Báo cáo khoa học: "Growth relationships between root and shoot in walnut seedlings (Juglans regia L.)"

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Growth relationships between root and shoot in walnut seedlings (Juglans regia L.) J.S. Frossard A. Charron A. Lacointe Laboratoire de Bioclimatologie, INRA, Centre de Recherches de Ctermont-Ferrand-Theix, Domaine- de-Crouelle, 63039 Clermont-Ferrand, France house. After 1 mo, 10 seedlings per yr were Introduction minirhizotrons and grown out- transplanted into doors, under natural conditions (continental cli- It is well known that the periodicity of root mate). Root and shoot growths were measured the year may be the growth throughout weekly, during 2 yr for the 1985 and 1986 seed- same as or different from that of shoot lings, and during 1 yr for the 1987 seedlings. growth (Riedacker, 1976; Kramer and From September to March, bud dormancy Koslowski, 1979; Frossard and Lacointe, studied using the MTB test (Bailly and was 1988), depending upon the species. It is Mauget, 1989}. difficult to interpret the published results because they were obtained on trees of different ages under different climatic Results conditions. It is particularly difficult to give precise answers to the following questions: 1) is was a high variability between There the relative position within the annual plants during both the 1 st and the 2nd yr. cycle of root and shoot growth a general An example of between yr variability is characteristic of a given species? In other given in Figs. 1 (1985-1986) and 2 words, is there any evolution between (1986-1987). years, in the relative periodicity of root and shoot growth? 2) are the relationships bet- However, the relative growth patterns of ween variables describing growth equiva- the different organs were the same. There lent throughout the year? Answers to were ’l st yr’ and ’2nd yr’ patterns. During these questions are of particular interest the 1st growing season (sowing yr), root when working on seedling growth and and shoot growth occurred simultaneous- when investigating the carbon allocation to ly; during the 2nd season (2nd yr), leaf different organs (Lacointe, 1989). growth began first, followed by shoot elon- gation and root growth came last. In autumn, there was no relationship Materials and Methods between dynamics of bud dormancy and root growth (data not shown). No root For 3 yr (1985, 1986, 1987), walnuts were sown growth was observed in winter. in early June, in clay soil, and grown in a glass-
In order to specify the dynamics of The sowing yr analyses provided 3 very similar figures, and the same was true for relationships among growth variables, 5 both 2nd yr analyses. The results for the French principal components analyses 1985 sowing are presented in Figs. 3 were performed, one for each of the 3 sowing yr and one for each of the 2nd yr (sowing yr) and 4 (2nd yr). the average values for the 10 Comparison of component weights studied: on plants; taking as ’individuals’ the measure- (variables) vs principal components (mea- surement dates), for both years, enabled ment dates.
For some of them, such as LA or TLR, this synthetic overview of the growth dyna- mics was consistent with that which could be derived from the plots of the consid- ered variables vs time (Figs. 1 and 2). For SH, however, there was a large discrepan- cy: it was probably related to the biphasic growth pattern of the shoot, with a high rate in July/August, followed by much us to interpret the geometrical relation- ships among variables as time relation- ships. As an example, for the sowing yr, the number of growing roots (NGR) was maximal near August 10, the leaf area (LA) in late August, the shoot height (SH) and the shoot volume (SV) in late October and the total length or roots (TLR) in early November.
slower growth in late summer and autumn, radiation in this continental climate, for which could not be detected from the each year). individual curves. Similarly, the discrepan- Thus, it might be possible to study cy between the root growth variables, under controlled conditions particular rela- NGR and TLR, probably reflected the root tionships between a climatic factor (for growth pattern: an early multiplication of example, temperature) and growth, con- white tipped roots, followed by an active serving the same ranges as those obser- elongation. ved under natural conditions. Discussion and Conclusion References The results show that there was an evolu- Bailly O. & Mauget J.C. (1989) Physiological tion between years in the relative periodi- correlation and bud dormancy in the apple tree (Malus domestic:a Borkh.). Ann. Sci. For. city of root and shoot growth of walnut Forest Tree Physiology 46 suppl., 220s-222s seedlings. Since there was no relationship Frossard J.S. & Lacointe A. (1988) Seasonal bud dormancy and between root variations in carbon economy in vegetative growth, the reasons for the cessation of trees under temperate climate - a review. Bull. root growth might be related to carbon Soc. Fr. Bot. 1, 9-24 allocation or to climatic factors, such as Kramer P.J. & Kozlowski T.T. (1979) In: Phy soil or temperature (or both). siology of Woody Plants. Academic Press, New York, pp. 811 1 The specific relationships observed be- Lacointe A. (19Et9) Assimilate allocation and tween the growth variables during the 2 carbon reserves in Juglans regia L. seedlings. growing seasons were characteristic of Ann. Sci. For. Forest Tree Physiology 46 suppi., the walnut seedling and relatively in- 836s-840s dependent of climatic hazards because Riedacker A. (1976) Growth and regeneration they were obtained in different years (with rhythms of roots of ligneous species - a review. Ann. Sci. For. 33, 109-138 different patterns of temperature and