Carbon isotope fractionation in tree ring early and late wood in relation to intra-growing season water balance

We determined the stable carbon isotope composition (δ^1.3C) of cellulose extracted from early and late wood in Douglas fir [Pseudotsuga menziexii (Mirb.) Franco] tree rings. Data were obtained for the period 1962 to 1981, at the start of which the trees were 20 years old. A water balance model was used to calculate daily stand transpiration and water deficit. The model incorporates site factors (soil water availability, slope and aspect) and environmental variables (solar radiation, air temperature and rainfall). There was far greater variability in late wood than in early wood δ^1.3C. In wet years, late wood δ^1.3C was significantly lighter (by as much as 2δ) than early wood δ^1.3C but in dry years this difference was reversed. Differences between spring and summer cumulative transpiration accounted for almost 60δ of the variability in differences between early and late wood δ^1.3C. We found excellent correspondence between summer cumulative transpiration and late wood δ^1.3C, with estimates of transpiration accounting for up to 93% of the variability in δ^1.3C. Correlations between early wood δ^1.3C and spring transpiration were generally poor (r2<0.4), but we were able to identify those exceptional years in which there had been a very dry spring. Our results indicate that, while tree ring δ^1.3C correlates reasonably well with basal area increment, it is a far better indicator of inter- and intra-annual variability in water availability than radial growth.     

RFLP of RT-PCR products: Application to the expression ofCHS multigene family in poplar

A novel method for studying differential expression of multigene family members based on the high sensitivity of RT-PCR completed by restriction site polymorphism of DNA is described. This method allows the identification of specific patterns of expression of fourchalcone synthase genes in a Hunnegem poplar clone (Populus trichocarpa ×Populus deltoides).     

Comparative anatomy and systematics of woody Saxifragaceae. Aphanopetalum Endl.

The floral and vegetative anatomy of the small Australian genus Aphanopetalum were studied. Wood is described for the first time and is characterized by predominantly solitary pores, scalariform vessel element perforation plates with low bar numbers, imperforate tracheary elements with distinctly bordered pits, sparse axial parenchyma, and a combination of homocellular and heterocellular rayS. Starch occurs in both axial and ray parenchyma of the wood. Stems possess unilacunar, one-trace nodes and the uncommon feature of an endodermis with well-defined Casparian stripS. Leaves have anomocytic stomata, a bifacial mesophyll and semicraspedodromous venation or a combination of semicraspedodromous and brochidodromous venation. The tetramerous flowers are apetalous or have minute petals. The compound, half-inferior gynoecium consists of essentially totally united carpels. The pattern of floral vascularization resembles different Saxifragaceae sensu lalo in that the compound sepal-plane and petal-plane traces give rise to staman bundles as well as sepal, petal, and carpel wall venation in their respective planes. The ventral ovarian bundles are fused into a single ventral complex that subdivides at the top of the ovary to form ventral bundles and to supply the one ovule in each locule. Vegetative and floral features provide compelling evidence to suggest that Aphanopetalum has its nearest relatives among the Saxifragaceae sensu lato rather than Cunoniaceae. The genus is probably best treated as forming its own subfamily (or family) among the saxifragaean alliance.     

Involvement of putrescine in the inductive rooting phase of poplar shoots raised in vitro

Micropropagated poplar shoots rooted 100% on a rooting medium (A) containing NAA, but they did not root in the absence of auxin (NA). Putrescine, but not spermidine and spermine, promoted rooting up to 42% when added to the NA medium. Cyclohexylamine (CHA), an inhibitor of spermine synthase, also promoted (up to 36%) rooting in the absence of auxin. The inhibitors of polyamine biosynthesis DFMA (α-difluoromethylarginine) and DFMO (α-difluoromethylomithine), aminoguanidine (AG) and methylglyoxal-bis-guanylhydrazone (MGBG), inhibited rooting when applied in the presence of auxin and had no effect in its absence.
The rooting inductive phase (in the presence of auxin) was determined by periodical transfer of shoots from A to NA medium, and by changes in peroxidase activity, to be 7 h. Putrescine (not spermidine and spermine) accumulated to a maximum during the inductive phase. Both putrescine and CHA promoted rooting on NA medium when applied during the first 7 h. In contrast DFMA and AG inhibited rooting during this period. The results point to the involvement of putrescine and its Δ¹-pyrroline pathway, in the inductive phase of rooting in poplar shoots.     

零下低温对杂交杨树皮层膜脂组成的影响

以不耐寒的美洲黑杨（Ｐｏｐｕｌｕｓｄｅｌｔｏｉｄｅｓｃｖ．“Ｌｕｘ”Ｉ－６９／５５,父本）和耐寒性较强的欧美杨（Ｐ．ｅｕｒａｍｅｒｉｃａｎａｃｌｃｖ．Ｉ－４５／５１,母本）的４个杂交Ｆ＿１代无性系（９５杨、５５９杨、６００杨和１３８１杨）为材料,分析了零下低温寒潮前后枝条皮层的脂质组成。结果表明,寒潮影响下,皮层中磷脂含量增加而组成基本不变,膜脂脂肪酸组成的变化规律是：寒潮前脂肪酸不饱和指数（ＩＵＦＡ）值大的无性系,寒潮前后的ＩＵＦＡ值变化量小;寒潮前ＩＵＦＡ值较小的无性系,寒潮前后ＩＵＦＡ值变化量较大。本文借用力学概念,提出相对抗性概念,给出杨树无性系的相对抗性序列。序列表明Ｆ＿１代无性系的耐寒性已较不耐寒的父本提高,这与田间观察基本一致。     

The dendrochronological potential of decayed yew wood

A significant difficulty in the accurate ageing of many of the largest-diameter yew trees (Taxus baccata L.) found in the United Kingdom is their vulnerability to heartwood decay. This has presented a considerable barrier to extending yew chronologies beyond c.330 years into the past. Decayed wood often survives within the sound cylindrical structure of hollow and hollowing yews. Here we present the analysis of such decayed yew wood using a novel wet-scanning technique. Long series for four out of five large hollow yew trees sampled are successfully cross-matched to produce a 374-year-long mean series spanning 1532–1905. These newly dated series extend the previous mean UK yew chronology by 158 years. Although currently undated, the central decayed material from the largest yew at Selborne produces a 196-year series which is likely to include material from the 14th century. Given the number of large hollow yew trees surviving in the UK, this research highlights the potential for using decayed yew wood to improve the ageing of yew trees and extending a regional yew chronology.     

Wood distillate (pyroligneous acid) boosts nutritional traits of potato tubers

Potato is the fourth most widely consumed staple food in the world. This study investigated the effectiveness of 0.2% wood distillate (WD), a biostimulant derived from the pyrolysis of waste plant biomass, in boosting the nutritional quality of potato tubers. The results showed that application of WD significantly increased the content of soluble sugars (sucrose +56.3%; glucose +44.9%; fructose +62.2%), starch (+35.1%) and total carbohydrates (+16.8%). Antioxidants (total antioxidant power, polyphenols, flavonoids) and most mineral elements (K, Mg, Ca, Na, Fe, Zn) were not affected. A lower content of Cu (−17.8%) and P (−24.5%) was found in WD-treated potato.     

Genomic insights into selection for heterozygous alleles and woody traits in Populus tomentosa

Heterozygous alleles are widespread in outcrossing and clonally propagated woody plants. The variation in heterozygosity that underlies population adaptive evolution and phenotypic variation, however, remains largely unknown. Here, we describe a de novo chromosome-level genome assembly of Populus tomentosa, an economic and ecologically important native tree in northern China. By resequencing 302 natural accessions, we determined that the South subpopulation (Pop_S) encompasses the ancestral strains of P. tomentosa, while the Northwest subpopulation (Pop_NW) and Northeast subpopulation (Pop_NE) experienced different selection pressures during population evolution, resulting in significant population differentiation and a decrease in the extent of heterozygosity. Analysis of heterozygous selective sweep regions (HSSR) suggested that selection for lower heterozygosity contributed to the local adaptation of P. tomentosa by dwindling gene expression and genetic load in the Pop_NW and Pop_NE subpopulations. Genome-wide association studies (GWAS) revealed that 88 single nucleotide polymorphisms (SNPs) within 63 genes are associated with nine wood composition traits. Among them, the selection for the homozygous AA allele in PtoARF8 is associated with reductions in cellulose and hemicellulose contents by attenuating PtoARF8 expression, and the increase in lignin content is attributable to the selection for decreases in exon heterozygosity in PtoLOX3 during adaptive evolution of natural populations. This study provides novel insights into allelic variations in heterozygosity associated with adaptive evolution of P. tomentosa in response to the local environment and identifies a series of key genes for wood component traits, thereby facilitating genomic-based breeding of important traits in perennial woody plants.