Floral Ontogeny Research Articles

Forecasting of banana harvest (‘Williams’) in the subtropics using seasonal variations in bunch development rate and bunch mass

Forecasting banana supplies is an important priority both for growers and for the local marketing organisation. Achieving this requirement is complicated by the floral ontogeny of banana which induces flowering and fruit production throughout the year. At the two experimental localities Burgershall and Levubu, in the Eastern Transvaal, totals of 2571 and 2057 ratoon ‘Williams’ banana bunches, respectively, from uniform plantations, were analysed over a 3-year period. Mean flower emergence to harvest interval and mean bunch mass were calculated for 24 flowering periods of 15 days each. Seasonal variations at both localities were substantial and were related to temperatures prevailing at flower initiation and during fruit development. At Burgershall, the shortest flowering to harvest interval was 110 days (early summer flowering) and the longest 204 days (autumn flowering). Bunch mass varied from 57.8 kg (July flowering) to 37.2 kg (October flowering), the latter bunches resulting from winter flower initiation. Levubu data differed substantially from Burgershall, although the seasonal trends were similar. A practical crop forecasting model is proposed which is based on new flower counts every 15 days, and the overall box/bunch potential of the grower. Using the experimental data base, the total boxes are forecast from seasonal yield adjustment factors, and harvest spread is forecast from the harvest distribution of experimental bunches for each flowering period. Each cultivar-locality combination must be forecast separately, and the model assumes year-to-year uniformity, farm-to-farm uniformity, optimum management, and an absence of major damage due to wind, hail or frost.

Flowering and Fruiting Patterns of Phaseolus vulgaris L.

Spatial and temporal aspects of reproductive development were examined in morphological units-a compound raceme and subtending axillary flowers and trifoliolate leaf-of Phaseolus vulgaris. Flowering occurs acropetally, and the probability of flowering varies with the position of a bud in a unit: axillary, basal buds have a higher percentage of flowering than more distal buds on a raceme. The percentage of bud and fruit abortion also varies in relation to position within a unit. The axillary, basal buds are the first to flower and have the lowest percentage of abortion. All distal buds abort. Nonflowering buds abort in the green-bud stage of floral ontogeny. Growth and cytological analyses indicate that the aborting fruits contain embryos in the proembryo and early and late globular stages of embryogeny. The percentage of abortion at each stage varies with the position of the fruit within a unit. Axillary and basal fruits contain embryos in the late globular stage. Distal fruits contain embryos in the proe...

FLORAL DEVELOPMENT IN MYRISTICA (MYRISTICACEAE)

Myristica fragrans and M. malabarica are dioecious. Both staminate and pistillate plants produce axillary flowering structures. Each pistillate flower is solitary, borne terminally on a short, second‐order shoot that bears a pair of ephemeral bracts. Each staminate inflorescence similarly produces a terminal flower and, usually, a third‐order, racemose axis in the axil of each pair of bracts. Each flower on these indeterminate axes is in the axil of a bract. On the abaxial side immediately below the perianth, each flower has a bracteole, which is produced by the floral apex. Three tepal primordia are initiated on the margins of the floral apex in an acyclic pattern. Subsequent intercalary growth produces a perianth tube. Alternate with the tepals, three anther primordia arise on the margins of a broadened floral apex in an acyclic or helical pattern. Usually two more anther primordia arise adjacent to each of the first three primordia, producing a total of nine primordia. At this stage the floral apex begins to lose its meristematic appearance, but the residuum persists. Intercalary growth below the floral apex produces a columnar receptacle. The anther primordia remain adnate to the receptacle and grow longitudinally as the receptacle elongates. Each primordium develops into an anther with two pairs of septate, elongate microsporangia. In pistillate flowers, a carpel primordium encircles the floral apex eventually producing an ascidiate carpel with a cleft on the oblique apex and upper adaxial wall. The floral ontogeny supports the morphological interpretation of myristicaceous flowers as trimerous with either four‐sporangiate anthers or monocarpellate pistils.

Floral Development in Myristica (Myristicaceae)

Myristica fragrans and M. malabarica are dioecious. Both staminate and pistillate plants produce axillary flowering structures. Each pistillate flower is solitary, borne terminally on a short, second-order shoot that bears a pair of ephemeral bracts. Each staminate inflorescence similarly produces a terminal flower and, usually, a third-order, racemose axis in the axil of each pair of bracts. Each flower on these indeterminate axes is in the axil of a bract. On the abaxial side immediately below the perianth, each flower has a bracteole, which is produced by the floral apex. Three tepal primordia are initiated on the margins of the floral apex in an acyclic pattern. Subsequent intercalary growth produces a perianth tube. Alternate with the tepals, three anther primordia arise on the margins of a broadened floral apex in an acyclic or helical pattern. Usually two more anther primordia arise adjacent to each of the first three primordia, producing a total of nine primordia. At this stage the floral apex begins to lose its meristematic appearance, but the residuum persists. Intercalary growth below the floral apex produces a columnar receptacle. The anther primordia remain adnate to the receptacle and grow longitudinally as the receptacle elongates. Each primordium develops into an anther with two pairs of septate, elongate microsporangia. In pistillate flowers, a carpel primordium encircles the floral apex eventually producing an ascidiate carpel with a cleft on the oblique apex and upper adaxial wall. The floral ontogeny supports the morphological interpretation of myristicaceous flowers as trimerous with either four-sporangiate anthers or monocarpellate pistils.

FLORAL DEVELOPMENT IN CAESALPINIA (LEGUMINOSAE)

Utilizing scanning electron microscopy, we studied the early floral ontogeny of three species of Caesalpinia (Leguminosae: Caesalpinioideae): C. cassioides, C. pulcherrima, and C. vesicaria. Interspecific differences among the three are minor at early and middle stages of floral development. Members of the calyx, corolla, first stamen whorl, and second stamen whorl appear in acropetal order, except that the carpel is present before appearance of the last three inner stamens. Sepals are formed in generally unidirectional succession, beginning with one on the abaxial side next to the subtending bracts, followed by the two lateral sepals and adaxial sepal, then lastly the other adaxial sepal. In one flower of C. vesicaria, sepals were helically initiated. In the calyx, the first‐initiated sepal maintains a size advantage over the other four sepals and eventually becomes cucullate, enveloping the remaining parts of the flower. The cucullate abaxial sepal is found in the majority of species of the genus Caesalpinia. Petals, outer stamens, and inner stamens are formed unidirectionally in each whorl from the abaxial to the adaxial sides of the flower. Abaxial stamens are present before the last petals are visible as mounds on the adaxial side, so that the floral apex is engaged in initiation of different categories of floral organs at the same time.

Floral Development in Caesalpinia (Leguminosae)

Utilizing scanning electron microscopy, we studied the early floral ontogeny of three species of Caesalpinia (Leguminosae: Caesalpinioideae): C. cassioides, C. pulcherrima, and C. vesicaria. Interspecific differences among the three are minor at early and middle stages of floral development. Members of the calyx, corolla, first stamen whorl, and second stamen whorl appear in acropetal order, except that the carpel is present before appearance of the last three inner stamens. Sepals are formed in generally unidirectional succession, beginning with one on the abaxial side next to the subtending bracts, followed by the two lateral sepals and adaxial sepal, then lastly the other adaxial sepal. In one flower of C. vesicaria, sepals were helically initiated. In the calyx, the first-initiated sepal maintains a size advantage over the other four sepals and eventually becomes cucullate, enveloping the remaining parts of the flower. The cucullate abaxial sepal is found in the majority of species of the genus Caesalpinia. Petals, outer stamens, and inner stamens are formed unidirectionally in each whorl from the abaxial to the adaxial sides of the flower. Abaxial stamens are present before the last petals are visible as mounds on the adaxial side, so that the floral apex is engaged in initiation of different categories of floral organs at the same time.

RATE OF INDUCED CELLULAR DEDIFFERENTIATION IN CATHARANTHUS ROSEUS

During floral ontogeny in Catharanlhus roseus, approximately 400 epidermal cells are induced to rapidly dedifferentiate during postgenital fusion, an unequivocal case of intercellular communication between somatic plant cells. Some fusing cells completely dedifferentiate within 4.3 hr of cell contact, and by 8.9 hr virtually all the cells undergo the dramatic change in cell shape and cytological features. To our knowledge, this is the fastest case of induced cell differentiation reported to date in any eukaryotic system.

A contribution to the floral anatomy of Leptospermum laevigatum

A description of the floral parts is given. The anther is characterized by a prominent oil gland at the tip of the connective. The structure of the seed coat of the fertile and sterile seed differs. Most of the integumental tissue is destroyed during development and only the epidermis of the inner and outer integuments develops into the seed coat. A brief description of the vascularization of the flower and its floral ontogeny is also given. ’n Beskrywing van die blomdele word gegee. Die helmknop word gekenmerk deur die prominente olieklier op die punt van die helmbindsel. Die saadhuid van die vrugbare en steriele saadknop verskil. Slegs die epidermis van die buitenste en binneste integumente bly in die saadhuid behoue. ’n Kort beskrywing van die bearing van die blom en sy ontogenie word ook gegee.

FLORAL ORGANOGENESIS IN NICOTIANA TABACUM: A COMPARISON OF TWO CYTOPLASMIC MALE‐STERILE CULTIVARS WITH A MALE‐FERTILE CULTIVAR

Flower buds of two cytoplasmically male‐sterile cultivars and one male‐fertile cultivar of Nicotiana tabacum (L.) were studied by light and scanning electron microscopy to compare their floral ontogenies. In [gla]tbc, a cultivar with N. tabacum nuclear genes and N. glauca cytoplasm, the five small stamen primordia cease growth soon after they are initiated. They remain unchanged at the flanks of the ovary throughout flower maturation, so the mature flower appears stamenless. In `[pbg]tbc,‘ a N. tabacum cultivar with cytoplasm that was thought to have been derived from N. plumbaginifolia, the divergence from normal stamen development occurs before carpel emergence at which point the primordia are already notably smaller and less cylindrical than primordia of the male‐fertile cultivar. After carpel emergence the primordia continue to develop, forming pink structures called petalodes, which are more similar to petals than stamens. Histological sections show that formation of procambial vascular traces is similar in the abortive stamen primordia of [gla]tbc, the petalode primordia of `[pbg]tbc‘ and stamen primordia of male‐fertile N. tabacum.The two cytoplasmic male‐sterile cultivars studied here and one reported elsewhere show a common developmental stage at which the normal ontogenic pattern is altered. We suggest that this stage is the first visible point in N. tabacum androgenesis which requires genetic input from the mitochondrial genome.

FLORAL ONTOGENY IN CYCLAMEN PERSICUM ‘F‐1 ROSEMUNDE ROSE’ (PRIMULACEAE)

Floral ontogeny was examined in Cyclamen persicum ‘F‐1 Rosemunde Rose’ using a combination of light and scanning electron microscopy. The leaf plastochron index (LPI), earlier calculated for leaf elongation, was used to determine the length of each stage of floral development. LPI will provide a useful tool for selecting flowers of a given stage from large plant populations or from plants where flowers are small or inaccessible during early ontogenetic stages. Most features of floral development are similar to those previously described for other primulaceous genera. The petal‐stamen relationship, however, is unusual; stamens arise through periclinal cell divisions in the adaxial surface layers of common petal‐stamen primordia. Anatomical evidence suggests that the placenta is formed both by appendicular initials which give rise to the ovules and ventral carpellary bundles, and receptacular cells which form some, if not all, of the central axis.

Floral Ontogeny of Illicium floridanum, with Emphasis on Stamen and Carpel Development

Floral Ontogeny of Illicium floridanum, with Emphasis on Stamen and Carpel Development

Electrophoretic Changes in Soluble Proteins during Vegetative and Floral Development of Male and Female Papaya Plants

Summary Electrophoretic patterns of soluble proteins were investigated at vegetative and reproductive growth stages of dioecious papaya. Different protein patterns were observed in the leaf extracts of negetative seedlings and male and female plants. Male and female flowers also possessed a specific pattern of proteins. As the floral ontogeny of sex type proceeded, new bands were observed, while others gradually disappeared. Implications of these data on sex differentiation are discussed.

Ontogenetic Study of Floral Organs of Peach (Prunus persica) Utilizing Cytochimeral Plants

Cell lineages were followed throughout floral ontogeny in cytochimeral peaches [Prunus persica (L.) Batsch] by observations of chromosome number and nuclear size. The contribution of the three apical cell layers to the organs of the flowers was determined. In addition to the epidermal tissue, L-I produced several layers of cells at the suture of the ovary wall, seven or eight cell layers of the nucellus at the micropylar end of the ovule, and almost all of the integuments. L-II gave rise to extensive internal tissue in the calyx and corolla tubes and to all internal tissue of the petal, anther, and ovule except for a small region at the base of the latter two organs. L-III contributed significantly only to the central region of the calyx and corolla tubes and the ovary wall. A single apical layer gave rise to several different tissues, and at times a single tissue was made up of cells from 1–3 different apical layers. Within the limits imposed by their genotype the final form of differentiated cells was determined by their position in the mature organ and not by the apical layer from which they were derived. The corolla tube was shown to be a single structure, congenitally fused, and the ovary to be ontogenetically fused at the suture.

ONTOGENETIC STUDY OF FLORAL ORGANS OF PEACH (PRUNUS PERSICA) UTILIZING CYTOCHIMERAL PLANTS

Cell lineages were followed throughout floral ontogeny in cytochimeral peaches [Prunus persica (L.) Batsch] by observations of chromosome number and nuclear size. The contribution of the three apical cell layers to the organs of the flowers was determined. In addition to the epidermal tissue, L‐I produced several layers of cells at the suture of the ovary wall, seven or eight cell layers of the nucellus at the micropylar end of the ovule, and almost all of the integuments. L‐II gave rise to extensive internal tissue in the calyx and corolla tubes and to all internal tissue of the petal, anther, and ovule except for a small region at the base of the latter two organs. L‐III contributed significantly only to the central region of the calyx and corolla tubes and the ovary wall. A single apical layer gave rise to several different tissues, and at times a single tissue was made up of cells from 1–3 different apical layers. Within the limits imposed by their genotype the final form of differentiated cells was determined by their position in the mature organ and not by the apical layer from which they were derived. The corolla tube was shown to be a single structure, congenitally fused, and the ovary to be ontogenetically fused at the suture.

Organ Regeneration in Sterile Culture After Median Bisection of the Flower Primordia of Nicotiana tabacum

Tobacco flower apices at different developmental stages were bisected and cultured in vitro. Floral organs regenerated next to the cut and the type of response was related to the initial stage of the bud Up to and including the primordial sepal stage, petal and stamen primordia usually regenerated at least in one half and pistil primoidia in both halves At the primordial petal stage, only pistil regeneration occurred. Finally, all regenerative capacity was lost at the primordial carpel stage. The data support the view that the developing flower passes through a series of physiological phases which govern the sequential appearance of the floral organs. Under the experimental conditions, the normal sequence of organ initiation is not easily reversed or disrupted and so it appears committed to progress in one direction The technique resolves relatively distinct sepal- and carpel-forming phases but only one phase seems to govern the initiation of both petals and stamens The bud center was usually much more responsive to surgery than the meristem flanks. On this basis, it is suggested that changes in this central region during floral ontogeny may regulate organogenic events on the periphery of the meristem

Ontogenetical and experimental studies of the floral apex of Portulaca grandiflora. 2. Bisection of the meristem in successive stages

Floral apices at the stages of sepals, petals, stamens, upright carpels, and elevated carpels were bisected by microscalpels, and the regeneration of the meristem halves, their grafting together, and the production of new appendages were studied. At the sepal stage the two halves regenerated into twin flowers, producing petals, stamens, and carpels above the cut surfaces which grafted together. Cusick's finding that, for a particular organ to be formed alongside a wound, the incision must be made before organs of this kind have appeared in their normal positions, was supported. At the stage of petals, however, the twin flowers produced petals as the first new appendages above the cut surfaces. At the stage of stamens, the first appendages produced above the cut surfaces were carpels, again supporting Cusick. Sometimes the new carpels so formed constituted separate adjacent whorls on the twin flowers. At both stages of carpels, the rest of the floral apex (receptacle) showed no regeneration except rapidly grafting together. The reunited receptacle was then used as in normal ontogeny, in formation of carpel margins on which ovules would later have been borne. Generally, cells beneath wound surfaces showed few divisions, compared with the vigorous responses of bisected shoot apices of other plants. Grafting, which did not occur in the terminal regions of bisected shoot apices, readily occurred at cut surfaces of halved floral apices, and this latter response became progressively more rapid in later stages of floral ontogeny. This grafting, along with progressive loss of potential for production of new lateral appendages, are interpreted as manifestations of aging in this determinate meristem, and support the hypothesis that differentiation is concomitant with loss in capacity for growth.

Studies on the Monimiaceae. I. Floral morphology and gametophyte development of Hedycarya arborea J.R. et.G. Forst. (subfamily Monimioideae)

Inflorescences, flowers, and floral vascularization of the New Zealand endemic species Hedycarya arborea are described. Varying carpel vasculature suggests derivation of the uniovulate condition in Hedycarya from ancestors having multiovulate carpels with ovules in two rows, Floral ontogeny is described and it is noted that the terminal stigmatic region of the carpel develops from a solid terminal meristem, in contrast to many woody Ranales in which the stigma consists of crests surrounding the carpel cleft. The stigmatic surface is a mass of globose projections, apparently serving as pollen traps. No comparable type of stigma has previously been reported in the woody Ranales. The microsporangium has a typically thickened endothecium and a tapetum of the secretory type with tapetal cells becoming binucleate during the first meiotic division of pollen mother cells. Pollen mother cell division is of the successive type with cytokinesis by centrifugally extending cell plates. The generative cell is cut off towards the distal face of the microspore. The pollen, in permanent tetrads, is shed in the two-celled condition. Ovules are bitegmic, crassinucellate, and anatropous with a Polygonum type of embryo sac development. Some comparisons are made with the Australian species Hedycarya angustifolia.

Studies on the Monimiaceae. III. Gametophyte development of Laurelia novae-zelandiae A. Cunn. (subfamily Atherospermoideae)

Floral ontogeny and gametophyte development of the New Zealand endemic species Laurelia novae-zelandiae is described. The microsporangium has three to five wall layers inside the epidermis, including a typically thickened endothecium and a tapetum of the secretory type in which the cells become binucleate during the first meiotic division of pollen mother cells. Cytokinesis of pollen mother cells is of an unusual type in which centrifugal cell plates do not develop until the end of meiosis 11. The generative cell of the pollen grain is cut off against what represents a radial wall of the grain with reference to the tetrad stage. Pollen is two- or three-celled when shed. Ovules are bitegmic, crassinucellate, and anatropous with a Polygonum type of embryo sac development.

Floral ontogeny and an interpretation of the inferior ovary in Agave parryi

A study of the histogenesis of the flower of Agave parryi was made using serial sections as well as three-dimensional views of dissected floral primordia. It is shown that floral ontogeny supports the appendicular interpretation of the inferior ovary of Agave parryi in that the flower parts do not arise from a smooth, ring-like meristem located at the tip of the pedicel but, rather, the flower parts arise as separate primordia. This study corroborates an investigation by Kaplan which shows that ontogeny can be used to support, rather than contradict, floral vasculature in interpreting the appendicular nature of the inferior ovary.

FLORAL MORPHOLOGY, ORGANOGENESIS AND INTERPRETATION OF THE INFERIOR OVARY IN DOWNINGIA BACIGALUPII

The inflorescence of Downingia bacigalupii (Campanulaceae; Lobelioideae) is an indeterminate spike. Axillary flowers have a long, linear, inferior ovary with parietal placentation, a pentamerous synsepalous calyx, zygomorphic sympetalous corolla, syngenesious stamens, and a bicarpellate, syncarpous gynoecium. On the basis of floral vascular anatomy the inferior ovary is interpreted as appendicular, representing adnation of outer floral whorls to the gynoecium. Floral ontogeny shows that sepals are initiated in an adaxial to abaxial sequence rather than the 2/5 phyllotaxis reported for other members of Lobelioideae. Growth of the common bases of sepal lobes forms a floral cup and initiation of the following floral whorls occurs along the inner margins of the cup. Continued basal growth of the cup‐shaped bud results in the formation of the elongated inferior ovary. Earlier evidence for the interpretation of a cup‐shaped receptacle during development of epigynous flowers is reexamined and it is concluded that the concave floral bud of D. bacigalupii can also be interpreted as common growth of connate floral whorls, supporting interpretations based on vascular anatomy. Comparison of floral development between Downingia bacigalupii and Pereskia aculeata (Cactaceae) reveals ontogenetic differences between flowers with appendicular and receptacular cups.