Petal Type Research Articles

Elaborate Petals in Australian Spermacoce (Rubiaceae) Species: Morphology, Ontogeny and Function

Australian Spermacoce species display various types of elaborate petals. Their precise morphology, ontogenetic origin, and function are hitherto unknown. The aim of the present paper is to unravel the development and nature of the diverse types of elaborate petals in Spermacoce through a floral ontogenetic study. The floral ontogeny of six species characterized by different types of corolla appendages was studied by scanning electron microscopy and light microscopy. In order to elucidate the possible functions of the elaborate petals, field observations were conducted as well. Scanning electronmicrographs show that full-grown petals of Spermacoce lignosa, S. phaeosperma and S. redacta bear appendages on their ventral side. Despite their different appearance at anthesis, the appendages develop very similarly in all three species. They are initiated at the same developmental stage and are first visible as two arcs of primordia converging from the upper margins of the petal towards its midvein and downwards. In S. brevidens, S. caudata and S. erectiloba, the full-grown petals have two long, concave protuberances, which develop from the tissue at both sides of the petal's mid-vein. In these three species, initiation of appendages on the ventral side of the petals is also observed, but they are hardly visible on the mature petals. The two types of elaborate petals tightly enclose the anthers, both in bud and during most of the flowering period. Among Australian Spermacoce species, two types of elaborate petals can be distinguished. The former hypothesis that the two types of elaborate petals are essentially homologous is here rejected. Field investigations point out that the elaborate petals might play a role in the pollination biology of the species.

Reassessment of the presence of viroid species of the genus Pospiviroid in infected floral parts, using reverse transcription – polymerase chain reaction and infectivity assays

Potato spindle tuber viroid (PSTVd) is a seed-transmissible viroid that can be present in floral parts of the host. However, a recent study (Y. Zhu, L. Green, Y.-M. Woo, R. Owens, and B. Ding. 2001. Virology, 279: 69–77), using Agrobacterium -mediated inoculation and in situ hybridization, has shown that PSTVd is present in sepals, but absent in petals, stamens, and ovary of infected tomato plants. In earlier studies, the presence of PSTVd in floral parts was determined by polyacrylamide gel electrophoresis and infectivity assays. In the present study, the presence of PSTVd and other species of the genus Pospiviroid in floral parts of tomato and other host species was studied using the highly sensitive reverse transcription – polymerase chain reaction. The reassessment showed that PSTVd was present in all floral parts of tomato, as evidenced by strong bands of polymerase chain reaction products. Moreover, floral-organ extracts containing the infectious viroid caused characteristic PSTVd symptoms in tomato seedlings. Additionally, PSTVd and Tomato chlorotic dwarf viroid (TCDVd), a viroid nontransmissible to seed, were also detected in the floral parts of Nicotiana glutinosa, in which both viroids caused characteristic colour-break symptom in petals upon infection. Species of the genus Pospiviroid were also isolated from floral parts of cultivars of infected ornamental plants of Verbena × hybrida, on one side, and Impatiens walleriana and Impatiens hawkeri, on the other side, possessing respectively two different types of petals.

Floral ontogeny, petal diversity and nectary uniformity in Bruniaceae

Bruniaceae are a small family subendemic to the Cape Floristic Region. Flowers are actinomorphic, choripetalous, pentamerous and tetracyclic. The petals show diverse adaxial swellings, which have been quoted as an example of diplophylly. Developmental studies confirm the true choripetaly of the flowers, thus pointing to an affinity to the Apiales within the euasterids II. They reject, however, the hypothesis of diplophylly as the petal swellings grow out rather late and are not vascularized. According to the position, size and shape of the swellings, six petal types are distinguished, which in part have phylogenetic information. Nectaries occur on the upper part of the ovary. Nectar is exuded through modified stomata serving as secretory channels. All genera have gynoecial nectaries of the mesenchymatous type. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society, 2006, 150, 459–477.

Evolution and Development in the Amorphoid Clade (Amorpheae: Papilionoideae: Leguminosae): Petal Loss and Dedifferentiation

We used comparative developmental morphology to study the evolution of nonpapilionaceous corollas in the amorphoid clade of the tribe Amorpheae (Papilionoideae). This clade consists of five genera in which there are no papilionaceous corollas (five petals differentiated into one banner, two wing, and two keel petals). We studied the ontogenies of three nonpapilionaceous forms: corollas consisting of one petal (exemplified by Amorpha canescens), no petals (Parryella filifolia), and five petals in two types (Errazurizia megacarpa). We compared these to the ontogeny of a papilionaceous corolla (exemplified by the closely related Psorothamnus scoparius). In A. canescens, all petals initiated, but four did not grow beyond the primordial stage. In P. filifolia, no distinct petal primordia were visible. The corolla of E. megacarpa, which has only two types of petals, exhibits nonpapilionaceous characteristics at an early ontogenetic stage. Aside from the earliest primordial mounds, the petals of Psorothamnus and...

Origin of floral asymmetry in Antirrhinum.

Dorsoventral asymmetry in flowers is thought to have evolved many times from a radially symmetrical ancestral condition. The first gene controlling floral asymmetry, cycloidea in Antirrhinum, has been isolated. The cycloidea gene is expressed at a very early stage in dorsal regions of floral meristems, where it affects growth rate and primordium initiation. Expression continues through to later stages in dorsal primordia to affect the asymmetry, size and cell types of petals and stamens.

<i>Hibiscus</i> 属植物に関する研究 (第9報)

1. The flower type of syriacus was classified into 3 groups and 9 types based on the investigation of 54 different clones.Group I. Single flowered type (25 clones)I-a Narrow petal type (7 clones)I-b Medium petal type (13 clones)I-c Broad petal type (5 clones)Group II. Semi-double flowered type (20 clones)II-a Gion-mamori type (4 clones)II-b Hanagasa type (7 clones)II-c Rose type (9 clones)Group III. Double flowered type (9 clones)III-a Irregular type (2 clones)III-b Chrysanthemum type (3 clones)III-c Pompon type (4 clones)2. The Group I (Single flowered type) could also be divided into three sub-groups according to the number of petals per flower, viz. i) number of petals 5 (basic number) (9 clones), ii) number of petals 5-6 (12 clones) and iii) number of petals 8-11 (4 clones). Even in flowers with petals twice as many as the basic number, petals were of the same size as basic one and were arranged in a single row, so that the flowers remained single in appearance. The size of flower was the most variable in this group, ranging continuously from 7.6 to 13.3cm in diameter (Table 1, Fig. 1, 2, 3 and 6).3. The Group II (Semi-double flowered type) consisted of flower type in which inner petals were much smaller than outer single-row petals. Those with a small number of inner petals were classified as Type II-a (Gion-mamori), while those with large number of inner petals as Type II-b (Hanagasa). In Type II-c (Rose), inner petals were somewhat larger in size than II-a and b and some of them were originated from the style. Type II-a was as fertile as the flowers of Group I, while II-b rarely produced seeds and II-c never produced seeds (Table 2, Fig. 4 and 5).4. In Group III (Double flowered type) inner and outer petals were of the same size. In Type III-a (Irregular), styles of about 1/3 of the flowers were transformed into petals. In Type III-b (Chrysanthemum), petals were rather smaller and were more or less regularly arranged, and styles of 1/2-2/3 of the flowers turned into petals. In Type III-c (PomPon), the small spherical flowers possessed the smallest but numerous petals, and the whole style was transformed into petals. Some examples of prolification were found in the last type; such flowers consists of more than 70 petals (Table 3, Fig. 7 and 8).