Báo cáo lâm nghiệp: "Occurrence of foliar nitrate reductase activity not induced by nitrate in symbiotic nitrogen-fed black alder (Alnus glutinosa)"

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Nội dung Text: Báo cáo lâm nghiệp: "Occurrence of foliar nitrate reductase activity not induced by nitrate in symbiotic nitrogen-fed black alder (Alnus glutinosa)"

Occurrence of foliar nitrate reductase activity not induced by nitrate in symbiotic nitrogen-fed black alder (Alnus glutinosa) S. Benamar G. Pizelle 1 1 2 G. Thiéry 1 Laboratoire BP 239, 54506 de Physiologie V6g6tale et Foresti6re, Facult6 des Sciences, Vand&oelig;uvre-/ès-Nancy Cedex, and Physiologie 2 V6g6tale, ENSAIA, 54500 Vand&oelig;uvre-/ès-Nancy, France Introduction 1618 h, 25/18°C and 60/80%, respectively; pho- ton flux density: 200 jlE from Metalarc 1 h 2 m- ’ Sylvania lamps. Black alder (Alnus glutinosa (L.) Gaertn.) Axenic and non-axenic plants were grown on acquires nitrogen from its environment by in test tubes and on a vermiculite-sand perlite symbiotic nitrogen fixation within its acti- mixture (v/v), respectively. Nodulation was ob- norhizas and by uptake of combined nitro- tained, if necessary, by inoculation with a pure Frankia suspension in axenic cultures and with gen from the soil solution. N0 represents 3 an actinorhizal suspension in non-axenic cul- the major form of combined nitrogen in tures. The nodulated plants were grown on an alder soils, which possess a high capacity N-free solution; 4 mM NaN0 was added to this 3 for nitrification (Bollen and Lu, 1968). It is solution to supply the nitrate-fed plants. well established that black alder has the Leaf NR activity was determined as de- ability to reduce N0 in both roots and 3 scribed by Pizelle and Thidry (1986) with the leaves (Pizelle and Thiéry, 1974; 1986). modification that the concentration of KNO 3 The present study was performed on was 0.05 M in the incubation medium. young black alders grown under axenic or non-axenic conditions and supplied with nitrate or nitrate-free nutrient solution. The objectives were to: 1) evaluate the effect Results of nitrogen source and plant age on leaf nitrate reductase (NR) activity measured in vivo; 2) verify that leaf NR activity was Effect of nitrogen source and plant age not due to an artifact of microbial origin; 3) the leaf NR activity on examine the relationship between plant growth and leaf NR activity. The nodulated plants grown without com- bined nitrogen expressed leaf NR activi- Materials and Methods ties which were higher than those of the plants supplied with nitrate (Fig. 1The Young black alders were grown in a growth leaf NR activities of both N and ing X -f’ 2 chamber; tight/dark cycle, temperature and RH:
nitrate-fed alders presented great varia- ed by Btacquiere and Troelstra (1986). tions between plants and, in one plant, From these results, we conclude that the between dates of measurement. In addi- leaves of A. glutinosa present a constitu- tion, these data show that NR can be ac- tive NR activity not induced by nitrate. tive in the leaves of the plants not supplied with nitrate. This NR activity, not induced Comparison of the constitutive leaf NR by nitrate was termed ’constitutive’ NR. activity in symbiotic nitrogen-fed black Blacqui6re and Troelstra (1986) postu- alders lated that leaf NR activity measured in vivo in alder might be of microbial origin. In order to determine whether the varia- This hypothesis was tested by using tions of leaf NR activity previously ob- plants in axenic culture. served (Fig. 1 ) were a coincidence or whether the plants could be distinguished Leaf NR from each other by the level of their en- of in axenic activity plants culture zyme activity, we followed the individual leaf NR activities of symbiotic nitrogen-fed alders for several weeks. The data pre- The axenic leaf tissues from nodulated or sented in Table II allowed us to distinguish non-nodulated alders grown with or with- at least 2 groups of plants having signifi- out nitrate expressed notable NR activity cantly different levels of leaf NR activity: (Table I). These findings indicate that the one group having low enzyme activity NR activity originates in leaf tissues, and (plants 1-3) and one having high enzyme not in microbial phyllosphere, as suggest- activity (plants 9-12).
The variations of the NR activity of each Relationship between constitutive leaf NR group (Fig. 2) show that the means of the activity and plant growth enzyme activities of the 1 st and 2nd groups are consistently lower and higher, respectively, than that of the 12 plants The data given in Table II show a high cor- assayed. Thus young black alders could relation between growth and mean NR be distinguished by the level of their activity in the leaves of each plant constitutive leaf NR activity. Hence, the (r= 0.841, n=12, P
herbaceous (Lee and Stewart, 1978) and of unusual nitrate flux, hypothetical are young woody plants (Lee et al., 1985) roles which might be attributed to this NR supplied with nitrate. However, in the case activity. Regardless of its yet unknown of symbiotic nitrogen-fed A. glutinosa of role(s), the constitutive NR activity of the the present study, the leaf NR activity was leaves of A. gliutinosa must have a phy- correlated with the plant growth even if it siological significance, since its level is did not contribute to the nitrogen nutrition positively correlated with plant growth. of the plant. Hence, this enzymatic activity could be a good indicator of the growth potential of young black alders. Conclusion References Our results show that the leaves of Alnus glutinosa have a constitutive NR activity not induced by nitrate nutrition and not T & Troelstra S.R. (1986) Nitrate Blacqui6re due to an artifact of microbial origin. But it reductase activity in leaves and roots of Alnus is difficult to specify the role of this en- glutinosa (L.) Gaertner. Plant Soil95, 301-3133 zyme activity. Diaphorase activity (Guerre- Bollen W.B. & Lu K.C. (1968) Nitrogen transfor- ro et aL, 1981 ), iron nutrition (Smarelli and mation in soil beneath red alders and conifers. Castignetti, 1986), intervention in the case In: Biology of Alder. (Trappe J.M., Franklin J.F.,
Tarrant R. & Pizelle G. & Thiéry G. (1974) Reduction des Hansen G.M., eds.), Forest Ser- nitrates par les feuilles, les racines et les vice-USDA, Oregon, pp. 141-148 nodules d’aune glutineux (Alnus glutinosa L. Guerrero M.G., Vega J.M. & Losada M. (1981) Gaertn.) C.R. Acad. Sci. Paris, S6r. D. 279, The assimilatory nitrate reducing system and its 1535-1537 regulation. Annu. Rev. Plant Physiol. 32, 169- 204 Thiéry G. (1986) Reduction of ni- Pizelle G. & Lee D.K., Kim G.T. & Lee K.J. (1985) Variations trate in theperennial tissues of aerial parts of in peroxidase and nitrate reductase activities Alnus glutinosa. Physiol. Plant. 68, 347-352 and growth of Populus alba x Populus glandu- losa F clones. J. Korean For. Soc. 70, 63-71 1 Smarelli J. Jr. & Castignetti D. (1986) Iron ac- Lee J.A. & Stewart G.R. (1978) Ecological quisition by plants: the reduction of ferrisidero- aspects of nitrogen assimilation. Ad! Bot Res. phores by higher plants NADH:nitrate reduc- 6, 1-43 tase. Biochim. Biophys. Acta 882, 337-342