Fructan variation in the rhizophores of Vernonia herbacea (Vell.) Rusby, as influenced by temperature

Abstract

(recebido em 07/11/98; aceito em 24/03/99) ABSTRACT -(Fructan variation in the rhizophores of Vernonia herbacea (Vell.) Rusby, as influenced by temperature). The influence of climatic variations on fructan content in tropical regions is not well known. The present study deals with the effects of temperature on fructan contents in rhizophores of plants of Vernonia herbacea, a native species from the Brazilian cerrado vegetation. Intact plants and fragmented rhizophores were subjected to different temperatures under natural and controlled environmental conditions. Rhizophores of plants in pre-dormant stage (aerial parts showing some yellowish leaves) presented higher fructan content at 5 o C than those kept at 25 o C, whereas in dormant plants (aerial parts absent) temperature treatments did not affect fructan contents. Fragmented rhizophores obtained from dormant plants presented higher levels of fructo-polysaccharides at the end of the experiment than at the beginning of the treatment, regardless of the temperature they were stored, whereas fragments obtained from vegetative plants showed a decrease in fructan content under the same treatments. It was concluded that variations observed in fructan contents are related to the phenological state of the plants prior to the treatment rather than to extraneous temperatures they are subjected to during this stage. RESUMO -(Variações nos frutanos de rizóforos deVernonia herbacea (Vell.) Rusby, em função da temperatura). As relações entre variação nos conteúdos de frutanos e a variação nas condições climáticas e edáficas em regiões tropicais são pouco conhecidas. O objetivo deste trabalho foi investigar o efeito da temperatura no conteúdo e composição dos frutanos presentes em rizóforos de Vernonia herbacea, uma planta nativa do cerrado brasileiro. Plantas intactas e fragmentos de rizóforos foram submetidos a diferentes temperaturas. Ao final do tratamento de frio (5 o C) plantas intactas em início de dormência (parte aérea presente) apresentaram conteúdo de frutanos maior que o das plantas mantidas a 25 o C. Plantas completamente dormentes (sem a parte aérea) apresentaram poucas diferenças no conteúdo de frutanos quando mantidas a 5 ou 25 o C. Independentemente da temperatura utilizada, fragmentos de rizóforos, isolados de plantas em fase de dormência, apresentaram ao final do experimento um aumento no conteúdo de polifrutanos em relação ao início do tratamento; no entanto, fragmentos isolados de plantas em fase de brotação apresentaram diminuição no conteúdo de polifrutanos. Concluiu-se que as variações observadas estão mais relacionadas com o estádio fenológico da planta do que com o tratamento de temperatura.

Anatomy and fructan distribution in vegetative organs of Dimerostemma vestitum (Asteraceae) from the campos rupestres

“…Inulin sphero-crystals were also distributed in the parenchyma cells of secondary vascular tissue in the xylopodium of D. vestitum. The location of fructans in vascular tissues as already documented for other species , the rapid polymerization and depolymerization process of such polysaccharides (Pollock 1986) and their adherence to cell walls, as in C. chlorolepis (Vilhalva et al 2011) provide evidences that fructans may play important roles in the adaptation of species to campos rupestres, as it has been proposed for other Cerrado physiognomies with fire occurrence (Gomes et al 2014) and unfavorable conditions of soil, water and temperature (Dias-Tagliacozzo et al 1999, Portes et al 2008). …”

Fructans and water suppression on intact and fragmented rhizophores of Vernonia herbacea

“…These organs, named rhizophores (Menezes et al, 1979), guarantee the perenation of the plants during unfavourable periods of drought in the cerrado, which coincide with the low temperatures of winter. Dias-Tagliacozzo et al (1999) have shown that low temperatures have no direct effect on fructan metabolism in intact plants nor in fragmented rhizophores of V. herbacea. The authors suggested that differences observed in fructan contents and in the proportion of the individual members of the homologous fructan series were due mostly to changes imposed by low temperatures on the rates of metabolic processes characteristic of the phenological stages of the plants at the moment the experiments were performed.…”

Low temperature and defoliation affect fructan-metabolizing enzymes in different regions of the rhizophores of Vernonia herbacea

“…Fructan storage is induced at high sucrose concentration (Pollock and Cairns, 1991), whereas the breakdown occurs for reserve mobilization when energy supply is needed, e.g. after defoliation (Morvan-Bertrand et al, 2001;Van den Ende et al, 2001;Asega and Carvalho, 2004) or to increase oligofructan concentrations under stress (Dias-Tagliacozzo et al, 1999;.…”