A Band Model of Cambium Development: Opportunities and Prospects

More than 60% of tree phytomass is concentrated in stem wood, which is the result of periodic activity of the cambium. Nevertheless, there are few attempts to quantitatively describe cambium dynamics. In this study, we develop a state-of-the-art band model of cambium development, based on the kinetic heterogeneity of the cambial zone and the connectivity of the cell structure. The model describes seasonal cambium development based on an exponential function under climate forcing which can be effectively used to estimate the seasonal cell production for individual trees. It was shown that the model is able to simulate different cell production for fast-, middle- and slow-growing trees under the same climate forcing. Based on actual measurements of cell production for two contrasted trees, the model effectively reconstructed long-term cell production variability (up to 75% of explained variance) of both tree-ring characteristics over the period 1937−2012. The new model significantly simplifies the assessment of seasonal cell production for individual trees of a studied forest stand and allows the entire range of individual absolute variability in the ring formation of any tree in the stand to be quantified, which can lead to a better understanding of the anatomy of xylem formation, a key component of the carbon cycle.

Manipulating phloem transport affects wood formation but not nonstructural carbon concentrations in an evergreen conifer

Wood formation is a crucial process for carbon sequestration, yet how variations in carbon supply affect wood formation and carbon dynamics in trees more generally remains poorly understood.To better understand the role of carbon supply in wood formation, we restricted phloem transport using girdling and compression around the stem of mature white pines and monitored the effects on local wood formation and stem CO2 efflux, as well as nonstructural carbon concentrations in needles, stems, and roots.Growth and stem CO2 efflux varied with location relative to treatment (i.e., above or below on the stem). We observed up to a two-fold difference in the number of tracheids formed above versus below the manipulations over the remaining growing season. In contrast, the treatments did not affect mean cell size noticeably and mean cell-wall area decreased only slightly below them. Surprisingly, nonstructural carbon pools and concentrations in the xylem, needles, and roots remained largely unchanged, although starch reserves declined and increased marginally below and above the girdle, respectively.Our results suggest that phloem transport strongly affects cell proliferation and respiration in the cambial zone of mature white pine, but has little impact on nonstructural carbon concentrations. These findings contribute to our understanding of how wood formation is controlled.HighlightRestrictions in phloem transport designed to affect carbon supply, lead to changes in wood formation and stem respiration of mature white pines without substantially changing local nonstructural carbon concentrations.

Transcriptomic Profiling of Cryptomeria fortunei Hooibrenk Vascular Cambium Identifies Candidate Genes Involved in Phenylpropanoid Metabolism

Cryptomeria fortunei Hooibrenk (Chinese cedar) is a coniferous tree from southern China that has an important function in landscaping and timber production. Lignin is one of the key components of secondary cell walls, which have a crucial role in conducting water and providing mechanical support for the upward growth of plants. It is mainly biosynthesized via the phenylpropanoid metabolic pathway, of which the molecular mechanism remains so far unresolved in C. fortunei. In order to obtain further insight into this pathway, we performed transcriptome sequencing of the C. fortunei cambial zone at 5 successive growth stages. We generated 78,673 unigenes from transcriptome data, of which 45,214 (57.47%) were successfully annotated in the non-redundant protein database (NR). A total of 8975 unigenes were identified to be significantly differentially expressed between Sample_B and Sample_A after analyzing their expression profiles. Of the differentially expressed genes (DEGs), 6817 (75.96%) and 2158 (24.04%) were up- and down-regulated, respectively. 83 DEGs were involved in phenylpropanoid metabolism, 37 DEGs that encoded v-Myb avian myeloblastosis viral oncogene homolog (MYB) transcription factor (TF), and many candidates that encoded lignin synthesizing enzymes. These findings contribute to understanding the expression pattern of C. fortunei cambial zone transcriptome. Furthermore, our results provide additional insight towards understanding the molecular mechanisms of wood formation in C. fortunei.

Characterization of indole-3-acetic acid in cambial zone tissue by ultra-performance liquid chromatography-tandem mass spectrometry

The developmental plasticity of plants according to changes in their growth conditions is mediated by signaling molecules called hormones. The major classes of plant hormones are auxin, gibberellins, abscisic acid, and ethylene. Among these, the most important is indole-3-acetic acid (IAA). Quantification of IAA in an extract of approximately 10 mg obtained from the cambial zone of Eucalyptus leaves was performed by ultra-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC/ESI-MS/MS). The leaves were extracted using acetone, and the extract was analyzed using a reverse-phase column (Acquity UPLC BEH C18, 2.1 mm × 100 mm, 1.7 µm) at a flow rate of 0.2 mL/min with gradient elution of an aqueous mobile phase (containing 0.1% formic acid) with methanol. This gradient elution provided an excellent performance in terms of specificity/selectivity, linearity, precision, and ruggedness/stability. In addition, the run time was short (6 min), with excellent linearity (R2 > 0.99) in the range of 10–70 ng/mL. The structure of IAA was elucidated using UPLC/ESIMS/MS, operating and quantifying in multiple reaction monitoring (MRM) mode.

Rooting and growth of root cuttings of two old rose cultivars ‘Harison’s Yellow’ and ‘Poppius’ treated with IBA and biostimulants

Propagation by root cuttings is an easy and low-cost method for plant taxa with an ability to produce rhizomes or suckers. This research examined the possibility of using root/rhizome cuttings in the propagation of two difficult-to-root old rose cultivars, ‘Harison’s Yellow’ and ‘Poppius’. A plant-based preparation (Root Juice), titanium (Tytanit), and IBA (Chryzotop Green 0.25% IBA, Rhizopon AA 020 XX 2.00% IBA) were tested as rooting and growth enhancers for thick, medium, and thin rhizome/root cuttings. Additionally, observations were made to identify the site of the initial root and shoot formation. Shoots appeared before roots, without polarity. The visible swellings differentiating in new root/shoot buds in these two rose cultivars were placed along the rhizome. The primordia of root and shoot buds were situated near the pith rays and the vascular cambial zone. The trial reported here showed significant effects of the thickness of root cuttings and the preparations used in terms of rooting success and growth characteristics. Medium-sized cuttings of rose ‘Harison’s Yellow’ (45.0%), and thin cuttings of ‘Poppius’ (74.3%) achieved the highest rooting percentages. The most effective treatment was with Chryzotop Green, but Root Juice 0.01% and Tytanit 0.04% (‘Poppius’) and 0.02% (both cultivars) also had positive activity. Root Juice and Tytanit can be suggested for rooting cuttings of these roses as eco-friendly preparations.

Sample size and cardinal orientation in cambial activity analysis: a case study

ABSTRACTRadial growth dynamics of woody species is studied by different methods. the annual monitoring of cambial activity has been recommended as the method of greatest accuracy in research and appropriate for studies in protected areas for biological conservation, because it is largely nondestructive. Nevertheless, sampling protocols still need more standardization and precision. this study aims to investigate the influence of cardinal orientation on the number of cells in the cambial zone, and to evaluate the number of trees needed to conduct histological studies of cambial activity in Cedrela odorata, a tropical species with well-defined annual growth in the Atlantic Forest of South America/Brazil. Seventeen trees were evaluated during the period of intense cambial activity, with the sampling of four quadrants of the stem, according to cardinal orientation. the variance of cambial cell numbers was calculated for different numbers of trees. the results showed that radial growth variance was not related to cardinal orientation, but that at least 12 trees should be sampled for robust data on cambial dynamics.

Agronomic and Anatomical Indicators of Dwarfism and Graft Incompatibility in Citrus Plants

Poncirus trifoliata var. monstrosa (T. Ito) Swingle is a rootstock used in Brazilian citriculture for its potential to induce dwarfism and the viability of densified crops. Its recommendation is still restricted due to lack of research on the performance and compatibility of different types of scion under specific conditions of soil and climate. The aim of this study was to correlate plant size and productive efficiency with anatomical indicators of dwarfism or graft incompatibility between citrus scion cultivars and the ‘Flying Dragon’ trifoliate orange (FD) and ‘Rangpur Lime’ (RL) as rootstocks. The experimental design was of randomised blocks with split plots, with the experiment conducted in an orchard from the fourth to the sixth year of cultivation, under localised irrigation. The treatments consisted of two rootstocks (FD and RL) in the plots and five scion cultivars (Tahiti acid lime, and Natal, Navel, Lima Sorocaba and Pera oranges) in the sub-plots, with four replications per treatment. The agronomic performance of the plants was evaluated, together with the characteristics of samples containing the cambial zone and secondary xylem below, above and within the graft region. The FD rootstock gives the smallest size and greatest productive efficiency. The ‘Navel’ orange has good anatomical plasticity, adjusting itself more efficiently to the rootstocks. Visual symptoms of incompatibility between the ‘Pera’ orange grafted onto the FD can be seen at 64 months after planting. Vessel size and frequency, as well as the size and disposition of the cambial zone, are related to dwarfism and graft incompatibility.