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Effects of phosphorus nutrition on the response of photosynthesis to CO2 and O2, activation of ribulose bisphosphate carboxylase and amounts of ribulose bisphosphate and 3-phosphoglycerate in spinach leaves (1988)

Brooks, A. ; Woo, K. C. ; Wong, S. C.

Springer

Photosynthesis research 15 (1988), S. 133-141

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ISSN: 1573-5079

Keywords: phosphorus nutrition ; photosynthesis ; ribulose bisphosphate carboxylase ; ribulose bisphosphate ; 3-phosphoglycerate ; O2 partial pressure

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Phosphorus-deficient spinach plants were grown by transferring them to nutrient solutions without PO4. Photosynthetic rates were measured at a range of intercellular CO2 partial pressures from 50–500 μbar and then the leaves were freeze-clamped in situ to measure ribulose bisphosphate carboxylase (Rubisco) activity and metabolite concentrations. Compared with control leaves, deficient leaves had significantly lower photosynthetic rates, percentage activation of Rubisco, and amounts of ribulose bisphosphate and 3-phosphoglycerate at all CO2 partial pressures. After feeding 10 mM PO4 to the petioles of detached deficient leaves, all these measurements increased within 2 hours. At atmospheric CO2 partial pressure the photosynthetic rate was stimulated in 19 mbar O2 compared with 200 mbar. At higher CO2 partial pressures this stimulation was less but the percentage stimulation in deficient leaves was no different from controls in either CO2 partial pressure. It was concluded that phosphorus deficiency affects both Rubisco activity and the capacity for ribulose bisphosphate regeneration, and possible causes are discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00035257

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Model calculation of the thermal conductivity of polymer crystals (1985)

Choy, C. L. ; Wong, S. P. ; Young, K.

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Physics Edition 23 (1985), S. 1495-1504

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ISSN: 0098-1273

Keywords: Physics ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: A linear lattice model without adjustable parameters provides an accurate description of the magnitude and temperature dependence of the thermal conductivity of Kc of polyethylene crystals parallel (∥) and perpendicular (⊥) to the chain direction. The model shows that heat is transported principally by phonons polarized transverse (T) to the chain direction. Phonons polarized longitudinal (L) to the chain direction contribute about 20% to the heat transport along the chain direction, and negligibly to heat transport perpendicular to the chain direction. Thermal resistance is caused by LTT three-phonon umklapp scattering in the parallel direction, and by TTT scattering in the perpendicular direction. The calculated values for large crystals are Kc∥ = 465 W m-1 K-1, Kc∥ = 0.16 W m-1 K-1 at 300 K, in agreement with experimental estimates and implying an anisotropy ratio of Kc∥/Kc⊥ ≈ 3000. The axial thermal conductivity of polyethylene crystals is extremely high and comparable to that of copper. Comparison with experimental data on semicrystalline samples at lower temperature yields a crude value of mean free path for boundary scattering of about 50 nm, agreeing in order of magnitude with the size of crystalline blocks.

Additional Material: 2 Ill.