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The geometry of tree branches can have considerable effect on their efficiency in terms of carbon export per unit carbon investment in structure. The purpose of this study was to evaluate different design criteria using data describing the form of Picea sitchensis branches. Allometric analysis of the data suggests that resources are distributed to favour shoots with the greatest opportunity for extension into new space, with priority to the extension of the leader. The distribution of allometric relations of links (branch elements) was tested against two models: the pipe model, based on hydraulic transport requirements, and a static load model based on the requirement of shoots to provide mechanical resistance to static loads. Static load resistance required the load parameter to be proportional to the link radius raised to the power of 4. This was shown to be true within a 95% statistical confidence limit. The pipe model would require total distal length to be proportional to link radius squared but the measured branches did not conform well to this model. The comparison suggests that the diameters of branch elements were more related to the requirements for mechanical load. The cost of following a hydraulic design principle (the pipe model) in terms of mechanical efficiency was estimated and suggested that the pipe model branch would not be mechanically compromised but would use structural resources inefficiently. Resource allocation among branch elements was found to be consistent with mechanical stability criteria but also indicated the possibility of allocation based on other criteria, such as potential light interception by shoots. The evidence suggests that whilst branch topology increments by reiteration of units of morphogenesis, the geometry follows a functional design pattern.

Evidence supporting hydraulic limitation hypothesis was found using foliar δ13C in combination with nitrogen content per unit leaf area and statistical partitioning for three conifer species. One theory behind the productivity decline of mature forests is the hydraulic limitation hypothesis (HLH); leaf-level gas exchange is reduced with increasing forest canopy height via increased hydraulic resistance in the xylem pathway, which in turn limits photosynthesis via stomatal regulation. Foliar $$\delta$$ 13C can be used to assess the HLH as it reflects the history of leaf-level gas exchange. However, this method should be used with caution as co-varying factors, including light levels and foliar nutrient status, can also influence foliar $$\delta$$ 13C. We explore the potential use of foliar $$\delta$$ 13C to assess leaf-level hydraulic limitation using three coniferous species across three height classes (short, intermediate and tall) in northern Idaho, USA. Foliar samples were collected from multiple canopy locations varying in height from each height class to measure $$\delta$$ 13C of bulk foliar materials as well as sugar and starch extracted from the samples. We also quantified nitrogen content per unit leaf area (Narea) as an integrated measure of nutrient status and light environment of a given foliar sample, which can partly account for various non-stomatal limitations for photosynthesis, and thus affect foliar $$\delta$$ 13C. Using sequential ANOVAs, we tested the hypothesis that foliar $$\delta$$ 13C variation was attributable to foliar sample height changes after accounting for Narea. The hypothesis was supported by analyses using foliage samples from the top canopy location across the three height classes for each conifer species, especially for bulk foliage and extracted sugar. In conclusion, we found evidence supporting the HLH using foliar $$\delta$$ 13C from three conifer species.

A method that applies the terrestrial laser scanning to estimate leaf areas of individual trees in a mature conifer forest is presented. It is based on the theory of conventional optical LAI determinations, but refined for the inclusion of 3D depth information from the laser scanner. For each objective tree, we first used a single scan to measure local gap fractions beyond determined crown depths and combined this scan with other scans to delineate the geometrical dimensions of the crown. Then, through integrating the information from both aspects, the local leaf area density and the corresponding volume were derived. Finally, the total leaf area was obtained as the scalar product of these two variables. As most procedures were implemented on segmented 2D range images, the method possesses high efficiency. Additionally, through using gap fraction beyond determined crown depths, it solved the zero gap fraction problem encountered in segmented hemispherical photograph analysis. The method was tested on 11 trees in a 39 years old Norway spruce (Picea abies [L.] Karst.) stand located in southern Bavaria, Germany. Through correlation of the results with the estimates obtained with allometric equations, the accuracy was validated. The influence of the crown depth, for measuring gap fraction, and the segment size on estimation were also analyzed.

The proteomic analysis of vascular tissues in rubber tree reveals differentially expressed proteins related to laticifer differentiation in mature phloem and secondary cell wall formation in mature xylem for latex/wood-yield improvement. Rubber tree (Hevea brasiliensis) is a latex-producing plant that has worldwide economic importance for the rubber and wood industries. Natural rubber latex is produced from laticiferous vessels (laticifers) located in the secondary phloem tissue of rubber trees. Improving latex production from rubber tree clones by studying the molecular genetics of vascular development has received much attention, but less information has been obtained from proteomic approaches. This study performed a comparative proteomic analysis of the vascular tissues in high latex-yield and high wood-yield rubber tree clones. One primary vascular tissue (newly developed stem) and two secondary vascular tissues (mature phloem/laticifers and mature xylem/wood) were investigated by qualitative/quantitative proteomic analysis using GeLC-MS/MS. The differentially expressed proteins (DEPs) in the specific vascular tissues were analyzed, and the protein functions in the biological processes related to vascular development and to the specific characteristics of each clone were clarified. The predicted protein–protein interaction network and GO annotation revealed DEPs related to photosynthesis, carbohydrate metabolism, energy production and jasmonic acid-responsive proteins involved in positive regulation of laticifer differentiation in mature phloem of the high latex-yield clone, while DEPs related to cell cytoskeleton maintenance, secondary cell wall components and auxin-, brassinosteroid-, abscisic acid-responsive proteins involved in xylem differentiation were abundant in mature xylem of the high wood-yield clone. This is the first report to demonstrate the correlation and functions of DEPs in phloem/laticifers and xylem/wood differentiation in rubber trees. The regulation of vascular development could be useful in improvement of latex and wood yields from rubber trees.

Conifer radial growth reductions may be related to unusual snow conditions or a mismatch between frost hardiness level and minimum temperature, but not typically to low winter temperature extremes. The aim of this study was to examine if temperature conditions potentially causing frost damage have an effect on radial growth in Norway spruce and Scots pine in Finland. We hypothesized that frost damage occurs and reduces radial growth after (1) extreme cold winter temperatures, (2) frost hardiness levels insufficient to minimum temperatures, and (3) the lack of insulating snow cover during freezing temperatures, resulting in increased frost and decreased temperatures in soil. Meteorological records were used to define variables describing the conditions of each hypothesis and a dynamic frost hardiness model was used to find events of insufficient frost hardiness levels. As frost damage is likely to occur only under exceptional conditions, we used generalized extreme value distributions to describe the frost variables. Our results did not show strong connections between radial growth and the frost damage events. However, significant growth reductions were found at some Norway spruce sites after events insufficient frost hardiness levels, and alternatively, after winters with high frost sum of snowless days. Scots pine did not show significant growth reductions associated with any of the studied variables. Thus, radial growth in Norway spruce may be more sensitive to future changes in winter conditions. Our results demonstrate that considering only temperature is unlikely to be sufficient in studying winter temperature effects on tree growth. Instead, understanding the effects of changing temperature and snow conditions in relation to tree physiology and phenology is needed.

Analysis of polyamines and amino acid profiles in Araucaria angustifolia immature seeds from two mother tree genotypes in 2 consecutive years, and their association with the establishment of embryogenic cultures. Polyamines (PAs) and amino acids are an important source of nitrogen in plants. They are known to participate in plant development and their levels are associated with specific zygotic and somatic embryogenesis stages, which means that they may be useful as biochemical markers of developmental stages. The present study carried out an analysis of PA and amino acid profiles in immature Araucaria angustifolia seeds from two mother tree genotypes over 2 consecutive years, and their association with the initiation and maintenance of embryogenic cultures (ECs). The results showed that initiation of ECs in A. angustifolia, as observed in other conifers, depends on harvest year and mother tree genotype. PA and amino acid profiles showed that seeds from distinct mother trees and harvest years are different from one another. These differences were reflected in the initiation of ECs. The metabolic analysis indicates that conjugated Spd, ornithine, and asparagine profiles are candidates as biochemical markers for selection of mother trees. These results will allow for the testing of a large number of mother trees as explant sources and the selection of those with higher potential for somatic embryogenesis.

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Mimosa luisana seeds germinate after 7 years of storage, suggesting that they have a long span life; an interesting characteristic for environmental restoration of semi-arid zones. Mimosa luisana is endemic to Mexico, provides ecosystem services and is economically and culturally important. This species exhibits morphological, anatomical and physiological qualities that make it potentially valuable in ecological restoration. This study evaluated the effects of seed age on seed germination, survival seedlings and growth of M. luisana, on the assumption that seed age positively influences the parameters related to germination. Mature fruits were collected at the semiarid Tehuacan–Cuicatlan Valley and the seeds were extracted. Healthy seeds were measured and weighed to obtain a uniform sample. Seed moisture content, imbibition rate, germination percentage, survival seedlings and growth were quantified. Seeds that were 84 months old showed the lowest moisture content (4.65%) and imbibition rate of unscarified seeds increased as seeds were older. Scarification considerably promoted germination, which was epigeal and phanerocotylar. Regardless of seed age, seedling growth was slow, with the presence of foliar cotyledons which persisted after the appearance of the protophylls, and the characteristics of an adult plant were observed until the day 22 after sowing. Mimosa luisana seeds are long-lived and the germination percentage depends on the age of the seed and whether or not it was scarified.