Effects of leaf and branch removal on carbon assimilation and stem wood density of Eucalyptus grandis seedlings

Abstract

The rate of leaf CO 2 assimilation (A l ) and leaf area determine the rate of canopy CO 2 assimilation (A c ) can be thought proportional to assimilate supply for growth and structural requirements of plants. Partitioning of biomass within plants and anatomy of cells within stems can determine how assimilate supply affects both stem growth and wood density. We examined the response of stem growth and wood density to reduced assimilate supply by pruning leaf area. Removing 42% of the leaf area of Eucalyptus grandis Hill ex Maiden seedlings did not stimulate leaf-level photosynthesis (A l ) or stomatal conductance, contrary to some previous studies. Canopy-level photosynthesis (A c ) was reduced by 41% immediately after pruning but due almost solely to continued production of leaves, and was only 21% lower 3 weeks later. Pruning consequently reduced seedling biomass by 24% and stem biomass by 18%. These reductions in biomass were correlated with reduced A c . Pruning had no Communicated by M. Adams effect on stem height or diameter and reduced wood density to 338 kg m −3 compared to 366 kg m −3 in control seedlings. The lower wood density in pruned seedlings was associated with a 10% reduction in the thickness of fibre cell walls, and as fibre cell diameter was invariant to pruning, this resulted in smaller lumen diameters. These anatomical changes increased the ratio of cross-sectional area of lumen to area cell wall material within the wood. The results suggest changes to wood density following pruning of young eucalypt trees may be independent of tree volume and of longer duration.

Effects of partial defoliation on closed canopy Eucalyptus globulus Labilladière: Growth, biomass allocation and carbohydrates

“…Determination of the under-bark cross-sectional area of sapwood at 0.1 m (A S0.1 , m 2 ), 1.3 m (A S1.3 , m 2 ) and from the base of the three crown zones followed the procedures described in Medhurst et al (1999). Stem wood density ( ; kg m −3 ) was measured using method described in Thomas et al (2006). Bark was removed from stem discs for each crown zone.…”

Consumo de água em plantios de eucalipto: parte 2 modelagem da resistência estomática e estimativa da transpiração em tratamentos irrigados e não-irrigados

“…Dentre as variáveis ambientais analisadas, destacaram-se: irradiância solar global, temperatura, déficit de pressão de vapor e umidade solo. Muitos estudos foram realizados no sentido de quantificar a magnitude dos efeitos climáticos sobre o controle estomático nas trocas gasosas entre o dossel vegetal e a atmosfera, destacando-se os realizados por Hall et al (1976), Sheriff (1979), Landsberg e Butller (1980), Ludlow (1980), Jarvis (1980), Whitehead et al (1981), Schulze et al (1987), Tenhunen et al (1987), Mielke et al (1999), Gao (2000), Soares e Almeida (2001), Thomas et al (2006) e Souza (2005.…”

Growth of Poinsettia as Affected by Cultivar, Thinning, and Pot Size

“…Compensatory responses of plants to shoot removal by pruning or by herbivores may involve an enhanced vigor of remaining shoots (Naor et al, 2002), an increase of leaf assimilation rate, or an alteration of growth patterns to favor leaf area (Thomas et al, 2006). The manipulation of the sink-source ratio by removing vegetative or generative organs is used in vegetable and ornamental production to control growth and yield (Heuvelink and Buiskool, 1995;Jovicich et al, 1999).…”