For the control medium variant (MT), the calli were cultivated for one month on solid medium NBMCo (N6 - macroelements, Chu, 1978; B5 - microelements, Gamborg, 1968; MS - vitamins, Murashige-Skoog, 1962) added with: 30 g/l saccharose; 7.0 g/l agar; without hormones; pH = 5.8.

For S1 the calli were treated with salt solution (5 g/l NaCl) for one hour, then cultivated on the same medium NBMCo for one month.

A₁ - the calli were taken over the solid medium variant A1 (1 mM ABA) where they were cultivated for one month.

M₂ - the calli were taken over the solid medium variant M2 (530 mM mannitol) where they were cultivated for one month.

The composition of the culture medium influences both the callus mass (m) and the quantity of amino acids. For the callus belonging to the genotype W 153R, the salt solution S1 causes both the diminution of the callus mass and a lower percentage content of amino acids. Levels of individual amino acids varied independently. The content of aspartic acid and tyrosine increased obviously and the content of threonine, glycine, and alanine diminished significantly. Other amino acids had little variation. On mannitol medium, although the callus mass is greater, the total content of amino acids is lower (4.39%), and the amino acids' relation with the control variant is very different. The proline was diminished, and glutamic acid, lysine and aspartic acid increased. ABA leads to a severe diminution of glutamic acid and to a slight increase of proline and arginine.

In the case of the hybrid genotype Lc 15 x L 649 the results show a different behaviour. The treatment with salt solution leads to a severe diminution of the callus mass, but the total content of amino acids is strikingly higher, and for each amino acid. At the same time, a modification of the relation between the amino acids can be observed, namely glutamic and aspartic acids diminish in comparison with the other amino acids, and lysine and proline levels increase. On the ABA medium there was a significant increase of proline and a diminution of aspartic acid in comparison with the other amino acids.

These results show that the metabolic response of the callus exposed to the stress factors (NaCl, abscisic acid and mannitol) is specific to the genotype.

Table 1. Modifications in the amino acid content of the callus obtained from immature maize embryos for an inbred line and a hybrid under stress conditions (S₁; A₁; M₂) (mg/100 g dry matter)
 

AMINO ACID	W 153R				Lc 15 x L 649
	MT m = 65.6 mg	S1 m = 51.9 mg	A1 m = 35.4 mg	M2 m = 92.9 mg	Mt m = 56.7 mg	S1 m = 26.6 mg	A1 m = 29.7 mg
ASPARTIC ACID	417.0	579.0	326.0	718.0	454.0	655.0	385.0
THREONINE	219.0	164.0	207.0	165.0	107.0	136.0	151.0
SERINE	183.0	171.0	198.0	152.0	108.0	145.0	230.0
GLUTAMIC ACID	1026.0	1048.0	690.0	808.0	801.0	892.0	824.0
PROLINE	168.0	159.0	272.0	117.0	167.0	416.0	520.0
GLYCINE	529.0	381.0	257.0	204.0	324.0	371.0	301.0
ALANINE	676.0	309.0	320.0	196.0	249.0	350.0	413.0
METHIONINE	119.0	131.0	142.0	76.0	121.0	131.0	85.0
VALINE	212.0	198.0	200.0	176.0	195.0	345.0	232.0
ISOLEUCINE	141.0	154.0	167.0	145.0	142.0	404.0	191.0
LEUCINE	204.0	188.0	223.0	215.0	200.0	388.0	262.0
PHENYLALANINE	670.0	710.0	287.0	408.0	502.0	552.0	384.0
TYROSINE	321.0	449.0	381.0	373.0	369.0	724.0	450.0
HISTIDINE	190.0	174.0	263.0	153.0	126.0	472.0	291.0
LYSINE	210.0	197.0	219.0	173.0	199.0	438.0	449.0
ARGININE	320.0	351.0	561.0	246.0	324.0	728.0	740.0
CYSTEINE	109.0	125.0	144.0	68.0	113.0	-	59.0
TOTAL AMINO ACIDS %	5.71	5.49	4.86	4.39	4.50	7.15	5.97
PRO/TAA %	2.94	2.90	5.60	2.66	3.71	5.82	8.71
GLU/TAA %	17.97	19.09	14.20	18.40	17.80	12.48	13.80
LYS/TAA %	3.68	3.59	4.51	3.94	4.42	6.13	7.88
ASP/TAA	7.31	10.55	6.71	16.34	10.08	9.16	6.0

PRO - proline; GLU - glutamic acid; LYS - lysine; ASP - aspartic acid; TAA - total amino acids; S1 - salt solution treatment (1h) - 5 g/l NaCl;
A₁ - 1 mM ABA solid medium; M2 - 100mM mannitol solid medium
 
 

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