Cytokinins antagonize the jasmonates action on the regulation of potato (Solanum tuberosum) tuber formation in vitro

Cucurbita pepo L. (squash, pumpkin) is a highly polymorphic vegetable species of major importance. Our study characterized a spectrum of C. pepo germplasm for the ability to regenerate in vitro by direct organogenesis from cotyledon explants. Cultivars tested included both cultivated subspecies, texana and pepo, and nearly all of their respective cultivar-groups. Direct shoot regeneration occurred in all accessions, and was generally high (56–94%), with a single exception of 22% (‘Bolognese’). There was no significant difference between the percentage regeneration of the two subspecies. Shoot regeneration per responding explant was uniform (1.2–1.6 shoots per explant). Only ‘True French’ produced statistically more shoots (3.9 per explant) than other accessions. The morphology of regeneration varied. Most cultivars produced long shoots, often fasciated, amid a few small buds. Some subspecies pepo cultivars (Beirut, Yugoslavia 7, Ma’yan and True French) produced short, massive, hollow shoots, sometimes accompanied by shoots that were more normal. Two subspecies texana cultivars (Creamy Straightneck and Small Bicolor) produced single (sometimes double) shoots without other buds. The production of chimeric (mixoploid) regenerants varied and there was a tendency to regenerate chimeric plants from the widest-fruited accessions (i.e. lowest length-to-width ratio) in each subspecies. Subspecies pepo Pumpkin Group ‘Tondo di Nizza’ showed significantly greater production of chimeric regenerants. In comparison with the great range of variation observed in fruit shape, the variation of in vitro responses (mostly less than 2-fold in regeneration and shoot production) was less than expected.     

Efficient plant regeneration from long-term callus cultures of rice by spermidine

A significant reduction in regeneration potential with increasing age (upto 12months) in rice (Oryza sativa L. cv.TN-1) embryogenic callus cultures was observed. Spermidine, while having an inhibitory effect on plant regeneration in fresh callus cultures, promoted morphogenesis in long-term callus cultures. A massive accumulation of polyamines, particularly putrescine (5-fold) was observed in 12 month old cultures resulting in a change of putrescine /spermidine ratio, which seems to be important for maintaining the morphogenetic response. Application of exogenous spermidine to 12 month old cultures showed increased levels of polyamines and restored the putrescine/spermidine ratio comparable to that found in freshly induced cultures, concomitantly, promoting the plant regeneration via somatic embryogenesis in long-term rice callus cultures.Abbreviations PA Polyamines - PCA Perchloric acid - PUT Putrescine - SPD Spermidine - SPM Spermine     

Pathways of stand development in ageing Pinus sylvestris forests

Question: What are the main pathways of long‐term stand development in forest ecosystems on oligotrophic and acidic sandy soils? Location: Nine forest reserves at different locations in The Netherlands; all ageing Pinus sylvestris forests that are no longer managed and where massive regeneration of broad‐leaved species is often reported. Methods: Agglomerative cluster analysis was used to define structural classes from forest reserve data. Sequences of structural classes, representing different trajectories of stand development, were constructed with the aid of a process based gap model. Results: Four main pathways of stand development could be distinguished. Three pathways are linked to gap dynamics, and lead towards dominance of Betula, Quercus or Fagus. They differ in light availability for regeneration and/or seed tree availability. The fourth pathway comprises of development patterns after major disturbances. Conclusions: The new methodological approach, combining the empirical strength of forest reserve data with the predictive ability of a process based model, made it possible to detail and quantify insights into structure and dynamics of forests on poor sandy soils. Some factors not included in the study can substantially influence pathways, especially those where Quercus and Fagus potentially play an important role.     

The beneficial role of extracellular reactive oxygen species in apoptosis-induced compensatory proliferation

Apoptosis-induced proliferation (AiP) maintains tissue homeostasis following massive stress-induced cell death. During this phenomenon, dying cells induce proliferation of the surviving cells to compensate for the tissue loss, and thus restore organ size. Along with wound healing and tissue regeneration, AiP also contributes to tumor repopulation following radiation or chemotherapy. There are several models of AiP. Using an “undead” AiP model that causes hyperplastic overgrowth of Drosophila epithelial tissue, we recently demonstrated that extracellular reactive oxygen species (eROS) are produced by undead epithelial cells, and are necessary for inducing AiP and overgrowth. Furthermore, hemocytes, the Drosophila blood cells, are seen adjacent to the undead epithelial tissue, and may secrete the TNF ortholog Eiger that signals through the TNF receptor to active Jun-N-terminal kinase (JNK) in the undead tissue and induce proliferation. We propose that undead epithelial tissue triggers an inflammatory response that resembles recruitment of macrophages to human epithelial tumors, and that these tumor-associated macrophages release signals for proliferation and tumor growth of the epithelium. This Extra View article summarizes these recent findings with a focus on the role of eROS for promoting regeneration and inflammation-induced tumorigenesis.     

海南岛木麻黄林林下植物天然更新影响因素的研究

木麻黄海防林是海南岛重要的海岸生态屏障,天然更新对其持续发挥防护功能具有重要意义。调查发现海南岛大多数木麻黄林林下天然更新困难,然而却存在局部更新良好的现象。为了探究天然更新存在巨大差异的原因,并为促进海南海防林由人工林向近自然林转化提供一定的理论基础,通过分析不同林地更新质量的差异,研究影响木麻黄海防林林下天然更新的主要影响因素。该研究在海南岛木麻黄海防林中共设置73块临时样地,采用方差分析和相关分析等统计方法,分别研究林地所属气候区、林分条件、土壤因子和凋落物累积量对天然更新质量和密度的影响。结果表明:(1)湿润气候区的木麻黄林下更新要显著优于半干旱区;(2)木麻黄林分密度与更新密度和草本盖度存在显著负相关,但林分条件其他因子对更新影响不大;(3)不同更新质量样地的土壤pH和养分均无显著性差异,但铵态氮对幼苗、有机质对幼树的更新存在一定的促进作用;(4)凋落物的累计整体不利于天然更新的进行。结果说明气候因子、木麻黄林分密度、木麻黄凋落物积累量是木麻黄海防林林下植物天然更新的主要影响因素。     

Botryllus schlosseri,an emerging model for the study of aging,stem cells,and mechanisms of regeneration

The decline of tissue regenerative potential with the loss of stem cell function is a hallmark of mammalian aging. We study Botryllus schlosseri, a colonial chordate which exhibits robust stem cell-mediated regeneration capacities throughout life. Larvae, derived by sexual reproduction and chordate development, metamorphose to clonal founders that undergo weekly formation of new individuals by budding from stem cells. Individuals are transient structures which die through massive apoptosis, and successive buds mature to replicate an entire new body. As a result, their stem cells, which are the only self-renewing cells in a tissue, are the only cells which remain through the entire life of the genotype and retain the effects of time. During aging, a significant decrease in the colonies’ regenerative potential is observed and both sexual and asexual reproductions will eventually halt. When a parent colony is experimentally separated into a number of clonal replicates, they frequently undergo senescence simultaneously, suggesting a heritable factor that determines lifespan in these colonies. The availability of the recently published B. schlosseri genome coupled with its unique life cycle features promotes the use of this model organism for the study of the evolution of aging, stem cells, and mechanisms of regeneration.     

海南岛木麻黄海防林天然更新特征及更新树种筛选

天然更新是森林资源再生产的一个重要的生态学过程,良好的天然更新可促进人工林向近自然林的方向转变。为了解海南木麻黄海防林天然更新现状和特征,筛选出自然条件下天然更新良好的树种。该研究在海南岛木麻黄海防林内共计设立临时样地73块,样地总面积为2.51 hm~2,采用典型抽样的调查方法对海南全岛木麻黄海防林天然更新状况进行系统调查,应用天然更新密度及物种丰富度等指标对干、湿不同气候区木麻黄天然更新特征进行比较分析,并应用更新密度、更新指数等指标对天然更新质量较好的树种进行筛选。结果表明:(1)海南岛木麻黄海防林下天然更新质量整体不佳,木麻黄自身虽无法实现天然更新,但局部其他树种天然更新良好,更新良好的比例为15.1%。(2)湿润区天然更新丰富度及物种多样性远优于半干旱区,其中湿润区样地更新树种为28科、50属、59种,半干旱区样地更新的树种为6科、6属、6种。(3)乔木更新情况优于灌木。(4)潺槁木姜子、鸦胆子、台湾相思、榄仁树等具有较强的天然更新性能,适合与木麻黄混交,可以作为木麻黄海防林的混交树种或伴生树种。     

斗竹的开花生物学特性研究

通过野外观测及光学解剖,观察了斗竹(Oligostachyum spongiosum)开花林相、开花动态、花器官构造、结实情况,以及花后林相更新等生物学特性,采用光学显微技术结合石蜡制片,对斗竹的大、小孢子的发生及雌、雄配子体的发育过程进行研究。结果表明：(1)斗竹为一次性整体开花竹类,花期为4月下旬～5月下旬,花期约持续45 d,成花量大。(2)花序为圆锥状混合花序,每花序由4枚小穗构成;小穗细长,每枚小穗由5～17枚小花组成;小花为颖花,顶部小花不发育,外稃、内稃各1枚;浆片3枚,卵圆形;雄蕊4～6枚(多为6),每枚花药具有4个花粉囊,花药壁发育为基本型,绒毡层为腺质型,小孢子四分体为左右对称型,成熟花粉粒为2 细胞型,球形,表面纹饰颗粒状,具单个萌发孔,花粉发育过程中部分花药出现异常收缩及空腔的败育花粉粒;雌蕊1枚,柱头3叉,羽毛状,子房1室,胚珠倒生,厚珠心,胚囊为蓼型,成熟胚囊结构及发育过程均正常;雌雄同熟,异花授粉,果实为颖果。(3)斗竹花后全林死亡,结实率低,自然条件下结实率为8.1%。研究结果为研究竹子系统分类、开花机制,开展杂交育种及竹林更新复壮工作等提供基础性资料。     

Ecological consequences of a massive flowering event of bamboo (Chusquea culeou) in a temperate forest of Patagonia,Argentina

Question: What changes occur as a consequence of the massive flowering and senescence of the dominant understory species of bamboo, Chusquea culeou (E. Desvaux)? In this study, we documented some of the ecological consequences of this rare event that occurred in 2001, the previous flowering having occurred more than 60 years ago. Location: Nothofagus temperate forest, Patagonia, Argentina. Methods: We assessed changes in environmental variables and bamboo biomass post‐flowering in an old‐growth southern beech forest. In addition, we monitored the demography of emergent Ch. culeou seedling and Nothofagus nervosa saplings, comparing non‐flowered (live understory) and flowered (senescent understory) patches within the forest matrix. Results: Bamboo flowering dramatically increased light availability in the forest understory but, surprisingly, other environmental changes were not observed. Bamboo seedlings emerged in both patch types, and experienced gradual but modest mortality through time. Bamboo dieback promoted higher survivorship and an increment in biomass, height, number of leaves and buds in the saplings of Nothofagus nervosa. Conclusion: The high density of bamboo seedlings 5 years after the flowering event and the independence of emergence from environmental variables suggest that understory regeneration is a gradual process that is not strongly regulated by initial seedling density or resource limitation. In contrast, microenvironmental conditions created after the flowering event significantly increased Nothofagus sapling growth and survival. These results suggest that overstory forest regeneration could be enhanced in this temperate forest in the first years after this infrequent bamboo flowering event.     

Regeneration of a dominant Mediterranean dwarf-shrub after fire

Abstract. The regeneration after fire of the dominant east Mediterranean dwarf-shrub Sarcopoterium spinosum was studied under various habitat and geographic conditions in northern Israel, northern Crete and the Aegean coast of Turkey. Age structures of regenerating stands were determined 3–9 yr after fire on 13 1 mx 1 m sample stands by analysis of growth rings in the taproot crown of 874 plants. S. spinosum regenerated either by massive seedling recruitment in some habitats or by resprouting from surviving meristems in others. This versatility facilitates adaptation of the species to widely different environmental conditions and is a factor in the maintenance of its dominance after fire at occupied sites. In the years after fire, the growth of younger plants within the stand at all sites was severely suppressed by the older shrubs. Consequently, the age structure of the stands was dominated by one or two older cohorts that became established soon after fire. In addition, on most habitats, older shrubs (usually older than 6 yr) were often composed of clusters of plants that suggested clonal proliferation of ramets. The strongly peaked age structure, together with the appearance of clonal regeneration on the older plants, suggests that subsequent maintenance of the stand was not dependent on recurrent seedling recruitment. This can explain the persistence of S. spinosum in stands of herbaceous vegetation despite the extreme sensitivity of the seedlings to competition under such conditions.     

Thidiazuron promotes in vitro regeneration of wheat and barley

Summary Thidiazuron (TDZ) is a substituted phenylurea which has been shown to be an efficacious regulator of in vitro morphogenesis of many dicot plant species. However, information regarding the effect of TDZ on in vitro regeneration of monocot species is limited. We investigated the effects of TDZ on in vitro regeneration of barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) and found that it promoted shoot regeneration from callus in these two important cereal species. Plant regeneration from calluses derived from immature embryo culture of barley and wheat was observed in regeneration media with a wide range of TDZ concentrations (0.045–45 μM). Shoot regeneration from barley calluses was the highest (38.3% for cv. Golden Promise) at 4.5 μM (1 mg l⁻¹) TDZ, while the optimal TDZ level for wheat regeneration seemed to be 0.9 μM (0.2 mg l⁻¹) (87% for cv. Bob White and 49.4% for cv. Hi Line). Roots developed normally when the regenerated wheat and barley shoots from TDZ-containing media were transferred to the rooting medium. Comparison with other plant growth regulators commonly used in wheat and barley regeneration media suggested that TDZ was among the best for in vitro regeneration of wheat and barley. Both authors contributed equally     

Influence of low-intensity magnetic fields on the development of satellite muscle cells of a newborn rat in primary culture

The influence of Earth magnetic field shielded down to 0.3 μT and static magnetic field (60–160 μT) on the proliferation and differentiation of satellite muscle cells in primary culture has been investigated. A stimulatory effect of static magnetic fields on the rate of the formation of massive multinucleate myotubes and an increase in the intracellular calcium concentration ([Ca²⁺] _i ) have been detected for magnetic fields of the microtesla range. On the other hand, it was shown that the reduction of earth magnetic fields to 0.3 μT leads to inhibition of proliferation and differentiation of skeletal muscle cells in primary culture. Since the formation of contractile myotubes during in vitro experiments is similar to the regeneration of skeletal muscle fibers under muscle damage in vivo, it may be concluded that weak magnetic fields have a strong effect on intracellular processes by influencing all phases of muscle fiber formation. It is necessary to take this fact into consideration when forecasting probable complications of skeletal muscle regeneration during long-term exposure of man to low-intensity magnetic fields and also for the potential use of low static magnetic fields as a tool to recover the affected myogenesis.     

Ultrasonic treatment stimulates multiple shoot regeneration and explant enlargement in recalcitrant squash cotyledon explants in vitro

Ultrasonic treatment (0.5–2 min) stimulated multiple shoot regeneration to high levels in vitro from recalcitrant cotyledon explants of commercial squash (Cucurbita pepo L.) cultivars Ma’yan and Bareqet, on Murashige and Skoog [Physiol Plant 15:473–497, 1962] (regeneration) medium augmented with 4.4 μM benzyladenine. At this stage, unsonicated control explants regenerated only a few very small shoots or bud-like structures. Ultrasound also stimulated massive explant growth. Ultrasound treatment resulted in further multiple shoot production (five times greater than control) after explant transfer to elongation medium (Murashige and Skoog [Physiol Plant 15:473–497, 1962] medium with 0.44 μM benzyladenine and 2.9 μM gibberellic acid). Longer ultrasonic treatments (5 or 10 min) promoted multiple shoot regeneration and explant growth accompanied by hyperhydration. Scanning electron microscope observations showed that 2 min ultrasound changed the joint area between epidermal cells and removed some of the surface from the cotyledon epidermal cells, without gross surface injury to the explants. Longer periods of ultrasound (5–10 min) caused further surface erosion. Rubbing the explant contact surface with chloroform or sandpaper emulated the effect of sonication on shoot regeneration and explant growth, demonstrating that ultrasound exerts its morphogenic influence by surface removal. Sonication of explants from other batches of squash seeds (of cultivars Ma'yan and True French), that regenerated without such treatment, reduced regeneration and caused hyperhydration. This is the first report of stimulation of in vitro regeneration by ultrasound treatment. Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Plant regeneration capacity of mesophyll protoplasts from Brassica napus and related species

Protoplasts from a total of thirty-six genotypes of Brassica species – B. napus, B. campestris (syn. B. rapa), B. juncea, and three distant relatives, Orychophragmus violaceus, Isatis indigotica and Xinjiang wild rape – were analysed for shoot regeneration using a feeder culture system. With the exception of B. campestris and Xinjiang wild rape, some genotypes of all the species could regenerate plants with high efficiency (above 20% of isolated calli initiating shoots). Several genotypes with high regeneration ability were elite breeding lines. Culture conditions as well as genotype had a significant impact on shoot regeneration frequency. In particular, silver nitrate added to the regeneration medium at doses of 6 and 30 μM improved shoot regeneration frequency to 25.4% and 52.2% of isolated calli, respectively, compared to 7.3% percent shoot regeneration without silver nitrate in seven responsive genotypes. Addition of silver nitrate to the regeneration medium also induced shoot regeneration in non-responsive genotypes. Intact plants could be obtained within three months from protoplast isolation in the regenerative genotypes using the current culture system. Advantages of mesophyll protoplasts as compared to protoplasts isolated from hypocotyls for genetic manipulation in Brassica species are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Rigenerazione e totipotenza

Abstract

Regeneration and totipotency.—Regeneration and totipotency of cells and nuclei in plants and animals are discussed. The paper consists of the following sections: regeneration in coelenterates and planarians; limb regeneration in amphibians; regeneration of mammalian liver; Wolffian lens regeneration in urodeles; nuclear transplantation in animal eggs; regeneration of plants from single cells (in vivo; in vitro; from somatic cell hybrids); general remarks.     

Regeneration and coexistence of two Abies species dominating subalpine forests in central Japan

Summary The mechanism of coexistence of the dominant firs Abies veitchii and A. mariesii is described in relation to regeneration patterns for climax subalpine forests of the northern Yatsugatake Mountains, central Honshu, Japan. Two mature stand types, pure conifer stands of Abies spp., and mixed stands of Abies spp. and hardwoods (mainly the birch Betula ermanii), are distinguished. Pure stands are likely to show simultaneous decay, followed by evenaged regeneration of stand-floor seedlings (<20 cm tall), Rapidly growing A. veitchii dominates over A. mariesii in this type of regeneration, which is occasionally invaded by light-demanding Betula. In constrast, mixed stands degenerate rather slowly, followed by the regeneration of Abies from the bank of suppressed saplings (>20 cm tall), which persist only in mixed stands. The more shade-tolerant A. mariesii is supeior in this type of regeneration, while Betula does not succeed, and mixed stands change to pure stands with time. The fact that two patterns of Abies regeneration occur in a certain ratio in the forest is what enables the two Abies species to coexist. A simple dynamical system model supports this conclusion.     

Structure and tree-fall gap dynamics of old-growth Nothofagus forests in Tierra del Fuego,Argentina

Abstract. Tree size and age structure, tree-fall and gap characteristics, and regeneration in gaps were studied in Nothofagus-dominated old-growth forests in Tierra del Fuego, Argentina. Gap-phase regeneration has resulted in all-aged populations for N. pumilio, N. betuloides, and Drimys winteri, and regeneration in gaps appears to be maintaining coexistence between species in mixed stands. N. betuloides fills many gaps via advance regeneration and some individuals persist for > 150 yr in the understory. Multiple periods of release and suppression indicate that N. betuloides may take advantage of several gap events to reach the main canopy. Likewise, Drimys grows well under closed canopy and can rapidly respond to gap formation, sometimes impeding the regeneration of N. betuloides. In contrast, N. pumilio regenerates in gaps mainly from seed or from advance regeneration of small, ephemeral seedlings. Gap turnover times in Fuegian forests were estimated at 300 - 500 yr, although gap formation was highly episodic and possibly associated with regionally extensive windstorms, earthquakes, and stand-level dieback. 92 % of gaps involved multiple tree-falls, and at least 53 % involved secondary expansion. Gap and tree-fall characteristics in Tierra del Fuego were similar to results from northern Patagonia, Chile, and New Zealand; however, we emphasize that regeneration of Nothofagus spp. and Drimys winteri in gaps depends on associated vegetation and varies along both local and regional environmental gradients.     

Factors influencing shoot regeneration from cotyledons of tetraploid <Emphasis Type="Italic">Isatis indigotica</Emphasis> fort

Summary An efficient in vitro plant regeneration system from cotyledons was established in tetraploid Isatis indigotica Fort. Factors influencing shoot regeneration from cotyledons, including culture medium type, combinations of plant growth regulators, and sucrose concentrations in the medium, as well as illumination were investigated. Murashige and Skoog's (MS) medium was found to be best for promoting shoot regeneration, followed by Gamborg's B₅ and White's medium. The highest shoot regeneration frequency was achieved from cotyledons cultured on MS medium supplemented with 2.0 mgl⁻¹ (8.9 μM) 6-benzyladenine and 1.0 mgl⁻¹ (5.4 μM) α-naphthaleneacetic acid (NAA), with 97.9% regeneration, associated with a high number of multiple shoots developed per explant (8.6 shoots per explant). A sucrose concentration of 3% present in the medium and light conditions were beneficial for shoot regeneration. The shoots developed were rooted in a half-strength MS medium supplemented with 1.0 mgl⁻¹ (5.4 μM) NAA and successfully transplanted in soil in pots with over 85% survival. The establishment of an efficient plant regeneration procedure from cotyledons provides a basis for the rapid in vitro multiplication of tetraploid Isatis indigotica Fort., one of the most extensively used medicinal plants in China currently under great shortage.