Floral Scale Research Articles

MELANOSIS AS A FACTOR REDUCING GRAIN QUALITY IN PROSO MILLET (PANICUM MILIACEUM L.) (A REVIEW)

Possible causes of melanosis in millet have been studied for a long time, and numerous efforts have been made to breed resistant cultivars, but still there are no sources of high resistance to this disease. The purpose of this article is to provide an overview of the most important results of research into the nature of melanosis in millet, a disease without outward manifestation on plants or seeds, and search for ways to reduce its harmfulness. Although the disease’s infectious nature has been confirmed by all researchers, no one has succeeded in identifying the causative agent of melanosis. It is assumed that melanosis may be provoked by both bacteria and fungi as well as through their complex effect on a plant. Weather conditions conducive to a spread of infection have not been identified either. According to some reports, dry and warm weather increases the risk of infection and spreading of the disease; according to others, more humid and warm conditions are to blame. A possible effect of millet grain shape on the level of disease manifestation has not been clearly explained, but there is evidence that the degree of floral scale closeness and thickness as well as the grain size do enhance mechanical protection of seed from infection. When floral scales are tightly closed, coarsehulled fine grains are as much protected from exposures as possible, which may add to the plant’s defense against the infection. Selecting plants with better developed grain-enclosing scales would help to breed proso millet cultivars resistant to melanosis. The infection can be transmitted by insects, wind or rain from any crop fields infested with the microflora that causes the disease. Its causative agents are specific to a definite area of millet cultivation, which is determined by the temperature regime and indirectly confirmed by conflicting data concerning the effect of air temperature and precipitation on the development of melanosis. The duration of the growing season, in its turn, can also have an impact on the development of damage under the husk of millet grain. Early-ripening millet forms are more resistant to the disease.

Total Control – Pollen Presentation and Floral Longevity in Loasaceae (Blazing Star Family) Are Modulated by Light, Temperature and Pollinator Visitation Rates

Stamen movements can be understood as a mechanism influencing pollen presentation and increasing outbreeding success of hermaphroditic flowers via optimized male function. In this study we experimentally analyzed the factors regulating autonomous and thigmonastic (triggered by flower visitors) stamen movements in eight species of Loasaceae. Both types of stamen movements are positively influenced by light and temperature and come to a virtual standstill in the dark and at low temperatures (12°C). Pollen presentation is thus discontinued during periods where pollinators are not active. Overall stamen presentation increases with increasing flower age. Contrary to expectation, no geometrical correlation between the floral scale stimulated and the stamen fascicle reacting exists, indicating that the stimulus is transmitted over the receptacle and stamen maturation dictates which and how many stamens react. Thigmonastic stamen presentation is dramatically accelerated compared to autonomous movement (3–37 times), indicating that the rate of stamen maturation can be adjusted to different visitation schedules. Flowers can react relatively uniformly down to stimulation intervals of 10–15 min., consistently presenting comparable numbers of stamens in the flower c. 5 min. after the stimulus and can thus keep the amount of pollen presented relatively constant even under very high visitation frequencies of 4–6 visits/h. Thigmonastic pollen presentation dramatically reduces the overall duration of the staminate phase (to 1/3rd in Nasa macrothyrsa). Similarly, the carpellate phase is dramatically reduced after pollination, down to 1 d from 4 d. Overall flower longevity is reduced by more than 2/3rds under high visitation rates (<3 d versus 10 d under visitor exclusion) and depleted and pollinated flowers are rapidly removed from the pool. Complex floral behaviour in Loasaceae thus permits a near-total control over pollen dispensation schedules and floral longevity of the individual flower by an extraordinary fine-tuning to both biotic and abiotic factors.

Taxonomic study of Korean Scirpus L. s.l. (Cyperaceae) 1. Morphology of Bolboschoenus (Asch.) Palla, Schoenoplectus (Rchb.) Palla, Schoenoplectiella Lye, Scirpus L., and Trichophorum Pers.

Scirpus L. s.l. of Cyperaceae has been regarded as a monophyletic group, but the taxa of Scirpus s.l. were rearranged into the five independent genera in recent molecular phylogenetic research: Bolboschoenus (Asch.) Palla, Schoenoplectus (Rchb.) Palla, Schoenoplectiella Lye, Scirpus L., and Trichophorum Pers. In this study, we examined the morphological characteristics and presented the delineation of the five genera of Scirpus s.l., including 21 taxa from South Korea. As a result of our investigation and analysis of domestic collections and those from abroad, the each taxon could be identified using key characteristics of the rhizome features; a cross-section of culm; the degree of development and the width of leaves; the shapes of the membranous region of leaf sheath; and the shapes and size of inflorescence, bract, floral scale, and achene. These major characteristics are illustrated and artificial keys are suggested in this study. In addition, we suggest a new combination for an unrecorded taxon of Schoenoplectiella that was discovered in Gangwon-do, Goseong-gun and give it the Korean name, as 'a-do-song-i-go-raeng-i'.

Eleocharis reznicekii (cyperaceae), a new species from the mexican high plateau

Se describe e ilustra Eleocharis reznicekii (Cyperaceae, subg. Eleocharis, serie Eleocharis), especie con características morfológicas intermedias entre las de Eleocharis densa y las de dos especies de la subserie Eleocharis (E. macrostachya y E. palustris). Se distingue por tener tallos conspicuamente comprimidos (3-5 veces más anchos que gruesos en fresco) y estilopodio sésil sobre una base anular fina. De E. densa se distingue además por tener espiguillas menos densas, estilos en su mayoría bífidos y aquenio casi liso a 30x, más redondeado hacia el ápice. De E. macrostachya y E. palustris lo hace por su hábito más robusto, espiguillas oblongas a linear-oblongas, gluma proximal envolviendo únicamente 1/3 a poco más de 1/2 de la base de la espiga, y por tener la gluma proximal y 1 a 2(3) glumas subproximales sin flor. Hasta ahora, E. reznicekii se conoce solamente del estado de Durango, en el Altiplano Mexicano y piedemonte de la Sierra Madre Occidental.

The Floral Scales in Hellmuthia (Cyperaceae, Cyperoideae) and Paramapania (Cyperaceae, Mapanioideae): An Ontogenetic Study

In 1976 the monotypic genus Hellmuthia was placed in the Hypolytreae s.l., but was subsequently ascribed to the Mapanioideae, tribe Chrysitricheae, mainly because of the presence in Hellmuthia of two lateral, mapanioid-like floral scales with ciliated keels, the anatomy of the nutlet, the embryo and the inflorescence. Recently, based on cladistic analyses and supported by pollen ontogenetic evidence, Hellmuthia was transferred to a Cyperaceae, tribe Cypereae, clade mainly consisting of Ficinia and Isolepis. In this study, the floral ontogeny in Hellmuthia was investigated and compared with the floral ontogeny in Paramapania, with special attention for the floral scales. Freshly collected inflorescences of Hellmuthia membranacea and Paramapania parvibractea were investigated using scanning electron and light microscopy. In the conical 'spikelet' in Hellmuthia, proximal bracts occur, each axillating an axis with empty glume-like structures, or a reduced spikelet. Hence, it is a reduced partial inflorescence. In Hellmuthia, the stamen primordia originate before the primordia of the perianth-gynoecium appear. Moreover, a third adaxially positioned 'floral scale' was observed for the first time. The position and relative time of appearance of the floral scales in Hellmuthia are typical for perianth parts in Cyperoideae. The basal position of Hellmuthia within a clade of species with usually perianthless flowers, allows the presence of rudiments of a perianth in Hellmuthia to be interpreted as a primitive state. Development of the lateral 'scales' in Paramapania follows a different pattern. Therefore, it was decided that the lateral 'scales' in Paramapania are different from the lateral perianth parts in Hellmuthia. The pollen grains in Hellmuthia are cyperoid, with one polar and five lateral apertures, of which the membrane is covered with sexinous bodies. The pollen surface is granulate and perforate with microspines. The floral ontogeny in Hellmuthia occurs according to the general cyperoid pattern. The lateral scales in Hellmuthia are perianth parts, and they are not homologous to the lateral 'scales' in Paramapania.

Eleocharis aestuum (Cyperaceae), a New Tidal River Shore Spikesedge of the Eastern United States

Eleocharis diandra is an annual spikesedge of northeastern U.S. river and lake shores. This species has a complicated taxonomic history and has been included in the synonymy of other members of the Eleocharis ovata complex by various researchers. Its differing applications are due, in part, to the existence of a previously un- described taxon. The new species Eleocharis aes- tuum is described from the eastern United States and is restricted to freshwater tidal river commu- nities. This species is similar to E. diandra in its marked absence or reduction of perianth bristles, but it differs in floral scale and tubercle morphol- ogy. Despite limited regional variation in morphol- ogy, E. aestuum is morphologically separable from

Developmental Implications of Photoperiod Sensitivity in Soybean (Glycine max [L.] Merr.)

Although the effects of photoperiod and temperature on flowering time are well established, their underlying physiology and implications for other aspects of growth and development require further investigation. The pattern of development in soybean (Glycine max L. Merr.) cultivars Biloxi (photoperiod sensitive) and Fiskeby V (photoperiod insensitive) are compared in an environment where photoperiod sensitivity was not expressed (11-h photoperiod) and in an environment where photoperiod sensitivity was maximally expressed (15.5-h photoperiod). A floral staging scale was developed to study the pattern of floral initiation and to compare rates of floral development. There were inherent differences between cultivars in earliness of flowering, vegetative development, and, therefore, in yield potential. When photoperiod sensitivity was not expressed, cv Biloxi had a short vegetative phase and floral primordia were apparent 14 d after sowing. Expression of photoperiod sensitivity, beginning 8-9 d after sowing, resulted in a much extended vegetative phase with increased rates of leaf initiation. Cultivar Fiskeby V had a minimal vegetative phase; floral primordia were apparent 9 d after sowing and initiation of primary nodes was complete 3 d later. There were inherent differences between cultivars in the duration of the transitional period between the initiation of the first lateral floral primordium and the initiation of the terminal inflorescence, a period that is important in determining yield potential. The pattern of floral initiation observed was primarily acropetal and reflected the competence of meristems to respond to the floral promoter. Meristems developing in the prophyll axes had consistently lower rates of leaf initiation and remained vegetative longer than other lateral meristems, indicating that there are subtle differences in the distribution of floral signals or that these meristems have different threshold requirements.

Possibility of Natural Hybridization between Cyperus iria L. and Cyperus microiria Steud.

No experimental evidence of hybridization between Cyperus iria L. and C. microiria Steud. has heretofore been documented, though occurrence of natural interspecific hybrids in the genus Cyperus has been reported by Koyama (1953, 1961). The authors have obtained new types of plants from an experimental field after a mixed planting of these two species. The new plants showed an intermediate form between the two in shape of floral scale and floret density. They were longer in spikelet length and had a greater number of florets, though seed fertilities were evidently lower than those of the parent species. The seeds of new plants were dormant in each of the reciprocal crossings between C. iria and C. microiria, and the dormancy could be broken by a stratification at 15°C for one month. This character was considered to have been inherited from the dormant parent C. microiria. Progenies of the new type plants also showed a clear segregation in the characters of spikelet and floret morphology. It can thus be confirmed that these plants obtained from mixed planting in the experimental field are to hybrids between C. iria and C. microiria.

A study of Scirpus acutus and Scirpus validus in the Saskatchewan River delta

A study of Scirpus populations (section Pterolepis) in the Saskatchewan River Delta was conducted to examine morphological and ecological characters of the Scirpus acutus Muhl. and S. validus Vahl complex to determine whether or not they should be differentiated as species.Population collections from stands of Scirpus and stands of suspected clonal hybrids were taken in 1966 and 1968 from various locations within the delta of the Saskatchewan River. Environmental data such as water depths were recorded at time of collection.Two morphologically and ecologically distinct groups emerged; their hybrids were sterile or nearly so. The features of panicle ray length and floral scale length: achene length ratio were found to be diagnostic morphological criteria for separating the Scirpus examined into two sets of distinct populations. These two sets of populations differed ecologically in terms of water depth tolerances: the S. acutus type tolerates between 60 and 150 cm, whereas the S. validus type occurs only at depths less than 65 cm.It was concluded that in the geographic area in which they were studied, these two separate populations would best be regarded as separate species.