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

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). …”

Increased expression of fructan 1-exohydrolase in rhizophores of Vernonia herbacea during sprouting and exposure to low temperature

“…Attempts to clone different 1-FEH transcripts from V. herbacea during sprouting and from plants induced to sprout are underway, aiming at the identification of different 1-FEH gene products involved in plant responses to the removal of aerial organs and to adverse environmental conditions, including low temperature. It was previously reported that the increase in 1-FEH activity in pot-grown plants of V. herbacea induced to sprout was similar to that observed in intact plants submitted to low temperature (Portes et al, 2008). However, when excised plants were submitted to low temperature, there was a two-fold increase in 1-FEH activity, suggesting the occurrence of two different control mechanisms, one triggered by defoliation and sprouting and the other by low temperature, as suggested earlier for C. intybus (Van den Ende et al, 2001).…”

“…Indeed, the results presented here, referring to 1-FEH activity and fructan mobilization, are in accordance with earlier reports of experiments conducted with pot-grown plants. In that case, plants were originated by vegetative propagation of the rhizophores and kept in a greenhouse, thus presenting a potentially lower degree of genetic and environmental variation (Portes and Carvalho, 2006;Portes et al, 2008). Moreover, the physiological significance of the present results cannot be overlooked since the levels of transcripts of 1-FEH mRNA and the in vivo composition of the fructan pool were in most instances consistent with the variations in 1-FEH activity detected during the sprouting process and after low temperature storage.…”

“…Fructans were extracted from frozen samples as described by Portes et al (2008). Crude extracts were ethanol precipitated and the fructo-oligosaccharides and fructo-polysaccharides were separated by centrifugation.…”

“…In these organs, changes in fructan composition are associated with the phenological cycle (Carvalho and Dietrich, 1993). In V. herbacea, 1-FEH activity is detected especially during the sprouting phase, mainly in the proximal region of the rhizophores, where buds give rise to new shoots (Portes and Carvalho, 2006), and is significantly increased when plants are induced to sprout by defoliation (Asega and Carvalho, 2004) and/or subjected to cold storage (Portes et al, 2008). Conversely, fructan biosynthesis occurs in the vegetative phase, in the apical tissues, or the distal region, of the rhizophores.…”