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11
EFFECT OF SODIUM NITRATE ON ELEMENT TRANSLOCATION IN
TOMATO PLANTS
Mitova Ivanka Georgieva
Professor, Dr (PhD),
N.Poushkarov Institute of Soil Science, Agrotechnologies and Plant Protection,
Sofia, Bulgaria
Dinev Nikolai Slavov
Professor, DSc,
N.Poushkarov Institute of Soil Science, Agrotechnologies and Plant Protection,
Sofia, Bulgaria
ABSTRACT
A green house experiment with tomato plants and application of NaNO3 in increasing dose was carried out. Increased Na level led to enhanced penetration of Na into the above ground part of the plant and reduced access of N, K+, Ca2+, Mg2+, SO2, Cl and B to vegetative parts as well as of Cu and Fe- to fruit. Tomato plants can be successfully grown at Na concentration of about 650 mg/L, where the concentrations of the trace elements Mn, Cu, Fe and B are brought to the optimal. The results could be useful for investigations on soils with salinization process of degradation.
Keywords: tomato, sodium, trace elements, cation, anion
Introduction
The problem of whether Na+ can substitute K+ as a cation of N03+ in fertilizer application of green house grown tomatoes presents both academic and practical interest (Mitova and Dinev,2011; Stoicheva et al., 2011). Recent investigation on sodium applied at Na:K ratio of 1:8 to 1:32 increased the growth and yield of the tomato plant. (Idowu and Aduayi, 2007). The ions accumulation and balance were closely related to types of salts which were applied to. Under Na-salt stress, Na+, K+ and Cl- were the main osmolytes in both the roots and leaves, whereas K-salt stress decreased the contribution of Na+ and increased the contribution of K+ (Xiaoping Wangab et al., 2015). Investigations that salt stress increased the uptake of Na, Mg and chloride ions in tomato plants. Sodium reduced the uptake of potassium due to ion antagonism. Sulphate uptake in tomato plants was increased by salt application only under soil salinity Phosphate ion uptake was significantly reduced by salt stress( Ullah et al., 1994). Additionally, the cheapest fertlizer KCl, for instance, contains considerable amount of NaCl. This is why in
The sodium salt was used mainly for methodological considerations, namely, through its buffer proportion to be able to maintain pH of the nutrient solution within the limits of the optimum. After the ripening of the fruits of the first flower cluster, the plants were divided into two parts-upper, above the first flower cluster, and lower-below the first flower cluster. The content of the aggregate nitrogen, according to Kehldal, as well as the content of the air dry weight was determined in the leaves
Western country farming practices it is applied only on sugar beet, cabbage and barley. The choice of fertilizers is not so wide in our country. Besides, the issue is of environmental significance in relation to the irrigation water and manure. The investigation is necessary also due to the relatively wide distribution of saline soils. This degradation process covers about 40,000 ha (1% of cultivated area).
The aim of the study was to demonstrate the impact of growing nitrogen rates as NaNO3 on the tomato assimilation of major nutrient macro and trace elements
Material and methods
The experiment was conducted with growing rates of NaN03 as a source of nitrogen. The study has been done under glasshouse conditions with tomatoes of the variety "Triumph" in a sand culture, in vessels with a volume of 8 litres, in 6 repetitions. A Hogland - Arnon nutrient solution has been used together with an addition of increasing quantities of chemically pure salt of sodium nitrate (Table 1).
Table 1.
of these two parts of the plants and in the fruits from the first cluster. The macro and trace elements levels were determined in the leaves of the upper and lower parts of the plant (above and below the first flower cluster), and in the fruit picked from the first flower cluster. In order to clarify the relationships among the nutrient macro elements, their contents in the plants are presented in ionic form as cations, anions and their balance. The trace elements were determined according to ISO (ICP - AES-
Concentration of NaNO3 in Arnon- Hogland nutrient.
Variants NaNO3 Concentration (mg.l-1)
N NO3" Na
1 1275 210 930.75 344.25
2 1912 315 1395.6 516.4
3 2550 420 1861.5 688.5
4 3187.6 525 2326.95 860.65
5 3825.2 630 2794.4 1032.8
6 5100.0 840 3723.0 1377.0
ISO 22036:2008 and AAS (ISO 11047:1998) by Perkin-Elmer 2100).
Result and discussion
Trace elements can cause plant weight fluctuations without considerable changes in the ionic balance (according to Rinkis, 1979; Shkolnik, 1974; Sauchelli, 1989).
Potassium: Considerably higher K content was found in the
Sodium: Only the lowest rate of fertilizer treatment produced Na content within optimal limits. In the next treatment the Na level dramatically increased by about three times in the fruit and over five times in the leaves. The other treatments tested produced continuous growth in the Na concentration thus reaching in the sixth treatment 2.7% in the leaves and 0.84% in the fruit, i.e. 9-10 times higher level than after the first fertilizer treatment. The Na concentration in the leaves of the upper and the lower plant part was the same only in the first treatment. In all the successive treatments the lower located leaves had higher Na levels than the upper located and younger ones
Calcium: The Ca content was within optimal limits both in the leaves and the fruit. As expected it had higher concentration values in the lower leaves than in those in the upper part of the plant. With the growing NaO3 rate in the nutrient medium, however, the Ca level decreased. Thus while in the first treatment its content was 75% treatment its content went as low as 25% of the cation total amount.
Magnesium: The Mg content was closer to the lower limit of the optimal. Its concentration in the fruit was about twice higher than the Ca concentration and from 4 to 5 times lower than the K con-centration. The higher the NaNO3 level in the nutrient
tomato vegetative parts than in the fruit. The younger leaves in the upper part of the plant had a slightly higher content than the older leaves of the lower. The higher NaN03 level in the nutrient soluton provokes the lower K concentration both in the fruit as well as in the leaves. The decrease was greater in the older leaves than in the younger ones. Generally, the K content was within the optimal range being closer to the lower limit (Table 2).
solution the considerably reduced Mg level in the leaves. In the fruit, however, the Mg level remained constant. It was present in elevated concentrations in the leaves located in the lower part of the plant compared to the leaves of the upper part.
The cation sum of K+, Ca2+, Na+ and Mg2+ was the greatest in the lower part of the plants fol-lowed by that in the younger leaves in the upper part. In the fruit the cation amount was 3,5 -4 times lower than in the leaves. With the increase of the NaNO3 the cations in the leaves was continuously decreasing whereas in the fruit it decreased up to the third and fourth treatment and then started to rise again.
Content of anions
Nitrates: The nitrates level was on the whole lower than what is commonly accepted as the optimum for the leaves of the top part leaves and very slight in the fruit.
Sulphates: The sulphate content of the tomato plants was within optimal limits. It was markedly higher in the leaves of the lower part than in those in the upper part. The fruit contained between 2 to 4 times less sulphate than the leaves.
Phosphates: All the plants had lower than optimum levels of phosphates. There was almost no difference among the young and the old leaves and the fruit regarding the phosphorus content.
Table 2.
Cation and anion level in tomato plants in relation to the concentration of NaN03 in the nutrient solution
Variant Cations (mg/equ./kg DM'1) Anions (mg/equ./kg DM'1) Xc-Xa
К Na Mg Са Xc N03 Cl S04 H2PO, Xa
Leaves upper part above 1st flower cluster
1 946 130 550 2100 3726 151 450 264 78 943 2783
2 970 660 410 1850 3790 340 307 234 104 899 2824
3 796 850 345 1750 3741 362 217 216 104 860 2842
4 770 910 287 1650 3617 382 200 200 130 912 2705
5 742 995 235 1500 3472 405 175 136 130 846 2626
6 665 1120 197 1250 3232 415 150 104 126 795 2437
Leaves lower part below 1st flower cluster
1 946 130 605 2650 4337 39 415 460 81 995 3336
2 870 690 490 2500 4550 81 162 348 88 679 3871
3 770 900 385 2300 4355 110 118 300 100 628 3727
4 742 975 362 1950 4029 135 75 254 98 562 3467
5 692 1049 280 1850 3871 139 70 204 98 511 3360
6 512 1200 181 1700 3593 142 50 130 98 420 3173
Fruit at the 1st flower cluster
1 640 43 115 60 858 13 190 64 98 365 493
2 485 112 118 60 772 7 175 56 110 348 431
3 460 156 115 35 766 - 138 56 107 301 465
4 435 192 115 35 777 - 130 60 100 292 485
5 460 196 107 40 803 - 105 56 98 258 544
6 408 365 115 140 1028 - 110 52 94 256 772
The anion sum (NO3 + Cl + S02-+ H2PO4) was greater in the top part of the plants than in the leaves of the lower part. (Table 2). In the fruit it was 2-3 times smaller than in the leaves. In all the three plant parts examined the rising NaNO3 rate resulted in decreasing anion content. The cation vs anion ratio was the lowest in the fruit and the highest in the leaves located in the lower part of the plant. In the younger leaves at the top part of the plant this ratio stayed quite constant in each treatment . In the older leaves of the lower plant part, however, the cation vs anion ratio increased with the increasing NaNO3 rate and the
difference between the older and the younger leaves concerning this parameter grew simultaneously as well. In the fruit the cation vs anion ratio also grew with the increasing of the NaNO3 rate.
Trace elements content
Zinc: The zinc content was within optimal limits. It was substantially higher in the lower located leaves than in those on the top, irrespective of the fertilizer treatments. In the upper located leaves its content decreased from the first to the third treatment inclusive and then started to rise again. The zinc level in the fruit remained unchanged (Table 3).
Table 3.
Effect of the increasing level of NaN03 in the nutrient solution on the trace element content in tomato plants.
Variants Trace elements (mg/Kg DM)
Zn Mn Cu Fe B
Leaves above the first flower cluster
1 135 30 5.3 24 37.6
2 125 36 5.5 34 34.8
3 115 45 5.8 28 35.2
4 120 45 6.0 30 30.0
5 135 45 5.9 32 27.2
6 105 43 5.8 34 28.4
Leaves below the first flower cluster
1 205 36 6.2 20 37.6
2 130 40 5.9 30 35.2
3 220 45 5.9 32 35.2
4 150 40 6.8 34 25.4
5 255 41 6.4 36 21.6
6 185 41 6.6 44 22.0
Tomato fruit
1 37 11 2.3 44 8.6
2 39 12 2.2 31 9.6
3 37 13 2.3 28 8.0
4 37 12 2.8 24 6.6
5 31 11 2.0 19 8.8
6 38 11 2.0 17 7.4
Manganese: The manganese content was much lower than what is normally considered as optimal and did not change per treatment.
Copper: The copper content was less than the optimal as well. It was present in higher quantities in the lower leaves than in those on the upper part of the plant. The Cu content tended to increase in the upper leaves and in the fruit up to the 4th treatment and then began to decrease.
Iron: The iron level was substantially less than the optimal norm. In the upper leaves under the effect of NaNO3 the iron level was almost constant, whereas in the lower ones where its level was slightly higher, it tended to increase. In the fruit the Fe content was decreasing.
Boron: This element was present in much lower amount than the optimal (Dzikovich, 1970; Alt et. Al., 1973). The higher the NaNO3 the Bo content decreased more substantially in the lower leaves. This trend was less evident in the fruit.
At different NaNO3 rates the K+, Ca2+ and Mg2+ cations and the H2PO S042+ and Cl anions were present in constant quantities
in the nutrient solution. Only the sodium content tended to grow with increasing levels of NO3.
The increase of the NaNO3 rate in the nutrient solution produced changes in the content of all the cations and anions in the plant tissues. As sodium plays a compensatory role in the nutrient solution its content in the tissues increases. On the other hand, the K+, Ca2+ and Mg2+ content decreases. However the decrease of these elements' concentration was not compensated for by rise of sodium level, which resulted in general decrease of the cation sum. This can be accounted for by the fact that the intensity of sodium assimilation goes down with its rising concentration in the nutrient solution. For instance, if we compare the first and the second treatment the latter had five times higher sodium concentration, whereas, comparing the second and the sixth treatment the latter contained less than two times more sodium. The effect of NaNO3 on the total amount of inorganic anions should be noted as well. According to the results reported by Pitman et al (1987) experiments with barley and Nikova et al. (2011)- with tomato, the amount of inorganic anions should
be growing as it is growing in the nutrient solution and in the plant tissues. In our case, however, the anion quantity decreased as the tissue nitrate content growth was not due to its increased absorption but evidently due to its upset assimilation. The chlorine content of the tissues decreased parallel to the nitrates' increase. This relation is usually attributed to the antagonism between the two anions in their absorption (Eaton et. Al., 1971). The reduced total nitrogen level in the tissues however indicated the absence of such competitive influence outside the plant in this case.
The growing sodium level in the tissues at increasing concentrations of NO3 in the nutrient solution has been found and reported by other authors as well (Tifflin, 1972). It has been assumed that the sodium assimilation is related to the anion that accompanies it. In the presence of NO3 the sodium assimilation is more intense than in the presence of Cl (Bains et. Al., 1984; Sauchelli, 1989). Also, it appears that the tomato plant root system is unable to control the input of Na as well as its translocation to the above ground organs, which has been reported about other crops (Rinkis, 1979; Shkolnik, 1974;Tifflin, 1972).
Conclusions
The increasing of Na concentration in the nutrient solution due to the augmented NaN03 rate resulted in its increased translocation in the above ground part of the plant, reduced uptake of N, K+, Ca2+, Mg2+, S042+ and Cl, and a slight increase of P.
The increasing sodium concentration exercised an unfavourable effect on the uptake of the boron trace element, but had no effect on the uptake of Mn, Zn, Cu or Fe in the vegetative parts.
The increasing concentration of Na in the nutrient solution prevented the uptake of copper and iron in the tomato fruit.
Tomato plants can be successfully grown at Na concentration of about 650 mg 11 on condition that the concentrations of the trace elements Mn, Cu, Fe and B are brought to the optimal.
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