Báo cáo khoa học: "Polyphenolic and enzymatic characterization of ageing and rejuvenation of hybrid walnut trees (Juglans nigra x Juglans regia): relationship to growth"

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Polyphenolic and enzymatic characterization of ageing and rejuvenation of hybrid walnut trees (Juglans nigra x Juglans regia): relationship to growth A. Drouet 2 D. Cornu C. 1 A. Ouaras Jay-Allemand 1 Station dAm6lioration des Arbres Forestiers, INRA, Ardon 45160 Olh and et, l 2 Laboratoire de Physiologie du Vieillissement et de la S6nescence de.s V6gdtaux Sup6rieurs, Uni- versit6 d’Ort6ans, BP 6749, 45067 Orleans Cedex 02, France Key results and a brief discussion on Introduction different factors involved in walnut ageing and rejuvenation will be presented. This paper is mainly devoted to the poly- phenolic and enzymatic characterization of hybrid walnut rejuvenation in order to find better plant materials, treatments and conditions which are propitious to propa- Materials and Methods gation. Consequently, comparative study a of adult and rejuvenated annual shoots Two clones of x J. hybrid walnut (Juglans nigra undertaken. was regia), which grown in nursery in were a Rejuvenation, widely linked to vegeta- Orleans, were used. Each clone was repre- tive propagation, was described by Bonga sented by 2 different physiological situations: 1) a rejuvenated 13 yr old tree obtained by (1982) and it has been shown on hybrid annual coppicing in March for 10 yr, each stump walnut that the propagation success by in producing at least 60 sprouts; 2) 10 yr old adult vitro culture of cuttings was strongly form obtained from a cutting of a previous dependent upon severe annual coppicing stump sprout. (Cornu, 1977). First results with phenolic A detailed study of growth was undertaken to compounds and enzymes were obtained that samples were shoots at the same ensure during the annual growth of walnut: growth stage and to study the relationship be- tween growth rate and biochemical factors. For 1) juvenility and rejuvenation seemed to each sample, 5 shoots were cut, defoliated and be linked to high values of the ratio of typi- immediately immersed in liquid nitrogen for sub- cal polyphenols during the first stages of were taken on sequent lyophilization. Samples growth after bud burst (Jay-Allemand et 5 shoot elongation (10, 18 and 24 days during June; 2 July and 7 August) (Drouet et al., al., 1987; 1988); 2) enzyme activity 1989). Extraction, purification and high perfor- changes were found between adult and mance liquid chromatography (HPLC) methods rejuvenated shoots, while no difference were reported by Jay-Allemand et al. (1988) was noted in the total protein content and enzyme analyses were described by (Drouet et al., 1989). Drouet et al. (1989).
first growth wave, during the other hand, marked by 2 PAL peaks rejuvenation was which were absent in adult shoots (Fig. 2). However, no simple relationship has been found between this enzyme activity and the accumulation of studied polyphenols. Enzymes: z-glutamate:NAD oxidoreduc f tase (GDH) and D-glucose-6-phospha- + te:NADP oxidoreductase (G6PDH) The evolution of the 2 enzyme activities in rejuvenated and adult shoots is presented in Fig. 3. Ageing induced an accelerated and asynchronous functioning of these 2 enzymes. While GDH decreased steadily after bud burst. G6PDH activity increased during the first 20 d. On the contrary, the rejuvenation treatment induced both a late (40 d) and synchronous increase of these 2 enzyme activities. Results Phenolic compounds and phenylalanine ammonia lyase (PAL) Results on polyphenols are based on 2 main compounds (A and B), elucidated by a previous study using canonical discrimi- al., 1988). analysis (Jay-Allemand nant et The evolution of these compounds during elongation of adult and rejuvenation shoots is described in Fig. 1. A high level of compound A (undetermined structure) at the beginning of growth characterized rejuvenated shoots, while adult shoots were characterized by late accumulation of compound B (flavonol). Moreover, the ratio A/8 was always higher in rejuvenated shoots than in adult shoots. These results confirm and specify previous data. On the
In walnut, the accumulation of phenolic compounds (A and B) was not directly controlled by iPAL activity. This enzyme was linked to d acceleration (results rowth not published) and involved in lignification processes, while compound A decreased steadily and compound B remained stable when the elongation rate increased during the first growth period of stump sprouts. On the other hand, the initiation of and its acceleration seem to be growth linked to enzyme changes (GDH and Protein content decreased G6PDH). because of the synthesis of non-protein substances during growth (mainly lignin). Correlatively, activities of G6PDH (pentose phosphate pathway) and GDH (cellular detoxification of NH+) increased and ensured, respectively, the production of NADPH and NADH which are needed for active growth (Drouet et aL, 1989). The identification of the structure of the phenolic compounds associated with reju- venation and their enzymatic regulation (PAL and chalcone synthetase) remains a It will also be necessary to high priority. between specify relationships typical phe- Discussion nolic their compounds, metabolism, and growth rooting. Ageing and rejuvenation of walnut trees has been characterized by different bio- chemical factors. In addition, studies References undertaken on Prunus avium showed an increase of different flavonoids in phloem with ageing (Treutter et aL, 1987). More- Bon M.C. (1988) Aspects biochimiques du clo- over, Zimmerman et al. (1985) reported nage de sequoias g6ants (Sequoiadendron giganteum Buchl-:)z) jeunes et ages. Ph.D. The- changes of enzyme activities (ribonucle- sis, Université Clermont-Ferrand II, France ase, phosphatase, phenolase) during the Bonga Jt.M. (19F32) Vegetativend ropagation in p different stages of development of woody relation o juvenility, maturity a rejuvenation. In: Tissue Culture in Forestry. (Bonga J.M. & plants. Recently, a specific protein of cell Durzan D.J., eds.), Martinus Nijhoff, Boston, walls has been found to be associated pp. 387-412 with juvenility of Sequoia sempervirens Cornu D. (1977) La multiplication vegetative du (Bon, 1988). noyer hybride. Resultats d’une premiere cam- pagne. Perspectives d’avenir. Rev. Fr. For. All these data suggest that biochemical Tech. For. 29, 45’7-463 characteristics of ageing and rejuvenation Drouet A., Weiswald N., Jay-Allemand C. & could be related to root effects, tissue Cornu D. (1989) Pentose phosphate pathway quality and gene activation. and glutamate dehydrogenase activities in adult
and rejuvenated hybrid walnut trees. Plant Treutter D., Feucht W. & Schmid P.P.S. (1987) Physiol. Biochem. 27, 259-267 Ageing-dependent responses of phloem flavo- nids of Prunus avium graftings: flavanone-, fla- Jay-Allemand C., Cornu D. & Macheix J.J. vone- and isoflavone-glycosides. Sci. Hortic., (1987) Caract6risation de la rejuv6nilisation du 32, 183-193 par une étude spectropho- noyer (Juglans sp.)03-304 tométrique globadu contenu polyph6nolique. Zimmerman R.H., Hackett W.P. & Pharis R.P. Ann. Sci. For. 44,3 (1985) Hormonal aspects of phase changes Jay-Allemand C., Cornu D. & Macheix J.J. and precocious flowering in hormonal regulation (1988) Biochemical attributes associated with of development Ill. In: Encyclopedia of Plant rejuvenation of walnut tree. Plant Physiol. Bio- Physiology New Series, 11 (Pharis R.P. & Reid chem. 26, 139-144 D.M., eds.), Springer-Verlag, Berlin. pp. 79-115 5