Source-Sink Relations: The Role of Sucrose

Pollock, Christopher J.; Farrar, J. F.

doi:10.1007/0-306-48135-9_10

Cited by 44 publications

(32 citation statements)

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“…Evidence suggests that, in most species, flowering is particularly affected by the sucrose level (Bernier et al, 1993), however, the mechanisms of the action of this sugar on flowering transition are not yet clear (Pollock & Farrar, 1996). On the other hand, recent studies with Arabidopsis thaliana demonstrated that high sucrose levels (5% w/v) in the culture medium results in a delay of flowering time.…”

Section: Resultsmentioning

confidence: 99%

“…In different grass species, WSC content reduction caused by low irradiance, as well as by T0 MC T1 T2 T3 T4 T5 T11 T21 Haun's scale natural or induced defoliation, leads to a decrease in the enzymes involved in sugar metabolism and an increase of proteolytic enzymes (James et al, 1993;Pollock & Farrar, 1996;Dieuaide-Noubhani et al, 1997). Studies carried out with rice under different levels of irradiance showed a positive correlation between photosynthetic rate and irradiance (r 2 = 0.99), between soluble carbohydrates and irradiance, as well as between soluble carbohydrates and photosynthesis (r 2 = 0.98), indicating that carbohydrate levels reflect photosynthetic activity in response to irradiance (Conocono et al, 1998).…”

Section: Resultsmentioning

confidence: 99%

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Effects of irradiance on non-structural carbohydrates, growth, and hypoglycemic activity of Rhynchelytrum repens (Willd.) C.E. Hubb. (Poaceae)

2004

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Irradiance is a crucial factor in plant development. Different radiant energy levels cause different responses related to plant growth and the production and distribution of dry matter. Considering the relationship between light availability and metabolism of carbohydrates and derived compounds, the aim of this work was to assess the effects of irradiance on non-structural carbohydrate contents and composition, as well as on the hypoglycemiant activity of Rhynchelytrum repens, a pantropical grass species popularly used for diabetes treatment. Plants of R. repens growing under natural irradiance (NI) showed increased content of total soluble carbohydrate (TSC), higher fluctuations in starch content (SC) and higher number of tillers. The flowering process of these plants was preceded by an increase in sucrose. However, their water content was low when compared to that of plants cultivated under low irradiance (LI). The ratio root/aerial organs and SC showed no significant differences in plants grown under LI, although TSC increased and a lower number of tillers were observed during the experimental period. In both conditions, sucrose was the ubiquitous sugar and seemed to be involved in the flowering process. A reduction in the blood sugar level was observed through the intra-peritoneal (IP) administration of the precipitate of aqueous extracts obtained from plants growing in both conditions of light; the supernatant fraction showed no hypoglycemic effect.Key words: tropical grasses, soluble sugars, hypoglycemic activity, low irradiance. RESUMO

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Effects of irradiance on non-structural carbohydrates, growth, and hypoglycemic activity of Rhynchelytrum repens (Willd.) C.E. Hubb. (Poaceae)

2004

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“…Fructan synthesis is relatively insensitive to low temperature, which allows grasses to accumulate reserve carbohydrate during cold seasons, when the conditions allow photosynthesis but restrict growth or transport (Pollock & Jones, 1979). However, if sucrose accumulates in mesophyll cells it might cause down-regulation of photosynthesis (Pollock & Farrar, 1996;Jang & Sheen, 1994). Synthesis of fructan and cellular compartmentation of carbohydrates in leaf tissue could possibly play a key role in avoiding (1) downregulation of photosynthesis by high sugar concentrations in mesophyll cells and (2) the development of excess osmotic pressure which might lead to a damaging increase in turgor pressure.…”

Section: Introductionmentioning

confidence: 99%

Patterns of solute in individual mesophyll, bundle sheath and epidermal cells of barley leaves induced to accumulate carbohydrate

et al. 1997

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SUMMARYAfter cooling the roots and shoot apex of barley, there is a reduction in sucrose export from, and an increased total accumulation of carbohydrate and induction of fructan synthesis in, source leaves. We investigated carbohydrate accumulation in individual leaf cells. Using the microsampling technique and microfluorometric enzymatic assay, the amounts of various carbohydrates were measured in mesophyll, bundle sheath and epidermal cells. Epidermal cells take no part in carbohydrate partitioning and have very lovi^ concentrations of sugars even when leaf export is reduced. Even without cooling, however, there are remarkable changes in sucrose concentration (up to 200 mM) in mesophyll and bundle sheath cells during the photoperiod. The activity of acid invertase in samples from individual cells was very low, c. 3 fimol sucrose (g f. wt)~^ h^^. Interrelationships between these cell types and the control of fructan metabolism are discussed.

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“…Were experienced m 1994 and 199s with monthly mean concentrations of c. 130/(gm ' can aff'ect photosynthesis and storage (sink) organs of plants (Cooley & Manning, 1987;Reiling & Davison, 1994;Pleijel et al, 1995), Photosynthesis is disturbed by ozone, and (stress) factors which influence stomatal conductivity clearly affect uptake of ozone and consequently its impact (Fuhrer, 1995;Griinhage & Jager, 1996), Since Laisk, Kull & Moldau (1989) showed that the chloroplast in the mesophyll cell is not directly damaged by ozone, it is widely accepted that the first target within at cellular level within the leaf must be the plasma membrane (Willenbrink & Schatten, 1993;Mortensen & Engvild, 1995;Sandelius et al, 1995), This view is strengthened by measurements of antioxidants in the apoplast which are part of the plant defence system against oxygen radicals (Luwe & Heber, 1995;Polle & Rennenberg, 1994), and by investigations which show premature senescence of wheat leaves as a result of ozone exposure, as suggested by Lehnherr et al (1987) and Soja & Soja (1995), However, if sucrose accumulates in leaf cells, it might cause down-regulation of photosynthesis (Jang & Sheen, 1996;Pollock & Farrar, 1996) which could occur as a consequence of disturbance of the overall phloem loading process by previous damage to the mesophyll plasma membrane, and not only by reducing sink strength (Heath, 1987), Down-regulation of photosynthesis might result in photoinhibition, particularly if the defence systems again oxygen radicals within the mesophyll are diverted towards the apoplast. In order to get information on early physiological response of crop plants to ozone regimes which were monitored in North-Rhine Westphalia during the last years, spring wheat grown in a charcoal-filtered glasshouse was fumigated in specially designed exposure chambers for 14 d, during the main developmental stages.…”

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confidence: 99%

Physiological changes on agricultural crops induced by different ambient ozone exposure regimes

et al. 1997

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(This paper is dedicated to Professor Andreas Sievers on the occasion of his retirement) SUMMARY Spring wheat (Triticiim aestivum cv, Nandu) culti\ated under glasshouse conditions was exposed to ozone in large fumigation chambers for 2 wk. Different exposure regimes were applied as constant concentrations as well as with ozone peaks, parth' under equal dose-conditions, in times of high solar radiation during different stages of development (seedling, late tillering, anthesis). Chlorophyll fluorescence was monitored and amounts of carbohydrates (hexoses, sucrose, starch) and chlorophyll were measured in young leaves (seedling) and flag leaves (late tillering, anthesis) during and after ozone exposure. Although seedlings showed no significant response in photosynthesis, strong effects on photosynthesis and carbohydrate accumulation were measured when plants were fumigated during anthesis, especially after a heat stress period preceding ozone treatments. Under equal dose conditions chlorophyll fluorescence parameters (F.^.\F^^ and electron transport rate decreased and sucrose content of flag leaves increased significantly if ozone at a concentration of 220 //g rrr'^ was supplied for 4 h, indicating that peak concentrations show stronger effects than constant concentrations. The reaction of wheat plants is dependent on environmental conditions such as preceding heat stress and on the developmental stage during exposure. The results favour the h\ pothesis that photoinhibition and disturbance of photosynthesis are only secondary effects as a consequence of retarded sucrose export from the leaf, because of damage at the plasma membrane.

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Source-Sink Relations: The Role of Sucrose

Cited by 44 publications

References 91 publications

Effects of irradiance on non-structural carbohydrates, growth, and hypoglycemic activity of Rhynchelytrum repens (Willd.) C.E. Hubb. (Poaceae)

Effects of irradiance on non-structural carbohydrates, growth, and hypoglycemic activity of Rhynchelytrum repens (Willd.) C.E. Hubb. (Poaceae)

Patterns of solute in individual mesophyll, bundle sheath and epidermal cells of barley leaves induced to accumulate carbohydrate

Physiological changes on agricultural crops induced by different ambient ozone exposure regimes

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