Báo cáo lâm nghiệp: How the absolute growth rate of poplar adapts to the light-NO -dosage 3 G.A. Pieter

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Báo cáo lâm nghiệp: "How the absolute growth rate of poplar adapts to the light-NO -dosage 3 G.A. Pieter"How the absolute growth rateof poplar adapts to the light-NO -dosage 3 -G.A. PietersDepartment of Plant Physiological Research. Agricultural University Gen. Foulkesweg !2. 67038W Wageningen, The NetherlandsIntroduction bundles in the vascular cylinder increase in a systematic way; at the same time, phyllotactic order increases. According to Larson’s analyses, new procambial tracesThe growth of leaves and internodes on a develop long before the primordia they willbranch of poplar, grown under constant serve are visible at the apex.conditions, proceeds according to growthpatterns, which: 1) can be defined as Combining Larson’s data with ours, weorgan-specific relations between the rela- established a striking correspondence be-tive growth rate (RGR) and the age of the tween the development of the vascularorgan; and 2) are independent of irradi- system of poplar, the growth of the organsance. Consequently, the absolute growth and the development of absolute growthrate of such a branch cannot adapt to irra- rate of the plant. Adaptation proceeds viadiance via these growth patterns. A poplar enlargement of the primary vascular sys-plant adapts its absolute growth rate to (Pieters and van den Noort, 1988). A temhigh irradiance by a gradually faster pro- larger vascular system is reflected in a lar-duction of proportionally larger primordia ger apical volume and produces propor-at its apex. At the same time, the apical tionally more and larger leaf primordia,volume and the phyllotactic order are which grow out to a proportionally largerincreasing. It could be shown that the api- final size. Whenever an equilibrium iscal volume is proportional to the rate of reached between assimilate productionleaf area production (Pieters and van den and use in the plant, the primary vascularNoort, 1988). Under optimal conditions, system stops expansion and the branchthe stem elongation rate increases propor- grows linearly with time. Because thetionally to the leaf production rate and, on vascular system develops before thethe average, this results in internodes with primordia, we suggest that the growth of aconstant mature length. plant is a reflection of the development ct the vascular system. Larson (1975) analyzed the develop-ment of the vascular system of poplar. The Preliminary experiments with sunflowernumber and the length of the vascular and poplar (Pieters and van den Noort, to the scheme presented 35:45:20), according1985) suggested that the absolute growth in Table. Irate of a branch adapts in a way similar to Six and four plants were used, respectively,that of nitrate dosage. As the availability of for the 2 highest and the lowest nitrate dosage.(reduced) nitrate in the plant becomes Three times per week, length and thickness,limiting, the expansion of the vascular sys- respectively diameters of leaves and internodestem stops and the branch grows linearly were measured. The other measurements were made on harvested plants. The plants werewith time. harvested 3 times, and those grown at The aim of this article is to report the 0.0 mmol N0 twice. 3effects of photon fluence rate (PFR) and Chlorophyll was determined according tonitrate dosage on growth and some chem- Bruinsma (1963), the chemical analyses usingical properties of a poplar branch during the methods described by the Department of Soil Science and Plant Nutrition, AU, Wagenin-the adaptation to a nitrate dosage that is: gen.1) linear with time, and 2) in proportion toirradiance (cf. Ingestad, 1987). ...