Evaluation of seasonal antioxidant activity and total phenolic compounds in stems and leaves of some almond (Prunus amygdalus L.) varieties

Background

This study aimed to determine the seasonal changes of total antioxidant activity and phenolic compounds in samples taken from leaves (April, July, October) and stems (April, July, October, January) of some almond (Prunus amygdalus L.) varieties (Nonpareil, Ferragnes and Texas).

Results

It was indicated that antioxidant activity and phenolic compounds in leaves and stems of Nonpareil, Ferragnes and Texas showed seasonal differences. Antioxidant activity IC₅₀ of these varieties reached the highest value in April for leaves whereas in October for stems. The highest level of total phenolic compounds was in January for stems while in October for leaves.

Conclusions

These results showed that total antioxidant activity and phenolics in leaves and stems of almond varieties changed according to season and plant organ.     

Plant development controls leaf area expansion in alfalfa plants competing for light

Background and Aims

The growth of crops in a mixture is more variable and difficult to predict than that in pure stands. Light partitioning and crop leaf area expansion play prominent roles in explaining this variability. However, in many crops commonly grown in mixtures, including the forage species alfalfa, the sensitivity and relative importance of the physiological responses involved in the light modulation of leaf area expansion are still to be established. This study was designed to assess the relative sensitivity of primary shoot development, branching and individual leaf expansion in alfalfa in response to light availability.

Methods

Two experiments were carried out. The first studied isolated plants to assess the potential development of different shoot types and growth periods. The second consisted of manipulating the intensity of competition for light using a range of canopies in pure and mixed stands at two densities so as to evaluate the relative effects on shoot development, leaf growth, and plant and shoot demography.

Key Results

Shoot development in the absence of light competition was deterministic (constant phyllochrons of 32·5 °Cd and 48·2 °Cd for primary axes and branches, branching probability of 1, constant delay of 1·75 phyllochron before axillary bud burst) and identical irrespective of shoot type and growth/regrowth periods. During light competition experiments, changes in plant development explained most of the plant leaf area variations, with average leaf size contributing to a lesser extent. Branch development and the number of shoots per plant were the leaf area components most affected by light availability. Primary axis development and plant demography were only affected in situations of severe light competition.

Conclusions

Plant leaf area components differed with regard to their sensitivity to light competition. The potential shoot development model presented in this study could serve as a framework to integrate light responses in alfalfa crop models.     

The effect of season on VA mycorrhiza of the almond tree and of phosphate fertilization and species of endophyte on its mycorrhizal dependency

Summary Prunus dulcis (Miller), a tree which is able to develop in low fertility soils, forms VA mycorrhiza. Under glasshouse conditions the growth and P concentration in the leaf tissue of non-mycorrhizal plants, given a customary agronomic dose of P-fertilizer, were lower than those of mycorrhizal plants. The relative mycorrhizal dependency¹⁴ values of the almond tree were higher when a mixture of locally isolated (mainlyGlomus fasciculatus) was used as inoculum. These indigenous endophytes were more tolerant of added fertilizers thanGlomus mosseae taken from the pot-culture collection.The amount of VA infection and the number of Endogonaceae spores in the rhizosphere of almond trees growing in the field steadily increase from winter (the flowering season of this crop) until summer or early autumn.     

Enhanced shoot multiplication in Ficus religiosa L. in the presence of adenine sulphate,glutamine and phloroglucinol

Ficus religiosa (Pipal) is a long-lived valuable multipurpose forest tree. The tree is exploited because of its religious, ornamental and medicinal value and the regeneration rate in natural habitat is low. An in vitro propagation protocol has been developed from nodal segments obtained from a 45–50-year old tree. The highest bud break frequency (100 %) followed by maximum number of multiple shoots (13.9) as well as length (2.47 cm) were obtained on Woody Plant medium (WPM) supplemented with 1.0 mg/l BAP along with 0.5 mg/l IAA. Two modifications in this medium resulted in enhanced shoot regeneration-one with 200 mg/l glutamine + 150 mg/l ADS (called as MM-1) giving 32.5 shoots per nodal explant while another modification—with 200 mg/l glutamine + 150 mg/l ADS + 100 mg/l phloroglucinol (called as MM-2) giving 35.65 shoots per explant. These two media were used for sub-culturing of shoots for 4 months. The rate of shoot multiplication was same during the first three sub-cultures on MM-1 and the shoots regenerated were healthy, afterwards shoot multiplication declined. While on MM-2, shoot multiplication declined after first sub-culture and shoots underwent the problem of early leaf fall. Rooting was best induced in micro-shoots excised from proliferated shoot cultures on semi-solid as well as liquid WPM modified with 2.0 mg/l IBA and 0.5 mg/l IAA. The in vitro-raised plantlets were potted and acclimatized under culture room conditions for 25–30 days before transfer to soil conditions, where the established plants showed more than 90 % survival.     

Analysing growth and development of plants jointly using developmental growth stages

Background and Aims Plant growth, the increase of organ dimensions over time, and development, the change in plant structure, are often studied as two separate processes. However, there is structural and functional evidence that these two processes are strongly related. The aim of this study was to investigate the co-ordination between growth and development using mango trees, which have well-defined developmental stages.Methods Developmental stages, determined in an expert way, and organ sizes, determined from objective measurements, were collected during the vegetative growth and flowering phases of two cultivars of mango, Mangifera indica. For a given cultivar and growth unit type (either vegetative or flowering), a multistage model based on absolute growth rate sequences deduced from the measurements was first built, and then growth stages deduced from the model were compared with developmental stages.Key Results Strong matches were obtained between growth stages and developmental stages, leading to a consistent definition of integrative developmental growth stages. The growth stages highlighted growth asynchronisms between two topologically connected organs, namely the vegetative axis and its leaves.Conclusions Integrative developmental growth stages emphasize that developmental stages are closely related to organ growth rates. The results are discussed in terms of the possible physiological processes underlying these stages, including plant hydraulics, biomechanics and carbohydrate partitioning.     

A reappraisal of the role of abscisic acid and its interaction with auxin in apical dominance

BACKGROUND AND AIMS: Evidence from pea rms1, Arabidopsis max4 and petunia dad1 mutant studies suggest an unidentified carotenoid-derived/plastid-produced branching inhibitor which moves acropetally from the roots to the shoots and interacts with auxin in the control of apical dominance. Since the plant hormone, abscisic acid (ABA), known to inhibit some growth processes, is also carotenoid derived/plastid produced, and because there has been indirect evidence for its involvement with branching, a re-examination of the role of ABA in apical dominance is timely. Even though it has been determined that ABA probably is not the second messenger for auxin in apical dominance and is not the above-mentioned unidentified branching inhibitor, the similarity of their derivation suggests possible relationships and/or interactions. METHODS: The classic Thimann-Skoog auxin replacement test for apical dominance with auxin [0.5 % naphthalene acetic acid (NAA)] applied both apically and basally was combined in similar treatments with 1 % ABA in Ipomoea nil (Japanese Morning Glory), Solanum lycopersicum (Better Boy tomato) and Helianthus annuus (Mammoth Grey-striped Sunflower). KEY RESULTS: Auxin, apically applied to the cut stem surface of decapitated shoots, strongly restored apical dominance in all three species, whereas the similar treatment with ABA did not. However, when ABA was applied basally, i.e. below the lateral bud of interest, there was a significant moderate repression of its outgrowth in Ipomoea and Solanum. There was also some additive repression when apical auxin and basal ABA treatments were combined in Ipomoea. CONCLUSION: The finding that basally applied ABA is able partially to restore apical dominance via acropetal transport up the shoot suggests possible interactions between ABA, auxin and the unidentified carotenoid-derived branching inhibitor that justify further investigation.     

Current-year and subsequent-year effects of crop-load manipulation and epicormic-shoot removal on distribution of long, short and epicormic shoot growth in Prunus persica

BACKGROUND AND AIMS: The distribution of canopy growth among different shoot types such as epicormic, long and short shoots is not well understood in the peach tree. In this experiment, the effects of crop load and early epicormic sprout removal on current and subsequent-year distribution of vegetative growth among epicormic, long and short shoots was investigated in Prunus persica. METHODS: Field trials were conducted in Winters, California, in 2003-2004. Crop load was manipulated with fruit thinning in 2003 to produce trees that were de-fruited, commercially thinned or full crop, and half of the trees in each cropping treatment had all current year epicormic sprouts removed at the time of fruit thinning. Yield was recorded and trunk and root carbohydrates were sampled to confirm the effect of 2003 crop load differences on tissue carbohydrate concentration. All current-season vegetative-shoot extension growth was harvested from half of the trees in each treatment in the autumn of 2003 and from the other half in the autumn of 2004. Epicormic, long and short shoots were separately evaluated for dry weight, node number and leaf-stem parameters. KEY RESULTS: In 2003, long-shoot dry weight and node number were significantly affected by crop load; however, short-shoot dry weight and node number were not significantly affected. The 2003 crop-load treatments did not affect 2004 vegetative growth of any shoot type. Some re-growth of epicormic shoots followed early epicormic sprout removal: by the end of the 2003 season, trees in the early shoot-removal treatment had approximately one-third of the epicormic-shoot dry weight as unpruned trees. CONCLUSIONS: Fruit thinning promoted distribution of growth similar to that of de-fruited trees. While thinning was effective in increasing fruit size, it exacerbated the problem of epicormic sprouting. Early epicormic sprout removal did not stimulate the excessive epicormic re-growth in the same or subsequent year relative to previously studied summer pruning methods.     

Regeneration of almond from immature seed cotyledons

Adventitious shoots were regenerated from immature cotyledons of four almond cultivars (`Ne Plus Ultra', `Nonpareil', `Carmel' and `Parkinson'). Open-pollinated fruit were collected from orchard-grown trees 100–115 days after full bloom. The proximal ends of the cotyledons were excised and the embryonic axes discarded. The effects of different concentrations of thidiazuron (TDZ) and indole-3-butyric acid (IBA) and the presence or absence of light for the first 7 days of culture were determined. Shoot regeneration rates were highest for cotyledons cultured for 8 weeks on Murashige and Skoog (MS) basal medium containing TDZ (10.0 M), followed by 4 weeks on medium without plant growth regulators. Regeneration levels were further improved if cotyledons were maintained in darkness for the first 7 days. IBA (0.5 M) significantly reduced the development of adventitious shoots. The frequency of cotyledons that developed adventitious shoots under the optimum tested conditions for `Ne Plus Ultra', `Nonpareil', `Carmel', and `Parkinson' were 80.0%, 73.3%, 100.0% and 86.7%, respectively.     

Analysis of S-RNase alleles of almond (Prunus dulcis): characterization of new sequences, resolution of synonyms and evidence of intragenic recombination

Cross-compatibility relationships in almond are controlled by a gametophytically expressed incompatibility system partly mediated by stylar RNases, of which 29 have been reported. To resolve possible synonyms and to provide data for phylogenetic analysis, 21 almond S-RNase alleles were cloned and sequenced from SP (signal peptide region) or C1 (first conserved region) to C5, except for the S ₂₉ allele, which could be cloned only from SP to C1. Nineteen sequences (S ₄ , S ₆ , S ₁₁ –S ₂₂ , S ₂₅ –S ₂₉ ) were potentially new whereas S ₁₀ and S ₂₄ had previously been published but with different labels. The sequences for S ₁₆ and S ₁₇ were identical to that for S ₁ , published previously; likewise, S ₁₅ was identical to S ₅ . In addition, S ₄ and S ₂₀ were identical, as were S ₁₃ and S ₁₉ . A revised version of the standard table of almond incompatibility genotypes is presented. Several alleles had AT or GA tandem repeats in their introns. Sequences of the 23 distinct newly cloned or already published alleles were aligned. Sliding windows analysis of Ka/Ks identified regions where positive selection may operate; in contrast to the Maloideae, most of the region from the beginning of C3 to the beginning of RC4 appeared not to be under positive selection. Phylogenetic analysis indicated four pairs of alleles had ‘bootstrap’ support > 80%: S ₅ /S ₁₀ , S ₄ /S _8, S ₁₁ /S ₂₄ , and S ₃ /S ₆ . Various motifs up to 19 residues long occurred in at least two alleles, and their distributions were consistent with intragenic recombination, as were separate phylogenetic analyses of the 5′ and 3′ sections. Sequence comparison of phylogenetically related alleles indicated the significance of the region between RC4 and C5 in defining specificity.An erratum to this article can be found at     

Partial shoot reiteration in Wollemia nobilis (Araucariaceae) does not arise from 'axillary meristems'

Background and Aims

Conifers are characterized by the paucity of axillary buds which in dicotyledonous trees usually occur at every node. To compensate, conifers also produce ‘axillary meristems’, which may be stimulated to late development. In juvenile material of Wollemia nobilis (Araucariaceae: Massart''s model) first-order (plagiotropic) branches lack both axillary buds and, seemingly, axillary meristems. This contrasts with orthotropic (trunk) axes, which produce branches, either within the terminal bud or as reiterated orthotropic axes originating from axillary meristems. However, plagiotropic axes do produce branches if they are decapitated. This study investigated how this can occur if axillary meristems are not the source.

Methods

The terminal buds of a series of plagiotropic branches on juvenile trees were decapitated in order to generate axillary shoots. Shoots were culled at about weekly intervals to obtain stages in lateral shoot development. Serial sections were cut with a sliding microtome from the distal end of each sample and scanned sequentially for evidence of axillary meristems and early bud development.

Key Results

Anatomical search produced no clear evidence of pre-existing axillary meristems but did reveal stages of bud initiation. Buds were initiated in a group of small starch-rich cortical cells. Further development involved de-differentiation of these small cells and the development of contrasting outer and inner regions. The outer part becomes meristematic and organizes the apex of the new branch. The inner part develops a callus-like tissue of vacuolated cells within which vascular cambia are developed. This kind of insertion of a branch on the parent axis seems not to have been described before.

Conclusions

Axillary meristems in Wollemia characterize the leaf axils of trunk axes so that the origin of reiterated shoots is clear. Plagiotropic axes seemingly lack axillary meristems but still produce axillary branches by distinctive developmental processes. These observations demonstrate limited understanding of branch initiation in trees generally.     

Pleiotropy of FRIGIDA enhances the potential for multivariate adaptation

An evolutionary response to selection requires genetic variation; however, even if it exists, then the genetic details of the variation can constrain adaptation. In the simplest case, unlinked loci and uncorrelated phenotypes respond directly to multivariate selection and permit unrestricted paths to adaptive peaks. By contrast, ‘antagonistic’ pleiotropic loci may constrain adaptation by affecting variation of many traits and limiting the direction of trait correlations to vectors that are not favoured by selection. However, certain pleiotropic configurations may improve the conditions for adaptive evolution. Here, we present evidence that the Arabidopsis thaliana gene FRI (FRIGIDA) exhibits ‘adaptive’ pleiotropy, producing trait correlations along an axis that results in two adaptive strategies. Derived, low expression FRI alleles confer a ‘drought escape’ strategy owing to fast growth, low water use efficiency and early flowering. By contrast, a dehydration avoidance strategy is conferred by the ancestral phenotype of late flowering, slow growth and efficient water use during photosynthesis. The dehydration avoidant phenotype was recovered when genotypes with null FRI alleles were transformed with functional alleles. Our findings indicate that the well-documented effects of FRI on phenology result from differences in physiology, not only a simple developmental switch.     

Changes in vascular and transpiration flows affect the seasonal and daily growth of kiwifruit (Actinidia deliciosa) berry

Background and Aims

The kiwifruit berry is characterized by an early stage of rapid growth, followed by a relatively long stage of slow increase in size. Vascular and transpiration flows are the main processes through which water and carbon enter/exit the fruit, determining the daily and seasonal changes in fruit size. This work investigates the biophysical mechanisms underpinning the change in fruit growth rate during the season.

Methods

The daily patterns of phloem, xylem and transpiration in/outflows have been determined at several stages of kiwifruit development, during two seasons. The different flows were quantified by comparing the diurnal patterns of diameter change of fruit, which were then girdled and subsequently detached while measurements continued. The diurnal courses of leaf and stem water potential and of fruit pressure potential were also monitored at different times during the season.

Key Results

Xylem and transpiration flows were high during the first period of rapid volume growth and sharply decreased with fruit development. Specific phloem import was lower and gradually decreased during the season, whereas it remained constant at whole-fruit level, in accordance with fruit dry matter gain. On a daily basis, transpiration always responded to vapour pressure deficit and contributed to the daily reduction of fruit hydrostatic pressure. Xylem flow was positively related to stem-to-fruit pressure potential gradient during the first but not the last part of the season, when xylem conductivity appeared to be reduced.

Conclusions

The fruit growth model adopted by this species changes during the season due to anatomical modifications in the fruit features.     

Purification, structure and immunobiological activity of an arabinan-rich pectic polysaccharide from the cell walls of Prunus dulcis seeds

The structure and bioactivity of a polysaccharide extracted and purified from a 4M KOH + H3BO3 solution from Prunus dulcis seed cell wall material was studied. Anion-exchange chromatography of the crude extract yielded two sugar-rich fractions: one neutral (A), the other acidic (E). These fractions contain a very similar monosaccharide composition: 5:2:1 for arabinose, uronic acids and xylose, respectively, rhamnose and galactose being present in smaller amounts. As estimated by size-exclusion chromatography, the acidic fraction had an apparent molecular mass of 762 kDa. Methylation analysis (from the crude and fractions A and E), suggests that the polysaccharide is an arabinan-rich pectin. In all cases, the polysaccharides bear the same type of structural Ara moieties with highly branched arabinan-rich pectic polysaccharides. The average relative proportions of the arabinosyl linkages is 3:2:1:1 for T-Araf:(1-->5)-Araf:(1-->3,5)-Araf:(1-->2,3,5)-Araf. The crude polysaccharide extract and fractions A and E induced a murine lymphocyte stimulatory effect, as evaluated by the in vitro and in vivo expression of lymphocyte activation markers and spleen mononuclear cells culture proliferation. The lymphocyte stimulatory effect was stronger on B- than on T-cells. No evidence of cytotoxic effects induced by the polysaccharide fractions was found.     

Synergistic effect of BAP and GA3 on in vitro flowering of Guizotia abyssinica Cass.-A multipurpose oil crop

Apical and axillary buds of Guizotia abyssinica Cass., isolated from seedlings raised in vitro, were cultured. High frequency of shoot regeneration was achieved on MS medium with BAP (1 mgl⁻¹). Effect of BAP, Kn and GA₃ applied successively in culture on shoot regeneration and flower bud formation has been studied. The shoots differentiated in cultures elongated on this medium. These rooted subsequently on half strength MS medium. The shoots flowered in vitro on MS medium with a combination of BAP (0.1mgl⁻¹) + GA₃ (0.1 mgl⁻¹). The plantlets thus formed were successfully hardened with 90 % survival.     

Identifying ontogenetic, environmental and individual components of forest tree growth

Background and Aims

This study aimed to identify and characterize the ontogenetic, environmental and individual components of forest tree growth. In the proposed approach, the tree growth data typically correspond to the retrospective measurement of annual shoot characteristics (e.g. length) along the trunk.

Methods

Dedicated statistical models (semi-Markov switching linear mixed models) were applied to data sets of Corsican pine and sessile oak. In the semi-Markov switching linear mixed models estimated from these data sets, the underlying semi-Markov chain represents both the succession of growth phases and their lengths, while the linear mixed models represent both the influence of climatic factors and the inter-individual heterogeneity within each growth phase.

Key Results

On the basis of these integrative statistical models, it is shown that growth phases are not only defined by average growth level but also by growth fluctuation amplitudes in response to climatic factors and inter-individual heterogeneity and that the individual tree status within the population may change between phases. Species plasticity affected the response to climatic factors while tree origin, sampling strategy and silvicultural interventions impacted inter-individual heterogeneity.

Conclusions

The transposition of the proposed integrative statistical modelling approach to cambial growth in relation to climatic factors and the study of the relationship between apical growth and cambial growth constitute the next steps in this research.     

Multiple introductions boosted genetic diversity in the invasive range of black cherry (Prunus serotina; Rosaceae)

Background and Aims

Black cherry (Prunus serotina) is a North American tree that is rapidly invading European forests. This species was introduced first as an ornamental plant then it was massively planted by foresters in many countries but its origins and the process of invasion remain poorly documented. Based on a genetic survey of both native and invasive ranges, the invasion history of black cherry was investigated by identifying putative source populations and then assessing the importance of multiple introductions on the maintenance of gene diversity.

Methods

Genetic variability and structure of 23 populations from the invasive range and 22 populations from the native range were analysed using eight nuclear microsatellite loci and five chloroplast DNA regions.

Key Results

Chloroplast DNA diversity suggests there were multiple introductions from a single geographic region (the north-eastern United States). A low reduction of genetic diversity was observed in the invasive range for both nuclear and plastid genomes. High propagule pressure including both the size and number of introductions shaped the genetic structure in Europe and boosted genetic diversity. Populations from Denmark, The Netherlands, Belgium and Germany showed high genetic diversity and low differentiation among populations, supporting the hypothesis that numerous introduction events, including multiple individuals and exchanges between sites, have taken place during two centuries of plantation.

Conclusions

This study postulates that the invasive black cherry has originated from east of the Appalachian Mountains (mainly the Allegheny plateau) and its invasiveness in north-western Europe is mainly due to multiple introductions containing high numbers of individuals.