	ND	31.9 ± 7.50b
Within each column values followed by the same letters are not significantly different at P < 0.05 using Tukey's multiple range test. Values are mean ± standard deviation (n = 5). GRA, glucoraphanin; 4GPdB, 4-(B-D-glucopyranosyldisulfanyl) butyl GSL; GER, glucorucin; GBS, Glucobrassicin; d4MCB, dimeric 4-mercaptobutyl, GSL; 4MGB, 4-methoxyglucobrassicin; ND, not detected.

Hoagland , DR and Arnon , DI . 1938 . The Water Culture Method for Growing Plants Without Soil , Berkley : California Agric Expt Sta . Circ 347

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