Accumulation of fructans following oxygen deficiency stress in related plant species with different flooding tolerances

Abstract

SUMMARYIn the present work we compare responses to hypoxia of the carbohydrate content of related plant species, which grow naturally on sites prone to flooding {Senecio aquaticus Hill., Myosotispalustris (L.) Lehm. Rchb.) with plants from habitats with only a low risk of oxygen shortage (Senecio jacobaea L., Myosotis arvensis (L.) Hill.). Whilst the amounts of glucose, fructose and sucrose changed only slightly following hypoxia and peaked at a maximum approximately double that of the aerated control specimens, the fructan content increased fivefold to tenfold. In nearly all the plants studied, fructan became the main polysaccharide reserve. For example, the flooding-tolerant Senecio aquaticus accumulated the highest amount, in particular fructans with a degree of pol^^merization up to 35 compared with 10 under control conditions. Nearly 70% of the soluble carbohydrates were fructans, compared with 30 % under aerated conditions.In all species tested the starch fraction marginally increased or remained constant. Fructans were found to accumulate as a response to oxygen deficiency in both flooding-tolerant and intolerant species but with higher absolute values and ratios between fructan and starch in the fiooding-tolerant species. At 24 h after the otiset of hypoxic treatment, the sugar content rose, in spite of the diminished photosynthetic rates. The ability to accumulate fructans seems to vary in plants coping with oxygen shortage but could be interpreted as advantageous in comparison to starch synthesis in terms of (i) the location of the fructan metabolism in the vacuoles, with no negative feedback in the photosynthetic apparatus and (ii) the possibility of storage of sucrose in the form of fructose polymers without the intermediate stages and energy-using processes which are indispensable for starch synthesis. These results might indicate that fructan metabolism could play a role in the tolerance of oxygen deficiency.

Localization of sucrose synthase in wheat roots: increased in situ activity of sucrose synthase correlates with cell wall thickening by cellulose deposition under hypoxia

“…The physiological roles for cell wall thickenings are not clear, their function as a barrier for apoplastic movement is uncertain, and most arguments suggest mechanical reinforcement of the root tissue (Degenhardt and Gimmler 2000). Reduced sink activity is reflected by the strong retardation of growth in the root system (50% of control; Albrecht et al 1997). The increased cellulose content in the stele and exodermis adds mechanical support within root structures and may compensate for the progressive dissolution of cortical cells during aerenchyma formation.…”

“…In many grasses and dicots subjected to hypoxia Suc is converted into fructans, which are stored in the vacuole (Albrecht et al 1997;Albrecht and Biemelt 1998). In many grasses and dicots subjected to hypoxia Suc is converted into fructans, which are stored in the vacuole (Albrecht et al 1997;Albrecht and Biemelt 1998).…”

“…Sugars accumulate in the root axis but also in the tip region following hypoxia Previously, we demonstrated that sugars accumulate in root systems of intact plants in hypoxia, but never during anoxia (Albrecht et al 1993(Albrecht et al , 1997. Here, we examined the gradient of sugars along the axis of the root.…”

Impacts of abiotic stresses on the physiology and metabolism of cool‐season grasses: A review

“…Past research has demonstrated that pre‐stress stored carbohydrate content is positively correlated with improved survival under flooding conditions. That has been attributed not only to their positive effects on maintenance of anaerobic respiration (Albrecht, Biemelt, & Baumgarten, ; Vriezen, Zhou, & van der Straeten, ) under flooding conditions but also due to their ability to recover after the end of stress (He, Patick Bentley, & Scott Holaday, ). For example, the high flood tolerance of Phalaris arundinacea , a known invasive grass species, has been ascribed to its high content of fructose polymers in its rhizomes (Tamura & Moriyama, ) as well as its more efficient use of carbohydrates under flooding conditions (Qin, Li, Chen, & Xie, ).…”

Short photoperiods induce fructan accumulation and tuberous root development in Dahlia seedlings

“…Other reports include the effects of drought stress (Pilon‐Smits et al. , 1995), hypoxia (Albrecht et al. , 1993, 1997), carbon dioxide (Smart et al.…”