Differences in the location of subcotyledonary buds among Epilobium angustifolium L., E. dodonaei Vill. and E. fleischeri Hochst. (Onagraceae) and effects on architecture and population structure

STÖCKLIN, J., 1992. Differences in the location of subcotyledonary buds among Epilobium angustifolium L., E. dodonaei Vill. and E. fleischeri Hochst. (Onagraceae) and effects on architecture and population structure . Morphological and architectural features in the two closely related pioneer plant species Epilobium dodonaei and E. fleischeri are examined in cultivation and in the field and compared with E. angustifolium. In E. angustifolium , the aerial shoot system is renewed every year from buds on horizontal roots and results in a horizontal spread and a clonal growth form. In E. dodonaei , bud formation is restricted to the hypocotyl and in larger plants to the transitional region between root and shoot. Consequently this species shows no vegetative mobility and develops a shrub-like habit. The alpine E. fleischeri combines the habit of E. angustifolium and E. dodonaei and may either develop successive generations of shoots from the transitional region between root and shoot and/or exploit new areas by horizontal roots and the formation of shoots from root buds. The simple difference in the location of renewal buds is accentuated by cumulative growth. The study shows that E. dodonaei and E. fleischeri , which often are considered as subspecies, are separated by fundamental differences in their architectural models. The ecological and demographic implications of these differences are discussed.     

Quantitative analysis of major axis development inViburnum dilatatum andV. wrightii (Caprifoliaceae)

The architectural development ofViburnum dilatatum andV. wrightii was investigated quantitatively. In both species, the major axis is developed from terminal buds of vegetative shoots and from axillary buds on the most distal nodes of reproductive shoots. The architecture of the two species is formed mainly by four branching patterns: a monopodial pattern (M), a sympodial pattern producing a pair of opposite daughter shoots (SP), a sympodial pattern producing a single daughter shoot (SS), and a pattern terminated with a dormant or dead bud (D). In the process of the architecture formation, four successive stages are recognized: 1) height growth, where the M pattern is dominant; 2) crown formation, in addition to the M pattern, the SP pattern occurs frequently; 3) crown expansion, the M and SP patterns are also frequent; 4) over mature, the M pattern becomes dominant again. These four stages are common to the two species, butViburnum wrightii proceeds with the crown formation stage more rapidly and stays in the crown expansion stage for a longer time thanV. dilatatum. The crown ofViburnum wrightii is thus more branched than that ofV. dilatatum.     

Estimation of dieback process caused by herbivory in an endangered root-sprouting shrub species,Paliurus ramosissimus (Lour.) Poir., using a shoot-dynamics matrix model

Mortality, a critical parameter for population dynamics, is difficult to measure in long-lived trees or clonal herbaceous species because of the extremely low frequency of deaths. A model based on shoot recruitment would be helpful to estimate the population fate of species without a sufficient number of observed deaths. Existing matrix models are applicable to the dynamics of physiologically independent shoots, but not to physiologically dependent ones. We developed a shoot-dynamics model for plants with physiologically-dependent shoots, and used the model to estimate the effects of herbivory and conservation measures on the dynamics of a long-lived, shoot-sprouting shrub species, Paliurus ramosissimus (Rhamnaceae). Two populations of the endangered shrub have been severely damaged by herbivory by sika deer. The damage was mainly to new sprouting shoots. No deaths of individual plants were observed during an 8-year survey, and we could not estimate mortality. Thus, prediction of population dynamics based on births and deaths of individuals was impossible. Because P. ramosissimus is a shoot-sprouting species, we instead estimated the decline of individuals using a shoot-dynamics model. Using this model, we estimated the time to an 80 % decrease in shoot number per individual in the two populations at 37.8 and 37.2 years. These lengths suggest an immediate need for conservation measures to prevent herbivory even though no death of any individual was observed in the field survey. The estimated recovery times from the herbivory damage were 28.7 and 29.2 years if herbivory of new shoots is completely prevented by conservation measure.     

Impact of a gall-inducing aphid on Pistacia atlantica Desf. trees

The impact of gall-inducing aphids on shoot development was analyzed in 900 shoots from 20 pistachio trees, Pistacia atlantica Desf. (Anacardiaceae): 600 in which the axillary—lateral buds were galled by Slavum wertheimae HRL during the previous growth season, and 300 ungalled shoots. Although P. atlantica is a compensating tree, and the aphids do not attack the apical buds, further development of shoots from the apical buds was stopped in 62% of the galled shoots, while only 8.7% of nongalled shoots stopped their growth. Further development was stopped more often on shoots carrying two or more galls than on shoots supporting only one gall. To assess the hypothesis that bud destruction by the aphids explains this pattern, a field experiment was conducted in 140 shoots, distributed across seven trees. One, two or three axillary buds from five shoots of each tree were removed for each treatment, and five other shoots were marked as controls. Only 14 shoots (10%) of the 140 did not develop. The growth of the other shoots was not very different among the treatments. The colonization of the apical shoots, which developed on previously treated shoots, by three other galling aphid species was monitored. Removing lateral buds considerably reduced the establishment of Geoica sp. galls (70% of them colonized control shoots), but weakly influenced Forda riccobonii (Stefani). It also contributed only 5% of the total variance of the distribution of Smynthurodes betae West. The different results of the survey and the experiment show that the impact of S. wertheimae galls on the future growth of shoots from apical buds is more complex than the simple physical destruction of the axillary buds. Handling editor: Graham Stone     

中国鼠李科植物属的空间分布特点研究

在ArcGIS软件中,以中国鼠李科植物物种分布数据为基础,以县为基本单元,制作属的空间分布数据,从空间分布图中提取各属的斑块面积、周长、数目,计算属的Simpson均匀度指数、形状指数及最大斑块指数,分析中国鼠李科植物属的空间分布特点,为确定其空间分布最小范围、定量研究及植物的保护、利用、资源的开发和恢复提供依据。结果表明:①麦珠子属、对刺藤属、苞叶木属、小勾儿茶属、蛇藤属、咀签属和翼核果属为狭域属,马甲子属、猫乳属、雀梅藤属、枳椇属、勾儿茶属、枣属和鼠李属为广域属,狭域属和广域属均占中国鼠李科植物总属数的50%。狭域属的总面积小于30×10⁴km²,其中小勾儿茶属主要分布在我国亚热带中部,其他狭域属主要分布在北回归线附近及其以南地区;广域属的总面积大于40×10⁴km²,分布在我国大部分地区,西北地区呈零星分布。②中国鼠李科植物中,鼠李属的分布范围和总面积最大,几乎涵盖所有属的分布范围,它能体现出鼠李科植物在中国的空间分布及其特点。③麦珠子属是中国鼠李科植物中唯一呈连续分布且分布最狭窄的属,其他属均为间断分布。苞叶木属、咀签属、勾儿茶属和鼠李属呈现只有主分布区,对刺藤属、雀梅藤属和枳椇属呈主次分布区,小勾儿茶属、蛇藤属、翼核果属、马甲子属、猫乳属和枣属均呈星散分布。     

A fruit and leaves of Rhamnaceous affinities from the late Cretaceous (Maastrichtian) of Colombia

Although Rhamnaceae are distributed worldwide today, the former hypothesis for its Laurasian origins may need to be reconsidered in view of recently discovered fossils from the Guaduas Formation of central Colombia (～68 Ma), including fossil leaves (Berhamniphyllum) and a fruit (Archaeopaliurus boyacensis). Recent phylogenetic studies calibrate the stem of Rhamnaceae at 64 Ma and divide the family into three groups, rhamnoid, ampeloziziphoid, and ziziphoid. Although the fruit, Archaeopaliurus boyacensis, resembles that of Paliurus and suggests a relationship to the Paliureae in the ziziphoid group, associated leaves of Berhamniphyllum conform in architecture to those found today only in the Rhamneae tribe. The Maastrichtian age of these fossils predates the ages previously estimated for the Rhamneae tribe (28.5 Ma) and the Paliureae tribe (31.6 Ma) using a modified clock approach. Based on the new megafossil evidence, two alternative ideas are proposed: (1) that these fossils predate the extant tribes or (2) that the family diversified into modern tribes earlier than previously proposed.     

Morphological studies in the tribe Colletieae (Rhamnaceae): analysis of architecture and inflorescences.

A morphological study of vegetative and reproductive structures was carried out on the tribe Colletieae (Rhamnaceae) composed of six genera and 20 species. The plant habit variation, from trees (up to 8 m high) to prostrate shrubs and tangled bushes, suggests structural differences within the group. All the species have an architecture represented by a sequence of monopodial shoots with limited growth, linked sympodially and with acrotonic dichasial ramification. Foliage leaves are decussate and an axillary complex with two serial meristems is associated with each leaf axil. Ancillary shoots (thorn-tipped branches, short shoots, secondary branches and reproductive shoots) are present at the nodes. A single structural plan was observed throughout the tribe. Most of the variability may be ascribed to different strategies for adaptation to environmental conditions, specially xeromorphy. Reproductive structures, in terms of inflorescences, also show conspicuous variation throughout the tribe. Three different models are described; in the first two models individual flowers or 3–7 flowered cymes constitute the paracladia of either deciduous monotelic synflorescences, or of synflorescences proliferating into vegetative long shoots; in the third, uniflorous paracladia arise from perennial short-shoots. Nevertheless, a link within them can be established through steps of truncation, proliferation, reduction and acquisition of rhythmic growth.     

Preformed and neoformed extension of shoots and sylleptic branching in relation to shoot length in Tsuga canadensis

Summary Shoot systems developed over 3 successive years were investigated on 55 understorey Tsuga canadensis (L.) Carr. trees. Paired comparisons of preformed-leaf content of terminal buds and numbers of leaves produced on new shoots showed that neoformed leaves were produced in large numbers. Parent-shoot character was not useful in predicting numbers of preformed leaves, was better related to total leaves produced, but left the majority of the variation unexplained. This reflected the capacity of any terminal bud to produce a shoot with more or less neoformation, depending on conditions for growth. All shoots over 6 cm long produced sylleptic shoots that bore from two to many leaves and were arranged in a mesitonic pattern along the parent. Some of the longer sylleptic shoots produced lateral buds or second-order sylleptic shoots. Monopodial second-year extensions of sylleptic-shoot axes followed an acrotonic pattern, as did proleptic shoots from the few lateral buds borne on the parent shoots. Such lateral buds were more frequent on shorter parent shoots: they typically occurred near the proximal and distal ends. Duration of shoot extension was positively correlated with shoot length: terminal buds became evident as shoot extension neared cessation.     

Clonal strategies of a woody weed: Melia azedarach

Melia azedarach L., a weedy tree that typically reproduces by seeds, may exhibit clonal growth following disturbance (e.g. fire, herbivory, animal injury). A dynamic and holistic study (sensu Hallé et al., 1978) was carried out in order to determine the architecture and the vegetative growth strategies, in plants collected from undisturbed and disturbed areas in the ‘El Palmar’ National Park. The architectural and morphological observations can be summarized as follows: (a) Tree architecture is determined by a monopodial trunk that produces tiers of orthotropic monopodial branches. (b) The root system consists of a tap root with woody primary lateral roots that exhibit plagiotropic growth and are typically found within the first few centimeters (ca. 4 cm) of the soil profile. (c) Root buds were produced in all (fire treated and control) plagiotropic root cuts when incubated under controlled conditions. Root suckers developed from the differentiation of parenchymatous cells produced by meristematic activity in the cambial zone. The ecological implications of vegetative reproduction on the invasive capacity of this species are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Winter bud content according to position in 3-year-old branching systems of 'Granny Smith' apple

An investigation was made of the number of preformed organs in winter buds of 3-year-old reiterated complexes of the 'Granny Smith' cultivar. Winter bud content was studied with respect to bud position: terminal buds were compared on both long shoots and spurs according to branching order and shoot age, while axillary buds were compared between three zones (distal, median and proximal) along 1-year-old annual shoots in order 1. The percentage of winter buds that differentiated into inflorescences was determined and the flowers in each bud were counted for each bud category. The other organ categories considered were scales and leaf primordia. The results confirmed that a certain number of organs must be initiated before floral differentiation occurred. The minimum limit was estimated at about 15 organs on average, including scales. Total number of lateral organs formed was shown to vary with both bud position and meristem age, increasing from newly formed meristems to 1- and 2-year-old meristems on different shoot types. These differences in bud organogenesis depending on bud position, were consistent with the morphogenetic gradients observed in apple tree architecture. Axillary buds did not contain more than 15 organs on average and this low organogenetic activity of the meristems was related to a low number of flowers per bud. In contrast, the other bud categories contained more than 15 differentiated organs on average and a trade-off was observed between leaf and flower primordia. The ratio between the number of leaf and flower primordia per bud varied with shoot type. When the terminal buds on long shoots and spurs were compared, those on long shoots showed more flowers and a higher ratio of leaf to flower primordia.     

Warm spring temperatures induce persistent season-long changes in shoot development in grapevines

Background and Aims

The influence of temperature on the timing of budbreak in woody perennials is well known, but its effect on subsequent shoot growth and architecture has received little attention because it is understood that growth is determined by current temperature. Seasonal shoot development of grapevines (Vitis vinifera) was evaluated following differences in temperature near budbreak while minimizing the effects of other microclimatic variables.

Methods

Dormant buds and emerging shoots of field-grown grapevines were heated above or cooled below the temperature of ambient buds from before budbreak until individual flowers were visible on inflorescences, at which stage the shoots had four to eight unfolded leaves. Multiple treatments were imposed randomly on individual plants and replicated across plants. Shoot growth and development were monitored during two growing seasons.

Key Results

Higher bud temperatures advanced the date of budbreak and accelerated shoot growth and leaf area development. Differences were due to higher rates of shoot elongation, leaf appearance, leaf-area expansion and axillary-bud outgrowth. Although shoots arising from heated buds grew most vigorously, apical dominance in these shoots was reduced, as their axillary buds broke earlier and gave rise to more vigorous lateral shoots. In contrast, axillary-bud outgrowth was minimal on the slow-growing shoots emerging from buds cooled below ambient. Variation in shoot development persisted or increased during the growing season, well after temperature treatments were terminated and despite an imposed soil water deficit.

Conclusions

The data indicate that bud-level differences in budbreak temperature may lead to marked differences in shoot growth, shoot architecture and leaf-area development that are maintained or amplified during the growing season. Although growth rates commonly are understood to reflect current temperatures, these results demonstrate a persistent effect of early-season temperatures, which should be considered in future growth models.     

Execution of the auxin replacement apical dominance experiment in temperate woody species

The classic Thimann-Skoog or auxin replacement apical dominance test of exogenous auxin repression of lateral bud outgrowth was successfully executed in both seedlings and older trees of white ash, green ash, and red oak under the following conditions: (1) decapitation of a twig apex and auxin replacement were carried out during spring flush, (2) the decapitation was in the previous season's overwintered wood, and (3) the point of decapitation was below the upper large irrepressible lateral buds but above the lower repressible lateral buds. Although it has been suggested that neither auxin, the terminal bud, nor apical dominance have control over the outgrowth of the irrepressible buds during spring flush, there is evidence in the present study that indicates that such control over the repressible buds exists. In seedlings, second-order branching, which resulted from decapitation of elongating current shoots, was also inhibited by exogenous auxin in the three species. Hence, the auxin replacement experiments did work on year-old proleptic buds (of branches of older trees) that would have entered the bud bank and also on current buds of seedlings. Cytokinin treatments were ineffectual in promoting bud growth.     

Evidence that cytokinin controls bud size and branch form in Norway spruce

Shoot elongation in many coniferous species is predetermined during bud formation the year before the shoot extends. This implies that formation of the primordial shoot within the bud is the primary event in annual shoot growth. Hormonal factors regulating bud formation are consequently of utmost importance. We followed the levels of the endogenous cytokinins zeatin riboside (ZR) and isopentenyladenosine (iPA) in terminal buds, whorl buds and lower lateral buds of the uppermost current-year whorl shoots of 15- to 20-year-old trees of Norway spruce [ Picea abies (L.) Karst.] from June to September. Cytokinins were isolated with affinity chromatography columns, purified by high performance liquid chromatography, and quantified by ELISA. The level of ZR was low in June but increased gradually in all buds until September. Throughout the measurement period, the ZR level was highest in terminal buds and lowest in the scattered lateral, buds, with the whorl buds intermediate. The level of iPA peaked in July and decreased later without any consistent differences among the three classes of buds. The development of different kinds of buds was followed by scanning electron microscopy. We found that bud growth was greatest during August and September. The final size of primordial shoots within the buds varied considerably and the weight of the terminal bud was three times that of the whorl buds and more than five times that of the other lateral buds.
We conclude that the increase in ZR level during the period of active bud development is indicative of the importance of cytokinin for this process. Furthermore, the positive correlation between the level of ZR and bud growth during the period of predetermination of next year's branch growth suggests that this hormone indirectly controls the form of single branches in the spruce tree.     

Evidence that cytokinin controls bud size and branch form in Norway spruce

Shoot elongation in many coniferous species is predetermined during bud formation the year before the shoot extends. This implies that formation of the primordial shoot within the bud is the primary event in annual shoot growth. Hormonal factors regulating bud formation are consequently of utmost importance. We followed the levels of the endogenous cytokinins zeatin riboside (ZR) and isopentenyladenosine (iPA) in terminal buds, whorl buds and lower lateral buds of the uppermost current-year whorl shoots of 15- to 20-year-old trees of Norway spruce [ Picea abies (L.) Karst.] from June to September. Cytokinins were isolated with affinity chromatography columns, purified by high performance liquid chromatography, and quantified by ELISA. The level of ZR was low in June but increased gradually in all buds until September. Throughout the measurement period, the ZR level was highest in terminal buds and lowest in the scattered lateral, buds, with the whorl buds intermediate. The level of iPA peaked in July and decreased later without any consistent differences among the three classes of buds. The development of different kinds of buds was followed by scanning electron microscopy. We found that bud growth was greatest during August and September. The final size of primordial shoots within the buds varied considerably and the weight of the terminal bud was three times that of the whorl buds and more than five times that of the other lateral buds.
We conclude that the increase in ZR level during the period of active bud development is indicative of the importance of cytokinin for this process. Furthermore, the positive correlation between the level of ZR and bud growth during the period of predetermination of next year's branch growth suggests that this hormone indirectly controls the form of single branches in the spruce tree.     

Rendiconti delle Sedute e Brevi Comunicazioni

Summary

In this research we describe the embryology relating to the ovule from the first stages of the archesporium to the grown up gametophyte in Rhamnus Alaternus L., Colletia cruciata Gill. et Hook., Colletia spinosa Lam. Paliurus aculeatus Lam. and Hovenia dulcis Thunb. We ascertain everywhere a very analogous behaviour in the formation of the gametophyte, which is of the Normal type, except a very few irregularities, while the condition of the archesporium is various in the different species. We describe also the microsporogenesis observed in three species. We establish the aploid numbers 12 for Paliurus aculeatus, 11 for Colletia spinosa and the diploid number 22 for Colletia cruciata. We describe at last a remarkable parthenocarpic capacity in Colletia spinosa and the sterility probably due to a scanty vital mutation in an individuum of Paliurus aculeatus.     

Overexpression of the maize Teosinte Branched1 gene in wheat suppresses tiller development

The number of viable shoots influences the overall architecture and productivity of wheat (Triticum aestivum L.). The development of lateral branches, or tillers, largely determines the resultant canopy. Tillers develop from the outgrowth of axillary buds, which form in leaf axils at the crown of the plant. Tiller number can be reduced if axillary buds are not formed or if the outgrowth of these buds is restricted. The teosinte branched1 (tb1) gene in maize, and homologs in rice and Arabidopsis, genetically regulate vegetative branching. In maize, increased expression of the tb1 gene restricts the outgrowth of axillary buds into lateral branches. In this study, the maize tb1 gene was introduced through transformation into the wheat cultivar "Bobwhite" to determine the effect of tb1 overexpression on wheat shoot architecture. Examination of multiple generations of plants reveals that tb1 overexpression in wheat results in reduced tiller and spike number. In addition, the number of spikelets on the spike and leaf number were significantly greater in tb1-expressing plants, and the height of these plants was also reduced. These data reveal that the function of the tb1 gene and genetic regulation of lateral branching via the tb1 mode of action is conserved between wheat, rice, maize and Arabidopsis. Thus, the tb1 gene can be used to alter plant architecture in agriculturally important crops like wheat.     

The effect of decapitation on the levels of IAA and ABA in the lateral buds of Betula pendula roth

The level of IAA and ABA in lateral buds of birch shoots 24 h and 5 days after the decapitation of the apical bud was determined. Twenty four hours after decapitation, when visible signs of outgrowth of lateral buds were not observed yet, an increase in the level of IAA and a decrease of ABA, as compared with the buds of non-decapitated shoots, was found. Five days later, when lateral buds were in the period of intensive outgrowth, a decrease in the levels of IAA and ABA was observed. It has been suggested that removing the source of auxin, by the decapitation of the apical bud makes possible the lateral buds to undertake the synthesis of their own auxin. It could lead to the decrease in the content of ABA. These all events could create suitable conditions for the outgrowth of lateral shoots.     

In vitro Propagation of Ginkgo biloba by Using Various Bud Cultures

The purpose of this research is micropropagation of Ginkgo biloba L. Apical and nodal meristems removed from plantlets or apical buds from a tree were used as explants. Meristems produced an extensive callus and single or rare multiple shoots on Murashige and Skoog medium with different growth regulators and endosperm extract (En) obtained from mature seeds of the same species. For successful root production it was necessary to transfer the shoots to a rooting medium with En. This revised version was published online in July 2006 with corrections to the Cover Date.     

Plant architecture and meristem dynamics as the mechanisms determining the diversity of gall-inducing insects

Plant architecture is considered to affect herbivory intensity, but it is one of the least studied factors in plant–insect interactions, especially for gall-inducing insects. This study aimed to investigate the influence of plant architecture on the speciose fauna of gall-inducing insects associated with 17 species of Baccharis. Five architectural variables were evaluated: plant height, number of fourth-level shoots, biomass, average level and number of ramifications. The number of galling species associated with each host plant species was also determined. To test the effects of plant architecture on gall richness at the individual level, we used another data set where the number of fourth-level shoots and gall richness were determined for B. concinna, B. dracunculifolia, and B. ramosissima every 3 weeks during 1 year. The average similarity between host species based on gall fauna was low (9%), but plants with the same architectural pattern tended to support similar gall communities. The most important architectural trait influencing gall richness at the species level was the number of fourth-level shoots, which is indicative of the availability of plant meristems, a fundamental tissue for gall induction and development. This variable also showed a positive correlation with gall richness at the individual level. We propose that variations in gall richness among host species are driven by interspecific differences in plant architecture via availability of young, undifferentiated tissue, which is genetically controlled by the strength of the apical dominance. Plant architecture should have evolutionary consequences for gall communities, promoting insect radiation among architecturally similar plants through host shift and sympatric speciation. We also discuss the role of plant architecture in the global biogeography of gall-inducing insects. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Bud Structure in Relation to Shoot Morphology and Position on the Vegetative Annual Shoots of Juglans regia L. (Juglandaceae)

The length and basal diameter of all lateral and terminal budsof vegetative annual shoots of 7-year-oldJuglans regia treeswere measured. All buds were dissected and numbers of cataphylls,embryonic leaves and leaf primordia were recorded. Each axillarybud was ranked according to the position of its associated leaffrom the apex to the base of its parent shoot. Bud size andcontent were analysed in relation to bud position and were comparedwith the size and number of leaves of shoots in equivalent positionswhich extended during the following growing season. Length andbasal diameter of axillary buds varied according to their positionon the parent shoot. Terminal buds contained more embryonicleaves than any axillary bud. The number of leaves was smallerfor apical and basal axillary buds than for buds in intermediatepositions on the parent shoot only. All new extended shootswere entirely preformed in the buds that gave rise to them.Lateral shoots were formed in the median part of the parentshoot. These lateral shoots derived from buds which were largerthan both apical and basal ones. Copyright 2001 Annals of BotanyCompany Juglans regia L., Persian walnut tree, branching pattern, preformation, bud content, shoot morphology