Cinnamate 4-hydroxylase (C4H) is the second enzyme in the phenylpropanoid pathway which participates in the synthesis of numerous phenylpropanoid compounds such as flavonoids, lignins, suberins and others. We identified a gene putatively coding for Class I C4H in apricot and plum and we analyzed the expression pattern of this gene under different apricot/plum graft combinations with different degree of compatibility. The full-length cDNA is 1 739 bp with a 1 515 bp open reading frame encoding a protein of 504 amino acids. Like other C4Hs, the predicted C4H polypeptides included conserved domains of cytochrome P₄₅₀. The genomic sequence of the apricot C4H gene was interrupted by two introns 335 bp and 904 bp long. Several regulatory motifs including P-, A-, L- and H-boxes, which were conserved across phenylpropanoid metabolism-related genes in higher plants, were found in a 1 300 bp upstream promoter region of the apricot C4H gene. A phylogenetic analysis showed that all Prunus sequences clustered together and were closely related to Malus and Rubus C4H genes. The transcription of Class I PruC4H was detected in all the examined graft combinations, which suggested its rather constitutive character.

The aim of this work was to characterize a nucleotide sequence MK14 that originated from a plasmid library obtained via degenerate oligonucleotide primed polymerase chain reaction (DOP-PCR) amplification of laser microdissected Y-chromosomes of Silene latifolia. This sequence showed significant similarity to parts of two adjoining genes from bacterial representatives of the genus Ralstonia. MK14 sequence contains a part of a conserved domain, and phylogenetic analysis based on this region confirmed its relationship to Ralstonia-derived sequences. Genomic Southern blot analysis proved the presence of this fragment in the genome of S. latifolia. We hypothesize that this insertion is of bacterial origin, and was probably gained via horizontal gene transfer. Moreover, MK14 insertion is shared by some closely related Silene species, suggesting an ancient spontaneous transformation by an ancestor of bacteria from the genus Ralstonia.

Ethylene response factors (ERFs) are involved in many plant development events and stress defenses. In this study, an ERF gene, VvERF3b, was cloned from the leaves of Vitis vinifera. VvERF3b belongs to ERF group VIIIa. Expression of the gene was induced by abscisic acid, ethephon, and salicylic acid, but not by NaCl. Promoter sequence analysis of the VvERF3b gene revealed that there are several potential cis-acting elements that may be potentially recognized and bound by the transcription factors related to hormones and stress responses. Deletion analysis showed that the 5'-flanking sequence of -1047 to -585 from the transcriptional start site is essential to the high expression of the VvERF3b gene, whereas the sequence fragment of -1324 to -1047 revealed suppression effect. The result indicated that the region appears to contain cis-acting elements that can be bound by the proteins in a transcription complex to induce the inhibition of gene expression.

Small heat shock proteins (sHSPs) are crucial components of the plant response to heat shock. We identified and analyzed eight sHSP genes of Capsella bursa-pastoris to better understand the ability of this species to adapt. Eight genes were initially cloned and sequenced from the mature embryo cDNA pool. They belong to the cytosolic I (CI), cytosolic II (CII), and cytosolic III (CIII) subfamilies. One CI sHSP gene was homologous to that of C. rubella. Sequence analysis using 3' RACE revealed that there are two or more variable 3'-untranslated regions (UTRs) in these sHSP transcripts. The transcriptional levels of the eight sHSP genes were analyzed in different organs and developmental stages via qRT-PCR. Eight genes were significantly up-regulated in young leaves exposed to heat stress at 42 °C, and also showed differential responses to ABA treatment. We also compared expression of these genes with corresponding Arabidopsis sHSP genes and found some differences between the two species.

Thinopyrum intermedium is an important species with potential utilization value in breeding of wheat. In this study, the non-coding intergenic region of trnH-psbA was investigated to assess the genetic diversity and infer the maternal origin within T. intermedium accessions. Eleven haplotypes were distinguished among the thirty-five accessions of T. intermedium. They showed a relatively low nucleotide diversity (π) of 0.00473 ± 0.00037 and a moderately high haplotype diversity (H_d) of 0.733 ± 0.061. In the phylogenetic analysis, all accessions of T. intermedium were positioned into two clades, which corresponded to the different diploid donors. These results suggested that there were two phylogenetically divergent maternal donors in T. intermedium.

Iron is one of the essential micronutrients required by all living organisms. In this study, we isolated a gene encoding putative citrate synthase (CS) from Malus xiaojinensis, designated as MxCS1. The MxCS1 gene encodes a protein of 473 amino acid residues with a predicted molecular mass of 52.5 kDa and a theoretical isoelectric point of 8.67. The expression of MxCS1 was enriched in the leaf rather than in phloem and root, however, its expression was hardly detected in the xylem. The gene expression was strongly induced by Fe stress treatment in the M. xiaojinensis seedlings. Over-expression of MxCS1 improved Fe deficiency tolerance in transgenic Arabidopsis. We argued that MxCS1 is a new member of the CS genes, and it may function as a regulator in response to iron stress in plants.

In the present study, in vitro regeneration system for a recalcitrant woody tree legume, Leucaena leucocephala (cvs. K-8, K-29, K-68 and K-850) from mature tree derived nodal explants as well as seedling derived cotyledonary node explants was developed. Best shoot initiation and elongation was found on full-strength Murashige and Skoog (MS) medium supplemented with 3 % (m/v) sucrose, 100 mg dm^-3 myoinositol, 100 mg dm^-3 glutamine, 20.9 µM N ⁶-benzylamino-purine (BAP) and 5.37 µM 1-naphthalene acetic acid (NAA). Rooting was induced in half-strength MS medium containing 2 % (m/v) sucrose, 100 mg dm^-3 myoinositol, 14.76 µM indole-3-butyric acid (IBA) and 0.23 µM kinetin. The cultivar K-29 gave the best response under in vitro conditions. Rooted plantlets were subjected to hardening and successfully transferred to greenhouse. Further, somatic embryogenesis from nodal explants of cv. K-29 via an intermittent callus phase was also established. Pronounced callusing was observed on full-strength MS medium containing 3 % (m/v) sucrose, 100 mg dm^-3 myoinositol, 40.28 µM NAA and 12.24 µM BAP. These calli were transferred to induction medium and maximum number of globular shaped somatic embryos was achieved in full-strength MS medium fortified with 3 % (m/v) sucrose, 100 mg dm^-3 myoinositol, 15.0 µM 2,4-dichlorophenoxyacetic acid (2,4-D), 5.0 µM BAP and 1.0 mM proline. Moreover, an increase in endogenous proline content up to 28^th day of culture in induction medium was observed. These globular shaped somatic embryos matured in full-strength MS medium with 3 % (m/v) sucrose, 100 mg dm^-3 myoinositol, 10.0 µM BAP, 2.5 to 5.0 µM IBA and 0.5 mM spermidine.

Randomly amplified polymorphic DNA (RAPD) and inter simple sequence repeat (ISSR) markers were applied to assess the genetic stability of micropropagated olive (Olea europaea L. cv. Maurino) plants regenerated by axillary buds. Initial olive explants, isolated from one donor tree, were multiplied on Murashige and Skoog medium for 12 repeated subcultures. A total of 40 RAPD and 10 ISSR markers resulted in 301 distinct and reproducible band classes showing homogeneous RAPD and ISSR patterns. The amplification products revealed genetic stability among the micropropagated plants and between them and the donor plant. The results demonstrate the genetic stability of nine year old mature micropropagated olive plants cultured in field, and corroborated the fact that axillary multiplication is the safest mode for multiplication of true to type plants.

Apomixis represents an alteration of classical sexual plant reproduction to produce seeds that have essentially clonal embryos. In this report, hickory (Carya cathayensis Sarg.), which is an important oil tree, is identified as a new apomictic species. The ovary has a chamber containing one ovule that is unitegmic and orthotropous. Embryological investigations indicated that the developmental pattern of embryo sac formation is typical polygonum-type. Zygote embryos were not found during numerous histological investigations, and the embryo originated from nucellar cells. Nucellar embryo initials were found both at the micropylar and chalazal ends of the embryo sac, but the mature embryo developed only at the nucellar beak region. The mass of the nucellar embryo initial at the nucellar beak region developed into a nucellar embryo or split into two nucellar proembryos. The later development of the nucellar embryo was similar to the zygotic embryo and progressed from globular embryo to heart-shape embryo and to cotyledon embryo.

A new full-length cDNA encoding 3-hydroxy-3-methylglutaryl-CoA synthase (designated as TmHMGS, GenBank Accession No. AY644708), which catalyses the condensation of acetyl CoA and acetoacetyl CoA to form 3-hydroxy-3-methylglutaryl-CoA as an early step in the taxol biosynthetic pathway, was isolated from young leaves of Taxus × media by rapid amplification of cDNA ends (RACE) for the first time. The full-length cDNA of TmHMGS contained a 1431 bp open reading frame (ORF) encoding a deduced protein of 476 amino acid residues. The deduced protein had an isoelectric point of 5.23 and a calculated molecular mass of about 53 kDa. Amino acid sequence comparison analysis showed that TmHMGS had high similarity with a number of HMGSs ranging from Schizosaccharomyces pombe to humans, with much higher identity with other HMGSs from plants than those from yeast and humans. Phylogenic analysis showed that TmHMGS had closest relationship with HMGS from Pinus sylvestris. Tissue expression pattern analysis showed that TmHMGS expressed in needles and stems at similar level, but no expression could be detected in roots. Expression of TmHMGS was all induced by under different elicitors such as silver nitrate, ammonium ceric sulphate and methyl jasmonate, revealed that TmHMGS was an elicitor-responsive gene.

Thirteen genomic microsatellite (gSSR) and sixteen expressed sequence tag (EST)-SSR (eSSR) markers were compared to estimate genetic diversity among 29 cucumber (Cucumis sativus L.) accessions. gSSR markers detected mean 4.46 alleles with a mean polymorphic information content (PIC) of 0.664, against eSSR markers with mean 3.38 alleles and a mean PIC of 0.397. gSSRs amplified more null alleles than eSSRs. Genetic diversity within the accession set was estimated by construction of dendrograms using gSSR or eSSR data. There was a clear consistency between gSSR and eSSR trees in terms of positioning of most cucumber germplasms. gSSR markers could separate various types of cucumber germplasms on the whole, although clustering of some accessions was not based on their geographical origins in eSSR tree. eSSR markers identified an independent sub-cluster containing five accessions resistant to downy mildew, suggesting a probable relationship between eSSRs and disease-resistance trait in cucumber. The Mantel test between gSSR and eSSR matrices revealed a good fit correlation (r = 0.836). The general dendrogram constructed using the combined data of gSSRs and eSSRs was similar to those obtained separately with each marker.

Experiments were carried out to evaluate the effects of 4/2 light-dark cycles (4 h of light followed by 2 h of dark) on the rooting responses of shoots cultivated in vitro of the fruit tree rootstocks GF 677 (peach × almond hybrid), Mr.S. 2/5 (Prunus cerasifera), MM 106 (apple Nothern Spy × Paradise M1) and BA 29 (Cydonia oblonga). Under this light regime rooting percentage of GF 677, Mr.S. 2/5 and MM 106 shoots reached 100 % as in the control treatment (16/8), while in BA 29 shoots, short light-dark cycles increased rooting response by about 65 %. Moreover, the shoots of all rootstocks submitted to the 4/2 cycle showed an appreciable increase in root number and length, and an earlier root emergence of about 4 - 5 d compared to the 16/8 cycle. Finally, rooting percentage of BA 29 shoots submitted to the 4/2 light regime and treated with 0.2 mg dm^-3 indolebutyric acid (IBA), was equal to that reported with 0.4 mg dm^-3 IBA under the 16/8 regime, indicating that the former light regime also amplified the rhizogenic effect of auxin.

The trnS/psbC region of chloroplast DNA (cpDNA) was sequenced for 18 Elymus polyploid species, Hordelymus europaeus and their putative diploid ancestors. The objective was to determine the maternal origin and evolutionary relationships of these polyploid taxa. Phylogenetic analysis showed that Elymus and Pseudoroegneria species formed a highly supported monophyletic group (100 % bootstrap values), suggesting that Pseudoroegneria is the maternal genome donor to polyploid Elymus species studied here. The phylogenetic tree based on cpDNA sequence data indicates that E. submuticus contains a St-genome. Taking into consideration of our previously published RPB2 data, we can conclude that hexaploid E. submuticus contains at least one copy of St and Y genomes. Our Neighor-joining analysis of cpDNA data put Psathyrostachys juncea, Hordeum bogdanii and Hordelymus europaeus into one group, suggesting a close relationship among them.

Experiments were performed to optimize the macronutrients concentrations for in vitro rooting of Ceratonia siliqua micropropagated shoots. Several dilutions of Murashige and Skoog (MS) medium were tested: full-strength MS, half-strength MS (1/2MS), and 1/2MS + full N. The frequency of in vitro rooting was enhanced when the 1/2MS was used (50 % rooted shoots). Mature leaves from 20 - 30 year-old carob trees and from 2 year-old micropropagated plants were collected and the concentrations of macronutrients (N, P, K, Ca, Mg) assessed. Based on the mineral composition of the leaves a new medium was formulated and compared with the previous ones showing an increment of the rooting frequency to 80 %. Moreover, shoots rooted in the new medium did not show symptoms of apical necrosis that occurred in the other tested media.

Measurements of dependence of photosynthetic electron transport on irradiance and analyses of stable isotope ratios (δ¹⁸O, δ¹³C, δ¹⁵N) were performed on 4 to 6-year-old pine trees (Pinus sylvestris L.) in the primeval forest reserve of Białowieża and on 21-year-old pine trees of a plantation of different provenances at the Sękocin Forest Station near Warsaw, Poland. Small differences in maximum photosynthetic electron transport rates, ETR_max were related to growth. Stable isotope analyses suggest that water relations play an important role for the performance of P. sylvestris at the sites studied. The intraspecific comparisons showed a very high variability of photosynthetic capacity between needles of given trees and between individual trees under similar conditions. Differences between specific provenances were also observed. This is relevant for ecological niche occupation in a wide geographical growth range, where P. sylvestris is actually occurring. The high physiological plasticity demonstrated reveals a conspicuous trait of this tree species.

This study reports survival and physiological responses of micropropagated Ceratonia siliqua L. cvs. Galhosa and Mulata plants during ex vitro acclimatization under ambient (AC; 330 μmol mol^-1) or elevated (EC; 810 μmol mol^-1) CO₂ concentration and a photosynthetic photon flux density of 125 μmol m^-2 s^-1. CO₂ enrichment during acclimatization did not improve survival rate that was around 80 % for both treatments. Eight weeks after ex vitro transplantation, photosynthetic capacity and apparent quantum yield in acclimatized leaves were higher in comparison with those in in vitro-grown leaves, without any significant difference between CO₂ treatments. Chlorophyll content increased after acclimatization. However, EC led to a decrease in the total amount of chlorophyll in new leaves of both cultivars, compared to those grown at AC. Soluble sugars and starch contents were not markedly affected by growth EC, although starch had significantly increased after transfer to ex vitro conditions. EC induced an increase in the stem elongation and in the effective life of leaves, and a decrease in the number of new leaves.

A DNA-based, inter simple sequence repeat (ISSR) markers were used to monitor genetic stability in micropropagated plantlets of Nothapodytes foetida. A total of 146 clear and distinct bands were produced using 26 primers resulting in 3 212 fragments. Out of 146, 135 bands (92.4 %) were monomorphic and 11 bands (7.53 %) were polymorphic which ranged from 200 to 21 226 bp in size. The number of bands per each primer varied from 1 to 11 with an average of 5.6 bands per primer. The banding pattern for each primer was uniform and comparable to mother plant from which the cultures had been established. The dendrogram based on the unweighted pair-group method with arithmetic averaging (UPGMA) depicted about 97 % homology between the mother plant and micropropagated plants. An attempt was made to reintroduce the micropropagated plants in the natural habitat and over 500 plants were successfully established.

We isolated and characterized eleven polymorphic microsatellite loci for Aegiphila sellowiana an outcrossing pioneer tree species that is frequently used in reforestation programs of tropical riparian forests in Brazil. A total of 38 alleles were detected across a sample of 45 individuals of A. sellowiana, with an average number of 3.45 alleles per locus. The average polymorphic information content (PIC) was 0.430 and the observed (H_O) and expected (H_E) heterozygosity values varied from 0.156 to 1.000 and 0.145 to 0.730, respectively. Eight loci exhibited significant deviation from Hardy-Weinberg equilibrium (P ≤ 0.001) and 32 pair combinations of loci showed significant linkage disequilibrium (P ≤ 0.001). All 11 primers were tested for cross amplification in 12 species belonging to the family Lamiaceae and 5 species belonging to the related family Verbenaceae. The sequence and diversity information obtained using these microsatellites and their cross-transferability to other species of Lamiaceae as well as Verbenaceae will increase our understanding of genetic structures and species relationships within Aegiphyla and other genera of these families.

Hydraulic conductance of stem and petioles increased in response to an increase in xylem sap ion concentration, and decreased in response to a decrease in the ion concentration in six temperate deciduous tree species. The ion sensitivity of hydraulic conductance of stem and petioles was higher than the ion sensitivity of the stem alone. The ion sensitivity was lowest in the earliest developmental stages of the xylem, and had a seasonal maximum in the second half of summer. The ion sensitivity was highest in slow-growing species and lowest in fast-growing species. The ion sensitivity correlated negatively with mean radius of xylem conduits, hydraulic conductance of stem and petioles, hydraulic conductance of leaf laminae, and stomatal conductance, and positively with response of the hydraulic conductance of leaf laminae to HgCl₂, and stomatal response to a decrease in leaf water potential or abscisic acid. It was concluded that the high ion sensitivity of xylem hydraulic conductance is a relevant characteristic of slow growth and a conservative water use strategy.

To get insight into mechanism by which apple tree (Malus domestica Borkh.) regulates flowering, two apple flowering locus T (FT) homologues, MdFT1 and MdFT2, were isolated from the leaf cDNAs of cultivar Gala. The open reading frames (ORFs) of two MdFTs encoded 174 amino acids. The deduced amino acid sequence of MdFT1 and MdFT2 showed 94.3 % similarity to each other, while 72.6 and 76.0 % to AtFT protein, respectively. Semi-quantitative RT-PCR indicated their specific expression in leaves. Visualization of MdFT2-GFP fusion protein demonstrated its localization on membrane. Ectopic overexpression of either MdFT1 or MdFT2 in Arabidopsis significantly induced early flowering by activating the downstream flowering-related genes.

Twenty clones of the breeding population of Hevea brasiliensis were evaluated for phenetic diversity. The test-clones included six clones developed in Nigeria, ten Malaysian clones, two clones from Indonesia and a clone from each of Brazil and Sri Lanka. Data collected on fifteen seed characters in 1998 and 1999 were utilized for multivariate analysis. Cluster analysis of data matrix of clonal mean seed characters was conducted to produce principal component axes, dendrograms and Tocher's clusters in 1998, 1999 and the combined data. There was taxonomic isolation of the recent collection from Brazil (IAN 710) from the other clones that are either members or descendants of the Wickham collection of 1876. There was a continuum of phenetic diversity from the highly divergent to the closely related pairs of clones. The highly divergent clones are expected to produce heterotic progenies in crosses while crosses among clones with close phenetic similarity should be avoided. This will guide against inbreeding depression and genetic erosion.

The toxic aromatic compound 3-hydroxy-4-pyridone (HP) is an intermediate in both synthesis and degradation of mimosine, which is produced by the tree legume Leucaena leucocephala. The L. leucocephala root-nodule symbiont Rhizobium TAL1145 contains a dioxygenase (pydA) and a hydrolase (pydB) gene that produce enzymes necessary for the degradation of HP. In order to coordinately express both genes in plant tissues under a single promoter, three different pydA-pydB fusion constructs (G0, G3, and G7) with varying glycine linkers between the two genes were developed. Prior to transferring the fusion constructs into L. leucocephala, which is highly recalcitrant to genetic transformation, we tested the expression and activity of the hybrid proteins in Nicotiana tabacum, a model plant system that can be easily transformed and analyzed. Seven independent transgenic tobacco lines were generated by Agrobacterium-mediated transformation, and stable integration and expression of pydA-pydB in these transgenic lines were confirmed by polymerase chain reaction (PCR), reverse transcriptase PCR (RT-PCR) and Western analysis. Only one of the fusion constructs, G3, containing a 9-nucleotide linker between pydA and pydB, provided significant levels of resistance to 3 mM HP, indicating that the hybrid protein produced by this fusion construct could degrade HP.

We compared two populations of Populus cathayana Rehder, originating from altitudes 2 840 m and 1 450 m, to determine whether trees from different altitudes exhibit different tolerance to alkalinity. The tree cuttings were exposed to nutrient solutions with pH 7.9, 8.8, 9.8 and 10.4 and the salt concentration 200 mM. Na⁺ and K⁺ contents, and Na⁺/K⁺ ratios in leaves and roots were greatly affected by pH values. At pH 10.4, the Na⁺/K⁺ ratios in both leaves and roots sharply dropped in the higher altitude population but were maintained at higher levels in the lower altitude population. The patterns of pH-induced changes in contents of malondialdehyde and free proline, and antioxidative enzyme activities indicated that the higher altitude population exhibits greater tolerance to alkalinity stress than does the lower altitude population.

An in vitro method for propagation of Holarrhena antidysenterica Wall. has been developed using nodal explants from mature trees growing in the field. Irrespective of concentrations and combinations of growth regulators used, the axillary and terminal buds sprouted and elongated when inoculated on Murashige and Skoog (MS) medium. The highest numbers of shoots were formed when sprouted shoots were subcultured from MS basal medium onto MS medium containing 2 mg dm^-3 N⁶-benzyladenine (BA) and 0.5 mg dm^-3 α-naphthalene acetic acid (NAA). The shoot number further increased upon subculture on MS medium containing 0.5 mg dm^-3 BA. By repeated sub-culturing of shoots derived from nodal axillary buds, a high frequency multiplication rate was established. The elongated shoots were excised and rooted in auxin free MS basal medium. Ex vitro rooting of in vitro formed shoots was achieved upon dipping the microshoots for 2 min in 2 mg dm^-3 of indole-3-butyric acid solution. Successful field establishment and high (80-90 %) survival of plants was observed.

The aim of this work was to assess the responses of seedlings of five species of Nicotiana genus to red and far red radiation. N. acuminata exhibits positive photoblastic behaviour and germination was completely inhibited under far red and darkness. In N. glauca germination was reduced under far red and darkness, but the other species showed neutral behaviour. The hypocotyl elongation was inhibited in N. glauca and N. tabacum under white and far red radiation. In N. langsdorffii and N. debneyi hypocotyl was elongated under far red radiation. Only in N. acuminata red radiation promote greater hypocotyl elongation than dark condition. On the phylogenetic tree obtained from restriction analysis N. glauca and N. acuminata are grouped in one branch, while the other species, N. langsdorffii, N. debneyi and N. tabacum, are grouped in the other branch cluster. Moreover, the N. debneyi behaviours under different radiation treatments were similar to those of N. tabacum. These two species are allopolyploid members of the genus Nicotiana, as also was confirmed by this study.

Carbon translocation was affected by shade in different tropical tree species differing in successional status and degree of shade tolerance. Plants of the early-successional shade-intolerant species Cecropia pachystachya and Schizolobium parahyba and of the late-successional shade-tolerant species Myroxylon peruiferum and Hymenaea courbaril were grown under full sun (FS) and natural shade treatments (NS) and assessed for [¹⁴C]-sucrose translocation. Most of the ¹⁴C was retained in the fed leaf after a 24 h translocation period. Under FS, the growing apical part of the plant was the most intense sink for most species. Shade affected growth and sink intensity differently in early and late successional species. Growth was more markedly affected in the early species. Whereas these continued to invest carbon into the growing apical part of the plant under shade conditions, the late successional species invested relatively more into other sinks.

Fourteen efficient inter-simple sequence repeat (ISSR) primers were screened and optimized for detecting the genetic diversity in wild populations of Glycyrrhiza uralensis Fisch. By using these primers, 249 polymorphic bands out of a total of 270 (92.2 %) were generated from 70 individuals of 4 wild G. uralensis populations sampled from Inner Mongolia Province of China. Nei's gene diversity (h) and Shannon index (I) calculated from the data matrix of the ISSR phenotypes revealed a high level of genetic diversity with h = 0.268 and I = 0.415 within this plant. Analysis of molecular variation (AMOVA) showed that most of the genetic variation (81 %) occurred within the populations, whereas the variance among populations was only 19 %. The UPGMA tree based on Nei's unbiased genetic diversity illustrated that populations from Bulage and Bayanwusu were genetically close related, while the population from Shanghaimiao was found to be the most diverse from the other three. The high genetic diversity implies that the wild resources of this species could be restored soon if an appropriate and efficient protection strategy was employed. Our results also provided an optimized method for evaluating genetic diversity of G. uralensis using ISSR markers which was useful for further investigation.

Response of gas exchange traits to irradiance were studied in eight almond tree (Prunus amygdalus) cultivars: Desmayo Largueta, Falsa Barese, Garrigues, Lauranne, Marcona, Masbovera, Nonpareil and Ramillete, grafted on a hybrid rootstock almond × peach GF-677. From these responses cultivars can be classified from the best to the worst photosynthetic performance as follows: Falsa Barese, Masbovera, Marcona, Nonpareil, Ramillete, Desmayo Largueta, Lauranne and Garrigues. The highest net photosynthetic rate was 20.3 μmol m^-2 s^-1 in Falsa Barese. In the absence of water stress, photosynthetic rate was not limited by stomatal conductance. Consequently, non-stomatal limitations prevailed under such conditions.

To determine whether long-term growth in elevated atmospheric CO₂ concentration [CO₂] and nitrogen fertilization affects woody tissue CO₂ efflux, we measured stem CO₂ efflux as a function of temperature in three different size classes of shoots of Populus nigra L. (clone Jean Pourtet) on two occasions in 2004. Trees were growing in a short rotation coppice in ambient (370 µmol mol^-1) and elevated (550 µmol mol^-1, realised by a Free Air Carbon dioxide Enrichment system) [CO₂], and measurements were performed during the third growing season of the second rotation. Elevated CO₂ did not affect Q₁₀ or specific stem CO₂ efflux (E₁₀) of overall poplar shoots. The lack of any effect of N on stem CO₂ efflux indicated that nutrients were sufficient. Specific stem CO₂ efflux differed significantly between shoot sizes, emphasizing the importance of tree size when scaling-up respiration measurements to the stand level. Variation in stem CO₂ efflux could not be satisfactorily explained by temperature as the only driving variable. We hypothesize that transport of CO₂ with the sapflow might have confounded our results and could explain the high Q₁₀ values reported here. Predicting the respiratory carbon loss in a future elevated [CO₂] world must therefore move beyond the single-factor temperature dependent respiration model and involve multiple factors affecting stem CO₂ efflux rate.