Seasonal changes in chemical composition and construction costs of grapevine tissues

Modelling of the whole-vine carbon balance requires accurate estimates of tissue construction costs, i.e. the amount of glucose involved in the synthesis of a unit of biomass. In order to quantify construction costs during the vine's growth cycle, chemical compositions of leaves, stems, fruits, fine roots and trunk of 10-year-old grapevines (cv. Merlot) were determined in two seasons. Tissue construction costs were estimated using (i) an approach based on the quantification of the amount of glucose required for the synthesis of major chemical components of vine organs by the most probable metabolic pathways (coded as CCp) and (ii) a simpler technique in which costs were derived from tissue ash, carbon and nitrogen concentrations (coded as CCw). Both methods were well-correlated in all grapevine tissues despite CCp values were higher than CCwestimates. Grapevine leaves had higher concentrations of compounds with a high proportion of C and N atoms (proteins, lipids and phenolics) and higher CCw values throughout the season than other tissues. Small variation in CCw values however were observed seasonally in vegetative tissues despite their chemical composition varied considerably with plant development. Significant changes in CCw appeared in berry tissues between fruit set and maturity, reflecting a proportional increase in concentration of inexpensive metabolites (soluble sugars and organic acids)

Effects of nitrogen supply on must quality and anthocyanin accumulation in berries of cv. Merlot

Nitrogen supply to Merlot vines (Vitis vinifera L.), grown under controlled conditions, affected must quality and the anthocyanin content in berry skins irrespective of vegetative growth. High N supply delayed fruit maturation; berries had a higher arginine and a lower anthocyanin content with relatively more abundant acylated anthocyanins compared to berries of vines supplied with low N. During maturation the anthocyanin content in the skin of berries decreased; this was more significant in high-N vines. It is concluded that high nitrogen supply affects the metabolic pathway of anthocyanins in different ways, e.g. it delays the quantitative and qualitative biosynthesis and enhances their degradation during the final steps of berry maturation.

Interacting effects of soil fertility and atmospheric CO 2 on leaf area growth and carbon gain physiology in Populus × euramericana (Dode) Guinier

Two important processes which may limit productivity gains in forest ecosystems with rising atmospheric CO 2 are reduction in photosynthetic capacity following prolonged exposure to high CO 2 and diminution of positive growth responses when soil nutrients, particularly N, are limiting. To examine the interacting effects of soil fertility and CO 2 enrichment on photosynthesis and growth in trees we grew hybrid poplar ( Populus × euramericana ) for 158 d in the field at ambient and twice ambient CO 2 and in soil with low or high N availability. We measured the timing and rate of canopy development, the seasonal dynamics of leaf level photosynthetic capacity, respiration, and N and carbohydrate concentration, and final above- and belowground dry weight. Single leaf net CO 2 assimilation (A) increased at elevated CO 2 over the majority of the growing season in both fertility treatments. At high fertility, the maximum size of individual leaves, total leaf number, and seasonal leaf area duration (LAD) also increased at elevated CO 2 , leading to a 49% increase in total dry weight. In contrast, at low fertility leaf area growth was unaffected by CO 2 treatment. Total dry weight nonetheless increased 25% due to CO 2 effects on A. Photosynthetic capacity (A at constant internal p(CO 2 ), (( C 1 )) was reduced in high CO 2 plants after 100 d growth at low fertility and 135 d growth at high fertility. Analysis of A responses to changing C 1 indicated that this negative adjustment of photosynthesis was due to a reduction in the maximum rate of CO 2 fixation by Rubisco. Maximum rate of electron transport and phosphate regeneration capacity were either unaffected or declined at elevated CO 2 . Carbon dioxide effects on leaf respiration were most pronounced at high fertility, with increased respiration mid-season and no change (area basis) or reduced (mass basis) respiration late-season in elevated compared to ambient CO 2 plants. This temporal variation correlated with changes in leaf N concentration and leaf mass per area. Our results demonstrate the importance of considering both structural and physiological pathways of net C gain in predicting tree responses to rising CO 2 under conditions of suboptimal soil fertility.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65655/1/j.1469-8137.1995.tb04295.x.pd

Merkel Cells as Putative Regulatory Cells in Skin Disorders: An In Vitro Study

Merkel cells (MCs) are involved in mechanoreception, but several lines of evidence suggest that they may also participate in skin disorders through the release of neuropeptides and hormones. In addition, MC hyperplasias have been reported in inflammatory skin diseases. However, neither proliferation nor reactions to the epidermal environment have been demonstrated. We established a culture model enriched in swine MCs to analyze their proliferative capability and to discover MC survival factors and modulators of MC neuroendocrine properties. In culture, MCs reacted to bFGF by extending outgrowths. Conversely, neurotrophins failed to induce cell spreading, suggesting that they do not act as a growth factor for MCs. For the first time, we provide evidence of proliferation in culture through Ki-67 immunoreactivity. We also found that MCs reacted to histamine or activation of the proton gated/osmoreceptor TRPV4 by releasing vasoactive intestinal peptide (VIP). Since VIP is involved in many pathophysiological processes, its release suggests a putative regulatory role for MCs in skin disorders. Moreover, in contrast to mechanotransduction, neuropeptide exocytosis was Ca2+-independent, as inhibition of Ca2+ channels or culture in the absence of Ca2+ failed to decrease the amount of VIP released. We conclude that neuropeptide release and neurotransmitter exocytosis may be two distinct pathways that are differentially regulated

Somatostatin Inhibits Cell Migration and Reduces Cell Counts of Human Keratinocytes and Delays Epidermal Wound Healing in an Ex Vivo Wound Model

The peptide hormone somatostatin (SST) and its five G protein-coupled receptors (SSTR1-5) were described to be present in the skin, but their cutaneous function(s) and skin-specific signalling mechanisms are widely unknown. By using receptor specific agonists we show here that the SSTRs expressed in keratinocytes are functionally coupled to the inhibition of adenylate cyclase. In addition, treatment with SSTR4 and SSTR5/1 specific agonists significantly influences the MAP kinase signalling pathway. As epidermal hormone receptors in general are known to regulate re-epithelialization following skin injury, we investigated the effect of SST on cell counts and migration of human keratinocytes. Our results demonstrate a significant inhibition of cell migration and reduction of cell counts by SST. We do not observe an effect on apoptosis and necrosis. Analysis of signalling pathways showed that somatostatin inhibits cell migration independent of its effect on cAMP. Migrating keratinocytes treated with SST show altered cytoskeleton dynamics with delayed lamellipodia formation. Furthermore, the activity of the small GTPase Rac1 is diminished, providing evidence for the control of the actin cytoskeleton by somatostatin receptors in keratinocytes. While activation of all receptors leads to redundant effects on cell migration, only treatment with a SSTR5/1 specific agonist resulted in decreased cell counts. In accordance with reduced cell counts and impaired migration we observe delayed re-epithelialization in an ex vivo wound healing model. Consequently, our experiments suggest SST as a negative regulator of epidermal wound healing

Solid state and Material engineering approaches for highly shape selective alkylations

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The leaf carbon budget of salt-stressed olive plants

The carbon budget of fully-expanded leaves was calculated from diurnal profiles of gas exchange in one-year-old olive (Olea europaea L. cvs. Frantoio and Leccino) plants growing in soil culture and treated with 100 mM NaCI (external solution) for seven weeks. Daily leaf photosynthetic uptake of control plants was 0.375 and 0.520 mol CO2 m-2 leaf area over the 14.5 h light period for 'Frantoio and Leccino' respectively, whereas respiratory losses during the night period were 0.104 and 0.068 mol CO 2 m-2 for the same two cultivars. The daily carbon gain of stressed leaves was 63 and 42% of the controls in 'Frantoio" and Leccino" respectively. After seven weeks of stress, leaf maintenance payments were 9-17% and 23-29% of daily carbon gain in control and salt- treated plants of the two cultivars respectively. The expense of leaf growth was estimated as 14-44% of the daily carbon gain in control plants, whereas leaf growth required 34- 72% of the daily carbon gain of current seasons leaves in salt-stressed plant

Compartmentation of storage compounds in peach leaves

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Compartmentation of storage compounds in peach leaves

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Compartmentation of storage compounds in peach leaves

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