No abstract

The aim of this work was to evaluate the effects of repeated pruning interventions using different pruning methods on growth and physiology of Acer pseudoplatanus L. Trees were pruned in 2008 and 2010 according to widely used pruning techniques for urban trees, such as reduction cut, removal cut and heading (topping) cut. Crown dieback, growth of the plant and of the pruned branches, leaf morphological traits and leaf gas exchange were assessed during the two growing season after each pruning cycle. Topping cut (i.e. the pruning treatment which suppressed the primary axis without providing a substitute) induced changes on tree growth pattern (i.e. by increasing the release of adventitious watersprouts and root suckers and decreasing stem diameter growth), which were not observed in the other pruning treatments. At the leaf level only topping cut increased leaf area at the expense of leaf mass per area, which may contribute to explain the higher occurrence of dieback on topped branches than in control and in the other pruning treatments. Also, leaves on topped branches displayed higher chlorophyll content and higher activity of Calvin cycle enzymes, which did not translate in higher CO 2 assimilation. We show here that pruning method, not only its severity A c c e p t e d M a n u s c r i p t 2 (i.e. the amount of leaf area removed), modulates the morpho-physiological response of trees to pruning and that maintenance of apical control and apical dominance are key issues to preserve a structurally sound tree structure, as well as the long-term efficiency of the photosynthetic apparatus.

This experiment investigated the effect of different container design on growth and root deformation of littleleaf linden (Tilia cordata Mill.) and field elm (Ulmus minor Mill.). The trial was carried out over two growing seasons (2008 to 2009). In April 2008, 1-year-old bare-root seedlings of the two species were potted in three types of 1-L containers: Superoots® Air-Cell™ (The Caledonian Tree Company, Pathhead, UK), Quadro fondo rete (Bamaplast, Massa e Cozzile, Italy), and smooth-sided containers. At the beginning of the second growing season, the same plants were repotted in the following 3-L containers: Superoots® Air-Pot™ (The Caledonian Tree Company), Quadro antispiralizzante (Bamaplast), and smooth-sided containers. At the end of each growing season, a subset of the plants from each container type was harvested to determine shoot and root dry mass and root deformation (by dry weight of root deformed mass relative to the whole root mass). Chlorophyll fluorescence and leaf chlorophyll content were measured during the second growing season. For both species, at the end of first growing season, the poorest root architecture was observed in the smooth-sided containers, whereas Superoots® Air-Cell™ and Quadro fondo rete both reduced the percentage of deformed root mass. At the end of the second growing season, plants of both species grown in Superoots® Air-Pot™ showed less deformed root mass, whereas Quadro antispiralizzante provided good results only in littleleaf linden. A reduction of field elm root biomass and littleleaf linden shoot biomass was observed at the end of the trial in plants grown in Superoots® Air-Pot®. Plants grown in these containers showed less leaf chlorophyll content compared with plants grown in smooth-sided containers at the end of the second year.

▶ Covers research into mycorrhizas, including molecular biology, fungal systematics, development and structure, and effects on plants ▶ Presents original papers, short notes and review articles, along with commentaries and news items ▶ Offers a platform for new concepts and discussions ▶ Official organ of the International Mycorrhiza Society ▶ 100% of authors who answered a survey reported that they would definitely publish or probably publish in the journal againMycorrhiza is an international journal devoted to research into mycorrhizas -the widest symbioses in nature, involving plants and a range of soil fungi world-wide. The journal covers research into mycorrhizas, including molecular biology of the plants and fungi, fungal systematics, development and structure of mycorrhizas, and effects on plant physiology, productivity, reproduction and disease resistance. Coverage extends to interactions between mycorrhizal fungi and other soil organisms, and effects of mycorrhizas on plant biodiversity and ecosystem structure.Mycorrhiza presents original papers, short notes and review articles, along with commentaries and news items. It offers a platform for new concepts and discussions, and serves as the basis for a forum of mycorrhizologists from around the world.

This research evaluated the effectiveness of biodegradable mulches for weed control in container-grown ‘Martin’ giant arborvitae (Thuja plicata) and measured the effects of these mulches on evaporation and substrate temperature. The experiment was carried out in the 2008 and 2009 growing seasons. Four biodegradable mulching materials were tested and compared with a chemical control (oxadiazon) and a non-mulched/non-treated control. Two levels of overhead irrigation were evaluated: 1) daily irrigation to container capacity (well watered) and 2) daily irrigation to 30% of container capacity (water stressed). Two weed management regimes were used: 1) hand weeding three times during the growing season and 2) no weeding until the end of the growing season. Plants were potted in 3-L containers and arranged in a split–split plot design in an experimental nursery. Ornamental shoot dry weight was measured at the end of the growing season. Weed shoot dry weight per container was recorded after each hand weeding. Water content per pot (as a percentage of water-holding capacity) was measured by weighing containers every 2 hours during the day. Substrate temperature was measured in the warmest period of the day. Mulches limited weed growth to the same extent as the chemical control. In 2008, mulched plants resulted in a higher shoot dry weight than non-treated and non-mulched plants, while in the second year, no differences were observed. The black color of the 3-L containers was probably the main factor driving substrate temperature increase, indicating mulching materials did not affect substrate temperatures. In both experiments, container water content was unaffected by mulching materials. Results seem to demonstrate that transpiration is the main component of water loss from container-grown giant arborvitae plants.