Vicente Haroldo de Figueiredo Moraes

Rubber agroforests at the Tapajós river, Brazilian Amazon: environmentally benign land use systems in an old forest frontier region

Scientific and public attention concerned with natural rubber (Hevea brasiliensis) production in the Amazon has focused on the high-tech practice of double-grafted, leaf blight resistant and high-yielding rubber clones on the one hand, and the low-tech practice of extractive use of natural rubber stands on the other. The intermediate, traditional practice of enriching slash-and-burn plots with rubber trees and managing them in a secondary forest environment, in association with other timber and non-timber species, has largely been overlooked. We present results from a survey of 51 farmer families conducted on the eastern bank of the Tapajos river in the central Brazilian Amazon, focusing on the population zone of the Tapajos National Forest and its northern vicinity. Actively managed rubber agroforests were most common on the sandy river banks and on humus- and clay-rich and ferralitic soils near the edge of the plateau at a few kilometers from the river. There was a gradient in management intensity between the proximity of the villages at the river, where rubber was often a component of homegardens, and the distant groves on the plateau, which often resembled secondary forests. The spatial separation of access to water at the river and more fertile soils on the plateau, the historical practice of abandoning the rubber groves at times of low rubber prices, and a substantial risk of losing plantations to abiotic and biotic threats, especially fire, are identified as factors that have presumably favored the development of agroforests with low management intensity in the region. Although about half of the interviewed farmers expressed a preference for weeded plantations, almost 90% of them extracted vegetal products other than rubber from the agroforests or used them as hunting grounds, and 80% believed that associated vegetation had no negative influence on rubber yields. The often good health of old rubber trees in Amazonian agroforests is explained with lower pressure from root rots, the periodic abandonment and especially a tapping technique that is well adapted to a moist forest environment.

Relação entre a flexibilidade do caule de seringueira e a carência de boro

In some boron deficient crops, less lignin build up has been observed in xylem elements, which have thinner and weaker walls and also a lower translocation of carbohydrates from leaves to other plant organs. In order to detect these anatomical changes in the xylem of very flexible stem of rubber trees (Hevea spp.) displaying boron deficiency symptoms, a comparative anatomical study was made of the wall thickness, the degree of lignin and cellulose deposition as well as starch grain concentration in the wood parenchyma. No difference was found in thickness and lignin deposition in the walls of xylem elements of normal and boron deficient plants. However, the middle lamella of deficient plants was much thinner, with less intensive staining, reflecting a low supply of calcium pectate, which promotes the adhesion between cells and has its synthesis impaired by boron deficiency. The cause of the flexibility was considered to be due to a lower cohesion between cells.

Cyanogenesis and the onset of tapping panel dryness in rubber tree

O objetivo deste trabalho foi estudar a influencia da cianogenese no estabelecimento do secamento do painel de sangria (TPD) e os aspectos fisiologicos e histologicos do floema secundario do tronco (painel de sangria) em seringueira (Hevea spp.). Dois compostos cianogenicos, linamarina e KCN, foram aplicados separadamente na casca do tronco de arvores sadias de dois clones adultos (Fx 4098 e Fx 3899). Alteracoes na histologia, potencial de pressao de latex (ΨP) e potencial cianogenico (HCNp) foram monitoradas. Alem disso, os niveis HCNp foram determinados em plantas afetadas por TPD, em ambos os clones. A aplicacao de linamarina ou KCN em plantas saudaveis causou reducao em ΨP e formacao de tilosoides associados a coagulacao do latex in situ. O clone Fx 4098 apresentou o maior nivel de HCNp, e respostas mais intensas e rapidas aos compostos cianogenicos. Plantas com sintomas de TPD tem maior HCNp de que as sadias. Como as alteracoes histologicas observadas sao reconhecidos marcadores estruturais precoces de TPD, pode-se inferir que a liberacao excessiva de cianeto pode induzi-las em clones de seringueira sucetiveis

Assessment of rubber tree panels under crowns resistant to South American leaf blight

(3) In memoriam Abstract - The objective of this work was to assess the performance of panel clones under crowns resistant to South American leaf blight (Microcyclus ulei). The experiment was carried out with 18 panel clones crown-budded with Hevea pauciflora x H. guianensis, in a Xanthic Ferralsol (Oxisol) in Manaus, AM, Brazil. The following parameters were evaluated: dry rubber yield, plant nutritional status, and anatomical and physiological characteristics of the latex vessels. In the first three years of evaluation, the panel clones IAN 2878, IAN 2903, CNS AM 7905, CNS AM 7905 P1, and PB 28/59 showed the highest dry rubber yield potential, while the clones IAN 6158, IAN 6590, and IAN 6515 should not be recommended for crown budding. Higher potassium and copper foliar content in panel clones were associated to an increase in dry rubber yield. The simultaneous evaluation of anatomical and physiological characteristics of latex is fundamental for the selection of panel clones in the Amazon region. Crown budding is an efficient technology for South American leaf blight management in endemic regions.

Reaction of cassava leaves to Microcyclus ulei, causal agent of South American leaf blight of rubber tree

Young cassava (Manihot esculenta) leaves inoculated with conidiospores or treated with an autoclaved conidiospore suspension of Microcyclus ulei, a pathogen to several species of the genus Hevea, react strongly with induction of blue fluorescing compounds in the contact areas, demonstrating local cell growth and irregular tissue formation, leaf distortion and, occasionally, leaf abscission. Restricted hyphal growth also occurs in areas inoculated with living spores, but without formation of new conidiospores. The plant reaction resembles a complex resistance reaction to a biotrophic pathogen rather than a typical non host defense reaction.

Aplicação de KCN e linamarina e a incompatibilidade de enxertia por translocação no clone de seringueira IPA 1

To further evaluate previous indirect evidences of a role for the rubber tree cyanogenic glycosides, of which the main component is linamarin, this study evaluated the translocation incompatibility of the clone IPA 1 (Hevea brasiliensis) with budded crowns of clones of other species. Solutions of KCN were first applied, which caused rapid coagulation of the latex in the laticiphers of IPA 1, at very low concentrations, the same effect being observed in Fx 4098 at higher concentrations. The clone Fx 3864 presented no effect, only a slight reduction of the latex flow at the highest concentration. With linamarin solutions the necrosis, again preceded by latex coagulation, spread longer along the stem, indicating a higher mobility of linamarin than KCN. The clone IPA 1 behaved again sensitive to the lower concentrations of linamarin, with the higher concentrations causing the same effects on Fx 4098 and no effect on Fx 3864. With linamarin a build up of free HCN was detected in the bark of IPA 1. The incompatibility with IPA 1 is caused by the translocation of cianogenic glycosides from the budded crowns to the stem which is deprived of sufficient capacity to remove the HCN liberated by the hydrolisis of cyanogenic glicosides, while the Fx 3864 presented a very efficient detoxifying capacity.

Emissão de fluxos foliares, floração e ciclagem de nutrientes em clones de copa de Hevea pauciflora

The leaf phenology has been used as an important characteristic in the selection of Hevea spp. clones, while the nutrient content in litter is a good indicator of nutrient cycling. The objective of this study was to verify the effect of frequency of emission of fluxes of leaves and flowers in crown of Hevea pauciflora, nutritional status and quality of litter. Fifteen plants of ten-year-old of each clones (CNS G 112, CNS G 124 and CBA 2) were evaluated. In tropical Amazonia edaphoclimatic conditions, the leaf emergence and flowering of H. pauciflora occurs with higher intensity in the second semester (beginning of rainy season). The H. pauciflora has higher quantity of litter than the primary forest, and the foliar concentrations of 22.18 g kg-1 of N, 1.47 g kg-1 of P, 5.77 g kg-1 of K, 3.79 g kg-1 de Ca, 2.09 g kg-1 of Mg, 16.15 mg kg-1 of B, 6.14 mg kg-1 of Cu, 53.87 mg kg-1 of Fe, 66.20 mg kg-1 of Mn e 48.44 mg kg-1 of Zn can be utilized as reference for this specie of rubber tree.

Translocation of cyanogenic glycosides in rubber tree crown clones resistant to South American leaf blight

(3) In memoriam Abstract - The objective of this work was to assess the possible transport of cyanogenic glycosides from leaves of rubber tree crown clones (Hevea spp.) resistant to South American leaf blight to the trunk of the panel clones in which they are grafted. The cyanogenic potential (HCNp) of the crown clones was determined in the trunk bark, at different distances from the cambium, and its gradient was evaluated along the trunk. The correlation between the HCNp of the crown leaves and that of the trunk bark was also evaluated. HCNp determined in leaves showed a wide range variation in the species studied as crown clones, with the lowest values registered in H. nitida clones, and the highest ones in H. rigidifolia. In the trunk bark, the tissue layer nearer the cambium showed higher HCNp values. A positive basipetal gradient was observed along the trunk, i.e., there was an increase in HCNp from the apex toward the base. Although the grafted crowns influence the cyanogenic potential of the trunk bark of panel clones, the absence of correlation between the HCNp of the leaves and trunk bark indicates that the crown is not the main source of the cyanogenic glycosides found in the trunk.

Relationship between cyanogenesis and latex stability on tapping panel dryness in rubber trunk girth

The presence of high cyanogenic glycoside concentrations may predispose plant to the tapping panel dryness (TPD). This study aimed to verify the involvement of cyanogenesis in the reduction of latex stability and in the establishment of TPD. The following parameters were evaluated in rubber tree trunk bark: concentration of cyanogenic glycosides with determination of cyanogenic potential (HCNp) and latex stability with lutoid bursting index (LBI). The study of the relationship between cyanogenesis and TPD was performed by semiquantitative comparison of hydrogen cyanide (HCN) gas released from the trunk bark under the following conditions: without (0%) and with (100%) TPD. The positive correlations between HCNp values and LBI indicate that cyanogenic glycosides present in the bark reduce latex stability, resulting in low yield due to the short duration of flow during tapping. The largest amount of HCN released by trunk bark tissues when the plant exhibits TPD symptoms strengthens the evidence of the involvement of this compound in the establishment of this condition.

Análise quantitativa do sistema primário de laticíferos do caule de plantas jovens de clone e pés-francos de seringueira

O objetivo deste trabalho foi comparar a frequencia de laticiferos do sistema primario do caule com o numero de aneis de laticiferos de plantas jovens de clones e pes-franco de seringueira (Hevea spp.), como contribuicao a interpretacao dos resultados dos testes precoces de producao. Nos pes-franco foi encontrada baixa frequencia de laticiferos primarios nos quatro primeiros entrenos, enquanto nos clones ha um numero significativamente mais alto desse tipo de laticiferos a partir do primeiro lancamento. Como os laticiferos primarios tem origem no meristema subapical, essas diferencas quantitativas sao determinadas pelo tamanho da gema apical, que no primeiro lancamento dos clones e mais de tres vezes superior a do primeiro lancamento (epicotilo) dos pes-franco e mantem-se significativamente maior no segundo lancamento. Grande parte da producao de borracha, dos testes precoces de plantas de clones com cerca de um ano, provem, portanto, do sistema primario, que ocupa as camadas mais externas da casca e e expelido das plantas com mais de tres anos. Tal fato determina a falta de correlacao entre os resultados do miniteste de producao de clones e os do teste HMM, feito em plantas com cerca de tres anos. Por outro lado, tem sido registrada correlacao com o miniteste em plantas de pes-franco e o HMM em clones derivados desses pes-franco.