Sepal Primordia Research Articles

Morphological and anatomical development in the Vitaceae. IV. Floral development in Parthenocissus inserta

The floral ontogeny of Parthenocissus inserta, based on histological and three-dimensional observations, is presented. The inflorescence primordium arises in a leaf-opposed position at two of three nodes. It becomes subtended by a bract, and then bifurcates equally to form a lateral and a main arm. Inflorescence branches are initiated on both arms to form a series of dichasia. The transition from inflorescence branch primordium to floral primordium is marked by the initiation of three sepal primordia. Subsequently a ring primordium forms as the fourth and fifth sepal primordia are initiated, resulting in a calyx which encircles the floral apex. Petals and stamens arise simultaneously as five common petal–stamen primordia, alternating with the sepals. They bifurcate to form separate petal and stamen primordia. The petals are greenish, valvate, hooded, and are separate at maturity. The tetrasporangiate anthers are introrse and pollen is tricolporate. The gynoecium arises as a ring primordium. Two septa arise from the inner gynoecial wall and the floral apex, and will eventually form an essentially two-loculed superior ovary. Two ovules are initiated from the base of each septum. Each of the four ovules is anatropous and bitegmic at maturity. A disc arises from the base of the gynoecium. It appears as five pinkish protuberances of the ovary base at maturity and secretes a nectarlike substance. The fruit is a one- to four-seeded blue-black berry.

FLOWER CULTURE OF A MALE STERILE STAMENLESS‐2 MUTANT OF TOMATO (LYCOPERSICON ESCULENTUM)

Young floral buds of a male sterile stamenless‐2 (sl‐2/sl‐2) mutant of tomato were cultured, at the sepal primordia stage, in a liquid Murashige and Skoog medium containing either benzylaminopurine (BAP) or gibberellic acid (GA3) or both. In the basal medium (BM), the buds initiated petal and stamen primordia only and they showed limited development. In buds grown in BM supplemented with 10–6 M BAP, all types of organ primordia were initiated but the petals remained small and the stamens and carpels were immature. Well‐developed flowers with a normal complement of floral organs were, however, produced in a medium containing both BAP (10–6 M) and GA3 (10–7 M to 10–5 M). The development of stamens was variable and ranged from the complete absence of microsporogenesis to the formation of abnormal pollen. Gynoecium development was normal and ovules with megaspores were produced in the ovary. The results show that male sterility in the sl‐2/sl‐2 mutant can be expressed in vitro and that GA3 is essential for the in vitro growth and development of all the floral organs of this mutant.

Untersuchungen zur Blatt- und Blütenentwicklung bei Galium aparine L. (Rubiaceae)

Summary The development of the leaves and flower of Galium aparine was studied using microtome technique and the scanning microscope. The leaves develop from decussated primordia in a way which is typical of dicots. Simultaneously two common meristems emerge between them which divide into different numbers of primorida which, in turn, result into the phyllomes mostly referred to as stipules. Differences in the initiation at the shoot apex and a slight advance of the growth of leaf primordia are the only characters to discriminate the morphogenesis of different phyllomes of a whorl. The two to seven flowers of partial inflorescences develop successivly. The differentiation of the floral shoot apex begins with the simultaneous occurrence of the petal and staminal primordia. The inferior gynoecium produces a synascidiate and a symplicate zone developing placentas and ovules at an early stage of the development. Rudimentary sepal primordia were not detected.

A SCANNING ELECTRON MICROSCOPIC STUDY ON THE INITIATION AND DEVELOPMENT OF FLORAL ORGANS OF BRASSICA NAPUS (CV. WESTAR)

The initiation and development of the floral organs of Brassica napus L. (cv. Westar) were examined using the scanning electron microscope. After transition of the vegetative apex into an inflorescence apex, flower primordia were initiated in a helical phyllotactic pattern. The sequence of initiation of the floral organs in a flower bud was that of sepals, stamens, petals and gynoecium. Of the four sepal primordia, the abaxial was initiated first, followed by the two lateral and finally the adaxial primordium. The four long stamens were initiated simultaneously in positions alternating with the sepals. The two short stamens were initiated basipetal to and outside the long stamens, and opposite the lateral sepals. The petals arose on either side of the two short stamens and the gynoecium was produced from the remainder of the apex. During development, the sepal primordia curved sharply at the tips and tightly enclosed the other organs. Stamen primordia developed tetralobed anthers at an early stage while filament elongation occurred just prior to anthesis. A unique pattern of bulbous cells was present on the abaxial surface of the anther. Growth of petal primordia lagged relative to the other floral organs but expansion was rapid prior to anthesis. The gynoecium primordium was characterized by an invagination early in development. At maturity, there was differentiation of a papillate stigma, an elongated style and a long ovary marked externally by sutures and divided internally by a septum. Distinct patterns of cuticular thickenings were observed on the abaxial and adaxial surfaces of the petals and stamens and on the surface of the style. The patterns were less obvious on the sepals and ovary. Stomata were present on both surfaces of the mature sepals, on the style and restricted areas on the abaxial surface of the anthers and nectaries but were absent from the petals, the adaxial surface of the stamens and the ovary. No hairs were present on any of the floral organs.

A Scanning Electron Microscopic Study on the Initiation and Development of Floral Organs of Brassica napus (Cv. Westar)

The initiation and development of the floral organs of Brassica napus L. (cv. Westar) were examined using the scanning electron microscope. After transition of the vegetative apex into an inflorescence apex, flower primordia were initiated in a helical phyllotactic pattern. The sequence of initiation of the floral organs in a flower bud was that of sepals, stamens, petals and gynoecium. Of the four sepal primordia, the abaxial was initiated first, followed by the two lateral and finally the adaxial primordium. The four long stamens were initiated simultaneously in positions alternating with the sepals. The two short stamens were initiated basipetal to and outside the long stamens, and opposite the lateral sepals. The petals arose on either side of the two short stamens and the gynoecium was produced from the remainder of the apex. During development, the sepal primordia curved sharply at the tips and tightly enclosed the other organs. Stamen primordia developed tetralobed anthers at an early stage while filament elongation occurred just prior to anthesis. A unique pattern of bulbous cells was present on the abaxial surface of the anther. Growth of petal primordia lagged relative to the other floral organs but expansion was rapid prior to anthesis. The gynoecium primordium was characterized by an invagination early in development. At maturity, there was differentiation of a papillate stigma, an elongated style and a long ovary marked externally by sutures and divided internally by a septum. Distinct patterns of cuticular thickenings were observed on the abaxial and adaxial surfaces of the petals and stamens and on the surface of the style. The patterns were less obvious on the sepals and ovary. Stomata were present on both surfaces of the mature sepals, on the style and restricted areas on the abaxial surface of the anthers and nectaries but were absent from the petals, the adaxial surface of the stamens and the ovary. No hairs were present on any of the floral organs.

In vitro culture of young floral buds of tomato ( Lycopersicon esculentum mill.)

Young floral buds of tomato ( Lycopersicon esculentum Mill.), with sepal primordia only, were cultured successfully in a liquid medium containing Murashige and Skoog's salts, White's vitamins and glycine, 3% (w/v) sucrose and benzylaminopurine (BAP). In 5 weeks, 60–70% of the cultured buds showed normal flower development through to anthesis, and a full complement of floral organs was produced. In the anthers, microsporogenesis occured and microspores and pollen grains were formed. The gynoecium was differentiated into an ovary, style and a stigma, and the ovary contained many ovules, some of which had developing embryo sacs. The floral organs grown in vitro were, however, smaller in size than those produced in vivo. In the control medium, i.e. without BAP, the floral buds produced petal and stamen primordia only and they too showed limited growth. The data presented shows the importance of cytokinins in the initiation and development of organs in the excised floral buds.

Morphogenesis ofMalus domesticacv. Starking flower buds

Differentiation of reproductive buds of the Starking apple (Malus domestica) was studied by scanning electron microscopy. Differentiation of reproductive structures was initiated during the first week of January when the shoot apex flattened. In terminal flower primordia, sepal primordia were evident in the second week of January, petal and stamen primordia from the end of January to mid-February and carpel primordia in mid-February. Floral organs developed slowly from March to August and pollen sacs were only formed in the anthers at the end of this period. Development accelerated during September and ovules formed three weeks before full bloom. The carpels rapidly increased in length and fused with the receptacle at their dorsal ends. The inner and outer integuments of the ovule developed and the filaments of anthers lengthened rapidly during the last three weeks before full bloom. S. Afr. J. Plant Soil 1985, 2: 187–190

Effect of the previous crop on cortical cell number ofMalus domesticacv. Starking Delicious apple flower primordia, flowers and fruit

The effect of the crop of the previous season on cell size of the cortical region of flower primordia, flowers and fruit size in Starking Delicious apples was investigated. Cell number was monitored from the onset of differentiation of the sepal primordia of terminal flowers until maturity. A heavy crop during the previous season resulted in a decrease in cell number of the cortical tissue at the base of the developing flowers and fruit, and in reduced fruit size. The reduction in cell number was already evident eight weeks after the onset of differentiation of the sepal primordia. Although a decrease in the cell numbers of fruit was accompanied by large cells, these larger cells did not compensate for the reduction in cell numbers as determined by fruit size. The effect of crop size on fruit size persisted during the following two seasons notwithstanding thinning practices aimed at normalizing cropping levels. Lower cell numbers were evident when fruit of similar sizes were compared. S. Afr. J. Plant Soil 1985, 2: 191–196

The embryonic origins of avian cephalic and cervical muscles and associated connective tissues.

The objective of these experiments was to determine the embryonic origins of craniofacial and cervical voluntary muscles and associated connective tissues in the chick. To accomplish this, suspected primordia, including somitomeres 3-7, somites 1-7, and cephalic neural crest primordia have been transplanted from quail into chick embryos. Quail cells can be detected by the presence of a species-specific nuclear marker. The results are summarized as follows: (table; see text) These results indicate that muscles associated with branchial arch skeletal structures are derived from paraxial mesoderm, as are all other voluntary muscles in the vertebrate embryo. Thus, theories of vertebrate ontogeny and phylogeny based in part on proposed unique features of branchiomeric muscles must be critically reappraised. In addition, many of these cephalic muscles are composites of two separate primordia: the myogenic stem cells of mesodermal origin and the supporting and connective tissues derived from the neural crest or lateral plate mesoderm. Defining these embryonic origins is a necessary prerequisite to understanding how the mesenchymal primordia of cephalic muscles and connective tissues interact to form patterned, species-unique musculoskeletal systems.

Inflorescence and Floral Development in Pelargonium X hortorum

Abstract Floral initiation and development in the hybrid geranium, Pelargonium X hortorum Bailey, were examined using scanning electron microscopy. Inflorescence initiation was marked by a raising of the apex followed by the formation of convex flower primordia. In floral development, 5 sepal primordia were delimited, closely followed by 5 petal primordia. Imbricate sepals enclosed the floral apex during later developmental stages. Five antesepalous, then 5 antepetalous stamen primordia were initiated. Five gynoecial primordia arose, forming a pentagonal ridge, carpellary lobes, and eventually an elongate style with stigma. Three of the antepetalous stamen primordia developed into filaform starninodia.

Floral development in Caulophyllum thalictroides (Berberidaceae)

A study of floral development in Caulophyllum thalictroides led to a reevaluation of the structure of the flower. After the production of sepal primordia, common stamen–nectary primordia arise. Nectary primordia are produced abaxially as a result of bifurcations of the common stamen–nectary primordia. The nectaries therefore cannot be considered reduced petals as traditionally interpreted and are perhaps better regarded as staminal derivatives. Three whorls of sepals develop; the lowermost often being dimerous, while the upper two whorls are more typically trimerous. The interpretation of the lowermost whorl of sepals as bracts was questioned. The terminology with regards to the inflorescence was considered, and after examination of material from this taxon it was felt that the inflorescence is best described as a cymosely branched panicle.

Relationship of Number of Long Nights to Meristem Development and Flowering in Kalanchoe1

Abstract Cultivars of Kalanchoe blossfeldiana Poelln. varied in number of long nights required for complete flower initiation and development. ‘Montezuma’ and ‘Texas Sunset’ requried 14 long nights, while ‘Pixie’, ‘Nugget’, ‘Cactus Candy’, ‘Goddess’, ‘Tobasco’, ‘Osage Orange’, ‘Toltec’, ‘Adobe Rose’ and ‘Rotkappchen’ required 15 to 28 nights. Height of apical meristems increased in ‘Montezuma’ after 7 long nights, but changes were not evident in ‘Pixie’ until 9 long nights. Scanning electron microscopic analysis showed first evidence of sepal primordia in ‘Pixie’ after 28 long nights—6 nights later than ‘Montezuma’. Differences in the number of long nights required for flower induction were related to delayed floral initiation rather than organogenisis or maturation.

Inducing organ generation in vitro: sepal–petal structures from tobacco flower buds

Tobacco (Nicotiana tabacum L. cv. Wisconsin 38) floral buds with sepal primordia only will continue organ production in a normal manner when excised from the plant and placed on the surface of a simple defined medium lacking growth substances. Such a medium is said to be developmentally inert because it does not induce or direct developmental events in the explant but does permit completion of developmental instructions, if any, carried in the explant. If the medium is supplemented with 10.0 ppm kinetin the bud produces a large but variable number of structures having some characteristics of sepals and some characteristics of petals and then continues with the initiation of fairly normal stamens and then carpels. This paper describes these structures and discusses the effect of kinetin on the regulatory systems controlling floral organ generation.

Scanning Electron Microscope Examination of Flower Bud Differentiation in Sour Cherry1

Abstract Axillary buds on ‘Montmorency’ sour cherry (Prunus cerasus L.) shoots were examined by scanning electron microscopy. On June 10, 4 weeks after anthesis, a doming of the apex signified the initial change from the vegetative to the reproductive stage. Flower primordia differentiated acropetally in the axils of bracts between late June and mid-July. Bract and flower primordia formed until all available space on the apex was occupied. Flower primordia changed from ovate to round as development proceeded. Sepal primordia were evident on July 30, 11 weeks after anthesis, and petal primordia had formed by August 15. Concentric rings of stamen primordia then developed followed by carpel differentiation in early September.

Unicarpellate floral development in Potamogeton zosteriformis

Floral development in the species Potamogeton zosteriformis is compared with that of other species of Potamogeton previously investigated (P. densus and P. richardsonii). A spike inflorescence is found on which 6 to 20 flowers develop. These flowers develop their appendages acropetally; first, the four tepals are initiated followed by the four stamens opposite the tepals. As in the flower of P. densus, the two lateral stamens are each initiated as two separate primordia. Unlike any other Potamogeton species where four carpels generally arise, alternating with the tepal and stamen pairs, in P. zosteriformis a single carpel consistently develops on the central portion of the remaining floral meristem. Histological preparations did not reveal any vestigial procambial strands differentiating in the gynoecium. This unique floral development is examined from several points of view. Morphogenetic comparisons are made with other species of Potamogeton which develop tetramerous gynoecia. Morphologically the nature of the Potamogeton flower is reexamined and phylogenetically the possibility of P. zosteriformis as a link or transition between the bisexual and unisexual groups within the Najadales is considered.

The Regulation of Tobacco Floral Organ Initiation

Flower buds of tobacco (Nicotiana tabacum), excised before organ primordia are present or, except for the sepals, determined, will continue normal development and produce all floral organs in a usual sequence when placed on a simple, defined medium lacking growth substances By surgically manipulating organ primordia, it was possible to infer the source of influences regulating the initiation of each type of organ. The carpels, e.g., would emerge rarely if the primordial stamens were removed from a flower bud prior to carpel determination However, removal of either or both of the sepal or petal primordia had no such effect The initiation of the carpels depends on the regulatory influences of the primordial stamens and the bud apical region. Experiments similar to that outlined above indicated that (1) the initiation of the stamens depends on the regulatory influence of the sepal and petal primordia, (2) the initiation of the petals depends on the regulatory influence of the sepal primordia, and (3) the ini...

RELATIONSHIPS BETWEEN SHOOT GROWTH AND CHANGING PHYLLOTAXY OF RANUNCULUS

Growth of Ranunculus shoots through ontogeny is quantified by techniques utilizing scanning electron microscopy and studies on living plant material. The order of the contact parastichy phyllotaxy in the apical system is related to the relative plastochron rates of growth of the shoot. There is a change in the (2, 3) contact parastichy pattern of vegetative phyllotaxy to a transitional (3, 5) contact pattern which is maintained through sepal production. Formation of a 5(1, 1) whorl of petal primordia establishes a (5, 8) contact pattern with the sepal primordia. Subsequent initiation of stamen primordia, in spiral sequence, results in (5, 8, 13) triple contacts between petal and stamen primordia. The stamen primordia and carpel primordia arrangement is characterized by a (8, 13) contact parastichy pattern of phyllotaxy. Through ontogeny the volume of the shoot apex progressively increases but the shape of the apex, described by a second degree polynomial, remains constant. The plastochron and the relative plastochron rates of radial and vertical displacement of primordia progressively decrease during transition but there is no alteration of the chronological rate of apical expansion. The change in contact parastichy phyllotaxy through ontogeny is interpreted as a change in the relative positions of primordia insertion on the apex resulting from an increase in apical volume and an increased rate of primordia initiation.

Floral organogenesis inAntirrhinum majus (Scrophulariaceae)

The various appendages (sepals, petals, stamens and carpels) in the flower ofAntirrhinum are initiated in a centripetal sequence. The five sepal primordia are initiated in a rapid succession as discrete units. The calyx tube is formed due to the fusion of marginal meristems of adjacent sepal primordia. The corolla tube is also initiated by the fusion of marginal meristems at the back of stamen primordia. In the later stage of development, it extends in length by zonal growth. Of the five stamen primordia formed, the posterior one develops into a staminode. The septum, which bears placentae, grows from the summit of the floral apex as in typical axile placentation.

Floral Development and Blindness in Roses: An SEM Study1

Abstract Fresh, unfixed meristems of rose (Rosa hybrida L.) were viewed in the scanning electron microscope to determine the morphological differences and organogenesis of flowering and blind shoots. Gluteraldehyde fixed, ethanol dehydrated and critical point dried tissue was severely desiccated with individual cell walls becoming concave. Fresh tissue remained turgid for at least 10 min in the microscope. Visible signs of flower initiation were evidenced by the presence of sepal primordia followed by differentiation of petals, anthers and stigma. No evidence of flower initiation was observed in the blind shoot.

Floral organogenesis inCassia fistula L. (Caesalpiniaceae)

The five sepal primordia arise successively in clockwise sequence. Interprimordial growth initiates a short calyx tube. The petal primordia are formed almost simultaneously alternate to the sepal primordia. They are followed by the antesepalous stamen primordia which also appear simultaneously opposite the sepal primordia. The primordia of the antepetalous stamens are formed after the inception of the gynoecium. They are inserted inside the antesepalous stamen primordia. The floral apex grows up into a crescent-shaped gynoecial primordia. In floral developmentCassia differs from members of the Papilionaceae and Mimosaceae. The position of insertion of the leguminous carpel on the floral apex has been discussed and it was concluded that the carpel ofCassia is a terminal structure.