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Query: UMLS:C0016382 (flushing)
 6,387 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rapidly developing tumours at hypocotyls of Ricinus communis, induced by Agrobacterium tumefaciens strain C58, were characterized by strong differentiation of vascular bundles and their functional connection to the host bundles. The stem/tumour interface showed increased xylem, with numerous vessels accompanied by multiseriate unlignified rays. To know how nutrients efficiently accumulate in the tumour sink tissue, cell electropotentials (E(m)) in cross-sections were mapped. The measured cells were identified by injected Lucifer Yellow. Xylem and phloem parenchyma cells and stem/tumour-located rays hyperpolarized to E(m) values of about -170 mV, which suggest high plasma membrane proton pump activities. Rapidly dividing cells of cambia or small tumour parenchyma cells had low E(m). The tumour aerenchyma and the stem cortex cells displayed values close to the energy-independent diffusion potential. The lowest values were recorded in stem pith cells. Cell K(+) concentrations largely matched the respective E(m). The pattern of individual cell electropotentials was supplemented by whole organ voltage measurements. The voltage differences between the tumour surface and the xylem perfusion solution in stems attached to the tumours, the trans-tumour electropotentials (TTP), confirm the findings of respiration-dependent and phytohormone-stimulated high plasma membrane proton pump activity in intact tumours, mainly in the xylem and phloem parenchyma and ray cells. TTPs were inhibited by addition of NaN(3), CN(-) plus SHAM or N(2) gas in the xylem perfusion solution and by external N(2) flushing. The data provide functional evidence for the structural basis of priority over the host shoot in nutrient flow from the stem to the tumour.
J Exp Bot 2002 May
PMID:Evidence for high activity of xylem parenchyma and ray cells in the interface of host stem and Agrobacterium tumefaciens-induced tumours of Ricinus communis. 1197 25

Quercus seedlings have hypogeal cotyledons and tap roots, both of which act as storage organs. The importance of the storage function in the two organs may change as the seedling develops. Therefore, changes in carbohydrate reserves in cotyledons and roots of Q. crispula grown under 40 % and 3 % of full light from shoot emergence to the completion of the first leaf flush were monitored. In addition, a shoot-clipping treatment was performed to examine the relative contribution of the cotyledons and tap roots to resprouting. Cotyledons maintained large amounts of nonstructural carbohydrates during shoot development, and carbohydrates were still present in the cotyledons during the final phase of leaf flush. In addition, a notable increase in the amount of carbohydrates was observed in tap roots before leaf flush at both light levels. Since root development occurred before leaf flush, even in plants grown under 3 % light, the carbohydrate found in them presumably originated from seed reserves and was translocated to roots as storage reserves. When shoots were clipped at the leaf flushing stage, the amount of carbohydrate decreased only in the cotyledons after resprouting, suggesting that cotyledons act as the main storage organs during shoot development stages. However, it could be advantageous as a 'risk avoidance strategy' for the seedlings to store reserves in both cotyledons and roots, since cotyledons may be removed by predators during shoot development.
Ann Bot 2003 Oct
PMID:The role of roots and cotyledons as storage organs in early stages of establishment in Quercus crispula: a quantitative analysis of the nonstructural carbohydrate in cotyledons and roots. 1290 67

The maximum specific hydraulic conductivity (k(max)) of a plant sample is a measure of the ability of a plants' vascular system to transport water and dissolved nutrients under optimum conditions. Precise measurements of k(max) are needed in comparative studies of hydraulic conductivity, as well as for measuring the formation and repair of xylem embolisms. Unstable measurements of k(max) are a common problem when measuring woody plant samples and it is commonly observed that k(max) declines from initially high values, especially when positive water pressure is used to flush out embolisms. This study was designed to test five hypotheses that could potentially explain declines in k(max) under positive pressure: (i) non-steady-state flow; (ii) swelling of pectin hydrogels in inter-vessel pit membranes; (iii) nucleation and coalescence of bubbles at constrictions in the xylem; (iv) physiological wounding responses; and (v) passive wounding responses, such as clogging of the xylem by debris. Prehydrated woody stems from Laurus nobilis (Lauraceae) and Encelia farinosa (Asteraceae) collected from plants grown in the Fullerton Arboretum in Southern California, were used to test these hypotheses using a xylem embolism meter (XYL'EM). Treatments included simultaneous measurements of stem inflow and outflow, enzyme inhibitors, stem-debarking, low water temperatures, different water degassing techniques, and varied concentrations of calcium, potassium, magnesium, and copper salts in aqueous measurement solutions. Stable measurements of k(max) were observed at concentrations of calcium, potassium, and magnesium salts high enough to suppress bubble coalescence, as well as with deionized water that was degassed using a membrane contactor under strong vacuum. Bubble formation and coalescence under positive pressure in the xylem therefore appear to be the main cause for declining k(max) values. Our findings suggest that degassing of water is essential for achieving stable and precise measurements of k(max) through woody plant samples. For complete rehydration of woody samples, incubation in water under vacuum for 24 h is suggested as a reliable technique that avoids bubble problems associated with flushing under high positive pressure.
J Exp Bot 2011 Jan
PMID:Mind the bubbles: achieving stable measurements of maximum hydraulic conductivity through woody plant samples. 2114 11

We compared phenological patterns of tree species of the family Bombacaceae in three seasonal forests in Mexico and Costa Rica whose dry seasons vary in duration and intensity. The objectives were to (1) determine intraspecific variation in phenology between sites in different geographic locations with different precipitation regimes, (2) compare interspecific phenological patterns within sites during one year, and (3) document seasonal pollinator use of floral resources at one site in relation to the flowering phenology of these species. To determine the sequence of phenological events in trees of the family Bombacaceae across three study sites, phenology of marked individuals was recorded every 2 wk from September 2000 through August 2001 for six species. To estimate the importance of bombacaceous species in the diet of nectarivorous bats, pollen samples were collected from the bodies or feces of bats once every 2 wk during flowering. Our study suggests that phenological patterns of the Bombacaceae family in Neotropical dry forests are mainly constrained by phylogenetic membership and adaptive selective pressures associated with competition for pollinators. Abiotic factors related to precipitation and soil water content appear to be regulating leaf flushing and abscission, but the principal causes of flowering are related to ultimate factors associated with competition for pollinators. This study is the first that evaluates the phenological pattern of species and genera of the same family at different latitudes in a similar life zone.
Am J Bot 2003 Jul
PMID:Factors affecting phenological patterns of bombacaceous trees in seasonal forests in Costa Rica and Mexico. 2165 5

Phenology ranks among the best ecosystem processes for fingerprinting climate change since temperature explains a high percentage of the interannual or spatial variation in phenological onset dates. However, roles of other environmental variables, such as foliar nutrient concentrations, are far from adequately understood. This observational study examined the effects of air temperature and 11 nutrients on spring phenology of Betula pendula Roth (birch) along an urban-rural gradient in Munich, Germany, during the years 2010/2011. Moreover, the influence of temperature, nutrients, and air pollutants (NO2 and O3) on the amounts of pollen and catkin biomass in 2010 was evaluated. In addition to the influence of higher temperatures advancing phenological onset dates, higher foliar concentrations of potassium, boron, zinc, and calcium were statistically significantly linked to earlier onset dates. Since flushing of leaves is a turgor-driven process and all the influential nutrients are involved in cell extension, membrane function, and stability, there might be a reasonable physiological interpretation of the observed association. The amounts of pollen were negatively correlated with temperature, atmospheric NO2, and foliar iron concentration, suggesting that these variables restrict pollen production. The results of this study suggested an influence of nutritional status on both phenology and pollen production. The interaction of urbanization and climate change should be considered in the assessment of the impact of global warming on ecosystems and human health.
J Exp Bot 2013 Apr
PMID:Nutrient status: a missing factor in phenological and pollen research? 2363 Mar 29