Effect of plant trichomes on the vertical migration of Haemonchus contortus infective larvae on five tropical forages

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Ovary peltate trichomes of Zeyheria montana (Bignoniaceae): Developmental ultrastructure and secretion in relation to function

center dot Background and Aims Nectar production in the Bignoniaceae species lacking a nectariferous functional disc is ascribed to trichomatic glands around the ovary base and/or on the inner corolla wall. Nevertheless, knowledge about the secretion and function of these glands is very incomplete. The purpose of this paper is to study, from a developmental viewpoint, the ultrastructure, histochemistry and secretory process of the peltate trichomes on the ovary of Zeyheria montana, a species in the Bignoniaceae which has a rudimentary disc.center dot Methods Samples of the gynoecium at various developmental stages were fixed and processed for light and electron microscopy. Histochemistry and cytochemistry tests were performed to examine the chemical composition of exudates. Thin layer chromatography was used to determine the presence of alkaloids and terpenes in gynoecium and fruit extracts, and in fresh nectar stored in the nectar chamber.center dot Key Results Peltate trichomes at different developmental stages appear side by side from floral budding up to pre-dispersal fruit. Large plastids with an extensive internal membrane system consisting of tubules filled with lipophilic material, abundant smooth endoplasmic reticulum, few Golgi bodies, lipophilic deposits in the smooth endoplasmic reticulum and mitochondria, and scattered cytoplasmic oil droplets are the main characteristics of mature head cells. The secretion which accumulates in the subcuticular space stains positively for hydrophilic and lipophilic substances, with lipids prevailing for fully peltate trichomes. Histochemistry and thin layer chromatography detected terpenes and alkaloids. Fehling's test to detect of sugars in the secretion was negative.center dot Conclusions the continuous presence and activity of peltate trichomes on the ovary of Z. montana from early budding through to flowering and fruiting set, and its main chemical components, alkaloids and terpenes, suggest that they serve a protective function and are not related to the floral nectar source or to improving nectar quality.

Effects of light intensity and temperature on Cylindrospermopsis raciborskii (Cyanobacteria) with straight and coiled trichomes: growth rate and morphology

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Morphology of trichomes in Tibouchina sect. Pleroma (D-Don) Cogn. (Melastomataceae)

The Melastomataceae display greater trichome diversity. Dr. Wurdack, in his Atlas of hairs, recognized 46 types of trichomes for the Neotropical Melastomataceae through the Scanning Electron Microscope (SEM), and referred 17 of them to the genus Tibouchina. The trichome morphology has been extensively used in the delimitation of the taxa in Melastomataceae, as well as in previous studies by Cogniaux, the monograph of Brazilian Melastomataceae published in 1885. The morphology of the trichomes was essential for the delimitation of several species in Tibouchina section Pleroma. The use of SEM provided the best characterization of the 15 different types of trichomes recognized among the 41 species examined. These were described based on the morphological appearance, both optical microscopy and scanning electron microscopy, and illustrated by scanning electron micrographs and photomicrographs.

ANTI-HERBIVORE PROTECTION BY MUTUALISTIC SPIDERS and THE ROLE of PLANT GLANDULAR TRICHOMES

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Plant glandular trichomes mediate protective mutualism in a spider-plant system

1. Although several species of Peucetia (Oxyopidae) live strictly in association with plants bearing glandular trichomes worldwide, to date little is known about whether these associations are mutualistic.2. In this study we manipulated the presence of Peucetia flava on the glandular plant Rhynchanthera dichotoma in the rainy and post-rain season, to test the strength of its effects on leaf, bud, and flower damage and plant reproductive output. In addition, we ran independent field experiments to examine whether these sticky structures improve spider fidelity to plants.3. Peucetia suppressed some species of foliar phytophages, but not others. Although spiders have reduced levels of leaf herbivory, this phenomenon was temporally conditional, i.e. occurred only in the post-rain but not in the rainy season. Floral herbivory was also reduced in the presence of spiders, but these predators did not affect plant fitness components.4. Plants that had their glandular trichomes removed retained fewer insects than those bearing such structures. Spiders remained longer on plants with glandular trichomes than on plants in which these structures had been removed. Isotopic analyses showed that spiders that fed on live and dead labelled flies adhered to the glandular hairs in similar proportions.5. Spiders incurred no costs to the plants, but can potentially increase individual plant fitness by reducing damage to reproductive tissues. Temporal conditionality probably occurred because plant productivity exceeded herbivore consumption, thus dampening top-down effects. Specialisation to live on glandular plants may have favoured scavenging behaviour in Peucetia, possibly an adaptation to periods of food scarcity.

Trichomes related to an unusual method of water retention and protection of the stem apex in an arid zone perennial species

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A scanning electron microscopy study of the seed and post-seminal development in Angelonia salicariifolia Bonpl. (Scrophulariaceae)

The external morphology of seeds and post-germination developmental stages of Angelonia salicariifolia Bonpl. (Scrophulariaceae) were investigated using scanning electron microscopy. Some structural features of the seed exotesta and seedling in Angelonia are presented for the first time and are of potential taxonomic value for this neotropical genus. The seeds are very small (0.9-1.7 mm long and 0.5-0.9 mm wide), ovate, with a reticulate-crested exotesta, reticules arranged uniformly in longitudinal rows, with a high density of microcilia-like projections on the cell wall of the reticule base and on the edge of the crests. The hilum is located beside the micropyle at the narrow end of the seed. Germination is epigeal. During germination the radicle develops, followed by elongation of the hypocotyl and primary root. At this stage dense root hairs develop on the lower part of the hypocotyl. The apical bud-located between the cotyledons-begins to develop after the cotyledons have unfolded. The cotyledons are equal in size, sessile and ovate. The seedlings have two types of trichomes, one characteristic of the cotyledons and first pair of leaves (glandular, sessile, four-celled head with quadrangular shape) and the other characteristic of the hypocotyl and epicotyl (stalked, erect, elongate and three-celled with dome-shaped unicellular head). (C) 2001 Annals of Botany Company.

Biochemical and histological characterization of tomato mutants

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Adult attractiveness and oviposition preference of Bemisia tabaci (Genn.) (Homoptera: Aleyrodidae) B-biotype in cotton genotypes

Considerada importante praga do algodoeiro, a mosca-branca Bemisia tabaci biótipo B pode através de sua alimentação, diminuir o vigor das plantas, trasmitir vírus e prejudicar a qualidade da fibra. Visando avaliar a resistência de genótipos de algodoeiro, Gossypium hirsutum (L.), à mosca-branca Bemisia tabaci biótipo B, realizaram-se testes de atratividade e não-preferência para oviposição, com e sem chance de escolha, em telado, a temperatura ambiente. Verificou-se baixa atratividade das plantas dos genótipos Fabrika, CNPA Ita 90, Makina, Coodetec 407 e IAC 01-639 CPA 02-24 a adultos dessa mosca-branca, o que pode representar um componente de resistência destes materiais genéticos ao inseto. Os genótipos BRS Aroeira, Coodetec 406, Fabrika e Coodetec 401 apresentaram resistência do tipo não-preferência para oviposição, nos testes com e sem chance de escolha. Os números de tricomas e de glândulas de gossipol por cm² não foram adequados para se avaliar a não-preferência para oviposição de adultos da mosca-branca em genótipos de algodoeiro.

Nonpreference of whitefly for oviposition in tomato genotypes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Tipos de tricomas em genótipos de Lycopersicon

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Resistência de genótipos de soja à mosca branca Bemisia tabaci (Genn.) biótipo B (Hemiptera: Aleyrodidae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Aspectos biológicos do ácaro Brevipalpus phoenicis vetor da leprose dos citros em plantas de buva (Conyza canadensis)

O ácaro Brevipalpus phoenicis, vetor da leprose dos citros, é uma espécie polífaga que tem ampla gama de hospedeiros alternativos nos pomares cítricos, nos quais se pode manter e/ou incrementar suas populações. O objetivo deste trabalho foi estudar a sobrevivência, a oviposição e o modo de alimentação do ácaro B. phoenicis em plantas de buva (Conyza canadensis) com diferentes tamanhos. Para avaliação da sobrevivência e oviposição do ácaro B. phoenicis, foi utilizado o delineamento estatístico inteiramente casualizado, com cinco tratamentos e doze repetições. Os tratamentos estudados foram: (1) secções de caules de plantas menores que 20 cm, (2) entre 21 e 50 cm, (3) entre 51 e 100 cm e (4) maiores que 101 cm de altura; e (5) secções de ramos de laranja. Dez fêmeas adultas de B. phoenicis, procedentes de uma criação-estoque, foram transferidas para cada secção de caule de buva e ramos de citros como testemunha. Avaliou-se a sobrevivência e a oviposição dos ácaros até 120 horas após a transferência. Alguns aspectos comportamentais do ácaro B. phoenicis foram fotomicrografados, utilizando-se microscópico eletrônico de varredura. Verificou-se que as plantas de maior altura de buva foram mais favoráveis à sobrevivência do ácaro B. phoenicis do que as de menor tamanho. Contudo, a quantidade de ovos postos pelo ácaro não diferiu em relação à altura das plantas de buva. Com base nas fotomicrografias, constatou-se a preferência do ácaro B. phoenicis por se alimentar na base dos tricomas presentes na superfície do caule da planta de buva, justificado, possivelmente, pela maior turgescência das células encontradas nessa região da planta. Esses resultados reforçam a importância do manejo de buva nos pomares cítricos, pois a sua presença no campo pode favorecer a sobrevivência e o desenvolvimento do ácaro B. phoenicis, servindo, portanto, como hospedeira alternativa, o que pode contribuir para a disseminação do ácaro e, consequentemente, da leprose nos pomares cítricos.

Influência de tricomas do algodoeiro sobre os aspectos biológicos e capacidade predatória de Chrysoperla externa (Hagen) alimentada com Aphis gossypii Glover

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)