Estado nutricional e teor de glicosídeos cianogênicos em plantas de seringueira

Abstract

A presença de altos teores de glicosídeos cianogênicos pode predispor a planta ao secamento de painel. O objetivo deste trabalho foi verificar a influência do estado nutricional na formação dos glicosídeos cianogênicos na seringueira, utilizando dois experimentos: a) jardim clonal com copa de híbridos de Hevea pauciflora e H. guianensis var. marginata (CPAA C 01) e de H. rigidifolia (CPAA C 81); e b) viveiro com H. brasiliensis. No jardim clonal foram coletadas ao acaso, folhas de 23 plantas, enquanto no viveiro, foi realizado experimento em delineamento inteiramente casualisado com cinco repetições, com tratamentos em esquema fatorial 2 x 4, com duas doses de nitrogênio -N (0,8 e 1,6%, fonte: uréia) e quatro de manganês -Mn (0, 10, 50 e 100 mg kg). Na seringueira, independentemente da idade e da espécie de Hevea, os teores foliares de N, Mn e clorofila tiveram correlação positiva com o HCNp das folhas novas e diagnóstico, podendo assim serem utilizados em futuros processos de seleção. Em concentrações baixas de N (0,8%), as doses de Mn influenciaram a absorção de N, P, K, Ca, S, Fe e Mn pelas plantas de seringueira (Hevea brasiliensis), na fase de viveiro.Palavras-chave: Hevea spp., glicosídeo cianogênico, nutrição mineral, clorofila. Nutritional status and glycoside cyanogenic concentration in rubber tree plants AbstractThe presence of high cyanogenic glycosides concentrations may predispose plant to the tapping panel dryness (TPD). The aim of this work was to evaluate the effect of nutritional status in formation of cyanogenic glycosides in rubber tree. Two experiments were carried out: a) clonal nursery with crow clones hybrids of Hevea pauciflora x H. guianensis var. Marginata (CPAA C 01) and H. rigidifolia (CPAA C 81); and b) nursery with H. brasiliensis. In clonal nursery, twenty three foliar samples were collected, while in nursery, the experiment was carried out using a completely randomized design in factorial scheme 2 x 4 with five replicates. Two nitrogen doses (0.8 and 1.6%, urea as source) and four manganese doses (0, 10, 50 and 100 mg kg -1 , MnSO 4 as source) were used. Regardless of age and species of Hevea, only the N, chlorophyll and Mn concentrations showed relationship with the HCNp in young leaves. These variables should be used in future selection processes. At low N (0.8%) concentration, the Mn doses influenced the N, P, K, Ca, S, Fe and Mn uptake by rubber tree (Hevea brasiliensis) in the nursery condition.

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

“…In a trial under the same edafoclimatic conditions, Moraes et al (2012) also reported significant differences of HCNp in the trunk bark under different crowns, even if the lack of correlation between HCNp in the crown and in the trunk invalidated their hypothesis that the crown budded with different species of Hevea is the main source of cyanogenic glycosides in the trunk. Kongsawadworakul et al (2009) and Moraes et al (2011) affirmed that the presence of cyanogenic glycosides in the trunk of rubber tree is related to the reserves of nitrogen and energy (glucose), which can be used by these plants to produce latex. However, the tapping cut allows a quick exposure of cyanogenic glycosides to β-glucosidase, and the activity of this glycolytic enzyme may greatly influence the release of high amounts of toxic HCN, preventing its use as a nitrogen source by the enzymes involved in the detoxification process, which present lower activities than β-glucosidase (Blumenthal et al 1968).…”