Base Of Petals Research Articles

Anatomy of Ethylene-induced Petal Abscission in Pelargonium × hortorum

When viewed under the light microscope, the abscission zone at the petal base of Pelargonium × hortorum consisted of small cells which, when stained with Toluidine Blue, possessed densely stained cells walls. After treatment with 1 μl l-1 ethylene at 22°C, the force required to separate the petals from the receptacle declined after a lag phase of only 30 min, with separation complete 60-90 min later depending upon the stage of development of the flower. Transmission electron micrographs of the petal abscission zones showed evidence of cell wall degradation, particularly in the middle lamella. These cells also contained extensive rough endoplasmic reticulum and numerous Golgi bodies ribosomes. When abscission was complete, cells at the fracture face showed evidence of breakdown of cellular compartmentalization, often with little sign of an intact tonoplast. Scanning electron micrographs of recently-abscissed surfaces showed that the epidermal cells surrounding the abscisson zone were turgid and rounded, whereas those of the mesophyll cells were partially collapsed. The micrographic evidence is consistent with the hypothesis that ethylene-induced separation is caused by rapid enzymatic of the cell walls.

Effect of gibberellic acid on ACC content, EFE activity and ethylene release by floral parts of the senescing carnation flower

The application of gibberellic acid via the stem of intact preclimacteric carnation flowers inhibited the climacteric surge of ethylene evolution by the flowers. Gibberellic acid also inhibited the rate of ethylene production by all individual floral parts during both the early preclimacteric (low basal level of ethylene production) and the later climacteric stages of flower development. The extent of inhibition did however, vary from one floral part to another. The most pronounced inhibition was recorded in the petal bases between the preclimacteric and senescing stages. This suggests that the petal base is an important regulatory site for ethylene production and therefore may be involved in controlling the onset and degree of petal inrolling. In all floral parts endogenous levels of ACC were reduced with GA3 treatment, being more pronounced in the petal bases. The potential of the flowers to convert applied ACC to ethylene was not deminished by gibberellic acid.

Starch-iodine staining patterns in petals of cut roses

The starch distribution pattern and decline in starch content of Sonia rose petals were examined by starch-iodine staining. Flowers were harvested and held in 150 mg/L of sodium dichloroisocyanurate (DICA) or 150 mg DICA/L + 2% (w/v) sucrose, or were left on the plant. Starch was degraded initially from the outer margins of petals, then from the interveinal area nearest the petal margins, and finally towards the petal bases. Starch was first lost from the outermost petal and then sequentially towards the innermost petals. The rate of starch degradation was slowest in flowers left on the plant, intermediate in flowers harvested and kept in DICA + sucrose, and most rapid in flowers harvested and held in DICA. Preharvest treatments applied in an attempt to vary starch deposition (i.e. shading, leaf removal, and leaf removal with girdling) did not alter the normal starch-iodine staining pattern, reduce starch concentrations, or reduce vase life. However, flower pigmentation was less intense, abnormal flower development occurred, and dry weight and starch contents were reduced, suggesting that carbohydrate supply to the developing bud was affected. Thus, starch-iodine staining of cleared petals of mature Sonia roses was not useful for identifying flowers that developed under conditions of restricted carbon supply. In petals of flowers that had been harvested and held in cool storage (0-3�C) for 7 days, starch was degraded evenly from all parts across the petal. This diffuse pattern of starch degradation was sufficiently distinctive that it may prove a useful test for determining whether flowers have been cool-stored.

Floral morphology of southern African Orchideae. II. Habenariinae

The floral morphology of the southern African genera of Orchideae‐Habenariinae (Bonatea, Cynorkis, Habenaria, Platycoryne, Stenoglottis, Centrostigma and Roe‐perocharis) is surveyed paying special attention to the gynostemium. Ontogenetic data are provided for the species from which adequate material was available. It is shown that the floral architecture is essentially an elaboration and complication of that found in the better known Orchidinae. The structural similarities are particularly evident in the early ontogeny. Although the tribe Orchideae is commonly said to have gynostemia with erect anthers, a few Habenariinae are reported here to have reflexed anthers. In most cases both ‘auricles’ (filament excrescences) and ‘basal bulges’ (staminodes) are united to form the lateral gynostemium appendages. The primordia of both structures are clearly recognizable in the early ontogeny in all species studied. In Habenaria dregeana the basal bulges are only basally fused to the auricles, but in their main portion become adnate to the lip and petal bases: the auricles then solely form the lateral gynostemium appendages. It is suspected that this occurs also in other species not studied here. Systematic and phylogenetic aspects of the southern African representatives of the Habenariinae are discussed: the generic separation of Bonatea, Platycoryne and Centrostigma from Habenaria does not appear justified. Cynorkis, Roeperocharis and Stenoglottis are morphologically dissimilar to Habenaria. Based on the findings in the southern African taxa the status of the Habenariinae, Orchidinae, Orchideae and Diseae is discussed: there is no clear distinction between Habenariinae and Orchidinae; while the Diseae seem to represent a monophyletic group, the Orchideae are possibly polyphyletic.

Changes in flower bud development ofZinnia elegansJacq. as influenced by the growth retardant S-07

SummaryZinnia elegans treated with S-07((E)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol) produced single or half-double flowers, a result of fewer ray florets; this phenomenon was counteracted by GA3 treatment. The developmental changes in flowering induced by S-07 were further observed by scanning electron microscopy (SEM). Treatment of plants with S-07 delayed both the transition from the vegetative to the reproductive stage as well as the reproductive development of the shoot apex by about four days. In the floret formation stage, the petals of the control flowers elongated continuously and remained rounded whereas those of S-07 treated plants became flattened, split into five or six lobes and gradually covered the stamen primordia. The stamen primordia within the base of petals were larger and more well developed following S-07 treatment, compared with the control ones. Further, tubular florets were not formed after S-07 treatment at a late reproductive stage. It is therefore ...

Floral ontogeny inMazus pumilus (Scrophulariaceae)

InMazus pumilus, all the floral appendages are initiated in acropetal sequence in the second cell layer (except stamens) of the floral primordium by periclinal divisions. The actinomorphic calyx tube is formed due to zonal growth. The zygomorphy in corolla is evident from the inception of petal primordia which arise sequentially as independent units in order of one anterior, a pair of anterio-lateral followed by a pair of posterio-lateral. Later these primordia exhibit differential growth because of which zygomorphy becomes more pronounced. The upper corolla tube is formed by interprimordial growth and lower corolla tube by zonal growth. Stamens are initiated in the third layer of the floral apex. Unlike sepals and petals, in the development of stamens (4) underlying cells of corpus also contribute. Posterior stamen is absent. The stamens become epipetalous because of interprimordial and zonal growth in the common region below the bases of petals as well as stamens. The two carpel primordia arise as crescent shaped structures which become continuous due to interprimordial growth. The ovary is formed by a ring of zonal meristem. The style develops later between stigma and ovary because of intercalary growth. The residual apex grows vertically along with the ovary and forms the septum of the ovary. All the floral appendages exhibit similar pattern of histogenesis and early growth suggesting thereby the appendicular nature of these appendages.

Changes in Carbohydrates and Osmotic Potential during Rhythmic Expansion of Rose Petals

Abstract Rhythmic pulses of irreversible petal expansion in rose (Rosa hybrida L. ‘Sonia’) petals cause diurnal changes in the rate of flower opening. Time-lapse cinematography revealed a transient increase in the rate of rose flower opening that commenced shortly before the onset of a light period and lasted for a few hours. Petal expansion, which occurred sequentially from the outer to the innermost whorl, involved rhythmic increases in fresh and dry weights. The amount of expansion was greatest in the distal portion of each petal and least near the petal base. Periods of rapid expansion were accompanied by decreases in starch and increases in soluble sugars in the petals, but the total carbohydrate content of the petals remained constant during a light–dark cycle. During expansion, the osmotic potential of the outer petal increased from −790 to −690 kPa. Starch hydrolysis during petal growth appears to be important for maintenance of cell size, but it is not the factor controlling cell expansion.

Genetic studies of the pattern of floral pigmentation in Clarkia gracilis

The flowers of Clarkia gracilis subsp. sonomensis have large petals each with a large, central, red-purple spot while the flowers of subsp. gracilis are small and unspotted. Other pigmentation (anthocyanin) patterns also vary within and between these subspecies. We carried out a genetic analysis of differences in floral patterns and petal size. A novel basal petal spot appeared in the F2. The analysis indicated that the novel petal spot was specified by an allele in subsp. gracilis at a locus governing spot position. This allele is not normally expressed in subsp. gracilis because of the action of a modifier gene at a second locus. The study also indicated single factor inheritance for presence versus absence of pigmentation on the hypanthium, stamens, and the lower portion of the petals. Multifactorial inheritance was observed for differences in petal length and width. Most of the possible recombinant floral patterns were recovered in the F2 and F3. This system can be used to study developmental regulation of floral traits as well as ecological relationships between floral pattern and pollination system. The recovery of a normally unexpressed allele for basal petal spot points to the difficulty of extrapolating from phenotypic analysis to an understanding of morphological evolution.

Corolla tube formation in the Tubiflorae and Gentianales

Corolla tube formation was investigated anatomically for 22 species of the Polemoniaceae, Convolvulcaeae, Boraginaceae, Verbenaceae, Buddlejaceae. Scrophulariaceae, Gentianaceae, Menyanthaceae and Asclepiadaceae.The corolla tbe formation is basically similar among species, except for the cases ofNymphoides, Dichondra andCuscuta. The petal bases extend laterally to the interprimordial regions, the upward growth occurring at those regions just beside the petal bases, and connect mutually at the back of stamen primordia. The upward growth at the connected regions co-opeates with the growth of the expanding petal margins, resulting in the formation of the upper portion of the corolla tube. How-ever, developmental patterns are not always similar. InSwertia, Nymphoides andMenyanthes, the upward growth at the connected regions is meager. InDichondra andCuscuta, the mutual connection of petal bases is not seen.The lower portion of the corolla tube is formed by the elongation of the common base of petal and stamen primordia, resulting in the formation of the epipetalous condition of stamens, except for the case ofNymphoides. InNymphoides, the lower portion of the corolla tube results from the cup-like structure formed on the floral meristem before the initiation of petal primordia.

Some observations on the very rapid abscission of the petals ofGeranium robertianum L.

The petals of young flowers ofGeranium robertianum L. start to be shed 2.25 hours after exposure to 20 ppm ethylene whilst controls kept in air take approximately 8 hours longer. The detachment of the petal takes place at its junction with the receptacle. The cells in the region show evidence of cell wall degradation and fracture takes place by loss of cell cohesion along the line of the middle lamella. The petal base is surrounded by a canal of receptacle tissues which alter shape either during or immediately after fracture. It is proposed that these structural changes may produce stresses which facilitate fracture.

Corolla tube formation in six species of apocynaceae

Corolla tube formation inTrachelospermum asiaticum, Nerium indicum var.leucanthum, Anodendrom affine, Vinca major, Catharanthus roseus andAmsonia elliptica was investigated anatomically.The corolla tube formation among these species is basically similar. The bases of petal primordia extend laterally to the interprimordial regions, the upward growth occurrig at those regions just beside the petal bases. The extending petal bases connect with each other at the bases of the abaxial side of stamen primordia in the early stage of the corolla development. The upward growth at the coonnected regions results in the formation of a short corolla tube but is weakened rapidly. At the stage of the mutual connection of petal bases, a common base of petal and stamen primordia is initiated. This common base develops into the lower portion of the corolla tube, i.e. the portion below the stamen insertion.In a relatively late stage, adjacent margins, of the corolla lobes fuse postgenitally at their lower portions, resulting in the formation of almost all of the upper portion of the corolla tube.The corona inNerium andVinca is initiated by the active adaxial growth of the upper portion of the corolla tube.

Sites of ethylene production in the pollinated and unpollinated senescing carnation (Dianthus caryophyllus) inflorescence

Production of endogenous ethylene from the styles, ovary and petals of pollinated and unpollinated flowers of Dianthus caryophyllus L. was measured. The rate of ethylene production of cut, unpollinated flowers aged in water at 18°C was low until the onset of petal wilting, when a rapid surge of ethylene occurred in all tissues. The flower ethylene production was evolved mostly from the styles and petals. The bases of petals from unpollinated, senescing flowers evolved ethylene faster and sometimes earlier than the upper parts. Treatment of cut flowers with propylene, an ethylene analogue, accelerated wilting of flower petals and promoted endogenous ethylene production in all flower tissues. Pollination of intact flowers also promoted endogenous ethylene production and caused accelerated petal wilting within 2-3 days from pollination. Although the data are consistent with the hypothesis that ethylene forms a link between pollination of the style and petal wilting, in the unpollinated flower the style and petals can evolve a surge of ethylene independently of each other, about the time when the petals irreversibly wilt. The results are discussed in relation to the role of ethylene in flower senescence.

Papaver bracteatum Lindl., a Highly Rich Source of Thebaine

IN the Alborz mountains in the north of Iran, on the slopes facing the Caspian Sea, at altitudes ranging from 5,500 to 7,500 ft. from the sea level we have found vast areas covered with Papaver bracteatum Lindl. This wild annual poppy grows in abundance to a height of 2.5–3.5 ft. in sunny places, and blooms in June. Its flowers are 5–7 in. across and are scarlet in colour, black blotched at the base of petals and surrounded by conspicuous bracts (Fig. 1).

THE ORIGIN OF DIOECISM FROM HETEROSTYLY IN NYMPHOIDES (MENYANTHACEAE).

Heterostyly refers to a relatively rare combination of morphological, physiological, and genetic mechanisms which promotes outbreeding in certain angiosperms. Under conditions where the selective forces favoring this degree of outbreeding are reduced or removed, one or all of the components of this character complex may break down with the result that inbreeding partially or almost wholly replaces outbreeding. There are numerous examples of such a breakdown of heterostyly in the direction of increased selfpollination in taxa belonging to various plant families. Because the complex combination of floral mechanisms and incompatibility characteristic of heterostylous plants is apparently generally effective in promoting outbreeding, the breakdown of heterostyly in the opposite direction, namely in the direction of increased outbreeding, is uncommon. Nevertheless, there is evidence that in at least two angiosperm families (Rubiaceae and Menyanthaceae) heterostyly has been replaced by an even more effective outbreeding mechanism in the form of dioecism. The purpose of this paper is to discuss the breeding systems of various distylous and dioecious members of the menyanthaceous genus Nymphoides and to present an account of the probable origin of dioecism in this genus. Nymphoides has an almost cosmopolitan distribution, occurring primarily in tropical and subtropical areas but also in certain temperate regions of both the Northern and Southern hemispheres. The plants are aquatic or subaquatic, and are typically limited to the still water of ponds, lakes, and slow-moving streams. In all Nymphoides species examined, maturation of floral buds is underwater. In the morning of anthesis the buds are raised above the water level and flowering occurs. After a few hours the corolla withers, the pedicel deflects, and subsequent fruit development is underwater. DIOECIOUS SPECIES Dimorphic heterostyly is widespread in the genera of Menyanthaceae, but dioecism seems to have been previously unrecorded for this family (Gilg, 1895). The two species of Nymphoides indigenous to the United States are dioecious. These are N. cordata, an inhabitant of ponds and slow streams ranging from eastern Canada to Florida and Louisiana, and N. aquatica, a species of similar habitats ranging from New Jersey to Florida and Texas. The two species are closely related but are distinguishable on foliar, root, and floral characters. The floral morphology of these dioecious species is very similar. The ovary of pistillate flowers is capped by a short style and a large fleshy stigma. The vestigial stamens of such flowers are relatively large and conspicuous, consisting of white anthers and short filaments. Alternating with these non-polliniferous stamens are staminode-like clusters of yellow trichomes (Fig. 1). The yellow corolla bases and additional tufts of yellow trichomes at the basal petal margins provide additional color contrast to the white corollas. Staminate flowers have well-developed stamens that produce copious pollen. The pistil of such flowers essentially lacks a style or stigma, but the ovary is large and is filled with ovules of approximately the size and number of those produced by pistillate flowers (Fig. 1). Nevertheless, despite repeated polli-

Analysis of Petal Venation in Ranunculus. II. Number and Position of Dichotomies in R. repens var. pleniflorus

The venation pattern of the petals of Ranunculus repens var. pleniflorus was analyzed in terms of dichotomy number and position for six size-classes. Significant correlations were established between petal size (length, width, and area) and number of dichotomies. The latter is an approximate indication of the degree of venation complexity. The basic framework of petal venation is composed of a single trace which divides twice within a short interval at the petal base to produce three major veins. The midvein dichotomizes relatively little, compared to the two lateral veins. Within the laterals, dichotomies up to the sixth order are common, and seventh-order and eighth-order dichotomies occur rarely. At specific positions, dichotomies are statistically frequent; these are utilized to construct diagrammatic representations of "average" vein systems, which can be compared objectively between size-classes or with other taxa. In petals of all sizes there is a striking tendency toward amplification of the innermost shank of a dichotomy.

FLORAL PIGMENTS IN PAPAVER AND THEIR SIGNIFICANCE IN THE SYSTEMATICS OF THE GENUS

SummaryChromatographic analysis of the floral pigments of species of the genus Papaver revealed the presence of cyanidin and pelargonidin derivatives and in addition yellow compounds which were not anthocyanins. The distribution of these pigments among the poppy species supports Fedde's division of the genus into sections, and suggests an affinity between the sections Pilosa and Scapiflora. The pigments of three interspecific hybrids showed the biochemical versatility of the less versatile parent.The anthocyanins of petals and stamens frequently differed and the bases of petals normally contained petal and stamen pigments in mixture. High concentrations of cyanidin pigments were not found in the same floral parts as either yellow pigments or high concentrations of pelargonidin derivatives.