In vitro hermaphrodism induction in date palm female flower

This study explores and reports on the gain brought to the morphogenetic aptitude of female date palm inflorescences through in vitro hermaphrodism induction. It investigates the main factors involved in the process of sex modification through hormonal induction, such as the floral developmental stage and hormone combination and concentration. It demonstrates that the vestigial stamens (staminodes) of female date palm flowers display a new and high capacity to proliferate under particular in vitro conditions, without blocking carpel's development, leading to morphologically typical hermaphrodite flowers. This de novo activation of repressed stamens was found to occur rapidly. The isolated pollen mother cells appear in the obtained anther's locules and undergo an ordinary microsporogenesis process. The data show that hermaphrodism induction depended heavily on both the growth regulators applied and the flower's developmental stage. They also confirm the early theory that suggests that dioecious plants come from a hermaphrodite ancestor. Such hermaphrodism control can provide new prospects and opportunities for the investigation of the in vitro self-fertilization process. It can also be useful in improving the understanding of the genetic mechanism involved in sex organ development in date palm.     

Floral ontogeny and vasculature in Xyridaceae,with particular reference to staminodes and stylar appendages

We provide a detailed comparative study of floral ontogeny and vasculature in Xyridaceae, including Xyris, Abolboda and Orectanthe. We evaluate these data in the context of a recent well-resolved phylogenetic analysis of Poales to compare floral structures within the xyrid clade (Xyridaceae and Eriocaulaceae). Xyrids are relatively diverse in both flower structure and anatomy; many species incorporate diverse and unusual floral structures such as staminodes and stylar appendages. Xyridaceae possess three generally epipetalous stamens in a single whorl; the “missing” stamen whorl is either entirely absent or transformed into staminodes. Fertile stamens each receive a single vascular bundle diverged from the median petal bundle. In Xyris, the stamen bundle diverges at the flower base, but it diverges at upper flower levels in both Abolboda and Orectanthe. In species of Abolboda that possess staminodes, staminode vasculature is closely associated with the lateral vasculature of each petal. Despite the likely sister-group relationship between Eriocaulaceae and Xyridaceae, our character optimization indicates that the stylar appendages that characterize some Xyridaceae (except Xyris and Achlyphila) are non-homologous with those of some Eriocaulaceae. On the other hand, it remains equivocal whether the loss of a fertile outer androecial whorl occurred more than once during the evolutionary history of the xyrid clade; this transition occurred either once followed by a reversal to fertile stamens in Eriocauloideae and staminodes in some Xyridaceae, or twice independently within both Xyridaceae and Eriocaulaceae.     

Discovery of the human homolog of sex-determining region (SRY) gene in dioecious plants

Sex determination in the early developmental stages of dioecious crops is economically-beneficial. During this study, a human homology of SRY gene was successfully identified in dioecious crops. SRY gene sequences of date palm and jojoba were submitted to GenBank under the accession numbers KC577225 and MK991776, respectively. This is the first report regarding the novel sex-determination methodology of four dioecious plants (jojoba, date palm, papaya, and pistachios). SRY sex gene was found in all the tested dioecious plant and human samples. This novel approach is simple and of significant importance for breeders. It facilitates the unambiguous selection of jojoba and date palm female plants at an early age and reduces the plantation cost of cultivating non-productive male plants. This is a rapid sex-determination technique for dioecious plants and mammals at an early stage. This technique specifically targets the SRY sequence that has been comprehensively investigated in humans. The kit development for the SRY-based sex determination of various crops is in progress.     

FLORAL DEVELOPMENT OF HYDROCHARIS MORSUS-RANAE (HYDROCHARITACEAE)

In both male and female flowers of H. morsus-ranae the primordia of the floral appendages appear in an acropetal succession consisting of alternating trimerous whorls. In the male flower a whorl of sepals is followed by a whorl of petals, three whorls of stamens, and a whorl of filamentous staminodes. The mature androecial arrangement therefore consists of two antisepalous stamen whorls, an antipetalous whorl of stamens, and antipetalous staminodes. Shortly before anthesis, basal meristematic upgrowth between filaments of adjacent whorls produces paired stamens, joining Whorls 1 and 3, and Whorl 2 with the staminodial whorl. A central domelike structure develops between the closely appressed filaments of the inner stamen and staminodial whorl, giving the structure a lobed appearance. After petal inception in the female flower a whorl of antisepalous staminodes develop, each of which may bifurcate to form a pair of staminodes. During staminode development a girdling primordium arises by upgrowth at the periphery of the floral apex. The girdling primordium rapidly forms six gynoecial primordia, which then go on to produce six free styles with bifid stigmas. Intercalary meristem activity, below the point of floral appendage attachment, leads to the production of a syncarpous inferior ovary with six parietal placentae. The styles and carpels remain open along their ventral sutures. During the final stages of female floral development, several hundred ovules develop along the carpel walls, and three nectaries develop dorsally and basally on the three antipetalous styles.     

The Domestication Syndrome in Phoenix dactylifera Seeds: Toward the Identification of Wild Date Palm Populations

Investigating crop origins is a priority to understand the evolution of plants under domestication, develop strategies for conservation and valorization of agrobiodiversity and acquire fundamental knowledge for cultivar improvement. The date palm (Phoenix dactylifera L.) belongs to the genus Phoenix, which comprises 14 species morphologically very close, sometimes hardly distinguishable. It has been cultivated for millennia in the Middle East and in North Africa and constitutes the keystone of oasis agriculture. Yet, its origins remain poorly understood as no wild populations are identified. Uncultivated populations have been described but they might represent feral, i.e. formerly cultivated, abandoned forms rather than truly wild populations. In this context, this study based on morphometrics applied to 1625 Phoenix seeds aims to (1) differentiate Phoenix species and (2) depict the domestication syndrome observed in cultivated date palm seeds using other Phoenix species as a “wild” reference. This will help discriminate truly wild from feral forms, thus providing new insights into the evolutionary history of this species. Seed size was evaluated using four parameters: length, width, thickness and dorsal view surface. Seed shape was quantified using outline analyses based on the Elliptic Fourier Transform method. The size and shape of seeds allowed an accurate differentiation of Phoenix species. The cultivated date palm shows distinctive size and shape features, compared to other Phoenix species: seeds are longer and elongated. This morphological shift may be interpreted as a domestication syndrome, resulting from the long-term history of cultivation, selection and human-mediated dispersion. Based on seed attributes, some uncultivated date palms from Oman may be identified as wild. This opens new prospects regarding the possible existence and characterization of relict wild populations and consequently for the understanding of the date palm origins. Finally, we here describe a pipeline for the identification of the domestication syndrome in seeds that could be used in other crops.     

单性木兰（木兰科）花的形态发生

报道了单性木兰(Kmeria septentrionalis Dandy)花的形态发生过程。发现过去一直被认为是雌花条状披针形的“内轮花被片”,实际为退化雄蕊,它形态发生的时间与位置均与雄花的雄蕊相同,在成熟结构中仍可见药室残迹,说明单性木兰的雌性花是由两性花退化而来。通过与K. duperreana(Pierre) Dandy和Magnolia thailandica Noot. &; Chalermglin雌花的比较,发现它们雌花的形态相同,从而得知人们长期以来对此3种植物雌花的认识有误,原一直认为的“内轮花被片”实为退化雄蕊。     

Floral organogenesis and the developmental basis for pollinator deception in the asiatic dayflower, Commelina communis (Commelinaceae)

The upper half of flowers in Commelina communis deceptively lures potential pollinators with its showy petals and staminodes on the false promise of abundant pollen. This paper presents evidence that staminodization in the upper half is associated with a severe retardation of the entire upper floral hemisphere early in development. Possible consequences of this developmental retardation are seen also in the gynoecium, where the upper carpel of the three-carpellate ovary is underdeveloped and sterile at maturity. Only late in development do the upper petals and staminodes expand and acquire pigments necessary for their attractive function. We surmise that retardations of this severity are unlikely to be found for functionally fertile organs such as stamens and ovule-producing carpels, because key preparatory events preceding sporogenesis might otherwise be disrupted. Such differential growth about the floral apex resembles that known in some eudicots to be regulated by the TCP gene family; thus, future molecular developmental studies in Commelina may help to extend our understanding of the evolutionary genetics of floral monosymmetry to monocots.     

Reproductive developmental complexity in the African oil palm (Elaeis guineensis, Arecaceae)

Species of the palm family (Arecaceae) are remarkably diverse in their inflorescence and floral morphologies, which make them a particularly interesting group for studies of reproductive development and its evolution. Using light and scanning electron microscopy, we describe inflorescence and flower development in the African oil palm Elaeis guineensis from the initiation of the inflorescence meristem to flower maturity. In mature palms, the inflorescence develops over 2-3 years and is characterized by individual stages within which differentiation may be either relatively slow, as in the case of early inflorescence meristem development, or rapid, as in the case of flower organogenesis. The female inflorescence bears floral triads composed of single pistillate flowers flanked by two abortive staminate flowers, whereas the male inflorescence contains single functional staminate flowers. This suggests a possible evolutionary movement from an ancestral hermaphrodite inflorescence form containing fully functional floral triads to the situation of temporal dioecy observed at present. Wild type flowers are compared to those bearing an epigenetic homeotic abnormality, known as mantled, involving an alteration of the identity of the organs in the fertile and sterile androecium.     

The role of inner staminodes in the floral display of some relicMagnoliales

The inner staminodes (between stamens and carpels) in some relicMagnoliales (Austrobaileyaceae, Degeneriaceae, Eupomatiaceae, andHimantandraceae) are not just reduced stamens; they are very elaborate organs. InEupomatiaceae, Himantandraceae, and probablyDegeneriaceae they have their own secretory structures which do not occur on the stamens. These play an important role in floral biology. They contribute to the floral coloration pattern; they effect herkogamy by their position and by movements; they provide shelter and food tissue and food secretions (?) for pollinating beetles; they secrete odouriferous oils, mucilage (probably for pollen adherence) and water or nectar (?). For theHimantandraceae a new secretory region on the base of the inner staminode is described. These complicated inner staminodes are extreme specializations of primitive floral types. They have no counterparts in more advanced subclasses of the angiosperms.     

Flower development and anatomy of Clusia valerioi,a Central American species of Clusiaceae offering floral resin

The present paper is part of a study dealing with various aspects of reproduction of two Costa Rican Clusia species offering resin as a floral reward. It provides data on the floral development and flower (especially stamen and staminode) anatomy of one of the species, Clusia valerioi. In the early stages, both male and female flowers develop in the same manner. The bracts are distinguished by a decussate arrangement from the five sepals and five petals, which emerge in a spiral manner. In the male flowers the apical meristem forms five meristematic mounds (common stamen primordia) that are pentagonally arranged around the apical meristem in epipetalous position. From these mounds, the primordia of the proper stamina emerge in 3–5 whorls. Direction is centrifugal. In the centre, five hemispherical bulges arise which develop into carpel primordia. These, however, cease growth, stay rudimentary and are hidden by the stamens in the mature male flower. The adult stamens consist mainly of a thick angular filament column, while the two anthers situated at the flattened top are very small. One anther is annular and surrounds a second, hemispherical one right in the centre. At the periphery, these two pollen sacs (provided with a distinct wall of customary anatomy) are surrounded by a ring-like protuberance of the filament. The resin canals are situated at the periphery of the filament. Their schizogenous development is documented in cross sections. At anthesis, the resin is released from the ring-like filament protuberance by burst of the single-layered epidermis. In the female flower, the five meristematic mounds produce two whorls of staminode primordia. The development of the staminodes does not essentially differ from that of the fertile stamens, but some staminodes lack the central pollen sac and the other tissues do not develop into pollen grains. An attempt is made to derive the peculiar stamen morphology of Clusia valerioi and similar species from conventional stamens. Three hypotheses are proposed and discussed.     

Multiple bud cultures of 'Barhee' date palm (Phoenix dactylifera) and physiological status of regenerated plants

Adventitious bud clusters of date palm ‘Barhee’ were successfully established from juvenile leaves (<1 cm) using reduced amounts of 2,4-D (0.2 mg L⁻¹) to limit the risk of somaclonal variation. An average of 8.4 adventitious buds per explant were obtained. Histological examination showed that the superficial cell layers of leaves had the highest caulogenic capacity. High sucrose concentration (70 g L⁻¹) was used for the conversion of initial buds to multiple bud clusters. The promoting effect of temporary immersion on shoot proliferation was found to be significant when compared to cultivation on solid media. Elongation of shoots was also better using a thin film of PGR-free liquid medium instead of a solid medium. Anatomical observations indicated that roots from vitroplants were potentially functional at various developmental stages. However, only 12-month-old vitroplants were found to be physiologically able to control transpirational vapor loss. Additionally, the photochemical activity of photosystem II in these vitroplants was close to that measured in plants that were already acclimatized. As a result, 83.3% of regenerated plants were successfully acclimatized. No phenotypic variation was observed among more than 500 adventitious bud-derived plants. All regenerants survived after field transplantation. We found that the production of adventitious bud clusters in small bioreactors was able to provide an efficient micropropagation system for date palm cv. ‘Barhee’. An in vitro hardening step was a prerequisite for the successful transfer of vitroplants in soil.     

Use of morphometric parameters for tracking ovule and microspore evolution in grapevine (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L., cv. “Aragonez”) and evaluation of their potential to improve <Emphasis Type="Italic">in vitro</Emphasis> somatic embryogenesis efficiency from gametophyte tissues

Somatic embryogenesis induction from in vitro cultured stamens and carpels is highly dependent on explants’ inoculation at specific developmental stages. To establish good correlations between measurable morphometric parameters of flowers or flower buds and developmental stages of micro- and macrosporogenesis, this procedure is the easiest way to simplify the in vitro culture procedures. These correlations were established here for the most important Iberian grapevine cultivar, the “Aragonez”, named “Tempranillo” in Spain and “Tinta Roriz” in the north of Portugal, and were based in floral buds and anther measurements. The anther length, with a correlation coefficient of 0.90, proved to be the best morphometric parameter to follow microsporogenesis evolution. A correlation between micro- and macrosporogenesis evolutionary stages was also positively established, allowing the use of morphometric parameters for tracking ovule evolution as well. Carpels in several evolutionary stages were in vitro cultured to evaluate the aging effect on the capacity for somatic embryogenesis induction. Explants inoculated in the earliest stages of macrosporogenesis presented the best results. Media culture formulations were also tested for ovary culture, with the best results being achieved with a 5:1 auxin/cytokinin ratio.     

The evolution of staminodes in angiosperms: patterns of stamen reduction, loss, and functional re-invention

Stamens that have lost their primary function of pollen production, or staminodes, occur uncommonly within angiosperms, but frequently fulfill important secondary floral functions. The phylogenetic distribution of staminodes suggests that they typically arise during evolutionary reduction of the androecium. Differences in the genetic control and patterns of stamen loss between actinomorphic and zygomorphic flowers shape staminode development. In clades with actinomorphic flowers, staminodes generally replace an entire stamen whorl and staminode loss seems irreversible. In contrast, in clades with zygomorphic flowers staminodes evolve from a subset of the stamens in a whorl and staminodes can reappear in a lineage after being lost (e.g., Cheloneae, Scrophulariaceae). If staminodes do not adopt new functions during androecium reduction they are lost quickly, so that nonfunctional staminodes appear only in recently derived taxa. Alternatively, when staminodes assume new floral roles, either directly or indirectly after a nonfunctional period, they can become integral floral components which perpetuate within clades (e.g., Orchidaceae). Indirect evolution of staminode function allows greater flexibility of function by allowing staminodes to take over roles not performed by stamens, such as involvement in mechanisms to prevent self-pollination and mechanisms of explosive pollination. Multifunctional staminodes characterize lineages with universal or widespread staminodes.     

Developmental studies in orchid flowers II: Orchidoid species

The floral development of 11 species of Orchidoideae (sensu Rasmussen 1985) was studied by means of SEM, paying special attention to the early development of the gynostemium and its appendages. In contrast to the staminodes found in epidendroid and vandoid orchids, the 'auricles' of the tribe Orchideae are developed on the dorsal side of the fertile anther and therefore are not interpreted as staminodes. Presumed vestiges of the staminodes corresponding to those of the Epidendroideae and Vandoideae are differentiated in early developmental stages, but remain inconspicuous structures later on. The three-lobed rostellum originates entirely from the median carpel. The outstanding systematic position of the tribe Orchideae is briefly discussed.