Floral Heads Research Articles

Quality parameters and antioxidant properties in organic and conventionally grown broccoli after pre‐storage hot water treatment

Demand for broccoli has increased due to its high content of bioactive compounds. However, broccoli is a perishable commodity with a short shelf life mainly due to dehydration, yellowing and losses of bioactive compounds. Thus, efficient treatments to preserve broccoli quality are needed. The effect of heat treatment on senescence and antioxidant compounds evolution during storage at 20 °C was evaluated in organic and conventionally grown broccoli. Senescence evolved quickly as manifested by floral head yellowing, which was higher in conventional than in organic broccolis, but senescence was significantly delayed by heat treatment. All organic acids, including ascorbic acid, were found at higher concentrations in organic than in conventional broccoli at harvest but decreased during storage in all broccolis. Phenolic concentration and antioxidant activity (in both hydrophilic and lipophilic fractions) also decreased during storage, although these decreases were higher in conventional than in organic broccolis, and no differences were found attributable to heat treatment. Heat treatment was effective in delaying broccoli senescence, manifested by chlorophyll retention. In addition, organic broccoli maintained higher concentrations of bioactive compounds (ascorbic acid and phenolics) and antioxidant potential during storage than conventional broccoli, with higher potential health beneficial effects.

Bending in cut Gerbera jamesonii flowers relates to adverse water relations and lack of stem sclerenchyma development, not to expansion of the stem central cavity or stem elongation

We studied stem bending in cut Gerbera flowers (Gerbera jamesonii cv. Tamara). Bending might be due to turgor loss. During vase life water uptake decreased more rapidly than transpiration, hence the flowers lost water. Net water loss did not occur in the floral head, but was found in the stem. It was largest in the segment (10–15cm below the floral head) where bending was localised. When comparing flowers that showed stem bending with those that did not, on day 7 of vase life, the fresh weight loss of 5cm stem segments was higher in the stems that had bent. Covering the stems with a flexible, thin sleeve of polypropylene plastic reduced transpiration and increased the time to stem bending from d 7 to d 14 of vase life. Additionally, stem bending might relate to stem elongation and to stem morphology and anatomy. Stems elongated by 1–1.5cm, in the uppermost 10cm, during the first two days of vase life. No relationship was found between stem elongation and bending. At harvest, the stems contained a large central cavity, starting at about 5cm from the root–shoot junction, and ending about 10cm below the floral head. The cavity extended upwards and laterally during vase life, but no relationship was found between cavity formation and stem bending. A cylinder of sclerenchyma in the stems was found to end about 20cm below the floral head, in summer. Bending was correlated with the extent of sclerenchyma formation and stem lignin levels. It is concluded that stem bending is due to net water loss from the stem, particularly in the area of bending, and to low mechanical strength in the upper part of the stems, which lack a sclerenchyma cylinder.

Avaliação de germoplasma de camomila e densidade de semeadura na produção e composição do óleo essencial

O cultivo de camomila na região Sul do Brasil tem sido realizado utilizando-se como material genético a cultivar Mandirituba. Apesar da produção de capítulos florais e teor de óleos essenciais apresentado por esta cultivar ser considerado satisfatório, tem sido observada nas regiões produtoras a ocorrência de problemas fitossanitários que resultam em perdas significativas da produção. Este trabalho teve como objetivos comparar materiais genéticos de camomila provenientes da Holanda, Dinamarca e Mandirituba, e avaliar o efeito de diferentes densidades de semeadura no desenvolvimento das plantas, produção de capítulos, rendimento e qualidade do óleo essencial da cultivar Mandirituba, atualmente cultivada na região. Os experimentos foram conduzidos no município de Piraquara (PR). A extração do óleo essencial foi realizada por hidrodestilação em aparelho tipo Clevenger e a determinação da composição do óleo foi feita por cromatografia em fase gasosa acoplada ao espectrômetro de massa (GC/MS). Os materiais genéticos provenientes da Holanda e de Mandirituba apresentaram maior produção de biomassa seca de capítulos, em relação ao material genético da Dinamarca. A cultivar Mandirituba apresentou o maior rendimento de óleo essencial (4,71 mL g-1 ms), sendo também superior em relação à produtividade de óleo essencial (2,40 L ha-1). Os materiais procedentes da Dinamarca e de Mandirituba apresentaram composição do óleo essencial semelhantes. A densidade de plantio de 1,0 kg ha-1 da cultivar Mandirituba resultou em melhor desenvolvimento das plantas e maior produção de óleo essencial. Quantidades superiores a 3,0 kg ha-1 de sementes não resultaram em maior densidade de plantas tendo em vista a alta competição e percentual de plântulas mortas.

Relative Pollinator Effectiveness of Insect Floral Visitors to Two Sympatric Species of Wild Aster: Symphyotrichum lanceolatum (Willd.) Nesom and S. lateriflorum (L.) Löve & Löve (Asteraceae: Astereae)

Four parameters were used to determine pollinator effectiveness of floral visitors to two sympatric species of Symphyotrichum (S. lanceolatum and S. lateriflorum): (1) pollinator efficiency; (2) relative abundance of visitors; (3) amount of pollen carried on a visitor's body; and (4) visitor foraging time per capitulum. The most effective pollinators of S. lanceolatum were Apis mellifera (Apidae), Eristalis spp. (Syrphidae), Dolichovespula arenaria, and Polistes fuscatus (both Vespidae). Halictidae (sweat bees) and Tachinidae (Diptera) were also potentially effective pollinators. For S. lateriflorum, effective pollinators included D. arenaria, Vespula maculifrons (Vespidae), Lasioglossum spp. (Halictidae), and A. mellifera, with large syrphid flies also having moderate importance. The Halictidae was the only group of visitors that demonstrated a significant difference in the amount of time spent foraging the floral heads of these two aster species. Despite spending more time foraging the floral heads of S. lateriflorum, halictid bees carried the same average pollen load regardless of the species of Symphyotrichum from which they were collected. Halictid bees, however, are potentially more effective pollinators of S. lateriflorum than of S. lanceolatum.

Mite-Mediated Hyperphoretic Dispersal of <I>Ophiostoma</I> spp. from the Infructescences of South African <I>Protea</I> spp.

Ophiostomatoid fungi are well known as economically important pathogens and agents of timber degradation. A unique assemblage of these arthropod-associated organisms including species of Gondwanamyces G. J. Marais and M. J. Wingf., and Ophiostoma Syd. and P. Syd. occur in the floral heads (infructescences) of Protea L. species in South Africa. It has recently been discovered that Ophiostoma found in Protea flower-heads are vectored by mites (Acarina) including species of: Tarsonemus Canestrini and Fonzago, Proctolaelaps Berlese, and Trichouropoda Berlese. It is, however, not known how the mites carry the fungi between host plants. In this study, we consider two possible modes of mite dispersal. These include self-dispersal between infructescences and dispersal through insect vectors. Results showed that, as infructescences desiccate, mites self-disperse to fresh moist infructescences. Long-range dispersal is achieved through a phoretic association with three beetle species: Genuchus hottentottus (F.), Trichostetha fascicularis L., and T. capensis L. The long-range, hyperphoretic dispersal of O. splendens G. J. Marais and M. J. Wingf. and O. phasma Roets et al. seemed effective, because their hosts were colonized during the first flowering season 3-4 yr after fire.

Diversity of sunflower pollinators and their effect on seed yield in Makueni District, Eastern Kenya

A field experiment was carried out in 2004 and 2005 to identify the diversity of sunflower (Helianthus annuus L.) pollinators and their influence on seed yield in Makueni district, a semi-arid area in Eastern Kenya. Insect flower visitors were recorded, pollen counted from their body and pollination efficiency index for each visitor determined. Seed yield from plots where insect visitors had access to and where they were denied access was compared. The proportional difference of yield from this pollination scenario was used to estimate monetary net-gain by farmers that could be attributed to insect pollination. In total, individuals belonging to 14 insect species were observed visiting sunflower floral heads. These included six Lepidopteran species, five Hymenopteran species, two Dipteran species, and one Coleopteran species. Apis mellifera L. was the most frequent visitor and had the highest pollination efficiency index. Plots where insect visitors had access produced on average 53% more seed yield compared with plots where insect visitors were excluded. This translates to a net monetary benefit of 51% of the total annual market value of sunflower, accruing to farmers in Makueni district in 2005 due to insect pollination.

Senescence-associated genes in harvested broccoli florets

Broccoli, Brassica oleracea L. var italica, is an important vegetable crop known to be rich in vitamins and sulforaphane. However, rapid postharvest senescence in harvested floral heads reduces its value. Complex factors such as ethylene biosynthesis, temperature, and respiration are involved in this senescence process. Meanwhile, recent developments on postharvest biotechnology, as well as studies on functional genes related to postharvest senescence have provided an opportunity for conquering this problem. In this review, we will discuss the genes involved in broccoli senescence and the physical, chemical, or genetic methods to increase shelf life and reduce quality loss due to postharvest senescence.

Discovery of Fungus-Mite Mutualism in a Unique Niche

The floral heads (infructescences) of South African Protea L. represent a most unusual niche for fungi of the economically important genus Ophiostoma Syd. and P. Syd. emend. Z.W. de Beer et al. Current consensus holds that most members of Ophiostoma are vectored by tree-infesting bark beetles. However, it has recently been suggested that mites, phoretic on these bark beetles, may play a central role in the dispersal of Ophiostoma. No bark beetles are known from Protea. Therefore, identifying the vectors of Ophiostoma in Protea infructescences would independently evaluate the role of various arthropods in the dispersal of Ophiostoma. Infructescence-colonizing arthropods were tested for the presence of Ophiostoma DNA using polymerase chain reaction (PCR) and for reproductive propagules by isolation on agar plates. PCR tests revealed that few insects carried Ophiostoma DNA. In contrast, various mites (Proctolaelaps vandenbergi Ryke, two species of Tarsonemus Canestrini and Fonzago, and one Trichouropoda Berlese species) frequently carried Ophiostoma propagules. DNA sequence comparisons for 28S ribosomal DNA confirmed the presence of O. splendens G. J. Marais and M. J. Wingf., O. palmiculminatum Roets et al., and O. phasma Roets et al. on these mites. Two apparently undescribed species of Ophiostoma were also identified. Light and scanning electron microscopy revealed specialized structures in Trichouropoda and one Tarsonemus sp. that frequently contained Ophiostoma spores. The Trichouropoda sp. was able to complete its life cycle on a diet consisting solely of its identified phoretic Ophiostoma spp. This study provides compelling evidence that mites are the primary vectors of infructescence-associated Ophiostoma spp. in South Africa.

Quantifying a Rare Event: Pollen Theft by Honey Bees from Bumble Bees and Other Bees (Apoidea: Apidae, Megachilidae) Foraging at Flowers

Although honey bees (Apis mellifera L.) (Hymenoptera: Apidae) frequently raid conspecific colonies for pollen and nectar stores (Winston, 1987; Downs et al., 2001), they are rarely observed stealing pollen from foraging bees of other species (Laroca and Winston, 1978; Thorp and Briggs, 1980). Here I report observations of honey bees stealing pollen from three species of bee (Bombus impatiens Cresson (Apidae), Megachile montivaga Cresson (Megachilidae), and Melissodes desponsa Smith (Apidae)) at flowers of pasture thistle, Cirsium discolor (Muhl.) Spreng. (Asteraceae) in Indiana. This is the third report of such behavior, and like the others was observed at an Asteraceae species (Thorp and Briggs, 1980; Laroca and Winston, 1978). It is the first report to quantify the rarity of the behavior in Apis; based on this it is no surprise that there are few published reports. In addition, this is the first observation of pollen theft behavior in the eastern United States; previous reports were from California (Thorp and Briggs, 1980) and Kansas (Laroca and Winston, 1978). This is also the first report of a fast-flying (Melissodes) species being subject to cleptolecty (Thorp and Briggs, 1980), the theft of pollen from the pollen collecting apparatus of other bees by honey bees. I also report observations of honey bees collecting pollen from the abdomen of a bumble bee worker and a megachilid forager, similar to the pollen theft previously reported by Laroca and Winston (1978). I made these observations during a three-year (2001-2003) survey of bees in 5 sandy black oak savannas of northwestern Indiana. I netted bees at over 70 species of flowering plants from April-September each year, visiting each site approximately biweekly, and paying special attention to overlap in flower use by honey bees and native bees. Honey bees were commonly observed on flowers of Lupinus perennis L. (Fabaceae), Rubus spp. (Rosaceae), Scrophularia lanceolata Pursh. (Scrophulariaceae), Tradescantia ohiensis Raf. (Commelinaceae), Solidago spp. (Asteraceae) and Cirsium discolor, but pollen theft was only observed on C. discolor at a single site, and then only on three days. Pollen theft was observed on three days (30 August, 5 and 7 September 2003) at Conrad Station, Newton County, a savanna owned by The Nature Conservancy. Here, populations of C. discolor grow along abandoned railroad tracks. Common floral visitors include A. mellifera, B. impatiens, Bombus griseocollis (DeGeer), Melissodes desponsa, Megachile montivaga, and Ceratina spp. (Apidae). Two hives of A. mellifera were maintained 0.5 km from the thistle patch. Cirsium discolor stands 1-2 m high and has a large floral head (2.5-3.5 cm wide; Gleason and Cronquist, 1963) of several hundred blue, tubular florets that produce nectar and bright, white pollen presented on exserted stamens, which is easily seen on pollinators. The corolla tubes are approxi mately 2.5 cm deep, limiting nectar access to long-tongued species. On 30 August, approximately 10 B. impatiens workers were attacked by up to 2 Apis workers at a time between 11:00 and 11:30 a.m. At least some pollen appeared to be removed from each victim Bombus. Apis workers sought the corbicula loads on Bombus workers and usually removed a small amount of pollen, but never an entire corbicula load. Bombus responses were complacent and non-aggressive. One honey bee landed on a M. montivaga forager and took pollen from the dorsal portion of the abdomen, causing the victim to fly off. On 5 September at the same patch, six honey bees attempted to steal pollen on six occasions (one individual per occasion) from B. impatiens workers. On 3 of 5 attempts, a single honey bee removed part of a corbicula load. A sixth honey bee removed pollen from a bee's dorsal abdomen. Bumble bee responses were again limited. On three occasions they moved their rear legs back and forth as when grooming, twice they did not respond, and once the bumble bee flew from the flower. On 7 September, I photographed the activity (Fig. 1). Once again, between 10:30 and 11:30 a.m., honey bees robbed pollen from B. impatiens on many occasions. On one occasion a single honey bee attempted to

Ethylene insensitive and post-harvest yellowing retardation in mutant ethylene response sensor (boers) gene transformed broccoli (Brassica olercea var. italica)

A mutant broccoli ers (ethylene-response-sensor, boers) gene was obtained through site directed mutagenesis by replacing the isoleucine with phenylanine at the 62th residue. Two plasmids were constructed with this mutant gene regulated by the CaMV 35S promoter together with the nptII (kanamycin resistance gene) coding sequence and hpt (hygromycin resistance gene), respectively, for the pBI-mERSI62F and pSM1H-mERSI62F plasmids. Genetic transformation of the above two constructs via A. tumefaciens has been conducted to evaluate their effects on floret yellowing of harvested broccoli. Over a hundred transformants have been obtained on the selected cotyledon and hypocotyl explants. PCR and Southern analysis demonstrated integration of the transgenes in the transformants. However, through Southern hybridization, we determined that multi-site integration and DNA rearrangements had occurred in most transformants. Morphological and characteristic alternation such as slower plant growth, shorter plant height, easy branching, late bolting, and relative higher mortality in comparison with other transgenes were noted in some transformants. Transgenic lines showing delayed senescence in leaves and floral heads were obtained. The expression of transgene was confirmed by Northern blot analysis. The transformed progenies also showed ethylene insensitivity in seed germination, detached leaves and harvested florets. Nevertheless, in most lines, the yellowing was only delayed 1–2 days.

잇꽃의 식물병 발생양상과 주요 식물병의 약제방제

This study were carried out to identify pathogens and determine the seasonal occurrence and chemical control of safflower (Carthamus tinctorius) diseases from 2000 to 2002 in Gyengbuk province, Korea. Major diseases of safflower were, anthracnose caused by Colletotricum acutatum in open field, and gray mold by Botrytis cinerea in rain sheltered plastic house. Other diseases occurred were powdery mildew caused by Sphaerotheca fuliginea, collar rot by Sclerotium rolfsii, leaf spot by Alternaria carthami and A. alternata, rust by Puccinia carthami, root-rot and stem-rot by Phytophthora cactorum, root-rot and wilt by Fusarium oxysporum and damping-off by Pythium ultimum. Seasonal occurrence of anthracnose on safflower has begun from late April, and increased until harvesting, especially rapid increased after rainfall during stem elongation season that is from May to June. In open fields, maximum incidence of anthracnose was 67 ％ in late July. But in rain-sheltered plastic house, it was very low, about 5％ in July. Gray mold caused by Botrytis cinerea was most important disease in rain-sheltered plastic house cultivation. Maximum incidence of gray mold on floral head was 27.4％, whereas other diseases occurred below 1 ％. In the test of the chemical control of the safflower anthracnose, metiram WP, carbendazimkasugamycin WP and iminoctadintristhiram WP were the highest controlling chemicals. In chemical control of gray mold, iminoctadintristhiram WP, fluazinam WP and iprodion WP showed highest controlling effects.

First Report of a Tospovirus on Sunflower (Helianthus annus L.) from India.

Virus-like symptoms were observed on sunflower in and around Tirupati during January 1998. Infected plants exhibited severe mosaic, systemic necrosis along the stem and floral heads, leaf distortion, and ringspots on leaves. The causal virus, mechanically transmissible from sunflower to sunflower cvs. Morden, MHSF8, MHSF18, KBHS1, and Cargil, developed symptoms like those in the original plant. The virus caused chlorotic and necrotic spots on Chenopodium amaranticolor, chlorotic and necrotic rings on cowpea cv. C-152, chlorotic spots on Datura metal and Petunia hybrida, chlorotic rings and systemic infection on Gomphrena globosa, tarlike symptoms on Catharanthus roseus, and local brown lesions on Cassia tora (1). Virus was isolated from infected sunflower leaves (2), and particles in negatively stained preparations were enveloped and 80 to 90 nm in diameter. Cytopathic effects included accumulation of virus particles in the endoplasmic reticulum, the formation of viroplasm, and aggregates consisting of nonenveloped viral nucleocapsids in the cytoplasm of ultrathin sections of infected sunflower leaves. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis of capsid protein resolved as a single band of 31 kD. The dsRNA isolated from infected sunflower leaves resolved as three bands of 9, 4.9, and 3 kb in 2% agarose gel electrophoresis. In enzyme-linked immunosorbent assay, the purified virus reacted with homologous and Peanut bud necrosis virus (PBNV-ICRISAT, India) antisera and not to polyclonal antibodies to Iris yellow spot virus (Netherlands), Tomato spotted wilt virus-T (Georgia), Impatiens necrotic spot virus, and several isolates of Cucumber mosaic virus (CMV-B, CMV-C, CMV-To). In western blotting analysis, the virus coat protein reacted with homologous and PBNV antisera corresponding to coat protein band of 31 kD. In reverse transcription polymerase chain reaction, the viral RNA was amplified by using primers derived from NP gene sequence of PBNV and Watermelon silver mottle virus (WSMV). Based on these properties, the virus causing sunflower mosaic followed by necrosis in India was identified as a tospovirus, which may be as a distinct isolate of sero group IV.

The mating system of Liatris helleri (Asteraceae), a threatened plant species

Multilocus outcrossing rates were estimated for seven populations of Liatris hellen, a rare insect-pollinated composite. The mean multilocus outcrossing rate was 0.97 (SE = 0.02). None of the populations examined had multilocus outcrossing rates that differed significantly from 1.00, suggesting that the species is self-incompatible. Seed set was insignificant for 770 bagged floral heads, lending further support for this view. A small but significant amount of biparental inbreeding was detected in three of the seven populations.

The role of hybridization in evolution: old wine in new skins

Perhaps no one has had a greater influence on the development of hybridization theory than Dr. Ledyard Stebbins. However, his contributions have not been restricted to his writings or lectures alone. Many of you have marveled at the great authority with which Dr. Stebbins identified the hybrid status, parentage, and ploidal level of plants in the field or on herbarium sheets. He didn't seem to need all the modern techniques that the current generation of botanists is both blessed and burdened with. For example, I remember a short field trip with Dr. Stebbins in the fall of 1984 to look at some sunflower hybrids near Davis. The plants were dead, only a few dried leaves, stalks, and floral heads remained, yet he confidently identified parental, hybrid, and backcrossed generations. Ironically, after 2 yr of careful molecular studies, I essentially confirmed his initial observations (Rieseberg, Soltis, and Palmer, 1988). Thus, I came to the conclusion that he was able to see things in plants that escaped less careful or less knowledgeable observers such as myself.

Growth, Photosynthesis, and Resource Investment for Vegetative and Reproductive Modules of Artemisia Tridentata

Growth of vegetative and reproductive structures in Artemisia tridentata is temporally separated during the growing season; vegetative growth occurs during spring and early summer when soil moisture is most abundant, while reproductive growth occur during summer and fall when soil moisture may be limiting. Vegetative and reproductive structures may therefore exhibit contrasting efficiencies of resource acquisition and investment resulting from temporal differences in resource availability during their development. We examined the effect of water stress on growth, photosynthesis, and resource investment for vegetative and reproductive modules of Artemisia tridentata by applying supplemental water. No differences were observed in vegetative biomass between shrubs in the two watering treatments. Growth of vegetative structures occurred in the spring when water was not limiting, and shrubs in both watering treatments exerted little stomatal control over water loss. Conversely, reproductive growth occurred through the summer when water was limiting, and supplemental watering increased reproductive growth. Shrubs conserved water during summer by abscising leaves and lowering stomatal conductance of both vegetative and reproductive modules in response to decreases in xylem pressure potential and increases in evaporative demand. Leaf abscission can occur without decreasing the amount of carbon available for reproductive growth because inflorescences are capable of positive photosynthetic rates comparable to vegetative leaves. Water stress did not alter tissue construction costs or carbon and nitrogen contents for either vegetative or reproductive modules. Resource limitations were, however, reflected in the efficiency of water use during tissue construction; floral leaves and floral heads of shrubs not receiving supplemental water were produced with higher water—use efficiency. Conservative use of water during production of vegetative modules would offer no advantage to A. tridentata because neighboring species are also most active at this time. Reproductive growth in A. tridentata occurs during summer when neighboring species are largely dormant, and so efficient use of water may allow development of reproductive structures to continue throughout the summer even with limited supplies of water.

Male sterility in diploid Ageratum conyzoides L.

Genetic control, time of ms gene action over microsporogenesis, plant phenotype and the breeding value of a diploid (2n=20) male sterile Ageratum conyzoides are described. The male sterility is controlled by a recessive gene on a single locus. This gene acts immediately after the microspores are released from the tetrads. The floral heads of the male sterile plants are compact and their stigma protrusion is slow. This trait differentiates them from the male fertiles in which the stigma exsertion is brisk and prolific. The breeding value of this male sterility is low.

A review of the world fauna of Tenuipalpidae (Acarina: Tetranychoidea)

Abstract The false spider mites or Tenuipalpidae are plant feeders of considerable economic importance. Some of the species are host specific but the majority of them are polyphagous and have a wide host range. Quite a number of them have been found to be serious pests of fruit trees, cultivated crops and vegetables. They feed on almost all parts of host plants, usualJy on the underside of leaves near midrib or veins; but a few feed on twigs, floral heads and under the leaf sheaths of grasses or form galls on host plants. Altogether 574 species under 22 genera are known, of which 8 genera are monotypic. Still a lot remains to be explored to understand the world fauna of the Tenuipalpidae.

ADAPTIVE RADIATION IN THE HAWAIIAN SILVERSWORD ALLIANCE (COMPOSITAE-MADIINAE). I. CYTOGENETICS OF SPONTANEOUS HYBRIDS.

The silversword alliance of the Hawaiian Islands comprises one of the most spectacular arrays of life forms known in a relatively small, clearly natural plant group. Perhaps the best known member of this alliance is the Haleakala silversword (Argyroxiphium macrocephalum Gray). However, A. macrocephalum is only one of six species in a genus which includes plants called greenswords as well as those called silverswords (cf. St. John, 1973). They ordinarily form large basal rosettes of attractive silver or green leaves for a number of years before they finally produce an elongated inflorescence. Argyroxiphium macrocephalum normally does not branch and dies after producing its massive inflorescence (cf. Kobayashi, 1973a). It is thus, under normal conditions, an essentially herbaceous, monocarpic plant. The floral heads of sword plants are characteristically large (>3 cm) and radiate. Argyroxiphium occurs primarily as a pioneer plant on volcanic pumice or in bogs and is restricted to the islands of Hawaii and Maui. In marked contrast to Argyroxiphium the related endemic genus Dubautia of this alliance (sensu Keck, 1936) is comprised largely of woody, branched shrubs that produce small (<1.5 cm), discoid heads year after year. However, the genus shows a truly remarkable spectrum of variation from somewhat herbaceous, low-growing forms through woody shrubs to trees. Moreover, the recently rediscovered D. latifolia (Gray) Keck from Kauai is a large liana. Altogether there are about 25 species of Dubautia, some of which, like Argyroxiphium may also be found as pioneers on volcanic pumice or in bogs, but others are found in dry forests or in rain forests. Its distribution extends throughout the entire system of major islands from Hawaii to Kauai. A third, related Hawaiian endemic genus, Wilkesia, is comprised of two species, one of which is often monocarpic and produces a rosette of leaves at the summit of a usually unbranched woody stem (cf. St. John, 1971). The second species branches rather freely from the base and presumably flowers repeatedly. The heads of Wilkesia are fairly large and discoid. Wilkesia is found on dry slopes, primarily in Waimea Canyon, only on the island of Kauai. The remarkable array of life forms within the silversword alliance exploits almost every conceivable terrestrial habitat in Hawaii. Its representatives occur from near sea level to timberline and from areas that receive less than 45 cm of annual precipitation to perhaps the wettest place on earth, receiving about 1,300 cm of annual precipitation. These habitats range from very recent lava flows on Hawaii to mature rain forests on Kauai. In spite of the spectacular morphological and ecological diversity exhibited by the members of the silversword alliance, the occurrence of many natural intergeneric, intersubgeneric, and interspecific hybrids (Sherff, 1935, 1944; Kobayashi, 1973b; and Carr, 1978a) attests to the fact that they form a natural, genetically cohesive group that has in all probability resulted from rapid evolutionary differentiation after a single colonization by a progenitor, possibly in less than 10 million years (see Macdonald and Abbott, 1970 for a discussion of Hawaiian geology). Collectively, these plants constitute what may be considered an unparalleled ex-

Napdragons, Flower Thrips, Green Melon Aphid and Twospotted Spider Mite Control, 1979

Abstract Five insecticides were evaluated against the flower thrips, melon aphid and twospotted spider mite on snapdragons. The plants in a private garden in West Lafayette, Indiana were treated on July 3'79 using a B &amp; G stainless steel one gallon compressed air sprayer operating at 30 psi. A randomized block design was utilized with three replications; a single plant comprised a plot. At the time of treatment the plants were 12-14 inches high. One month after treatment a floral head was removed from each plant, bagged, taken to the laboratory, and placed in a Berlese funnel. Three days later the sample was removed and the mites, aphids and thrips counted under a binocular microscope.

Snapdragons, Flower Thrips and Green Peach Aphid Control, 1978

Abstract Fourteen insecticides were evaluated for the control of snapdragon pests between July 5 and July 26, 1978. The planting was located in a private garden in West Lafayette, Indiana. All of the treatments, except Temik, were foliar sprays applied with a one gallon B&amp;G Stainless steel sprayer operating at 30 psi. The Temik granules were weighed and sprinkled into a furrow around each individual plant. The furrow was then covered with soil. A randomized block design was utilized with three replicates. Each plot consisted of an individual plant 12-14 inch high. Three weeks after treatment (T/21) a floral head was removed from each plant, bagged, taken into the laboratory and placed in a Berlese funnel and the captured thrips and aphids counted under a binocular microscope.