Биологические науки/9. Биохимия и биофизика

Dr. of Biology Bukharina I.L.

Udmurt State University, Russia

Contents and dynamics of the main elements of mineral nutrition of shoots of plants in urban environment

The chemical composition of plant leaves is formed by both the direct and indirect influence of atmospheric pollution through the soil. The concentration of nutrients in assimilation organs is often used as a parameter to assess the industrial pollution in monitoring the state of plants. The industrial pollution causes the change in the element composition of the structural parts of plants, thus there is a lack or excess of certain elements, in other words, the ratio between different elements changes (Vinokurova, 2003; Sukhareva, Lukina, 2004; Bukharina and others, 2007; Darral, 1989; Innes, 1995).

Due to the number of studies it was found that high content of nitrogen in the leaves may be related to the ability of plants under stress conditions to increase the content of free amino acids as well as to absorb gaseous nitrogen pollutants such as nitrogen oxides and ammonia from the air and involve them in the metabolism (Barber, 1988; Vasfilov, 2003; Innes, 1995). The excess of nitrogen is toxic to plants because it causes inhibition of photosynthesis through the suppression of the synthesis of chlorophyll. There is a perception that the ratio of N:P:K is a homeostatic functional status of the plant organism.

The purpose of our research is to reveal the influence of urban environment on the exchange of the basic elements of mineral nutrition in plants.

The studies were conducted in Izhevsk. Izhevsk is a large industrial center of the Urals region with well-developed industry, transportation network and social infrastructure.

Species of woody plants which account for about 70% of green area of the city were the objects of the study. The studied plants had good or satisfactory life and middle-generative ontogenetic state. The studied species grew along highways and sanitary-protective zones (SPZ) of industrial enterprises that are the main polluters of the city such as “Avtozavod”, “Bummash”, “Izhstal”. The suburban area and the territory of the largest city park were selected as a conventional control zones (CCZ).

The soils in the conventional control zones have low levels of pollution. The level of soil pollution along highways and in sanitary-protective zones of industrial enterprises is assessed as moderately dangerous, and in the area of enterprises “Izhstal” and “Avtozavod” as extremely dangerous.

Twice during the vegetation period we determined the content of major mineral nutrients (nitrogen, potassium and phosphorus) in the stem part and in the leaves of one year old shoots of woody plants (Guidelines …, 1982). To interpret the obtained results we used the program “Statistica 5.5”.

The analysis revealed that the content of the basic elements of mineral nutrition depends on the peculiarities of species, place of growth conditions and period of plant vegetation as well as the interaction of these factors. In June and September the leaves of Betula pendula Roth, Salix caprea L., Tilia cordata Mill. and Sorbus aucuparia L. growing in different types of plantations do not have significant differences in a given indicator (Table 1) except for Betula pendula and Salix caprea in plantations growing along highways, and Tilia cordata Mill in plantations of sanitary-protective zones. During the first period of observation the leaves of Rosa majalis Herrm. growing in the CCZ are provided with nitrogen better in comparison with other types of plantations, during the second period - on the contrary. The stem part of one year old shoot of Betula pendula and Salix caprea growing in conditions of intensive industrial pollution has the higher indices of nitrogen content in June and in September than the indices of conventional control zones.

The reaction of introduced species is somewhat different. In June the leaf blades of Acer negundo L., Populus balsamifera L. and Malus baccata (L.) Borkh in the plantations along highways and SPZ of industrial enterprises contain nitrogen in quantities exceeding conventional control zone and during the leaf fall - on the contrary. Both the beginning and the end of the vegetation period of Caragana arborescens Lam. are characterized by the accumulation of nitrogen in the leaves of plants growing along the highways, and in September - in industrial zones too. In June the stem of the shoots of introduced woody plants growing in the highway plantations has more nitrogen content than those growing in the conventional control zones, while Caragana arborescens growing in the SPZ of industrial enterprises and highway plantations in the period of leave fall has more nitrogen in shoots.

Summarizing the results of the analysis received in both periods of observation we found out that the shoots of most species studied as in the sanitary-protective zones of industrial enterprises and in the highway plantations had significantly higher percentage of nitrogen content in comparison with the conventional control zone.

In our opinion, one reason for the high nitrogen content may be the absorption of nitrogen-containing pollutants from the air by leaves. The nitrogen oxides content analysis of air shows the maximum concentration and the highest indices of annual average concentration in the areas of research. The analysis of mineral forms of nitrogen in soils permissible for plants revealed their low content. The correlation between nitrogen content in the leaves with the concentration of nitric oxide in the air (correlation coefficient is r = 0.15, significance level is P = 0.049, n = 168) was calculated.

It should be emphasized that Caragana arborescen revealed a high correlation dependence of these indices (r = 0.98, Р = 3.5×10^-8). Of course, this type of plant should be the most widely used in landscaping areas of the city with high concentrations of nitrogen compounds in the air. The analysis of the relationship between total nitrogen in shoots and permissive forms of nitrogen for plants in soils showed weak. Of particular note Caragana arborescens for which the greatest correlation coefficient between the content of total nitrogen in leaves and nitrate in the soil was set (r = 0.78, Р < 0.05).

The analysis of the potassium content in the one year old structural parts of shoots showed the increase in the content of this element in the leaves of Betula pendula and Salix caprea growing in the highway plantations in June in comparison with those growing in the conventional control zones (Table 2). The increasing concentration of potassium in leaf blades of Tilia cordata, Sorbus aucuparia and Rosa majalis, growing in the plantations of SPZ of industrial plants and highway plantations is observed during the leaf fall period.

In the same types of plantations in stem part of the shoot of Betula pendula, Tilia cordata and Sorbus aucuparia in both periods of observation the potassium content was higher than in the CCZ. In Caragana arborescens in both types of plantings for special purposes, in September, while Malus baccata in both periods of observations the potassium content in shoots increased in comparison with those growing in the conventional control zones.

Summarizing the data, we can say that with the increasing degree of industrial pollution the potassium in the leaves of most studied species increases significantly, which may be related to changes in water exchange in plants under water deficit. The phosphorus content in leaves of introduced species in both periods of observation in the plantations of industrial zones and in highway plantations is lower than in the conventional control zones (Table 3). It was not possible to allot the distinct patterns of change in the phosphorus content in the leaf apparatus of native species. We received the similar test results on the content of this element in the stem parts of the shoot. At the same time in the conditions of intensive industrial pollution the stems of Salix caprea, Sorbus aucuparia and Malus baccata have higher phosphorus content.

Thus, in the conditions of industrial environment the increase in nitrogen and potassium contents in the structural parts of plants is accompanied by a decrease in phosphorus concentration, i.e. there is an imbalance in the content of major mineral elements of plant nutrition in a man-made environment.

Literature:

1. Barber, S. A. Bioavailability of nutrients in the soil. Mechanistic approach. M: Agropromizdat, 1988. 376 pp.

2. Bukharina, I. L., Povarnitsina, T. M., Vedernikov, K. E. Ecological and biological characteristics of woody plants in the urban environment: a monograph. Izhevsk: Izhevsk State Agricultural Academy, 2007. 216 pp.

3. Vasfilov S.P. Possible ways of negative influence of acid gases on plants // General Biology Magazine, 2003. T. 64. Pp. 146-159.

4. Vinokurova, R. I. Regularities of the accumulation and distribution of chemical elements in the phytomass of spruce-fir plantation zone of mixed forests of the Middle Volga region: Abstract of Biology PhD dissertation. Yoshkar-Ola, 2003. 273 pp.

5. Guidelines for feed analysis /Ed. L.M. Derzhavin. M.: Kolos, 1982. 74 pp.

6. Sukhareva, T.A., Lukin, N.V. Chemical composition and morphometric characteristics of the Siberian spruce needles in the Kola Peninsula in the degradation of forest succession // Forestry. 2004. № 2. Pp. 36-43.

7. Darral N.M. The effect of air pollutants on physiological processes in plants // Plant. Cell and Environment. 1989. V. 12. Pp. 1-30.

8. Innes J.L. Influence of air pollution on the foliar nutrition of conifers in Great Britain // Environ. Pollut. 1995. V. 88. Pp. 183-192.

Table 1 – The nitrogen content in the shoots of woody plants growing in the city areas of different functional purpose, % of absolutely dry mass (Izhevsk)

Plant species	Vegetation period	Places of plantations
		CCZ ^*		SPZ of industrial enterprises ^**		Highway plantings
		Leaves	Stems	Leaves	Stems	Leaves	Stems
Betula pendula Roth.	June	2.51	1.29	2.72	1.73	3.07	1.69
	September	0.68	0.77	0.63	2.82	0.61	2.62
Acer negundo L.	June	2.41	2.13	3.32	2.23	4.24	2.45
	September	2.41	0.94	1.33	1.24	1.30	1.77
Populus balsamifera L	June	1.87	2.27	2.92	1.54	2.96	2.92
	September	1.87	1.71	1.47	1.39	0.94	1.37
Tilia cordata Mill.	June	3.05	1.63	3.20	1.58	3.19	2.13
	September	0.91	2.50	1.50	2.29	0.67	1.19
Salix caprea L.	June	2.57	1.36	2.69	1.97	3.20	1.92
	September	1.07	1.47	0.96	1.76	1.34	1.90
Sorbus aucuparia L.	June	1.95	1.22	1.83	2.10	1.72	1.93
	September	0.99	0.38	0.90	2.04	0.71	1.52
Malus baccata (L.) Borkh	June	2.03	1.79	2.49	1.79	2.56	2.30
	September	1.00	0.75	1.13	1.49	1.09	0.60
Rosa majalis Herrm.	June	4.14	1.31	2.30	1.15	2.48	1.70
	September	0.79	2.02	1.81	1.42	1.15	1.62
Caragana arborescens Lam.	June	3.19	3.66	2.48	3.16	3.35	3.35
	September	0.01	0.01	2.00	1.78	3.05	2.36

Notes. *CCZ – conditional control zone; **SPZ – sanitary-protective zones of industrial enterprises. LSD₀₅ for leaves = 0.4; for stems = 0.2.

Table 2 – The potassium content in the shoots of woody plants growing in the city areas of different functional purpose, % of absolutely dry mass (Izhevsk)

Plant species	Vegetation period	Places of plantations
		CCZ^*		SPZ of industrial enterprises^**		Highway plantings
		Leaves	Stems	Leaves	Stems	Leaves	Stems
Betula pendula Roth.	June	1.27	0.37	1.27	0.41	3.07	0.47
	September	0.56	0.25	1.57	0.37	1.24	0.38
Acer negundo L.	June	1.81	0.83	2.42	0.75	1.90	0.83
	September	3.79	0.89	1.95	0.54	2.16	0.79
Populus balsamifera L	June	2.22	0.91	1.97	0.89	2.40	0.74
	September	1.56	0.63	2.72	0.61	1.51	0.77
Tilia cordata Mill.	June	2.34	0.50	1.77	0.66	2.08	0.66
	September	0.97	0.51	2.41	0.64	2.84	0.58
Salix caprea L.	June	1.35	0.46	1.85	0.59	2.58	0.80
	September	1.37	0.82	1.42	0.62	2.93	0.77
Sorbus aucuparia L.	June	1.79	0.42	1.38	0.57	0.92	0.57
	September	0.70	0.36	1.23	0.48	1.70	0.51
Malus baccata (L.) Borkh	June	2.17	0.55	1.96	0.80	1.85	0.92
	September	0.97	0.30	2.26	0.42	2.63	0.62
Rosa majalis Herrm.	June	2.03	0.57	1.28	0.86	1.23	0.75
	September	0.93	0.52	1.11	0.49	1.17	0.42
Caragana arborescens Lam.	June	2.18	8.41	1.58	4.86	2.82	0.86
	September	0.79	0.33	1.19	0.69	1.70	0.73

Notes. *CCZ – conventional control zone; **SPZ – sanitary-protective zones of industrial enterprises. LSD₀₅ for leaves = 0.10; for stems = 0.20.

Table 3 – The phosphorus content in the shoots of woody plants growing in the city areas of different functional purpose, % of absolutely dry mass (Izhevsk)

Plant species	Vegetation period		Places of plantations
			CCZ^*		SPZ of industrial enterprises^**		Highway plantings
			Leaves	Stems	Leaves	Stems	Leaves	Stems
Betula pendula Roth.	June		0.65	0.18	0.53	0.41	0.88	0.34
	September		0.37	0.14	0.70	0.32	0.22	0.28
Acer negundo L.	June		1.03	0.55	0.75	0.56	0.89	0.50
	September		0.38	0.79	0.32	0.31	0.28	0.39
Populus balsamifera L	June		0.70	0.56	0.49	0.48	0.50	0.53
	September		0.38	0.80	0.72	0.35	0.18	0.39
Tilia cordata Mill.	June		0.59	0.42	0.82	0.49	0.92	0.52
	September		0.33	0.36	0.45	0.67	0.11	0.36
Salix caprea L.	June	0.50		0.47	0.60	0.48	0.56	0.55
	September	0.46		0.10	0.23	0.28	0.48	0.59
Sorbus aucuparia L.	June	0.81		0.23	0.61	0.37	1.42	0.28
	September	0.45		0.21	0.67	0.63	0.72	0.47
Malus baccata (L.) Borkh	June	1.07		0.43	0.67	0.28	0.74	0.52
	September	0.50		0.22	0.83	0.39	0.43	0.37
Rosa majalis Herrm.	June	1.46		0.33	0.86	0.37	0.57	0.32
	September	0.79		0.76	0.40	0.80	0.19	0.46
Caragana arborescens Lam.	June	0.50		0.77	0.34	0.75	0.59	0.45
	September	0.25		1.34	0.14	0.36	0.25	0.79

Notes. *CCZ – conventional control zone; **SPZ – sanitary-protective zones of industrial enterprises. LSD₀₅ for leaves = 0.10; for stems = 0.10.