Branch Apices Research Articles

Larval Dispersal of the Weed Biological Control AgentOxyops vitiosa(Coleoptera: Curculionidae)

The Australian tree Melaleuca quinquenervia at both sites; no other larval stage were observed (Cav.) S. T. Blake (Myrtales: Myrtaceae) was inon the forest floor. troduced into Florida in the late 1800s, where While these data provide support for the hy it has naturalized and proven to be a superior pothesis that larvae freefall from canopies to competitor to most native vegetation. Florida forest floors, an alternative explanation for this M. quinquenervia wetland forests typically form phenomenon may be that 5th instar larvae are dense monocultures with continuous upper candisproportionately dislodged from the canopy and opies and low species diversity (Rayamajhi et al. subsequently recorded by observers. Therefore, a 2009). M. quinquenervia trees can exceed 30 m second method was employed in Feb 2003 that in height and tree architecture in dense stands is involved tracking larval dispersal in a more eas characterized by straight vertical trunks topped ily monitored environment. A 10 x 10 m area was by canopies restricted to the uppermost portions covered with a polyethelene plastic sheet that of the tree. Oxyops vitiosa Pascoe (Coleoptera: was staked to the ground. Five 2-m tall potted Curculionidae) is a biological control agent of M. quinquenervia trees were placed on top of the this exotic weed (Center et al. 2000). Weevil plastic sheeting and arranged to maximize spac larvae are specialized defoliators of M. quinqueing between individual trees in order to eliminate nervia foliage, consuming only expanding leaves any contact among their canopies. Ten late instar at branch apices (Pratt et al. 2004). Larvae exO. vitiosa larvae were placed in the canopies of ude a sticky orange secretion that covers the ineach tree. Immediately thereafter, the basal 10 tegument (Wheeler et al. 2002). This secretion cm of each tree trunk was coated with a layer of is often deposited on plant surfaces where imsticky material (Tanglefoot®) applied from an matures have crawled, leaving a trail. Larvae aerosol dispenser. Similarly, the sticky material complete 5 instars before seeking pupation sites was also applied to the surface of the plastic in a in the soil. When considering the heights of their 2 m radius around each tree. Searches for larvae host plants, we questioned how O. vitisoa larvae trapped on the sticky barrier at tree bases or in disperse from their feeding sites in the upper the sticky coating on the plastic commenced 24 h portions of the canopy to pupation substrates on later and were conducted twice daily (at 8 a.m. the forest floor. and 5 p.m.) for 2 wk. No larvae were found on the Two methods were used to investigate this basal barriers and no secretion trails led to these question. The first involved direct observation of areas. In contrast, 43 larvae were recovered on the forest floor and tree trunks for dispersing O. the plastic sheeting (86% recovery). Larvae were vitiosa larvae during the winter mo when larval found at both sampling times during the obser densities are highest. Observations were made at vation period, indicating that larval dispersal is 2 long-term M. quinquenervia research sites in not synchronized. Not surprisingly, larvae were Florida, one near Lake Okeechobee (N 26.784° W uniformly located within the drip line of study -80.950°) and the other along the Everglades buftrees. A small (~2cm) irregularly shaped yellow fer strip (N 26.050° W -80.433°). Both sites were secretion surrounded each larva, indicating the dominated by large M. quinquenervia trees growimpact point. The remaining 7 larvae were not ing in organic soils covered with thick layers of recovered and may have succumbed to predation leaf litter. A 2 h search was made during the last (Christensen et al. 2011). wk of Jan of both 2001 and 2002 by haphazardly Freefall of coleopteran larvae in search of suit reviewing stands for larvae moving down tree able pupation sites is a commonly assumed, but trunks or falling from the canopies. In addition, rarely observed, pathway for reaching the forest observers inspected trunks for dispersing larvae floor (Clark et al. 1998). Selection pressures that or trails of yellow secretions deposited by larvae may have influenced the evolution of this behavior while migrating downwards. These survey efforts include reducing the time required to reach pupa resulted in no evidence of larval dispersal via tion sites. Dropping limits energy expended in this this mode. Similarly, no direct observations were effort versus climbing down tree trunks. Expedit made of larvae dropping from M. quinquenervia ing larval dispersal to pupation sites also reduces canopies. By following the sound of objects strikexposure to natural enemies. Although O. vitiosa ing the ground, however, observers were occasionlarvae can survive the fall from M. quinquenervia ally able to locate fifth instars on the forest floor canopies, their mortality rates as a result of these

Role of axis reversal from the short‐shoot to long‐shoot habit for crown maintenance in slow‐growing Betula maximowicziana trees

Branch growth and its spatial arrangement determine crown architecture, leaf display, and, thus, the productivity of trees. Branch axes elongate by the sequential production of shoots with differing morphology and function, such as short shoots and long shoots. This study investigated ontogenetic changes in axis growth in Betula maximowicziana and quantified the role of axis reversal between the short-shoot and long-shoot habits, particularly reversal from the short-shoot to the long-shoot habit. From 8 trees with varying levels of growth vigor, 716 branch axes forming the basic crown architecture were sampled. Past growth of the branch axes was reconstructed from leaf and bud scale scars and compared between slow-growing and vigorously growing trees. Branch axes reversed more frequently between the long- and short-shoot habits in slow-growing trees than in vigorously growing trees. Short-shoot-origin axes that reversed to the long-shoot habit lived for longer periods and grew larger than axes that remained in the short-shoot habit. Short-shoot-origin axes reversed as they grew away from branch apices, typically >6 yr after they had originated. Reversal of short-shoot-origin axes to the long-shoot habit is an endogenous growth process of trees with reduced vigor. Like epicormic branching, the reversal may contribute to the maintenance of productivity of large old trees by prolonging axis longevity and filling the inner part of the crown. This study presents an ontogenetic change in branch growth, which broadens our perspectives on the growth and survival of long-living trees.

Morphology of immature stages of Dohrniphora cornuta (Bigot) (Diptera: Phoridae)

Morphology of all larval instars and puparium of Dohrniphora cornuta (Bigot), a most common phorid fly species indoors in China, is presented using scanning electron microscopy. The first instar larva was composed of 12 segments, each of segments 3-11 with six slender tubercles situated dorsally, dorsolaterally, and laterally in transverse row. These tubercles divided into two segments, of which the basal one was smooth, and the brush-shaped distal one was comprised of a cluster of fine spines. Antennae and maxillary palp complex were visible. Two slits could be seen at the posterior spiracle. Besides the presence of anterior spiracle, the tubercles of second instar became stouter than those of first instar and were covered by numerous long bristles from the base to top. The posterior spiracle contained four slits. Third larval instar was similar to second instar. The bubble membrane comprised of ≈120 globules with a pointed tip on their top presented at the segment 5 of third instar larvae. Puparia showed a retracted cephalic region and a pair of distinct pupal respiratory horns on the dorsum. The respiratory horns were long and bore numerous branches from base to apex. The apex of branch with two longitudinal slits was relatively broad and curled dorsally.

Pilidiella tibouchinae sp. nov. associated with foliage blight of Tibouchina granulosa (quaresmeira) in Brazil

Tibouchina granulosa (Melastomataceae), Brazilian glorytree (Brazilian common name - quaresmeira), a common tree of the Atlantic Forest of Brazil, is widely used as an ornamental for its violet or pink blossoms. Little is known about fungal diseases affecting this species, although these represent a known limitation for its cultivation in nurseries. Among these there is a foliage blight that occurs in combination with distortion of branch apices and die-back. A consistent association of a species of Pilidiella with the diseased tissues was observed. The fungus was isolated in pure culture and based on its morphology and DNA phylogeny, we conclude that it represents a new species, for which the name Pilidiella tibouchinae is introduced.

Testing the equi-resistance principle of the xylem transport system in a small ash tree: empirical support from anatomical analyses

In plants, water flows from roots to leaves through a complex network of xylem conduits. The xylem architecture is characterized by the conduit enlargement towards the stem base and the multiplication of conduits near the apices of lateral branches. The xylem architecture of a small ash tree was analysed by measuring the vessel hydraulic diameter (Dh) and number (N) at different heights along the stem and branches. Along the stem, Dh and N increased from the apex to the point of crown insertion. Below, Dh and N decreased and remained constant, respectively. In branches, the Dh and N of apices increased with distance from the ground (PL) (P < 0.001 and P < 0.0001, respectively), indicating that apical resistance (R(APEX)) becomes lower in the most peripheral branches (P < 0.0001). At the level of branch nodes along the stem, the total conductive area (AC) of the stem and branches just above the node was 11% higher than that of the stem just below the node (P = 0.024), whereas the conductivity (Kh) remained invariant above and below (P = 0.76). The difference in AC (ΔAC) between the branches and stem above each node increased with the distance of the node position from the stem apex (L). The xylem architecture of the analysed tree was characterized by anatomical modifications likely aimed at equilibrating the different path length effects on the hydraulic resistance of the different branches. Conduit tapering and multiplication seem to play a crucial role for the achievement of equal hydraulic resistance of all the leaves in the crown.

Distribution of the lime leafminer Phyllonorycter issikii (Lepidoptera, Gracillariidae) in natural stands

The spatial distribution of the lime leafminer Phyllonorycter issikii was studied in natural stands. The number of mines increased with shading of host-plant leaves. The maximum density of the miner was found in closed lime and spruce forests. The number of mines increased vertically from the tree top to its butt and horizontally, from the apex of branches to their base.

A new species of Sauvagesia (Ochnaceae) from the Espinhaço range of Minas Gerais, Brazil

The new species Sauvagesia lagevianae is described, illustrated, and discussed. This species is morphologically similar to S. glandulosa, but can be easily distinguished by its unique umbellate inflorescence arising from a distinct peduncle on the branch apex. Other diagnostic characters to identify S. lagevianae are the nodding, campanulate corollas, bi-apiculate anthers, and the small and strongly imbricate leaves with fewer and ascending secondary veins. The new species is only known from two nearby localities of “campo rupestre” vegetation in the Espinhaco range of Minas Gerais, Brazil.

Partial shoot reiteration in Wollemia nobilis (Araucariaceae) does not arise from ‘axillary meristems’

Conifers are characterized by the paucity of axillary buds which in dicotyledonous trees usually occur at every node. To compensate, conifers also produce 'axillary meristems', which may be stimulated to late development. In juvenile material of Wollemia nobilis (Araucariaceae: Massart's model) first-order (plagiotropic) branches lack both axillary buds and, seemingly, axillary meristems. This contrasts with orthotropic (trunk) axes, which produce branches, either within the terminal bud or as reiterated orthotropic axes originating from axillary meristems. However, plagiotropic axes do produce branches if they are decapitated. This study investigated how this can occur if axillary meristems are not the source. The terminal buds of a series of plagiotropic branches on juvenile trees were decapitated in order to generate axillary shoots. Shoots were culled at about weekly intervals to obtain stages in lateral shoot development. Serial sections were cut with a sliding microtome from the distal end of each sample and scanned sequentially for evidence of axillary meristems and early bud development. Anatomical search produced no clear evidence of pre-existing axillary meristems but did reveal stages of bud initiation. Buds were initiated in a group of small starch-rich cortical cells. Further development involved de-differentiation of these small cells and the development of contrasting outer and inner regions. The outer part becomes meristematic and organizes the apex of the new branch. The inner part develops a callus-like tissue of vacuolated cells within which vascular cambia are developed. This kind of insertion of a branch on the parent axis seems not to have been described before. Axillary meristems in Wollemia characterize the leaf axils of trunk axes so that the origin of reiterated shoots is clear. Plagiotropic axes seemingly lack axillary meristems but still produce axillary branches by distinctive developmental processes. These observations demonstrate limited understanding of branch initiation in trees generally.

Location of the stigmatic areas in Mutisia speciosa Aiton ex Hook. a new floral feature in Asteraceae

In Mutisieae species, the style branches are described as short and the stigmatic areas cover the inside of the style branches. As shown in preliminary observations, the Mutisia speciosa florets had long style branches (7 mm), bifurcate only at the apex (about 1.5 mm) and juxtaposed along the remaining length. The objective was to locate the stigmatic areas in M. speciosa. For this purpose, neutral red, 3% hydrogen peroxide and hand pollinations were used. For the pollinations, florets with cut apical portion of the branches (about 2 mm) and florets with intact branches were used. In the first group of florets, the pollen was deposited along the margins of the juxtaposed branches (about 5 mm), and in the second, the pollen was ventrally deposited on the bifurcated apical portion. Some of these florets were left on the plant until fruiting and others were analyzed under a fluorescence microscope to check pollen tube growth. The neutral red test defined two ventro-marginal bands fused at the apex of each style branch, consisting of papillose cells. Intense bubbling in the hydrogen peroxide test showed that only the bands are receptive. The pollinations resulted in fruit sets and growth of pollen tubes, confirming that the bands are receptive along their entire length. This result is new and indicates the need for further studies on the floral biology of tropical Asteraceae species to improve the understanding of their reproductive attributes.

Morphological phylogenetics of Puya subgenus Puya (Bromeliaceae)

Puya, a large genus mostly from South America, has been taxonomically divided into two subgenera: Puyopsis and Puya. The latter includes only eight species distributed mainly in Chile, extending to Argentina, Bolivia, and Peru. The species of subgenus Puya are recognized by the presence of a sterile apex of the inflorescence branches, whereas those of subgenus Puyopsis have fertile flowers all along the branches. The objectives of this article were to determine whether this diagnostic character was synapomorphic for subgenus Puya, and to explore the relationships between its species. Parsimony analyses were performed for 43 taxa and 93 morphological characters, 87 of which were discrete and six continuous. In the analysis that included all characters, a single most parsimonious tree was found that supported subgenus Puya by two synapomorphic character states, including the diagnostic character of a sterile inflorescence branch apex and a blooming pattern in which flowers open gradually from base to apex. The trees were better supported when the continuous characters were included. Further studies are suggested to resolve the infrageneric classification of Puya and the relationships of the species belonging to subgenus Puya.

Molecular evidence for Chondrophycus poiteaui var. gemmiferus comb. et stat. nov. (Ceramiales, Rhodophyta) from the Mexican Caribbean Sea: implications for the taxonomy of the Laurencia complex

Abstract Molecular studies were carried out on Chondrophycus gemmiferus and C. poiteaui (Rhodomelaceae) from the Mexican Caribbean Sea. These species are morphologically related, but differ mainly in the presence of the apiculate projection of epidermal cells near the apices of branches. Both species belong to Chondrophycus, as indicated by the presence of two periaxial cells per axial segment and a 90° arrangement of tetrasporangia, but share characteristics with Laurencia species (e.g., presence of secondary pit connections between adjacent epidermal cells). The phylogenetic position of these species was inferred by an analysis of chloroplast-encoded rbcL gene sequences of 21 taxa, using two members of the Rhodomelaceae and two of the Ceramiaceae as outgroups. The results corroborate the taxonomy of the Laurencia complex, which comprises the genera Laurencia, Chondrophycus and Osmundea, and indicate that rbcL provides an adequate phylogenetic signal to study the intergeneric and interspecific relationships within the complex. In spite of this, relationships within the clade formed by C. gemmiferus and C. poiteaui were not resolved by any analysis because of the low level of genetic variation between their rbcL sequences (0.01–0.02%). On the basis of both molecular data and morphological similarities, we concluded that C. gemmiferus should be considered as a variety of C. poiteaui and the following new combination is proposed: Chondrophycus poiteaui var. gemmiferus (Harvey) comb. et stat. nov.

Two species of Dasya (Ceramiales, Rhodophyta) from Bonin Islands, southern Japan, with the description of Dasya boninensis sp. nov.

SUMMARYTwo species of Dasya in the Dasyaceae (Ceramiales, Rhodophyta) are reported from Bonin Islands, southern Japan. Dasya murrayana Abbott et Millar, new to Japan, is characterized by the following set of features: the tufted habit (up to 30 erect axes developing from a basal disc), small‐sized (6–10 mm high and 350–500 μm in diameter in the middle region), thinly but completely corticated axes, rigid and incurved pseudolaterals forming corymbose heads at the apices of axes and branches, the absence of adventitious monosiphonous filaments, a large number of tetrasporangial stichidia and spermatangial branches per fertile pseudolateral and slender spermatangial branches (35–45 μm in diameter). Dasya boninensis Masuda, Kurihara et Kogame, sp. nov. is characterized by short but thick (10–30 mm high and 600–1000 μm in diameter at the middle portion), heavily corticated axes, indistinct pericentral cells except for the upper portion in transverse sections, soft, straight pseudolaterals and adventitious monosiphonous filaments densely covering the axis and branches, a small number of tetrasporangial stichidia and spermatangial branches per fertile pseudolateral, thick spermatangial branches (65–90 μm in diameter), and short‐necked cystocarps. A dichotomous key to the taxa found in Japanese waters is given.

Physiological and ecological implications of adaptive reiteration as a mechanism for crown maintenance and longevity

Reiteration is the process whereby architectural units are replicated within a tree. Both immediate (from apical buds) and delayed (from suppressed or adventitious buds) reiteration can be seen in many tree species where architectural units ranging from clusters of shoots to entire branches and stems are replicated. In large old trees and suppressed trees, delayed reiteration occurs without an obvious external stimulus such as defoliation or traumatic loss of the branch apex. This suggests that, in trees that are growth-limited, reiteration is an adaptive mechanism for crown maintenance. We discuss theories about the aging process and how delayed adaptive reiteration may help maintain crown productivity and increase longevity. These include: (1) reducing the respiration/photosynthesis ratio; (2) increasing hydraulic conductance to newly developing foliage; (3) reducing nutrient loss from the tree; and (4) rejuvenating the apical meristem. The ability to reiterate various architectural units may contribute to increasing lifetime reproductive output by prolonging tree longevity. Further studies on the physiological and ecological implications of reiteration are needed to understand its adaptive significance in the life history of trees.

Structure and development of air bladders in Fucus and Ascophyllum (Fucales, Phaeophyceae)

D.J. Garbary, A. Brackenbury, A.M. McLean and D. Morrison. 2006. Structure and development of air bladders in Fucus and Ascophyllum (Fucales, Phaeophyceae). Phycologia 45: 557–566. DOI: 10.2216/05-62.1Using optical and scanning electron microscopy the structure and development of the air bladders of Fucus vesiculosus and Ascophyllum nodosum are described in an ecological context from Nova Scotia. The air bladders consist of a bladder wall that surrounds an air space traversed by a complex network of white fibers. Microscopically, the fibers consist of branched, uniseriate filaments in which cells are uninucleate with a thin cytoplasmic region and thick cell walls. The filaments are formed from irregular sheets of cells consisting of a cluster of filaments surrounded by mucilaginous material. These become detached from the surrounding material as the bladder inflates. In very large bladders the filamentous network can be broken and leave a felt-like mat on the bladder wall. Bladders of F. vesiculosus have thinner walls than A. nodosum (300 µm vs 500 µm, respectively). In addition, successively older bladders in the former species become damaged and lose their structural integrity, whereas this does not occur in the latter species. After 10 years of age, almost 90% of bladders in A. nodosum are still intact with no change between year 1 and year 10. In the shorter-lived F. vesiculosus, more than 50% of the visible bladders have been damaged, and only one or two bladders remain intact near the apices of branches. We conclude that the bladders of A. nodosum are able to undergo repair when the bladder wall is punctured, whereas those of F. vesiculosus do not.

A class Vb chitin synthase in Colletotrichum graminicola is localized in the growing tips of multiple cell types, in nascent septa, and during septum conversion to an end wall after hyphal breakage

Previous complementation of a chitin synthase class Vb null mutant (Colletotrichum graminicola chsA) indicated that the encoded protein is responsible for approximately 30% of the conidial chitin, is essential for conidial wall strength in media with high water potential, and contributes to strength of hyphal tips. We complemented a chsA null mutant with chsA fused to the green-fluorescent protein (sgfp) gene driven by a heterologous constitutively expressed promoter. Comparisons of the strain with the ectopic chsA-sgfp to the wild type indicated that ChsA-sGFP serves the same biological functions as ChsA in that like the wild type, the chsADelta chsA::sgfp (EC) had conidia that did not explode and hyphal tips that did not swell. Confocal microscopy of ChsA-sGFP (EC) cells stained with the membrane stain FM 4-64 (N-(3-triethylammoniumpropyl)-4-(6-(4-(diethylamino)phenyl)hexatrienyl)pyridinium dibromide) indicated that ChsA is localized in the plasma membrane of the following: growing apices of hyphal branches, conidiophores, and falcate and oval conidia; in nascent septa; and in septa that are being converted to an end wall after hyphal breakage. The data support the hypothesis that chsA either directly or indirectly encodes the information for its localization, that ChsA is localized in the plasma membrane, and that the class Vb enzyme produces chitin synthase in multiple cells and after wall breakage.

Herbivory alters resource allocation and compensation in the invasive tree Melaleuca quinquenervia

Abstract. 1. Plants may compensate for the effects of herbivory, especially under favourable growing conditions, limited competition, and minimal top‐down regulation. These conditions characterise many disturbed wetlands dominated by introduced plants, implying that exotic, invasive weeds in these systems should exhibit strong compensatory responses.2. The Australian native Melaleuca quinquenervia is highly invasive in the Florida Everglades, U.S.A., where it experiences limited competition or herbivory from native species, making it a likely candidate for compensation. The introduced biological control agent Oxyops vitiosa feeds exclusively on the seasonal flushes of developing foliage at branch apices, which represents ≈15% of the total foliar biomass.3. The hypothesis that M. quinquenervia compensates for folivory by O. vitiosa was tested in a series of field‐based experiments. Trees experiencing folivory over four consecutive years maintained similar levels of foliar biomass after attack yet possessed twice the number of leaf‐bearing terminal stems as undamaged trees. The biomass of these stems was similar among attacked and unattacked trees, indicating that herbivore‐damaged trees produce greater quantities of smaller terminal branches. However, undamaged trees were 36 times more likely to reproduce than herbivore‐damaged trees.4. In a separate herbivore exclusion study, a single bout of herbivory on previously undamaged M. quinquenervia trees caused an 80% reduction in reproductive structures the following season. Herbivore‐damaged trees also possessed 54% fewer fruits than undamaged trees. An increase in the herbivory frequency (two bouts per year) or magnitude (100% simulated herbivory) did not result in a further reduction in fitness.5. It has been concluded that M. quinquenervia partially compensates for herbivory by producing new stems and replacing foliage, but this compensation results in a substantial reduction in reproduction.

Comparison of gene expression in trap cells and vegetative hyphae of the nematophagous fungus Monacrosporium haptotylum

Nematode-trapping fungi enter the parasitic stage by developing specific morphological structures called traps. The global patterns of gene expression in traps and mycelium of the fungus Monacrosporium haptotylum were compared. The trap of this fungus is a unicellular spherical structure called the knob, which develops on the apex of a hyphal branch. RNA was isolated from knobs and mycelium and hybridized to a cDNA array containing probes of 2822 EST clones of M. haptotylum. Despite the fact that the knobs and mycelium were grown in the same medium, there were substantial differences in the patterns of genes expressed in the two cell types. In total, 23.3 % (657 of 2822) of the putative genes were differentially expressed in knobs versus mycelium. Several of these genes displayed sequence similarities to genes known to be involved in regulating morphogenesis and cell polarity in fungi. Among them were several putative homologues for small GTPases, such as rho1, rac1 and ras1, and a rho GDP dissociation inhibitor (rdi1). Several homologues to genes involved in stress response, protein synthesis and protein degradation, transcription, and carbon metabolism were also differentially expressed. In the last category, a glycogen phosphorylase (gph1) gene homologue, one of the most upregulated genes in the knobs as compared to mycelium, was characterized. A number of the genes that were differentially expressed in trap cells are also known to be regulated during the development of infection structures in plant-pathogenic fungi. Among them, a gas1 (mas3) gene homologue (designated gks1), which is specifically expressed in appressoria of the rice blast fungus, was characterized.

Macronutrientes em folhas e frutos de cultivares de café arábica de porte baixo

O presente trabalho teve como objetivo avaliar a mobilização de macronutrientes de folhas para frutos em diferentes cultivares de café arábica, através de análises foliares periódicas. O experimento foi plantado em 1994 em solo Rhodic Hapludox, em Campinas Estado de São Paulo, Brasil. Foram coletadas folhas de ramos plagiotrópicos com frutos, o terceiro par a partir do ápice, para determinação de macronutrientes, em dezembro de 2002, fevereiro e maio de 2003. A colheita do experimento e a amostragem de frutos para análise química ocorreram em junho de 2003. Houve decréscimo no teor dos macronutrientes nas folhas do cafeeiro, durante a estação de crescimento do fruto, a exceção do cálcio que apresentou aumento, observando-se maior evidencia para o potássio. As cultivares de alta produtividade mostraram concentrações de macronutrientes ligeiramente superiores às de média produtividade. A diferença mais marcante ocorreu para o cálcio que acumulou mais nas ccultivares mais produtivas. Na casca e no grão de café, pela análise estatística, não houve diferença significativa na composição química entre as cultivares, à exceção para o cálcio presente na casca. Verificou-se uma relação inversa entre produtividade e o índice relativo de remobilização de nutrientes das folhas. Cultivares mais produtivas conseguiram produzir a mesma quantidade de matéria seca de grãos com valores mais baixos de remobilização dos nutrientes N, P e K das folhas dos cafeeiro.

Ultrastructure of trichoblasts in the red alga Osmundea spectabilis var. spectabilis (Rhodomelaceae, Ceramiales)

The apex of the tetrasporangial branches of Osmundea spectabilis var. spectabilis (= Laurencia spectabilis var. spectabilis) exhibits cavities in which tufts of multicellular trichoblasts occur. Trichoblast development in Osmundea spectabilis var. spectabilis begins with the differentiation of an epidermal cell within the crypt. This cell differentiates into a trichoblast mother cell (TMC). The TMC divides to form a two-celled incipient trichoblast. Successive periclinal divisions of the apical cell of the young trichoblast result in the formation of a multicellular developing trichoblast. With the exception of the apical cell all trichoblast cells are at the same developmental stage. They possess a large nucleus, abundant plastids with peripheral and some internal thylakoids and dictyosomes. Daughter chloroplasts result from one constriction or multiple fission of a single chloroplast. Dictyosomal cisternae and mucilage sacs contribute material to wall formation. Each differentiating trichoblast cell is surrounded by a bi-layered wall. The outer wall layer represents the trichoblast mother cell wall and the inner wall layer is the trichoblast cell wall. Mature trichoblast cells have thin walls, probably as a consequence of mucilage extrusion, the most likely function of trichoblasts in Osmundea.

Susceptibility of cypress seedlings to the eriophyoid mite Trisetacus juniperinus.

In Italian nurseries and young groves of evergreen cypress (Cupressus sempervirens L.), the eriophyoid mite Trisetacus juniperinus (Nal.) is considered a very serious pest. A rating system of damage symptoms was developed to investigate the susceptibility of different cypress seedling families to the mite. Based on this system, the seedlings were evaluated for three years in the nursery and in two field locations after transplanting. Data obtained in the nursery allowed the cypress families to be allocated to at least two different levels of susceptibility. These levels of susceptibility were generally also maintained in the field. However, the environmental conditions of the two transplanting localities significantly affected the susceptibility of each family. In all families, scores for each of the damage categories were strongly correlated positively to each other and negatively with the average increment in the height of plant over the duration of the field experiment. Assessment of the intensity of the symptoms peculiar to damage category A (buds enlarged, deformed, russet and/or branch apex folded) was sufficient to give the same susceptibility evaluation as if data for all damage categories were used. The evaluation of susceptibility on the basis of injury pattern may return very useful information for selection and certification of families of known susceptibility to eriophyoid mites.