Primary Inflorescence Research Articles

Inflorescence development in an Ornithogalum dubium hybrid as influenced by bulb temperature treatments

SummaryOrnithogalum dubium hybrid 327 clone 2 (‘327-2’) bulbs were stored dry at 10°, 16°, 22°, 28°, and 35°C for six weeks after harvest. After storage, bulbs were evaluated by nuclear magnetic resonance imaging (MRI) to obtain the spin-lattice relaxation time (T1) profile across the transverse section of intact bulbs, by scanning electron microscopy (SEM) to observe inflorescence development, and by forcing in a 18.5°/18°C greenhouse to observe growth and flowering responses. Bulbs treated at 10°C had the shortest T1 (0.33 ms) through the bulb which is largely composed of scales. Leaf emergence from bulbs treated at 10°C was delayed, and plants failed to flower. This indicated that bulbs were dormant and dormancy was not broken, thus delaying initiation of floral organs. Bulbs treated at 22°C and 28°C formed the primary inflorescence with several florets. At the base of the primary scape of bulbs treated at 22°C, a vegetative apex was observed by both MRI and SEM. In the centre of bulbs where both leaves and floral organs were present, T1 was longer than that of the scales. This suggests that dormancy in the scales was broken and the leaves and scape were ready to emerge. Flowering was fastest when bulbs were treated at 22°C. The number of florets was the highest (16.0 florets) and fewest (12.6 florets) when bulbs were treated at 22°C and 35°C, respectively. Ornithogalum dubium bulbs stored at 25° and 30°C for six weeks flowered from 14 and 17 bulbs, respectively, out of 22 and flowered earlier than when stored either at lower or high temperatures. The response obtained O. dubium ‘327-2’ hybrid was attributed to its pedigree involving O. dubium. Due to its non-destructive nature, MRI can be used to observe inflorescence development inside the bulbs during bulb storage and possibly to study the state of dormancy.

A developmental response to pathogen infection in Arabidopsis.

We present evidence that susceptible Arabidopsis plants accelerate their reproductive development and alter their shoot architecture in response to three different pathogen species. We infected 2-week-old Arabidopsis seedlings with two bacterial pathogens, Pseudomonas syringae and Xanthomonas campestris, and an oomycete, Peronospora parasitica. Infection with each of the three pathogens reduced time to flowering and the number of aerial branches on the primary inflorescence. In the absence of competition, P. syringae and P. parasitica infection also increased basal branch development. Flowering time and branch responses were affected by the amount of pathogen present. Large amounts of pathogen caused the most dramatic changes in the number of branches on the primary inflorescence, but small amounts of P. syringae caused the fastest flowering and the production of the most basal branches. RPS2 resistance prevented large changes in development when it prevented visible disease symptoms but not at high pathogen doses and when substantial visible hypersensitive response occurred. These experiments indicate that phylogenetically disparate pathogens cause similar changes in the development of susceptible Arabidopsis. We propose that these changes in flowering time and branch architecture constitute a general developmental response to pathogen infection that may affect tolerance of and/or resistance to disease.

EFFECT OF TEMPERATURE ON INFLORESCENCE QUALITY AND SHELF LIFE OF LACHENALIA CV. RONINA

Three temperature regimes, representing a cool, moderate and warm winter climate, were chosen to grow bulbs during the bulb preparation phase (year 1) and afterwards to determine the morphology and shelf life of these bulbs’ inflorescences during the pot plant phase (year 2). The best temperature regimes for the bulb preparation phase were the low and moderate temperature regimes, which represent the cool and moderate winter climate in South Africa. The moderate and low temperature regime treated bulbs produced more inflorescences than those of the high temperature regime. The lower the temperature regime treatment during the bulb preparation phase the higher were the peduncle length, rachis length, floret number as well as the peduncle cross section of the primary, secondary and tertiary inflorescences during the pot plant phase. The pot plant shelf life from bulbs of all three temperature treatments averaged 24 days, however, the low temperature regime treated bulbs beared inflorescences with the longest keeping ability.

A Revision of the Calamus aruensis (Arecaceae) Complex in New Guinea and the Pacific

The complex of citrate rattan species that includes Calamus aruensis presents significant taxonomic challenges throughout its range. A revision of the group from New Guinea and Australia through the west Pacific to its eastern limit in Fiji is presented here. The complex is recognised by its rather broad, cucullate leaflets, by the long, robust, strictly tubular bracts on the primary inflorescence axis and by the short, funnel-shaped bracts on the first order branches. Four species are recognised here, C. aruensis, C. vitiensis and two new species, C. pachypus and C. dasyacanthus. Calamus hollrungii and C. latisectus are placed in synonymy with C. aruensis, and C. stipitatus and C. vanuatuensis with C. vitiensis.

Inflorescence and Flower Development in Chinese Ixora

Experiments were conducted on 6-month-old chinese ixora (Ixora chinensis Lam.) from February 1999 to April 2000. Floral development was studied with scanning electron microscopy (SEM) to determine the flowering sequences. Morphological characters were used to clarify the stages of flowering processes. The time of organogenesis and flowering arrangement was established through field observations. Floral evocation occurred in early September, floral initiation occurred in the middle of September and floral differentiation began in late September. A distinctly convex apex with bracts around the shoulder indicated the beginning of reproductive development. Subsequently, primary inflorescence axes were observed and differentiated into secondary, tertiary, and quaternary inflorescence axes consecutively in about one and a half months. Once the terminal apex reached the inflorescence bud stage, it would flower without abortion, and this may be assessed as no return. The sepals, petals, stamens, and pistil were well developed thereafter and anthesis was achieved in January through March in the following year. The observation of floral differentiation sequences and investigation of floret arrangement made it certain that chinese ixora had cymose inflorescence (cyme), but not corymb. A quadratic equation was established to predict floret number from the differentiation level (a quantitative description of differentiation stage) of a developed inflorescence.

MINERAL CONTENT OF PRIMARY AND SECONDARY INFLORESCENCES OF ELEVEN BROCCOLI CULTIVARS GROWN IN EARLY AND LATE SEASONS

ABSTRACT During the last decade consumption of broccoli (Brassica oleracea L. var. italica) has been highly recommended, based on the presence of secondary plant metabolites with health protective effects. Apart from these compounds, broccoli might apport high levels of minerals, however, they are likely to be affected by cultivar, environment and type of inflorescence. Bioavailability of calcium (Ca) in broccoli is compared to milk, reinforcing the importance of this vegetable in human diets. In this study the phosphorus (P), potassium (K), Ca, magnesium (Mg), sulfur (S), and chloride (Cl) content was determined in the primary and secondary inflorescences of 11 broccoli cultivars grown in early and late seasons in order to highlight genotypical differences and seasonal effects on the mineral content. Results showed that the levels of all studied minerals, except K, were influenced by season. Calcium and Cl were higher (P<0.05) in spring/summer than in summer/winter whilst the opposite occurred for the other minerals. Calcium, S, and Cl levels were higher (P<0.001) in the secondary than in primary inflorescences whilst no difference was noted for the other minerals. Only Ca, Mg, and S seem to be dependent on genotype, which justifies the selection of a particular cultivar to increase the intake of these minerals. In this study the cultivar with the highest Ca levels was, on average, Tokyodome.

Two Unusual Calamus Species from New Guinea

Summary. The taxonomy of two rattan species with unusual inflorescence morphology is discussed. Calamus setiger (Calamoideae: Arecaceae) is reduced to synonymy with C. anomalus and a new species, C. essigii, is described. The rattan genus Calamus L. is distinguished from the five other genera in subtribe Calaminae (Calamoideae: Calameae, sensu Baker et al. 2000) by its strictly tubular, persistent primary inflorescence bracts and by the primary inflorescence branches emerging from the mouths of the bracts. By contrast, the primary bracts of other genera tend to split, usually to the base, and the primary inflorescence branches are thereby exposed or alternatively remain enclosed within the bracts. While this rule works in the vast majority of cases, there are some exceptions in the large and variable genus Calamus. One such exception is to be found in a small group of species from New Guinea in which each expanding primary branch bursts through the wall of the primary bract, splitting the bract near its base, rather than emerging from the mouth of the bract. Usually, the bract is split only at the base and remains tubular distally, but in some instances the bract may split throughout its length. Despite this unusual characteristic, the species are appropriately placed in genus Calamus as both possess a flagellum, a barbed, climbing organ representing a sterile inflorescence, a structure that occurs only in Calamus. As part of the Palms of New Guinea Project (Baker 2000), this unusual group has been revised and has been found to comprise two species, C. anomalus Burret and C. essigii W. J. Baker. The latter is described as new and C. setiger Burret is placed in synonymy with C. anomalus. The work is based on material from BM, K, L, LAE, MEL and NY. All duplicates recorded on specimen labels are listed while exclamation marks denote those duplicates seen by me. Preliminary conservation status assessments are provided following IUCN guidelines (IUCN 2001).

A New Species of Calamus (Arecaceae: Calamoideae) from North-East Thailand

Summary. Calamus temii T. Evans from Phu Luang Wildlife Sanctuary, north-east Thailand is described as a new species. It is distinctive in its combination of arborescent habit, grouped, concolorous leaflets less than 40 cm long, laminar, black rachis spines, strongly tattering primary and secondary inflorescence bracts (unusual in the genus), short, stout, appressed female rachillae and dark, almost globose fruits with a ruminate endosperm. It seems most similar to the poorly known Chinese species C. melanochrous Burret.

Relationship between free amino acids and glucosinolates in primary and secondary inflorescences of 11 broccoli (Brassica oleracea L var italica) cultivars grown in early and late seasons

AbstractAmino acids have been identified as the precursors of a class of secondary plant metabolites, the glucosinolates, but there is no report on the relationship between the two in vivo. In this work we have investigated the relationship between free amino acids and glucosinolates in 11 broccoli cultivars grown in early (April–July) and late (August–January) seasons. Free amino acids and glucosinolates were quantified by HPLC in primary and secondary inflorescences at maturity stage. Analysis of the data revealed that no significant correlation exists between free amino acids and glucosinolates, suggesting that the precursors of these compounds might be used during the first step of the biosynthetic process to form intermediates, the aldoximes and thiohydroximates, which will then be used in the second stage of the biosynthesis to form, apart from glucosinolates, other secondary plant metabolites.© 2001 Society of Chemical Industry

Glucose, fructose and sucrose content in broccoli, white cabbage and Portuguese cabbage grown in early and late seasons

AbstractConsumption of Portuguese cabbage and white cabbage is very high in Portugal, but diets including broccoli have been highly recommended owing to recognition of the health‐protective effects of secondary plant metabolites. Broccoli production is generally concentrated in the summer/winter season, but the demand for a fresh product throughout the year requires production in other seasons. Sugars might affect flavour and the acceptance of broccoli by consumers. This study reports the free fructose, glucose and sucrose content in primary and secondary inflorescences of 11 cultivars of broccoli, one white cabbage and four Portuguese cabbages grown in early (March–July) and late (August–January) seasons in the northern region of Portugal. On average the results show that the total free sugar content in the broccoli cultivars, except for cv Marathon, is significantly (P &lt; 0.05) lower than in the other cabbages. Fructose was the major sugar in the three types of Brassica, representing between 48.8 and 56.9% of the total sugar content in broccoli cvs Marathon and Senshi respectively and between 48.7% (cv Mirandela) and 53.8% (cv Murciana) in the other cabbages. Glucose was the second major sugar, while sucrose represented a maximum of 20.5% in broccoli cv Shogun and 11.1% in cv Murciana. The growing season influenced the free sugar content, with generally higher levels in the spring/summer than in the summer/winter season in broccoli, while an opposite tendency was noted in the other Brassica species. In broccoli the sugar levels in the primary inflorescences were generally lower than in the secondary inflorescences, except for sucrose.© 2001 Society of Chemical Industry

Total and Individual Glucosinolate Content in 11 Broccoli Cultivars Grown in Early and Late Seasons

Broccoli (Brassica oleracea L. Italica Group) is an economically important vegetable crop and its consumption may benefit human health. Glucosinolates, a group of secondary plant metabolites found generally in the cultivated Brassicaceae, may protect against the development of certain malignancies. The objective of this study was to evaluate total and individual glucosinolate content of broccoli cultivars widely grown in southern Europe following spring vs. summer planting (early vs. late crop, respectively). Glucosinolates in primary and secondary inflorescences taken from mature plants were analyzed separately by high performance liquid chromatography (HPLC). The cultivars contained primarily 4-methylsulfinylbutyl-, indol-3-ylmethyl- and 1-methoxyindol-3-ylmethyl-glucosinolates. Total and individual glucosinolate levels varied significantly between seasons, among cultivars and between inflorescences. `Shogun' contained the highest total glucosinolate levels (between 35.2 mmol·kg-1 dry weight in primary inflorescences of the early crop and 47.9 in secondary inflorescences of the late crop). Total and individual glucosinolate levels were generally higher in the late than in the early crop. Primary inflorescences generally contained the highest glucosinolate levels in the early crop but secondary inflorescences had the highest levels in the late one.

Free amino acid composition in primary and secondary inflorescences of 11 broccoli (Brassica oleracea var italica) cultivars and its variation between growing seasons

Eleven broccoli cultivars were grown in the field in spring/summer (April–July) and summer/winter (September–January). Free amino acid composition was determined by HPLC in primary and secondary inflorescences separately. A total of 17 amino acids were identified: L-alanine (Ala), L-arginine (Arg), L-asparagine (Asn), L-aspartic acid (Asp), glycine (Gly), L-glutamic acid (Glu), L-glutamine (Gln), L-histidine (His), L-isoleucine (Ile), L-leucine (Leu), L-methionine (Met), L-phenylalanine (Phe), L-serine (Ser), L-threonine (Thr), L-tryptophan (Trp), L-tyrosine (Tyr) and L-valine (Val). The major amino acid was L-glutamine, which represented on average between 39.5% (in cvs Durango and Green Valiant) and 55.5% (in cv Shogun) of the total amino acid content among cultivars, followed by L-glutamic acid with a variation between 12.1% (in cv Shogun) and 17.4% (in cv Marathon). A few amino acids represented less than 1% each (Gly, Leu, Met, Phen, Thr, Trp and Tyr). For most of the amino acids there were significant differences between cultivars, whilst only a few amino acids showed significant variations between inflorescences. Season also induced significant differences in the content of most of the identified amino acids. The cultivar with the highest total free amino acid content (323.9 mmol kg−1 DW) on average of both seasons (391.3 in spring/summer and 256.4 in summer/winter) was Shogun, whilst the others were above the minimum of 177.3 mmol kg−1 DW found in cv SK3. There was a general tendency for higher total amino acids levels in spring/summer than in summer/winter, but it was clear that this effect was dependent on the cultivar. © 2000 Society of Chemical Industry

Stamina pistilloida, the Pea ortholog of Fim and UFO, is required for normal development of flowers, inflorescences, and leaves.

Isolation and characterization of two severe alleles at the Stamina pistilloida (Stp) locus reveals that Stp is involved in a wide range of developmental processes in the garden pea. The most severe allele, stp-4, results in flowers consisting almost entirely of sepals and carpels. Production of ectopic secondary flowers in stp-4 plants suggests that Stp is involved in specifying floral meristem identity in pea. The stp mutations also reduce the complexity of the compound pea leaf, and primary inflorescences often terminate prematurely in an aberrant sepaloid flower. In addition, stp mutants were shorter than their wild-type siblings due to a reduction in cell number in their internodes. Fewer cells were also found in the epidermis of the leaf rachis of stp mutants. Examination of the effects of stp-4 in double mutant combinations with af, tl, det, and veg2-2-mutations known to influence leaf, inflorescence, and flower development in pea-suggests that Stp function is independent of these genes. A synergistic interaction between weak mutant alleles at Stp and Uni indicated that these two genes act together, possibly to regulate primordial growth. Molecular analysis revealed that Stp is the pea homolog of the Antirrhinum gene Fimbriata (Fim) and of UNUSUAL FLORAL ORGANS (UFO) from Arabidopsis. Differences between Fim/UFO and Stp mutant phenotypes and expression patterns suggest that expansion of Stp activity into the leaf was an important step during evolution of the compound leaf in the garden pea.

Free amino acid composition in primary and secondary inflorescences of 11 broccoli (Brassica oleracea varitalica) cultivars and its variation between growing seasons

Free amino acid composition in primary and secondary inflorescences of 11 broccoli (Brassica oleracea varitalica) cultivars and its variation between growing seasons

Free amino acid composition in primary and secondary inflorescences of 11 broccoli (Brassica oleraceavaritalica) cultivars and its variation between growing seasons

Eleven broccoli cultivars were grown in the field in spring/summer (April–July) and summer/winter (September–January). Free amino acid composition was determined by HPLC in primary and secondary inflorescences separately. A total of 17 amino acids were identified: L-alanine (Ala), L-arginine (Arg), L-asparagine (Asn), L-aspartic acid (Asp), glycine (Gly), L-glutamic acid (Glu), L-glutamine (Gln), L-histidine (His), L-isoleucine (Ile), L-leucine (Leu), L-methionine (Met), L-phenylalanine (Phe), L-serine (Ser), L-threonine (Thr), L-tryptophan (Trp), L-tyrosine (Tyr) and L-valine (Val). The major amino acid was L-glutamine, which represented on average between 39.5% (in cvs Durango and Green Valiant) and 55.5% (in cv Shogun) of the total amino acid content among cultivars, followed by L-glutamic acid with a variation between 12.1% (in cv Shogun) and 17.4% (in cv Marathon). A few amino acids represented less than 1% each (Gly, Leu, Met, Phen, Thr, Trp and Tyr). For most of the amino acids there were significant differences between cultivars, whilst only a few amino acids showed significant variations between inflorescences. Season also induced significant differences in the content of most of the identified amino acids. The cultivar with the highest total free amino acid content (323.9 mmol kg−1 DW) on average of both seasons (391.3 in spring/summer and 256.4 in summer/winter) was Shogun, whilst the others were above the minimum of 177.3 mmol kg−1 DW found in cv SK3. There was a general tendency for higher total amino acids levels in spring/summer than in summer/winter, but it was clear that this effect was dependent on the cultivar. © 2000 Society of Chemical Industry

158 Dormancy of Ornithogalum Evaluated by Nuclear Magnetic Resonance Imaging

Ornithogalum hybrid bulbs (selection 327-2) were stored dry at 10, 16, 22, 28, and 35 °C for 6 weeks upon harvest. After storage, bulbs were subjected to a nuclear magnetic resonance (NMR) imaging to obtain the longitudinal spin-lattice relaxation time (T1) profile across the cross section of intact bulbs and to a scanning electron microscopy (SEM) to observe an inflorescence development. Bulbs were forced in a greenhouse maintained at 21/19 °C. When bulbs were stored at 10, T1 was shorter through the cross section of bulbs and the shoot apex was under a vegetative stage. This suggests that dormancy was not broken during the storage, leaf emergence was delayed, and plants failed to flower. Bulbs stored at 22 and 28 °C formed the primary scape and inflorescence with several florets. At the base of the primary scape of bulbs stored at 22 °C, a vegetative apex was observed by both MR imaging (MRI) and SEM. In the center of bulbs where leaves and floral organs were present, T1 was longer as compared to the scales. This suggests that dormancy in the scales was broken and the leaves and scape were ready to emerge. Leaf emergence and flowering was the fastest when bulbs were stored at 22 °C and at 16 or 22 °C, respectively. Due to its nondestructive nature, MRI can be used to study the state of bulb dormancy and also the progress of inflorescence development during bulb storage prior to planting.

Deficiency in fatty acid synthase leads to premature cell death and dramatic alterations in plant morphology.

An Arabidopsis mosaic death1 (mod1) mutant, which has premature cell death in multiple organs, was isolated. mod1 plants display multiple morphological phenotypes, including chlorotic and curly leaves, distorted siliques, premature senescence of primary inflorescences, reduced fertility, and semidwarfism. The phenotype of the mod1 mutant results from a single nuclear recessive mutation, and the MOD1 gene was isolated by using a map-based cloning approach. The MOD1 gene encodes an enoyl-acyl carrier protein (ACP) reductase, which is a subunit of the fatty acid synthase complex that catalyzes de novo synthesis of fatty acids. An amino acid substitution in the enoyl-ACP reductase of the mod1 mutant causes a marked decrease in its enzymatic activity, impairing fatty acid biosynthesis and decreasing the amount of total lipids in mod1 plants. These results demonstrate that a deficiency in fatty acid biosynthesis has pleiotropic effects on plant growth and development and causes premature cell death.

Isolation and characterization of an Arabidopsis mutant, fireworks (fiw), which exhibits premature cessation of inflorescence growth and early leaf senescence.

To examine the mechanism underlying the reproductive development in monocarpic plants, we screened for mutants that exhibit premature cessation of inflorescence growth in Arabidopsis. We identified a novel mutant line that exhibited earlier cessation of flower formation and inflorescence stem elongation. This mutant also exhibited accelerated rosette leaf senescence after the cessation of the inflorescence growth. We designated the mutant fireworks (fiw) because flowers and siliques were clustered at the top of the fiw inflorescence. The fiw mutation was a single, recessive mutation and mapped on the lower part of chromosome 4. The fiw phenotype was not observable during vegetative growth, but the inflorescence growth was arrested more than 7 d earlier than the wild type (WT). Microscopic observation revealed that the fiw apical meristem was structurally preserved. The premature arrest of growth was observed not only in the primary inflorescence but also in the lateral inflorescence, which is consistent with the global proliferative arrest observed later in WT. Regardless of such dramatic phenotypic features, the fiw plants bore normal flowers and set fully matured siliques.

Inflorescence and Flower Development in the Hedychieae (Zingiberaceae): Scaphochlamys kunstleri (Baker) Holttum

Primary inflorescence bracts are initiated in a spiral phyllotactic pattern on the flanks of the inflorescence apex. A cincinnus primordium forms in the axil of each primary bract. A prophyll is initiated in the transverse plane and later extends around the periphery of the cincinnus to produce a sheathing, but not tubular, bract. The apex of the cincinnus forms a flower. Flower development begins with the enlargement and flattening of the floral apex. Sepal initiation is sequential but differs in the first two flowers of a cincinnus. The different sequences are likely the result of developmental constraints that operate at the time of sepal initiation. After initiation, the margins of the sepals become confluent and intercalary growth produces the synsepalous calyx. The periphery of the flower, interior to the sepals, now rises to form a ring primordium composed of three common petallandroecial primordia. The common primordia enlarge, flatten, and separate to produce a petal to the exterior and an androecial member to the interior. The outer androecium forms in the regions of the ring primordium left vacant by the formation of the other floral parts. The anterior outer androecial member soon ceases growth and contributes only initially to the formation of the labellum. The gynoecium shows heterochrony in its time of initiation, which occurs much earlier than in other species of Zingiberaceae. Gynoecial initiation takes place on the margins of the central flora cup, at the time of the separation of the common primordia. Three gynoecial primordia from in antipetalous positions. Septa development differs in the basal and apical portions of the ovary. At the base, the primordia grow inward and fuse to form the central axis of the ovary. At the apex, there is little radial growth of the primordia. They cease growth soon after initiation and produce a unilocular cavity. Ovules form at the junction of these two regions and project up into the cavity. Epigynous nectaries form after all other floral organs.

Arabidopsis thaliana responses to mechanical stimulation do not require ETR1 or EIN2.

Plants exposed to repetitive touch or wind are generally shorter and stockier than sheltered plants. These mechanostimulus-induced developmental changes are termed thigmomorphogenesis and may confer resistance to subsequent stresses. An early response of Arabidopsis thaliana to touch or wind is the up-regulation of TCH (touch) gene expression. The signal transduction pathway that leads to mechanostimulus responses is not well defined. A role for ethylene has been proposed based on the observation that mechanostimulation of plants leads to ethylene evolution and exogenous ethylene leads to thigmomorphogenetic-like changes. To determine whether ethylene has a role in plant responses to mechanostimulation, we assessed the ability of two ethylene-insensitive mutants, etr1-3 and ein2-1, to undergo thigmomorphogenesis and TCH gene up-regulation of expression. The ethylene-insensitive mutants responded to wind similarly to the wild type, with a delay in flowering, decrease in inflorescence elongation rate, shorter mature primary inflorescences, more rosette paraclades, and appropriate TCH gene expression changes. Also, wild-type and mutant Arabidopsis responded to vibrational stimulation, with an increase in hypocotyl elongation and up-regulation of TCH gene expression. We conclude that the ETR1 and EIN2 protein functions are not required for the developmental and molecular responses to mechanical stimulation.