The Control of Runner Development in the Strawberry Fragaria ananassa Duch

Factors controlling runnering of strawberry plants were studiedunder controlled and semi-controlled environments. Increasinglylong exposures to conditions favourable for runnering causeda subsequent increase in number of runners, their total length,number of daughters, and of dry matter produced by mother plants.Leaf and crown numbers of the mother plant showed no such parallelincrease. Temperature supplement to foliage, combined with alight interruption in the dark period, produced the greatestvegetative effect-except again on leaf number-when comparedto either factor individually, normal day extension for threehours by itself or combined with temperature supplement. Itwas suggested that the promotive effects of temperature andphotoperiod on runnering were due to increased activation ofvegetative buds on the rosette crown. Upon comparing constantand diurnally fluctuating temperatures under a constant longphoto-period in the phytotron it was found that, while all othermeasured vegetative criteria were closely similar, the totalrunner length produced by plants under fluctuating temperatureswas almost double that of those under constant temperatures.A temperature gradient from root to shoot stimulated vegetativegrowth in comparison to a gradient in the opposite directionand to lack of such gradient, irrespective of whether the temperaturecommon to both root and shoot was high or low. This was interpretedas resulting from either different temperature requirementsfor aerial and subterranean organs or from the occurrence oftranslocation gradients of substances which promote vegetativedevelopment of the shoots, e.g. kinins and gibberellin-likesubstances. The time interval between rooting of daughter plants and onsetof runnering was increased the later the rooting occurred, possiblydue to the advancing seasonal decline in conditions favourablefor vegetative development. The positional influence of theorder of the daughter along the runner chain, which was markedin flowering, was not found.     

Nitrogen translocation between clonal mother and daughter trees at a grassland–forest boundary

There is abundant evidence from short-term experiments using herbs that nutrients can be translocated from mother ramets to daughter ramets, but there is little long-term evidence from woody plants. Here, we examine translocation in field populations of a clonal tree over two growing seasons. We applied ¹⁵N to mothers or daughters in clones of Populus tremuloides at the northern edge of the North American Great Plains, where mother ramets form closed-canopy stands on relatively nutrient-rich soils, and daughter ramets occur nearby in relatively nutrient-poor grasslands. Unlabeled daughters in clones with labeled mothers had δ¹⁵N values significantly greater than those in unlabeled clones, confirming translocation from mothers to daughters. However, unlabeled mothers in clones with labeled daughters also had δ¹⁵N values significantly greater than those in unlabeled clones, indicating translocation from daughters to mothers. Further, the total foliage accumulation of added ¹⁵N was significantly (c. 10×) greater in mothers than in daughters, suggesting that more N was translocated from daughters to mothers, than from mothers to daughters. Thus, ¹⁵N moved both from mothers to daughters and from daughters to mothers, with net flow toward mothers. Because long-lived woody ramets in the field face nutrient competition from other ramets, interspecific neighbors, and soil microbes, the environmental availability of nutrients for uptake may be low for both mother and daughter ramets, causing translocation within a clone to be toward larger ramets with greater demand.     

Water integration in the clonal emergent hydrophyte, Justicia americana: benefits of acropetal water transfer from mother to daughter ramets

Clonal plant growth is common in aquatic freshwater plants and their success is largely attributed to the sharing of resources (e.g., photosynthates, minerals, and water) within the greater genet. The flow of materials within the clone is largely driven by source-sink dynamics, and in established genets may involve acropetal and/or basipetal flow. During the production of new ramets, however, the mother often provides needed resources to the daughter through acropetal flow. In this study, we consider the role of water sharing in a clonal hydrophyte, Justicia americana, when soil moisture levels around the daughter plant declined. The results of this study indicate that acropetal water sharing is an important function between mother and daughter ramets in this species, as indicated by sustained growth and higher survival in connected daughters residing in water-deprived soils. Interestingly, mother plants, when connected to a drought daughter, began to develop similar xeromorphic features (e.g., greater leaf succulence) even though the parent remained in flooded conditions. We suspect that some physical or chemical signal was conveyed from the daughter to the mother that ??forecast?? water scarcities, which could prepare the entire genet for potential drought conditions.     

Effects of nitrogen addition on clonal integration between mother and daughter ramets of Moso bamboo: a 13C-CO2 pulse labeling study

用¹³C-CO₂脉冲标记法研究氮添加对毛竹母子分株克隆整合的影响 相连分株间的资源共享(即克隆整合)是克隆植物的显著特征。克隆整合使毛竹(Phyllostachys pubescens)对多种环境条件具有较强的适应性。但毛竹通过克隆整合获得性能提升的机制尚不明确。本 研究区分并分析了毛竹光合碳的顶向整合和基向整合,以探究毛竹克隆片段如何在土壤氮异质性条件下 提高整体收益。本研究以由两株不同年龄毛竹分株组成 的克隆片段为研究对象,分株间通过根状茎连接。 每个分株设置氮添加或无氮添加两种处理,并通过单株母株或子株的¹³C-CO₂脉冲标记对光合碳的顶向整合和基向整合进行区分。研究结果表明,子株氮添加显著促进了光合碳由母株向子株的顶向整合,无论母株是否有氮添加,均向氮添加子株转运更多的光合碳。转运自无氮添加母株的光合碳主要分配至氮添加子株的 叶片,而转运自氮添加母株的光合碳则主要分配至根系。与无氮添加处理的子株相比,氮 添 加子株转运更多的光合碳至母株,且该过程不受母株氮添加的影响。转运自氮添加子株的光合碳主要 分配至无氮添加母株的根系和氮添加母株的叶片。这些结果说明,母株优先将更多的资源投入到具有高 养分可利用性的子株,随后子株作为更高效的资源采集点,根据母株的养分状况针对富集资源进行获取。通过这种方式,克隆植物可以降低资源获取成本并提高资源获取效率,最大限度地提升其整体表现。     

Photoperiodic induction of flowering in green and photobleachedChenopodium rubrum L. ecotype 184 - a short- day plant

Chenopodium rubrum L. ecotype 184 is a qualitative short-day plant with critical length of the night of eight hours that must be exceeded in order to flower: Five days after sowing, the plants were exposed to a various number of inductive cycles (14/10 h of däy/night cycle) to test the optimal photoperiodic conditions for flowering. In our experimental conditions the plants flowered with high percentage after more than four received inductive cycles, but there was no flowering below that. The plants grown on the herbicide Norflurazon (photobleached plants) showed different photoperiodic characteristics. There was negligible flowering of photobleached plants in the same experimental conditions as for the green ones.     

Polyamine translocation following photoperiodic flowering induction in soybean

Radioactivity translocation after [¹⁴C]-spermidine application over the third trifoliate leaf of soybean plants ( Glycine max . [L.] Merr, cv. Williams) was checked during the first 72 h of short day (SD) treatment to study the involvement of polyamines (PAs) in photoperiodic flowering induction. PAs and/or their metabolites were translocated from the supplied leaf to all parts of the plant. Radioactivity reached its highest concentration in the upper portion of the stem, i.e. the apical bud and the youngest leaf. After the beginning of the first inductive night, the detected radioactivity showed two peaks of maximal concentration. The first arose after the first inductive night, coinciding with the proper flowering induction process; the second one arose after the third inductive night, coinciding with the first morphological symptoms of the transition of vegetative meristems to the reproductive condition. Soluble free PAs showed a different balance in the apical bud of SD-induced plants compared with LD-non induced control plants. Soluble conjugated PAs were detected as traces. It is suggested that under flowering inductive conditions, PAs play a different role according to the stage of the flowering process. Thus, their translocation from the leaves to the axillary and apical buds might be related, in a first step, to the fact that they were part of the complex mechanism of the flowering signal, and in a second step, to the flower transition of vegetative buds.     

Control of daughter centriole formation by the pericentriolar material

Controlling the number of its centrioles is vital for the cell, as supernumerary centrioles cause multipolar mitosis and genomic instability. Normally, one daughter centriole forms on each mature (mother) centriole; however, a mother centriole can produce multiple daughters within a single cell cycle. The mechanisms that prevent centriole 'overduplication' are poorly understood. Here we use laser microsurgery to test the hypothesis that attachment of the daughter centriole to the wall of the mother inhibits formation of additional daughters. We show that physical removal of the daughter induces reduplication of the mother in S-phase-arrested cells. Under conditions when multiple daughters form simultaneously on a single mother, all of these daughters must be removed to induce reduplication. The number of daughter centrioles that form during reduplication does not always match the number of ablated daughter centrioles. We also find that exaggeration of the pericentriolar material (PCM) by overexpression of the PCM protein pericentrin in S-phase-arrested CHO cells induces formation of numerous daughter centrioles. We propose that that the size of the PCM cloud associated with the mother centriole restricts the number of daughters that can form simultaneously.     

Obligatory short‐day plant,Perilla frutescens var. crispa can flower in response to low‐intensity light stress under long‐day conditions

An obligatory short‐day plant, Perilla frutescens var. crispa was induced to flower under long‐day conditions when grown under low‐intensity light (30 µmol m^?2 s^?1). Plant size was smaller under lower light intensity, indicating that the low‐intensity light acted as a stress factor. The phenomenon is categorized as stress‐induced flowering. Low‐intensity light treatment for 4 weeks induced 100% flowering. The plants responded to low‐intensity light immediately after the cotyledons expanded, and the flowering response decreased with increasing plant age. The induced plants produced fertile seeds, and the progeny developed normally. The plants that flowered under low‐intensity light had greener leaves. This greening was because of the decrease in anthocyanin content, and there was a negative correlation between the anthocyanin content and percent flowering. Treatment with L‐2‐aminooxy‐3‐phenylpropionic acid, an inhibitor of phenylalanine ammonia‐lyase (PAL), did not induce flowering under non‐inductive light conditions and inhibited flowering under inductive low‐intensity light conditions. The metabolic pathway regulated by PAL may be involved in the flowering induced by low‐intensity light.     

Strawberry plant relationship through the stolon

Stolon is an elongated, two-node, vegetative, axillary shoot, which supports the ramet (rooted rosette) until it is completely independent on its own roots. The reciprocal capacity of the ramets, in a single runner chain, to sustain the growth and share locally abundant resources or to tolerate a local stress, is still in debate. This capacity may play an important role for improving nursery plant production and for better understanding the natural clonal multiplication. To describe strawberry stolon action, in plant-to-plant relationship, bare-rooted Camarosa ramets, joint in couples by their own stolons (generally, second and third ramet in a runner chain) were transplanted in two pots. The couples of ramets were treated in a factorial experiment with decortication (peeling a 2-mm ring of bark from the stolon), removal of root system or glyphosate application to one of the two ramets. In the studied system, the older ramet was referred as mother and the other as daughter. The two ramets were very similar in age and seem to act with a very limited hierarchic prevalence of the mother. When the root system of one ramet was eliminated, leaf number and chlorophyll content had a very slight decrease, independently in the mother ramet or in the daughter. The decortication did not reduce water integration, in any group of plants, but limited assimilate allocation towards the daughter ramet when the mother ramet had a severe root cut (not vice versa). The glyphosate action resulted localized in the sprayed ramet, which reduced chlorophyll content within 2 days and expired after 4 days.     

Morphogenesis of Asymmetry and Symmetry in Lemna perpusilla Torr

The determination of which of the two reproductive pockets ofLemna perpusilla will produce the first daughter frond undernon-flowering conditions, or the flower under inductive conditions,is related to asymmetric gradients within the mother frond whichmay be the result of the asymmetric position of the axillaryfrond. Treatments that encourage vigorous growth of axillaryfronds may overcome the normal situation of asymmetry and causea morphological symmetry which is qualitatively different fromthe symmetry induced by treatments (TIBA) which prevent thedevelopment of axillary fronds. The origin and maintenance ofasymmetry in Lemna are discussed. Lemna perpusilla Torr., morphogenesis, asymmetry of fronds, tri-iodobenzoic acid     

Effects of the loss of clonal integration on four sedges that differ in ramet aggregation

Although clonal growth is a dominant mode of plant growth in wetlands, the importance of clonal integration, resource sharing among ramets, to individual ramet generations (mother and daughter) and entire clones of coexisting species has not been well investigated. This study evaluated the significance of clonal integration in four sedge species of varying ramet aggregations, from clump-forming species (Clumpers –Carex sterilis, Eleocharis rostellata), with tightly aggregated ramets (rhizomes<1cm), to runner species (Runners –Schoenoplectus acutus, Cladium mariscoides), with loosely aggregated ramets. We manipulated clonal integration by either severing connections between target mother and daughter ramets or leaving connections intact, and then planted them in an intact neighborhood of a fen in Michigan, USA. We measured growth parameters of original and newly produced ramets over two growing seasons and conducted a final biomass harvest, to address four hypotheses. First, we expected integrated clones to accumulate more biomass than severed clones. However, final clone-level biomass and ramet production were the same for both treatments in all species although severing initially stimulated ramet production by Schoenoplectus and produced a more compact ramet aggregation in Cladium. Second, we hypothesized that mother ramets would experience a cost of integration, through reduced ramet or biomass production, while daughters would experience a benefit, through increased resource availability from mothers. Mother ramets of Cladium suffered a cost from integration, while Schoenoplectus mothers suffered a slight cost and Carex daughters saw a slight benefit. Finally, we hypothesized that integration would be more active in runner species than in clumper species. Indeed, we documented more active integration in runners than clumpers, but none of the study species were dependent upon integration for growth or survival once daughter ramets were established with their own roots and shoots. This study demonstrates that integration between established ramets may not be the most important advantage to clonal growth in this wetland field site. The loss of integration elicited varied responses among coexisting species in their natural habitat, somewhat but not completely related to their growth form, suggesting that a combination of plant life history traits contributes to the dependence upon clonal integration among established ramets of clonal species.     

Asymmetric cell divisions in flowering plants - one mother, "two-many" daughters

Plant development shows a fascinating range of asymmetric cell divisions. Over the years, however, cellular differentiation has been interpreted mostly in terms of a mother cell dividing mitotically to produce two daughter cells of different fates. This popular view has masked the significance of an entirely different cell fate specification pathway, where the mother cell first becomes a coenocyte and then cellularizes to simultaneously produce more than two specialized daughter cells. The "one mother - two different daughters" pathways rely on spindle-assisted mechanisms, such as translocation of the nucleus/spindle to a specific cellular site and orientation of the spindle, which are coordinated with cell-specific allocation of cell fate determinants and cytokinesis. By contrast, during "coenocyte-cellularization" pathways, the spindle-assisted mechanisms are irrelevant since cell fate specification emerges only after the nuclear divisions are complete, and the number of specialized daughter cells produced depends on the developmental context. The key events, such as the formation of a coenocyte and migration of the nuclei to specific cellular locations, are coordinated with cellularization by unique types of cell wall formation. Both one mother - two different daughters and the coenocyte-cellularization pathways are used by higher plants in precise spatial and time windows during development. In both the pathways, epigenetic regulation of gene expression is crucial not only for cell fate specification but also for its maintenance through cell lineage. In this review, the focus is on the coenocyte-cellularization pathways in the context of our current understanding of the asymmetric cell divisions. Instances where cell differentiation does not involve an asymmetric division are also discussed to provide a comprehensive account of cell differentiation.     

Daughter cells of Saccharomyces cerevisiae from old mothers display a reduced life span

The yeast Saccharomyces cerevisiae typically divides asymmetrically to give a large mother cell and a smaller daughter cell. As mother cells become old, they enlarge and produce daughter cells that are larger than daughters derived from young mother cells. We found that occasional daughter cells were indistinguishable in size from their mothers, giving rise to a symmetric division. The frequency of symmetric divisions became greater as mother cells aged and reached a maximum occurrence of 30% in mothers undergoing their last cell division. Symmetric divisions occurred similarly in rad9 and ste12 mutants. Strikingly, daughters from old mothers, whether they arose from symmetric divisions or not, displayed reduced life spans relative to daughters from young mothers. Because daughters from old mothers were larger than daughters from young mothers, we investigated whether an increased size per se shortened life span and found that it did not. These findings are consistent with a model for aging that invokes a senescence substance which accumulates in old mother cells and is inherited by their daughters.     

Effect of Photoperiod, Auxins and Gibberellic Acid on Rooting of Stem Cuttings of Bryophyllum tubiflorum

Photoperiod controls the initiation and development of roots on cuttings of Bryophyllum tubiflorum. Root initiation occurred when either the mother plant or the cuttings were exposed subsequently to SD conditions. Cuttings from LD plants exposed to LD did not root at all even after 4 weeks showing that short days are necessary for rooting of cuttings of this plant. The short day requirement can be substituted by IAA or IBA as roots were initiated in cuttings from LD plants when treated with the auxins under LD conditions. GA stimulates rooting of cuttings under SD conditions but does not replace the SD requirement. It failed to induce rooting under LD conditions.     

The metabolic pathway of salicylic acid rather than of chlorogenic acid is involved in the stress-induced flowering of Pharbitis nil

We examined the involvement of chlorogenic acid (CGA) and salicylic acid (SA) in the stress-induced flowering of Pharbitis nil (synonym Ipomoea nil). The incorporation efficiency of exogenously applied CGA and the deactivation rate of incorporated CGA were determined in cotyledons by high-performance liquid chromatography. The assay plants could not incorporate a sufficient amount of CGA via roots. The perfusion technique by which the assay solution was forced into the plant from the cut end of the hypocotyl improved the efficiency of CGA incorporation. However, no flower-inducing activity was detected, indicating that CGA was not involved in flowering. It was concluded that the close correlation between CGA content and flowering response is merely coincidence or a parallelism. Flowering under long-day conditions induced by low-temperature stress was completely inhibited by aminooxyacetic acid (AOA), an inhibitor of phenylalanine ammonialyase. The flower-inhibiting effect of AOA was nullified by co-applied t-cinnamic acid and by benzoic acid. This indicates that the metabolic pathway from t-cinnamic acid to SA via benzoic acid is involved in the stress-induced flowering. The results indicate that the metabolic pathway of SA is involved in the stress-induced flowering of P. nil not the metabolic pathway of CGA.     

Lemna paucicostata Hegelm. 6746: LIFE CYCLE AND CHARACTERIZATION OF THE COLONY TYPES IN A POPULATION

The sequence of frond emergence and the intervals required for daughter colony separation have been determined for Lemna paucicostata Hegelm. 6746 growing under standardized conditions. After separation of a new mother colony, the first daughter colony is produced from the left meristematic pocket and separates after approximately 60 hours, the second daughter, produced from the right pocket, separates after a further 30 hours, and the third daughter, again from the left, after a further 40 hours. The pattern of alternating longer and shorter intervals for separation of daughters continues throughout the life of the mother colony.     

Enhanced drought tolerance in tomato plants by overexpression of <Emphasis Type="Italic">SlMAPK1</Emphasis>

Bamboos, very relevant plants in many countries around the world, are propagated at large scale with extreme difficulties. Use of seeds is challenging because of plant’s sporadic flowering and long flowering cycles, together with seed recalcitrance and consumption by wild animals. Vegetative propagation of bamboo is mainly conducted by cuttings and by air layering. However, these methods are only useful at small-scale because they damage the mother plants, propagation material is bulky and difficult to be transported and is only available during few months of the year. Therefore, in vitro propagation offers the opportunity to obtain large progenies from elite genotypes. In most cases, when developing protocols for in vitro propagation of plants, specific conditions for individual species, genotypes and even development stages of the donor plants must be identified by trial-and-error experiments. Because of the size of and the large diversity observed in this plant family, it usually takes several months to define most adequate culture medium, combination of plant growth regulators and of other compounds for fostering the desired development in the explants. Therefore, in this detailed review, that also puts together results from hard-to-find literature, we list all identified cases, in which development of axillary shoots was used to propagate bamboo plants, by presenting successful ways for disinfection, in vitro bud sprouting, multiplication, rooting and acclimatization.     

Juvenility and flowering of Brunonia australis (Goodeniaceae) and Calandrinia sp. (Portulacaceae) in relation to vernalization and daylength

Background and Aims

The time at which plants are transferred to floral inductive conditions affects the onset of flowering and plant morphology, due to juvenility. Plants of Brunonia australis and Calandrinia sp. were used to investigate whether Australian native ephemeral species show a distinct juvenile phase that can be extended to increase vegetative growth and flowering.

Methods

The juvenile phase was quantified by transferring seedlings from less inductive (short day and 30/20°C) to inductive (vernalization or long day) conditions at six different plant ages ranging from 4 to 35 d after seed germination. An increase in days to first visible floral bud and leaf number were used to signify the end of juvenility.

Key Results

Brunonia australis was receptive to floral inductive long day conditions about 18–22 d after seed germination, whereas plants aged 4–35 d appeared vernalization sensitive. Overall, transferring plants of B. australis from short to long day conditions reduced the time to anthesis compared with vernalization or constant short day conditions. Calandrinia sp. showed a facultative requirement for vernalization and an insensitive phase was not detected. Floral bud and branch production increased favourably as plant age at time of transfer to inductive conditions increased. Younger plants showed the shortest crop production time.

Conclusions

Both species can perceive the vernalization floral stimulus from a very young age, whereas the photoperiodic stimulus is perceived by B. australis after a period of vegetative growth. However, extending the juvenile phase can promote foliage development and enhance flower production of both species.     

The fertility of daughters in common marmoset (Callithrix jacchus jacchus) family groups

Observations previously made in the field of inter-group mating raised questions concerning the fertility of daughters in family groups and about possible competition between mothers and daughters. To test whether daughters in captive family groups could become pregnant, daughters from four groups were placed with a strange male for a period of 30 min, twice a week for eight weeks. No changes were observed in the mother/daughter interactions during the time in which the daughters were allowed contact with the strange male. Two of the daughters showed signs of ovulation and the male only copulated with these animals. One daughter became pregnant, but it was aggression with her siblings rather than her mother which necessitated removing her from her family group.     

水分胁迫条件下草莓克隆分株间水分调控及其对光合功能的影响

以盆栽草莓(Fragaria×ananassa)为材料研究了水分胁迫下克隆植物草莓母株和子株间的水分调控机制及其与碳同化、光系统Ⅱ激发能分配的关系.实验材料分为匍匐茎连接和剪断两个大组,进行两步实验.第1步实验,对连接组和剪断组的所有母株控水,子株充分供水;4d后进入第2步实验,把连接组分为两小组,对其中一组充分供水子株开始控水,另一组保持不变.结果表明,土壤干旱引起母株叶片失水,并使其净光合速率和气孔导度显著降低.但是连接组中供水良好的子株能有效缓解缺水母株的水分胁迫.当供水良好的子株也开始受到干旱处理的时候,则会加剧与之相连母株的水分胁迫.受胁迫母株可以通过加强渗透调节能力和降低水势从相连子株获取水分.虽然土壤干旱会造成受胁迫母株叶片脱落酸(abscisic acid, ABA)含量的大幅度增加,但是与之相连子株的叶片ABA含量并没有增加;并且气孔导度与ABA变化趋势一致.(1)草莓母株和子株间的水分运输是由二者的水势差驱动的;(2)ABA不会通过匍匐茎在母株和子株间传递并影响相邻子株气孔导度;(3)在水分异质性较大情况下,生理整合可明显提高克隆系统的碳同化能力和光系统Ⅱ激发能利用效率.