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1.
Patrizia Trifil�� Fabio Raimondo Maria Assunta Lo Gullo Andrea Nardini Sebastiano Salleo 《Annals of botany》2010,106(2):333-341
Background and Aims
The hydraulic architecture and water relations of fruits and leaves of Capsicum frutescens were measured before and during the fruiting phase in order to estimate the eventual impact of xylem cavitation and embolism on the hydraulic isolation of fruits and leaves before maturation/abscission.Methods
Measurements were performed at three different growth stages: (1) actively growing plants with some flowers before anthesis (GS1), (2) plants with about 50 % fully expanded leaves and immature fruits (GS2) and (3) plants with mature fruits and senescing basal leaves (GS3). Leaf conductance to water vapour as well as leaf and fruit water potential were measured. Hydraulic measurements were made using both the high-pressure flow meter (HPFM) and the vacuum chamber (VC) technique.Key Results
The hydraulic architecture of hot pepper plants during the fruiting phase was clearly addressed to favour water supply to growing fruits. Hydraulic measurements revealed that leaves of GS1 plants as well as leaves and fruit peduncles of GS2 plants were free from significant xylem embolism. Substantial increases in leaf petiole and fruit peduncle resistivity were recorded in GS3 plants irrespective of the hydraulic technique used. The higher fraction of resistivity measured using the VC technique compared with the HPFM technique was apparently due to conduit embolism.Conclusions
The present study is the first to look at the hydraulics of leaves and fruits during growth and maturation through direct, simultaneous measurements of water status and xylem efficiency of both plant regions at different hours of the day. 相似文献2.
Alessandro Lovisetto Flavia Guzzo Nicola Busatto Giorgio Casadoro 《Annals of botany》2013,112(3):535-544
Background and Aims
The evolution of seeds together with the mechanisms related to their dispersal into the environment represented a turning point in the evolution of plants. Seeds are produced by gymnosperms and angiosperms but only the latter have an ovary to be transformed into a fruit. Yet some gymnosperms produce fleshy structures attractive to animals, thus behaving like fruits from a functional point of view. The aim of this work is to increase our knowledge of possible mechanisms common to the development of both gymnosperm and angiosperm fruits.Methods
B-sister genes from two gymnosperms (Ginkgo biloba and Taxus baccata) were isolated and studied. The Ginkgo gene was also functionally characterized by ectopically expressing it in tobacco.Key Results
In Ginkgo the fleshy structure derives from the outer seed integument and the B-sister gene is involved in its growth. In Taxus the fleshy structure is formed de novo as an outgrowth of the ovule peduncle, and the B-sister gene is not involved in this growth. In transgenic tobacco the Ginkgo gene has a positive role in tissue growth and confirms its importance in ovule/seed development.Conclusions
This study suggests that B-sister genes have a main function in ovule/seed development and a subsidiary role in the formation of fleshy fruit-like structures when the latter have an ovular origin, as occurs in Ginkgo. Thus, the ‘fruit function’ of B-sister genes is quite old, already being present in Gymnosperms as ancient as Ginkgoales, and is also present in Angiosperms where a B-sister gene has been shown to be involved in the formation of the Arabidopsis fruit. 相似文献3.
Background and Aims
Plants have evolved a variety of seed dispersal mechanisms to overcome lack of mobility. Many species embed seeds in fleshy pulp to elicit endozoochory, i.e. disseminating seed through the animal gut. In contrast to well-studied fleshy fruited plants, dry-fruited plants may exploit this dispersal mutualism by producing fleshy appendages as a nutritional reward to entice animals to swallow their diaspores, but this has been little studied. In this study, it is hypothesized that these accessory fruits represent co-adaptations facilitating the syndrome of mammalian endozoochorous dispersal.Methods
Field observations (focal tree watches, faecal surveys and fruiting phenology) with experimental manipulations (examination of seed germination and feeding trials) were conducted over 2 years in a native population of the raisin tree, Hovenia dulcis, which produces enlarged, twisted brown peduncles with external black seeds, in central China.Key Results
Birds were not observed to swallow seeds or carry infructescences away during 190 h of focal tree watches. However, H. dulcis seeds were detected in 247 faecal samples, representative of two herbivore and four carnivore mammalian species. Feeding trials revealed that peduncles attracted mammals to consume the entire infructescence, thereby facilitating effective seed dispersal. The germination rate of egested seeds proved higher than that of unconsumed seeds. It was also noted that this mutualism was most vulnerable in degraded forest.Conclusions Hovenia dulcis
peduncle sets are confirmed to adapt primarily to mammalian endozoochory, a mutualistic association similar in function to fleshy pulp or foliage. This demonstrates that plant organ systems can be adapted to unique mutualisms that utilize animal dispersal agents. Such an ecological role has until now been attributed only to bird epizoochory. Future studies should consider more widely the putative role of peduncle sets and mammalian endozoochory as a dispersal mechanism, particularly for those plants that possess relatively large accessory fruits. 相似文献4.
Induced polyploidy dramatically increases the size and alters the shape of fruit in Actinidia chinensis 总被引:1,自引:0,他引:1
Background and Aims
Some otherwise promising selections of Actinidia chinensis (kiwifruit) have fruit that are too small for successful commercialization. We have therefore made the first detailed study in diploid kiwifruit of the effects of chromosome doubling induced by colchicine on fruit size, shape and crop loading.Methods
Flow cytometric analysis of young leaves and chromosome analysis of flower buds and root tips was used to confirm the stability of induced autotetraploids. Fruit weight, size and crop load were measured in the third year after planting in the field and for three consecutive years. DNA fingerprinting was used to confirm the origin of the material.Key Results
There was a very significant increase in fruit size in induced autotetraploids of different genotypes of A. chinensis. With the commercially important diploid cultivar ‘Hort16A’, most regenerants, Type A plants, had fruit which were much the same shape as fruit of the diploid but, at the same fruit load, were much larger and heavier. Some regenerants, Type B plants, produced fruit similar to ‘fasciated’ fruit. Fruit of the autotetraploids induced from three female red-fleshed A. chinensis selections were also 50–60 % larger than fruit of their diploid progenitors. The main increase in fruit dimensions was in their diameters. These improved fruit characteristics were stable over several seasons.Conclusions
Chromosome doubling has been shown to increase significantly fruit size in autotetraploid A. chinensis, highlighting the considerable potential of this technique to produce new cultivars with fruit of adequate size. Other variants with differently shaped fruit were also produced but the genetic basis of this variation remains to be elucidated. Autoploids of other Actinidia species with commercial potential may also show improved fruit characteristics, opening up many new possibilities for commercial development. 相似文献5.
Christopher J. Atkinson Michael J. Davies June M. Taylor Helen Longbottom 《Annals of botany》2013,111(4):703-712
Background and Aims
Understanding the synthesis of ascorbic acid (l-AsA) in green tissues in model species has advanced considerably; here we focus on its production and accumulation in fruit. In particular, our aim is to understand the links between organs which may be sources of l-AsA (leaves) and those which accumulate it (fruits). The work presented here tests the idea that changes in leaf and fruit number influence the accumulation of l-AsA. The aim was to understand the importance of leaf tissue in the production of l-AsA and to determine how this might provide routes for the manipulation of fruit tissue l-AsA.Methods
The experiments used Ribes nigrum (blackcurrant), predominantly in field experiments, where the source–sink relationship was manipulated to alter potential leaf l-AsA production and fruit growth and accumulation of l-AsA. These manipulations included reductions in reproductive capacity, by raceme removal, and the availability of assimilates by leaf removal and branch phloem girdling. Natural variation in fruit growth and fruit abscission is also described as this influences subsequent experimental design and the interpretation of l-AsA data.Key Results
Results show that fruit l-AsA concentration is conserved but total yield of l-AsA per plant is dependent on a number of innate factors many of which relate to raceme attributes. Leaf removal and phloem girdling reduced fruit weight, and a combination of both reduced fruit yields further. It appears that around 50 % of assimilates utilized for fruit growth came from apical leaves, while between 20 and 30 % came from raceme leaves, with the remainder from ‘storage’.Conclusions
Despite being able to manipulate leaf area and therefore assimilate availability and stored carbohydrates, along with fruit yields, rarely were effects on fruit l-AsA concentration seen, indicating fruit l-AsA production in Ribes was not directly coupled to assimilate supply. There was no supporting evidence that l-AsA production occurred predominantly in green leaf tissue followed by its transfer to developing fruits. It is concluded that l-AsA production occurs predominantly in the fruit of Ribes nigrum. 相似文献6.
Background and Aims
Secondary growth is a main physiological sink. However, the hierarchy between the processes which compete with secondary growth is still a matter of debate, especially on fruit trees where fruit weight dramatically increases with time. It was hypothesized that tree architecture, here mediated by branch age, is likely to have a major effect on the dynamics of secondary growth within a growing season.Methods
Three variables were monitored on 6-year-old ‘Golden Delicious’ apple trees from flowering time to harvest: primary shoot growth, fruit volume, and cross-section area of branch portions of consecutive ages. Analyses were done through an ANOVA-type analysis in a linear mixed model framework.Key Results
Secondary growth exhibited three consecutive phases characterized by unequal relative area increment over the season. The age of the branch had the strongest effect, with the highest and lowest relative area increment for the current-year shoots and the trunk, respectively. The growth phase had a lower effect, with a shift of secondary growth through the season from leafy shoots towards older branch portions. Eventually, fruit load had an effect on secondary growth mainly after primary growth had ceased.Conclusions
The results support the idea that relationships between production of photosynthates and allocation depend on both primary growth and branch architectural position. Fruit load mainly interacted with secondary growth later in the season, especially on old branch portions. 相似文献7.
Background and Aims
Fruit set in indeterminate plant species largely depends on the balance between source and sink strength. Plants of these species show fluctuations in fruit set during the growing season. It was tested whether differences in fruit sink strength among the cultivars explained the differences in fruit-set patterns.Methods
Capsicum was chosen as a model plant. Six cultivars with differences in fruit set, fruit size and plant growth were evaluated in a greenhouse experiment. Fruit-set patterns, generative and vegetative sink strength, source strength and the source : sink ratio at fruit set were determined. Sink strength was quantified as potential growth rate. Fruit set was related to total fruit sink strength and the source : sink ratio. The effect of differences observed in above-mentioned parameters on fruit-set patterns was examined using a simple simulation model.Key Results
Sink strengths of individual fruits differed greatly among cultivars. Week-to-week fruit set in large-fruited cultivars fluctuated due to large fluctuations in total fruit sink strength, but in small-fruited cultivars, total fruit sink strength and fruit set were relatively constant. Large variations in week-to-week fruit set were correlated with a low fruit-set percentage. The source : sink threshold for fruit set was higher in large-fruited cultivars. Simulations showed that within the range of parameter values found in the experiment, fruit sink strength and source : sink threshold for fruit set had the largest impact on fruit set: an increase in these parameters decreased the average percentage fruit set and increased variation in weekly fruit set. Both were needed to explain the fruit-set patterns observed. The differences observed in the other parameters (e.g. source strength) had a lower effect on fruit set.Conclusions
Both individual fruit sink strength and the source : sink threshold for fruit set were needed to explain the differences observed between fruit-set patterns of the six cultivars. 相似文献8.
Background and Aims
Dry fruits remain around the seeds at dispersal in a number of species, especially the Brassicaceae. Explanations for this vary, but usually involve mechanisms of innate dormancy. We speculate that, instead, a persistent fruit may give additional protection through control of dehydration, to species growing in arid or Mediterranean environments where water is sporadic.Methods
X-rays and weight measurements were used to determine the extent to which Raphanus raphanistrum seeds within mature fruits imbibe water, and germination tests determined the roles of the fruit and seed coat in seed dormancy. Rates of water uptake and desiccation, and seedling emergence were compared with and without the fruit. Finally, germinability of seeds extracted from fruits was determined after various periods of moist conditions followed by a range of dry conditions.Key Results
Most seeds rapidly take up water within the fruit, but they do not fully imbibe when compared with naked seeds. The seed coat is more important than the dry fruit wall in maintaining seed dormancy. The presence of a dry fruit slows emergence from the soil by up to 6–8 weeks. The fruit slows the rate of desiccation of the seed to a limited extent. The presence of the fruit for a few days during imbibition somehow primes more seeds to germinate than if the fruit is absent; longer moist periods within the pod appear to induce dormancy.Conclusions
The fruit certainly modifies the seed environment as external conditions change between wet and dry, but not to a great extent. The major role seems to be: (a) the physical restriction of imbibition and germination; and (b) the release and then re-imposition of dormancy within the seed. The ecological significance of the results requires more research under field conditions. 相似文献9.
Post-pruning shoot growth increases fruit abscission and reduces stem carbohydrates and yield in macadamia 总被引:1,自引:0,他引:1
Background and Aims
There is good evidence for deciduous trees that competition for carbohydrates from shoot growth accentuates early fruit abscission and reduces yield but the effect for evergreen trees is not well defined. Here, whole-tree tip-pruning at anthesis is used to examine the effect of post-pruning shoot development on fruit abscission in the evergreen subtropical tree macadamia (Macadamia integrifolia, M. integrifolia × tetraphylla). Partial-tree tip-pruning is also used to test the localization of the effect.Methods
In the first experiment (2005/2006), all branches on trees were tip-pruned at anthesis, some trees were allowed to re-shoot (R treatment) and shoots were removed from others (NR treatment). Fruit set and stem total non-structural carbohydrates (TNSC) over time, and yield were measured. In the second experiment (2006/2007), upper branches of trees were tip-pruned at anthesis, some trees were allowed to re-shoot (R) and shoots were removed from others (NR). Fruit set and yield were measured separately for upper (pruned) and lower (unpruned) branches.Key Results
In the first experiment, R trees set far fewer fruit and had lower yield than NR trees. TNSC fell and rose in all treatments but the decline in R trees occurred earlier than in NR trees and coincided with early shoot growth and the increase in fruit abscission relative to the other treatments. In the second experiment, fruit abscission on upper branches of R trees increased relative to the other treatments but there was little difference in fruit abscission between treatments on lower branches.Conclusions
This study is the first to demonstrate an increase in fruit abscission in an evergreen tree in response to pruning. The effect appeared to be related to competition for carbohydrates between post-pruning shoot growth and fruit development and was local, with shoot growth on pruned branches having no effect on fruit abscission on unpruned branches. 相似文献10.
Sarah M. Pilkington Mirco Montefiori Amy L. Galer R. J. Neil Emery Andrew C. Allan Paula E. Jameson 《Annals of botany》2013,112(1):57-68
Background and Aims
Green kiwifruit (Actinidia deliciosa) retain high concentrations of chlorophyll in the fruit flesh, whereas in gold-fleshed kiwifruit (A. chinensis) chlorophyll is degraded to colourless catabolites during fruit development, leaving yellow carotenoids visible. The plant hormone group the cytokinins has been implicated in the delay of senescence, and so the aim of this work was to investigate the link between cytokinin levels in ripening fruit and chlorophyll de-greening.Methods
The expression of genes related to cytokinin metabolism and signal transduction and the concentration of cytokinin metabolites were measured. The regulation of gene expression was assayed using transient activation of the promoter of STAY-GREEN2 (SGR2) by cytokinin response regulators.Key Results
While the total amount of cytokinin increased in fruit of both species during maturation and ripening, a high level of expression of two cytokinin biosynthetic gene family members, adenylate isopentenyltransferases, was only detected in green kiwifruit fruit during ripening. Additionally, high levels of O-glucosylated cytokinins were detected only in green kiwifruit, as was the expression of the gene for zeatin O-glucosyltransferase, the enzyme responsible for glucosylating cytokinin into a storage form. Season to season variation in gene expression was seen, and some de-greening of the green kiwifruit fruit occurred in the second season, suggesting environmental effects on the chlorophyll degradation pathway. Two cytokinin-related response regulators, RRA17 and RRB120, showed activity against the promoter of kiwifruit SGR2.Conclusions
The results show that in kiwifruit, levels of cytokinin increase markedly during fruit ripening, and that cytokinin metabolism is differentially regulated in the fruit of the green and gold species. However, the causal factor(s) associated with the maintenance or loss of chlorophyll in kiwifruit during ripening remains obscure. 相似文献11.
Background and Aims
The Borasseae form a highly supported monophyletic clade in the Arecaceae–Coryphoideae. The fruits of Coryphoideae are small, drupaceous with specialized anatomical structure of the pericarp and berries. The large fruits of borassoid palms contain massive pyrenes, which develop from the middle zone of the mesocarp. The pericarp structure and mode of its development in Borasseae are similar to those of Eugeissona and Nypa. A developmental carpological study of borassoid palms will allow us to describe the process of pericarp development and reveal the diagnostic fruit features of borassoid palms, determine the morphogenetic fruit type in Borasseae genera, and describe similarities in fruit structure and pericarp development with other groups of palms.Methods
The pericarp anatomy was studied during development with light microscopy based on the anatomical sections of fruits of all eight Borasseae genera.Key Results
The following general features of pericarp structure in Borasseae were revealed: (1) differentiation of the pericarp starts at early developmental stages; (2) the exocarp is represented by a specialized epidermis; (3) the mesocarp is extremely multilayered and is differentiated into several topographical zones – a peripheral parenchymatous zone(s) with scattered sclerenchymatous elements and vascular bundles, a middle zone (the stony pyrene comprising networks of elongated sclereids and vascular bundles) and an inner parenchymatous zone(s); (4) differentiation and growth of the pyrene tissue starts at early developmental stages and ends long before maturation of the seed; (5) the inner parenchymatous zone(s) of the mesocarp is dramatically compressed by the mature seed; (6) the endocarp (unspecialized epidermis) is not involved in pyrene formation; and (7) the spermoderm is multilayered in Hyphaeninae and obliterated in Lataniinae.Conclusions
The fruits of Borasseae are pyrenaria of Latania-type. This type of pericarp differentiation is also found only in Eugeissona and Nypa. The fruits of other Coryphoideae dramatically differ from Borasseae by the pericarp anatomical structure and the mode of its development. 相似文献12.
Brunella Morandi Luigi Manfrini Pasquale Losciale Marco Zibordi Luca Corelli Grappadelli 《Annals of botany》2010,105(6):913-923
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. 相似文献13.
Background and Aims
Growth imbalances between individual fruits are common in indeterminate plants such as cucumber (Cucumis sativus). In this species, these imbalances can be related to differences in two growth characteristics, fruit growth duration until reaching a given size and fruit abortion. Both are related to distribution, and environmental factors as well as canopy architecture play a key role in their differentiation. Furthermore, events leading to a fruit reaching its harvestable size before or simultaneously with a prior fruit can be observed. Functional–structural plant models (FSPMs) allow for interactions between environmental factors, canopy architecture and physiological processes. Here, we tested hypotheses which account for these interactions by introducing dominance and abortion thresholds for the partitioning of assimilates between growing fruits.Methods
Using the L-System formalism, an FSPM was developed which combined a model for architectural development, a biochemical model of photosynthesis and a model for assimilate partitioning, the last including a fruit growth model based on a size-related potential growth rate (RP). Starting from a distribution proportional to RP, the model was extended by including abortion and dominance. Abortion was related to source strength and dominance to sink strength. Both thresholds were varied to test their influence on fruit growth characteristics. Simulations were conducted for a dense row and a sparse isometric canopy.Key Results
The simple partitioning models failed to simulate individual fruit growth realistically. The introduction of abortion and dominance thresholds gave the best results. Simulations of fruit growth durations and abortion rates were in line with measurements, and events in which a fruit was harvestable earlier than an older fruit were reproduced.Conclusions
Dominance and abortion events need to be considered when simulating typical fruit growth traits. By integrating environmental factors, the FSPM can be a valuable tool to analyse and improve existing knowledge about the dynamics of assimilates partitioning. 相似文献14.
Background and Aims
Andromonoecy, the presence of hermaphrodite and male flowers in the same individual, is genetically fixed or induced, e.g. by fruit set. Little is known about the forces triggering andromonoecy in the Apiaceae. In the present study, a natural population of the protandrous Chaerophyllum bulbosum was investigated to elucidate architectural constraints and effects of resource reallocation.Methods
Three sets of plants (each n = 15) were treated by hand pollination, pollinator exclusion and removal of low-order inflorescences. Fifteen untreated plants were left as controls.Key Results
Untreated plants produce umbels up to the third branch order, with increasing proportions of male flowers from 15 % (terminal umbel) to 100 % (third-order umbels). Fruit set correspondingly decreases from 70% (terminal umbel) to <10 % (second-order umbels). Insignificant differences from hand-pollinated plants do not reveal any sign of pollinator limitation at the study site. Bagged individuals show the same increase in male flowers with age as untreated plants, indicating that the presence of andromonoecy is not induced by fruit set. After umbel removal, individuals tend to present a higher number of hermaphrodite flowers and fruits in the umbels of second and third order. Three plants (25 %) produced an additional branch order composed of 100 % male umbels.Conclusions
Inherited andromonoecy and the plastic response to environmental conditions are interpreted as a self-regulating system saving investment costs and optimizing fruit set at the same time. 相似文献15.
Background and Aims
Seemannaralia appears to be fundamentally different from all other Araliaceae in the presence of a well-developed symplicate zone in its gynoecium, as well as in the ovule insertion in the symplicate zone (rather than in the cross-zone). The present investigation re-examined the floral structure of Seemannaralia with emphasis on the morphology and evolution of its gynoecium.Methods
Flowers and fruits of Seemannaralia gerrardii at various developmental stages were examined using light microscopy and scanning electron microscopy.Key Results
Ovaries in the flowers of Seemannaralia are bilocular. Each ovary locule corresponds to a carpel whose ascidiate part is distinctly longer than the plicate part. Each carpel contains one fertile ovule attached to the cross-zone, and one sterile ovule as well. The fruit is unilocular: its central cavity is occupied by a single large seed. In the course of fruit development, the growth of one ovule stops while another ovule develops into the mature seed. When this ovule outgrows the available space in the locule, the septum is ruptured, forming a united cavity of two carpels.Conclusions
Despite literature data, the synascidiate zone is well developed in the gynoecium of Seemannaralia, and the ovules are attached to the cross-zone. Its preanthetic and anthetic gynoecium has nearly the same structure as gynoecia of most other Araliaceae. The Seemannaralia fruit resembles the paracarpous gynoecium but its ground plan is very different because the central cavity is formed by mechanical rupture of the septum. The term ‘pseudoparacarpy’ (‘false paracarpy’) is proposed to describe this condition, which has not been reported to date for indehiscent fruits in any taxa other than Seemannaralia. In this genus, the pseudoparacarpy has probably resulted from a decrease in seed number in the course of the transition from zoochory to anemochory. 相似文献16.
Egea I Bian W Barsan C Jauneau A Pech JC Latché A Li Z Chervin C 《Annals of botany》2011,108(2):291-297
Background and Aims
There are several studies suggesting that tomato (Solanum lycopersicum) chromoplasts arise from chloroplasts, but there is still no report showing the fluorescence of both chlorophylls and carotenoids in an intermediate plastid, and no video showing this transition phase.Methods
Pigment fluorescence within individual plastids, isolated from tomato fruit using sucrose gradients, was observed at different ripening stages, and an in situ real-time recording of pigment fluorescence was performed on live tomato fruit slices.Key results
At the mature green and red stages, homogenous fractions of chloroplasts and chromoplasts were obtained, respectively. At the breaker stage, spectral confocal microscopy showed that intermediate plastids contained both chlorophylls and carotenoids. Furthermore, an in situ real-time recording (a) showed that the chloroplast to chromoplast transition was synchronous for all plastids of a single cell; and (b) confirmed that all chromoplasts derived from pre-existing chloroplasts.Conclusions
These results give details of the early steps of tomato chromoplast biogenesis from chloroplasts, with the formation of intermediate plastids containing both carotenoids and chlorophylls. They provide information at the sub-cellular level on the synchronism of plastid transition and pigment changes. 相似文献17.
Background and Aims
Increasing evidence challenges the conventional perception that orchids are the most distinct example of floral diversification due to floral or prezygotic isolation. Regarding the relationship between co-flowering plants, rewarding and non-rewarding orchids in particular, few studies have investigated whether non-rewarding plants affect the pollination success of rewarding plants. Here, floral isolation and mutual effects between the rewarding orchid Galearis diantha and the non-rewarding orchid Ponerorchis chusua were investigated.Methods
Flowering phenological traits were monitored by noting the opening and wilting dates of the chosen individual plants. The pollinator pool and pollinator behaviour were assessed from field observations. Key morphological traits of the flowers and pollinators were measured directly in the field. Pollinator limitation and interspecific compatibility were evaluated by hand-pollination experiments. Fruit set was surveyed in monospecific and heterospecific plots.Key Results
The species had overlapping peak flowering periods. Pollinators of both species displayed a certain degree of constancy in visiting each species, but they also visited other flowers before landing on the focal orchids. A substantial difference in spur size between the species resulted in the deposition of pollen on different regions of the body of the shared pollinator. Hand-pollination experiments revealed that fruit set was strongly pollinator-limited in both species. No significant difference in fruit set was found between monospecific plots and heterospecific plots.Conclusions
A combination of mechanical isolation and incomplete ethological isolation eliminates the possibility of pollen transfer between the species. These results do not support either the facilitation or competition hypothesis regarding the effect of nearby rewarding flowers on non-rewarding plants. The absence of a significant effect of non-rewarding P. chusua on rewarding G. diantha can be ascribed to low levels of overlap between the pollinator pools of two species. 相似文献18.
Chevalier C Nafati M Mathieu-Rivet E Bourdon M Frangne N Cheniclet C Renaudin JP Gévaudant F Hernould M 《Annals of botany》2011,107(7):1159-1169
Background
Endoreduplication is the major source of endopolyploidy in higher plants. The process of endoreduplication results from the ability of cells to modify their classical cell cycle into a partial cell cycle where DNA synthesis occurs independently from mitosis. Despite the ubiquitous occurrence of the phenomenon in eukaryotic cells, the physiological meaning of endoreduplication remains vague,although several roles during plant development have been proposed, mostly related to cell differentiation and cell size determination.Scope
Here recent advances in the knowledge of endoreduplication and fruit organogenesis are reviewed, focusing on tomato (Solanum lycopersicum) as a model, and the functional analyses of endoreduplication-associated regulatory genes in tomato fruit are described.Conclusions
The cyclin-dependent kinase inhibitory kinase WEE1 and the anaphase promoting complex activator CCS52A both participate in the control of cell size and the endoreduplication process driving cell expansion during early fruit development in tomato. Moreover the fruit-specific functional analysis of the tomato CDK inhibitor KRP1 reveals that cell size and fruit size determination can be uncoupled from DNA ploidy levels, indicating that endoreduplication acts rather as a limiting factor for cell growth. The overall functional data contribute to unravelling the physiological role of endoreduplication in growth induction of fleshy fruits. 相似文献19.
Mervi M. Sepp?nen Kirsi Pakarinen Venla Jokela Jeppe R. Andersen Alice Fiil Arja Santanen Perttu Virkaj?rvi 《Annals of botany》2010,106(5):697-707
Background
Timothy is a long-day grass species well adapted for cultivation in northern latitudes. It produces elongating tillers not only in spring growth but also later in summer. As the quantity and quality of harvested biomass is dictated by canopy architecture and the proportion of stem-forming flowering tillers, the regulation of flowering is of great interest in forage grass production.Methods
Canopy architecture, stem morphology and freezing tolerance of vernalized timothy were investigated in greenhouse and field experiments. The molecular control of development was examined by analysing the relationship between apex development and expression of timothy homologues of the floral inducer VRN1 and repressor VRN2.Key Results
True stem formation and lignification of the sclerenchyma ring occur in both vernalized and regrowing stems irrespective of the developmental stage of the apex. The stems had, however, divergent morphology. Vernalization enhanced flowering, and the expression of the VRN1 homologue was elevated when the apex had passed into the reproductive stage. High VRN1 homologue expression was not associated with reduction in freezing tolerance and the expression coincided with increased levels of the floral repressor VRN2 homologue. Field experiments supported the observed linkage between the upregulation of the VRN1 homologue and the transition to the reproductive stage in vernalized tillers. The upregulation of putative VRN1 or VRN2 genes was restricted to vernalized tillers in the spring yield and, thus, not detected in non-vernalized tillers of the second yield; so-called regrowth.Conclusions
The formation of a lignified sclerenchyma ring that efficiently reduces the digestibility of the stem was not related to apex development but rather to a requirement for mechanical support. The observed good freezing tolerance of reproductive timothy tillers could be one important adaptation mechanism ensuring high yields in northern conditions. Both VRN1 and VRN2 homologues required a vernalization signal for expression so the development of yield-forming tillers in regrowth was regulated independently of the studied genes. 相似文献20.
Muñoz-Fambuena N Mesejo C González-Mas MC Primo-Millo E Agustí M Iglesias DJ 《Annals of botany》2011,108(3):511-519