Vegetative Proliferation and Secondary Proliferated Inflorescences Development in Grass

We report the vegetative proliferation and new phenomenon of “secondary proliferated inflorescences” in the grass Ischaemum barbatum Retz, as determined by anatomical analysis of prepared sections of inflorescences. Leaves and shoots could be developed from the original spikelets of inflorescences and plantlets developed when these shoots were transplanted to moist soil. “Secondary proliferated inflorescences” is the first name here because some inflorescences that developed inadequacy are grown from the spikelet on the mother inflorescence. Our investigation showed that this form of vegetative proliferation and secondary proliferated inflorescences development of I. barbatum has arisen following late autumn fires of the previous year. It is suggested that the sudden onset of a fire could lead to a hormone imbalance or a chemical induction, which results in ephemeral vegetative proliferation even secondary proliferated inflorescences development in wild populations.(Author for correspondence. Tel: +86 (0)20 3725 2993; E-mail: magh@scib.ac.cn)     

Albino inflorescence proliferation of Dendrocalamus latiflorus

Summary Inflorescence proliferation is a plant tissue culture technique that, can be used to obtain in vitro inflorescences year-round without the intervening development of vegetative organs. In this study, we used albino mutant inflorescences of Dendrocalamus latiflorus as the original explant material to investigate, the effect of plant growth regulators on long-term inflorescence proliferation. The albino inflorescences proliferated on solidified Murashige and Skoog (MS) basal medium supplemented with thidiazuron (TDZ), and the optimal concentration for successful long-term inflorescence proliferation was 0.45 μM TDZ. A combination of α-naphthaleneacetic acid (NAA) with 0.45 μM TDZ inhibited the inflorescence proliferation. Inflorescences cultured on a TDZ-free medium supplemented with 26.82 μM NAA rooted in 21 d, vegetative shoots formed by 42 d and, in one case, flowering occurred after 63 d. The auxins 2,4-dichlorophenoxyacetic acid (2,4-D, 4.52 μM) and pieloram (4.14 μM) induced shoot formation. The protocol described can be used to produce large numbers of mutant inflorescences within a relatively short period of time.     

Shoot regeneration,re-flowering and post flowering survival in bamboo inflorescence culture

In vitro grown inflorescences of Bambusa edulis were used to investigate the process of vegetative shoot growth in detail. The findings revealed that auxins and ACC could be significant growth regulators in this process. Overall, auxins [NAA, indolebutyric acid (IBA), and 2,4-dichlorophenoxyacetic acid (2,4-D)] induced inflorescences to grow vegetative shoots. However, the efficiency of shoot regeneration varied. A greater percentage (27.3–34.5) of inflorescences in the 5 mg l⁻¹ NAA, 10 mg l⁻¹ NAA, and 1 mg l⁻¹ 2,4-D treatments formed more vegetative shoots than those exposed to other treatments. IBA promoted shoot regeneration less effectively than NAA and 2,4-D. Fifty percent of regenerated vegetative shoots flowered after 2 months when the medium was supplemented with 5 mg l⁻¹ NAA. All shoots that received 1 mg l⁻¹ 1-amino-cyclopropane-1-carboxylic acid (ACC) flowered in 5 mg l⁻¹ NAA medium. Rooted plantlets were used to examine their survival following in vitro flowering. All plantlets with vegetative shoots, even those with inflorescences, survived and grew.     

Sex ratio and sex expression in an urban population of the silver moss,Bryum argenteum Hedw.

ABSTRACT

Introduction. A well-supported pattern among dioicous bryophytes is male rarity. However, few assessments of bryophyte sex ratios have been made across environmental gradients to assess the role of environment in shaping population sex ratios.

Methods. We systematically surveyed 200 shoots from a 20?m² urban population of Bryum argenteum, and regenerated each shoot apex until sex expression occurred (up to 315 days).

Key results. Female shoots outnumbered male shoots 132 to 68, giving a sex ratio of 1.94♀: 1♂. The female bias was found in two transects in higher light environments but not in the third transect, which had a lower light level and an equal sex ratio. Female shoots took longer than male shoots to reach gametangial induction (122 vs. 60 days) and longer to produce 5 inflorescences (120 vs. 80 days). Male shoots produced an average of 10× the total number of inflorescences compared to female shoots (34 vs. 3.5 inflorescences). Despite producing more inflorescences, male plants also produced more regenerant shoots, thus contradicting the prediction that a higher prefertilisation reproductive effort in males trades off with vegetative proliferation. Female plants harboured significantly more associated microbes than male plants.

Conclusions. Our results support the role of light in influencing sex ratios in this species, suggest that trade-offs between reproduction and vegetative growth may not be strong for males, and indicate a potential role of a sex-specific microbiome in influencing sex ratios.     

Axillary shoot proliferation and in vitro flowering in an adult giant bamboo, Dendrocalamus giganteus Wall. Ex Munro

Summary Continuous axillary shoot proliferation and in vitro flowering were achieved using single node explants from a mature (over 70-yr-old) field clump of Dendrocalamus giganteus (giant bamboo). The shoots proliferated in a basal Murashige and Skoog medium with 6 mgl⁻¹ (26.6 μM) N⁶-benzyladenine (BA) and 2% sucrose. The rate of shoot proliferation gradually increased to over three-fold before in vitro flowering took place. In vitro flowering was not the expression of a species-specific mechanism believed to occur during gregarious flowering, as the mother clump did not flower. The rate of shoot proliferation decreased at flowering, accompanied by reversion of flowering. The development of axillary meristems into vegetative or generative shoots depended on the level of BA. The possible role of BA, changes in the rate of shoot proliferation decreased at flowering, accompanied by reversion of flowering. The development of axillary meristems into vegetative or generative shoots depended on the level of BA. The possible role of BA, changes in the rate of shoot proliferation leading to build up, and release of stress in relation to flowering and its reversion are discussed.     

A method for inflorescence proliferation

Most perennial plants must pass through a long juvenile phase of vegetative development before they are capable of flowering. We have developed a method specifying inflorescence proliferation to bypass juvenility and maintain the adult phase. Bamboo ( Bambusa edulis) inflorescences were amplified by incubation in Murashige and Skoog medium supplemented with 0.1 mg/l thidiazuron. Mutant albino inflorescences also proliferated in this medium. This method is equally effective with dicotyledonous plants. Ginseng ( Panax ginseng) buds were incubated in B5 medium supplemented with 1 mg/l benzyladenine and 1 mg/l gibberellic acid; new inflorescences developed from the base of the explants. Ginseng flowers were parthenocarpic and some of the fruit proliferated in vitro. Using the inflorescences as the material of somatic embryogenesis, we demonstrated that these were not mutations. The regenerated plants still had a juvenile phase and grew normally.     

The shoot apex of Podostemaceae: De novo structure or reduction of the conventional type?

The paper reviews and discusses various interpretations of the shoot apex of Podostemaceae with special reference to subfamily Podostemoideae. Main questions concern (1) the proposed absence of a shoot apical meristem (SAM) in apical “meristemless” shoot tips of Podostemoideae and, as the consequence, the endogenous inception of leaf-borne leaves and branches and (2) the predicted stem bifurcation below a “terminal” dithecous (double-sheathed) leaf positioned instead of a shoot apex, as it is reported for subfamily Podostemoideae. Does the “meristemless” shoot apex represent a true evolutionary novelty? Does the view of stem bifurcation represent a new ramification pattern with the consequence that the “classical root–shoot model” of angiosperms is not valid for Podostemaceae? Both interpretations do not conform to previous studies that are complemented here by new data on the SAM of Zeylanidium olivaceum and Thelethylax minutiflora (Podostemoideae). Although a SAM is difficult to observe in the vegetative shoots of many Podostemoideae, it becomes well visible when the shoot passes into the flowering stage approaching the conspicuous shoot apex of floriferous shoots. The arguments of the absence of a SAM in vegetative shoots are not convincing and the endogenous origin of “leaf-borne leaves” appears questionable. Consequently, the “meristemless” shoot apex cannot be considered as a structure having evolved de novo. In the less advanced subfamilies Tristichoideae and Weddellinoideae, the leaf primordia develop only from a few apical cells of the outer shoot layer. This allows the conclusion that the surface layer of the apex in these subfamilies corresponds to the horizontally spread single-layered apical meristem of subfamily Podostemoideae. Similarly, the view of shoot bifurcation does not conform to the diachsial–sympodial branching pattern occurring in the cymose inflorescences of many Podostemoideae. This fact contradicts the presence of a terminal leaf.     

In vitro differentiation of multiple shoot clumps from intact seedlings of switchgrass

Summary An efficient and reproduciblein vitro culture system has been developed for regeneration of multiple shoot clumps from intact seedlings of both lowland and upland cultivars of switchgrass (Panicum virgatum L.). The multiple shoots were induced on Murashige and Skoog medium supplemented with various combinations of 2,4-dichlorophenoxyacetic acid (2,4-D) and 1-phenyl-3-(1,2,3-thiadiazol-5YL)-urea (thidiazuron or TDZ). Maximum response was obtained with 4.5 μM 2,4-D and 18.2 μM TDZ. These shoots proliferated and rooted efficiently on MS medium without growth regulators. The developmental pattern of the multiple shoots indicated their origin from the enlarged shoot apex via proliferation of axillary buds and subsequent reprogramming of shoot meristems followed by secondary differentiation of adventitious shoots The simplicity of the protocol and direct production of multiple shoots make this a potential system that is highly attractive and amenable for microprojectile-mediated gene transfer.     

Prevention of flower formation in dicotyledons

Prevention of flower formation is important, for example for preventing the spread of transgenes from genetically modified plants or the spread of non-native species, for increasing vegetative growth or preventing the formation of allergenic pollen. The aim of this study was to determine whether flowering of dicotyledonous plants can be prevented by genetic manipulation without harmful effects on vegetative growth. Here we describe isolation of the BpMADS1 gene (similar to SEP3, formerly AGL9) from birch and show that it is expressed only in the inflorescences. In tobacco and Arabidopsis, the expression of BpMADS1::GUS was also virtually inflorescence-specific. Transgenic tobacco and Arabidopsis containing a BpMADS1::BARNASE construct grew well. In one tobacco line the formation of the inflorescence was completely prevented; in several other lines the flowers lacked stamens and carpels and therefore were sterile. The final dry weights of the shoots of the sterile tobacco lines were 140–200% of those of controls. In Arabidopsis, some of the transgenic lines containing the BpMADS1::BARNASE construct formed inflorescences. Some of these lines formed never flowers and some others formed occasionally single fertile flowers. Some other lines did not form inflorescences, but formed up to about one hundred leaves, even in long-day conditions. These results suggest that formation of flowers or inflorescences in widely different dicotyledonous plants could be prevented using the BpMADS1::BARNASE construct and that prevention of flowering may lead to increased vegetative mass.     

A Developmental Pattern of Flowering in Colored <Emphasis Type="Italic">Zantedeschia</Emphasis> spp.: Effects of Bud Position and Gibberellin

The restricted flowering of colored cultivars ofZantedeschia is a consequence of developmental constraints imposed by apical dominance of the primary bud on secondary buds in the tuber, and by the sympodial growth of individual shoots. GA₃ enhances flowering inZantedeschia by increasing the number of flowering shoots per tuber and inflorescences per shoot. The effects of gibberellin on the pattern of flowering and on the developmental fate of differentiated inflorescences along the tuber axis and individual shoot axes were studied in GA₃ and Uniconazole-treated tubers. Inflorescence primordia and fully developed (emerged) floral stems produced during tuber storage and the plant growth period were recorded. Days to flowering, percent of flowering shoots and floral stem length decreased basipetally along the shoot and tuber axes. GA₃ prolonged the flowering period and increased both the number of flowering shoots per tuber and the differentiated inflorescences per shoot. Activated buds were GA₃ responsive regardless of meristem size or age. Uniconazole did not inhibit inflorescence differentiation but inhibited floral stem elongation. The results suggest that GA₃ has a dual action in the flowering process: induction of inflorescence differentiation and promotion of floral stem elongation. The flowering pattern could be a result of a gradient in the distribution of endogenous factors involved in inflorescence differentialtion (possibly GAs) and in floral stem growth. This gradient along the tuber and shoot axes is probably controlled by apical dominance of the primary bud. Online publication: 7 April 2005     

SURVEY OF SHOOT ORGANIZATION IN THE ARACEAE

Shoot organization is examined in 87 species from 29 genera representing all six subfamilies of the Araceae and of Acorus, which has been placed in a separate family. Within each taxonomic group examined, the details of shoot organization are presented, including the types of segments and articles which make up the shoot, the degree of expansion of leaf blades, and the placement of buds along the shoots. Literature on shoot organization of the 29 genera is reviewed. The degree of correlation between shoot organization characteristics and systematic groupings is examined, and the utility of these characteristics for systematics is evaluated. It is found that within the taxa observed, the pattern of shoot organization provides a distinctive “fingerprint” at the generic or sectional level, sufficient for determination of the group. Some patterns which appear are pointed out: taxa with bisexual flowers usually produce a single inflorescence at the terminus of a vegetative article. A few taxa with bisexual flowers produce pairs of inflorescences at the ends of articles. Multiple inflorescences (more than two) at an article terminus occur only among taxa with unisexual flowers. Multiple inflorescences are associated with anisophyllous or homeophyllous sympodial growth, while single or paired inflorescences are associated with homeophyllous or intermittent homeophyllous sympodial growth. These patterns might be understood as the result of selection for flexibility of reproductive effort and of seasonal reproduction.     

Direct plantlet regeneration from male inflorescences of medicinal yam (Dioscorea floribunda Mart. & Gal.)

Summary Segments of male inflorescences of medicinal yam (Dioscorea floribunda) cultured on Murashige and Skoog (MS) medium supplemented with 13.94 μM kinetin (Kn) resulted in the conversion of floral buds into vegetative buds and these later developed into plantlets. Growth and multiplication of shoots could be obtained by culturing individual shoots in MS modified basal medium, replacing the MS standard three vitamins with 10.0 mgl⁻¹ thiamine in addition to 13.94 μM Kn. Root induction was also obtained simultaneously from the base of the shoots in the same medium. Such plantlets have been successfully transferred to potted soil, where they grew normally. Plantlets were also made to develop tubers on MS medium with 18.91 μM abscisic acid (ABA) and also with 2.68 μM α-naphthaleneacetic acid (NAA) and 40–50 gl⁻¹ sucrose.     

Development of secondary inflorescences and in vitro plantlets from inflorescence cultures of Amaranthus paniculatus

Immature inflorescences of Amaranthus paniculatus were used as explants for in vitro culture studies. When placed on a medium supplemented with 3–6 mg/l kinetin, explants developed into secondary inflorescences. Leaves and shoots developed following culture of inflorescence tissue on media containing 8–15 mg/l kinetin or 5–10 mg/l BAP. These shoots when subcultured on MS medium supplemented with 12 mg/l kinetin + 15% coconut milk, formed roots. These rooted plantlets later flowered in vitro.Abbreviations MS Murashige and Skoog - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indoleacetic acid - BAP 6-benzylaminopurine - Kn 6-furfurylaminopurine - CM coconut milk     

AXILLARY AND DICHOTOMOUS BRANCHING IN THE PALM CHAMAEDOREA

In both Chamaedorea seifrizii Burret and C. cataractarum Martius each adult foliage leaf subtends one axillary bud. The proximal buds in C. seifrizii are always vegetative, producing branches (= new shoots or suckers); and the distal buds on a shoot are always reproductive, producing inflorescences. The prophyll and first few scale leaves of a vegetative branch lack buds. Transitional leaves subtend vegetative buds and adult leaves subtend reproductive buds. Both types of buds are first initiated in the axil of the second or third leaf primordia from the apex, P2 or P3. Later development of both types of bud tends to be more on the adaxial surface of the subtending leaf base than on the shoot axis. Axillary buds of C. cataractarum are similarly initiated in the axil of P2 or P3 and also have an insertion that is more foliar than cauline. However, all buds develop as inflorescences. Vegetative branches arise irregularly by a division of the apex within an enclosing leaf (= P1). A typical inflorescence bud is initiated in the axil of the enclosing leaf when it is in the position of P2 and when each new branch has initiated its own P1. No scale leaves are produced by either branch and the morphological relationship among branches and the enclosing leaf varies. Often the branches are unequal and the enclosing leaf is fasciated. The vegetative branching in C. cataractarum is considered to be developmentally a true dichotomy and is compared with other examples of dichotomous (= terminal) branching in the Angiospermae.     

Flowering Gradient Along the Stem Axis in an Orchid Hybrid Aranda deborah

Decapitation stimulated the production of axillary shoots inAranda deborah. The nature of these axillary shoots, whethervegetative or reproductive, was shown to be correlated withtheir positions along the stem axis. The higher ones near theapex developed into inflorescences while the lower ones awayfrom the apex developed into vegetative shoots. These resultsindicated that a flowering gradient exists along the stem axisin this orchid hybrid.     

Shoot regeneration of dwarf dogwood (Cornus canadensis L.) and morphological characterization of the regenerated plants

Dwarf dogwoods (or the bunchberries) are the only suffrutex in Cornaceae. They are attractive ground cover ornamentals with clusters of small flowers surrounded by petaloid bracts. Little has been reported on plant regeneration of dogwoods. As a step toward unraveling the molecular basis of inflorescence evolution in Cornus, we report an efficient regeneration system for a dwarf dogwood species C. canadensis through organogenesis from rejuvenated leaves, and characterize the development of the plantlets. We used the nodal stem segments of vegetative branches as explants. Micropropogated shoots were quickly induced from axillary buds of nodes on an induction medium consisting of basal MS medium supplemented with 4.44 μM BAP and 0.54 μM NAA. The new leaves of adventitious shoots were used as explants to induce calli on the same induction medium. Nearly 65% of leaf explants produced calli, 80% of which formed adventitious buds. Gibberellic acid (1.45 μM) added to the same induction medium efficiently promoted quick elongation of most adventitious buds, and 0.49 μM IBA added to the basal MS medium promoted root formation from nearly 50% of the elongated shoots. The growth of plantlets in pot soil was characterized by the development of functional woody rhizomes, which continuously developed new aboveground vegetative branches, but not flowering branches, within the past 12 months. Potential reasons causing the delay of flowering of the regenerated plants are discussed. The establishment of this regeneration system facilitates developing a genetic transformation system to test candidate genes involved in the developmental divergence of inflorescences in Cornus. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Induction of <Emphasis Type="Italic">in vitro</Emphasis> flowering in the orchid <Emphasis Type="Italic">Dendrobium</Emphasis> Sonia 17

In this study, Dendrobium Sonia 17 plantlets were used to induce in vitro flowering. Inflorescences were induced and rooting was inhibited in the half-strength Murashige and Skoog medium containing 20 μM N ⁶-benzyladenine (BA). The medium with high P and low N contents was effective to induce inflorescences while the medium with low P and high N contents was only effective to promote forming of shoots. In addition, the induced in vitro inflorescences were able to multiply and maintain without exhibiting a distinctive vegetative phase. Different morphologies of in vitro flowers such as incomplete flower structures, abnormal and unresupinated in vitro flowers were observed.     

Control of bud inhibition in Cyperus

Summary The axillary buds in the leaf crown of Cyperus alternifolius seedlings remain completely inhibited although the shoot is determinate and has no active apex. Buds can be released by detachment of the crown from the plant or by direct application of aqueous enzyladenine (BA), and grow out as inflorescences or vegetative shoots. These arise from activated growth centers of the primordial reproductive branch system which is enclosed within the prophyll of the inhibited bud. Buds are also released by the growth retardant, (2-chloroethyl) trimethylammonium chloride (CCC). Gibberellic acid maintains bud inhibition in detached crowns and inhibits bud release caused by CCC or BA. Naphthaleneacetic acid somewhat reduces BA-induced bud release and causes abnormal root proliferation in CCC-treated crowns. It is suggested that a high level of gibberellin within the crown, possibly in relation to a low level of cytokinin, maintains bud inhibition.     

A Quantitative Analysis of the Uptake of Carbon and of the Supply of 14C-labelled Assimilates to Areas of Meristematic Growth in Lolium temulentum

A quantitative analysis of the ¹⁴C-labelled assimilate suppliedby leaves on the main shoot to terminal meristem, stem, tillers,and roots was conducted during parallel periods of reproductiveand vegetative development in Lolium temulentum. The initial rate of entry of carbon into the shoot varied withthe area and photosynthetic efficiency of the assimilating leaf.Subsequently, respiratory losses of carbon during translocationand incorporation of assimilate at the site of utilization alsovaried. The combined effect of these differences resulted inthe supply of recently assimilated carbon being twofold greaterin reproductive shoots than in vegetative shoots, while withinshoots the carbon supply of the youngest fully expanded leafranged from four-or five-fold greater than the oldest leaf inyoung shoots, to two-or three-fold greater in older shoots.In both reproductive and vegetative shoots, the two or threeyoungest leaves thus dominated the supply of carbon for meristematicgrowth. Meristematic tissue in expanding leaves and leaf primordia atthe terminal meristem of the vegetative shoot received 18–27per cent of the total shoot carbon. This meristem utilized aboutthe same proportion of shoot carbon when it developed into aninflorescence, indicating no major change in the level of meristematicactivity. The proportion of shoot carbon utilized in stem growthincreased as both reproductive and vegetative shoots aged; thisincreased meristematic activity in stem internodes was accompaniedby reduced export of carbon to roots, which received less than10 per cent of the shoot carbon when the experiments ended.The main shoot translocated 20–30 per cent of its recentlyassimilated carbon to developing and rooted tillers, which assinks for carbon were thus as important as the terminal meristemand stem. This outward flow of carbon continued relatively uncheckedwhen donor and receptor shoots developed inflorescences.     

Hydrophilous pollination and reproductive morphology in the seagrassPhyllospadix scouleri (Zosteraceae)

In the seagrassPhyllospadix scouleri (Zosteraceae) floral aggregates (spadices) occur on short lateral axes produced by subordinate vegetative shoots. The filamentous pollen is both dispersed on the surface of the sea as well as below the surface. In surface pollination, snowflake-like search vehicles (pollen rafts) float and collide with any rigid female inflorescences that emerge from the water surface. In submarine pollination, collinear bundles of pollen grains are dispersed. Analysis of seed set indicates ovule position within the inflorescence to affect likelihood of fertilization in submarine, but not surface-pollinated inflorescences. Agamospermy appears to be unlikely, but the strongly female-biased shoot sex ratio remains to be explained.