A pressure chamber and a root pressure probe technique have been used to measure hydraulic conductivities of rice roots (root Lp(r) per m(2) of root surface area). Young plants of two rice (Oryza sativa L.) varieties (an upland variety, cv. Azucena and a lowland variety, cv. IR64) were grown for 31-40 d in 12 h days with 500 micromol m(-2) s(-1) PAR and day/night temperatures of 27 degrees C and 22 degrees C. Root Lp(r) was measured under conditions of steady-state and transient water flow. Different growth conditions (hydroponic and aeroponic culture) did not cause visible differences in root anatomy in either variety. Values of root Lp(r) obtained from hydraulic (hydrostatic) and osmotic water flow were of the order of 10(-8) m s(-1) MPa(-1) and were similar when using the different techniques. In comparison with other herbaceous species, rice roots tended to have a higher hydraulic resistance of the roots per unit root surface area. The data suggest that the low overall hydraulic conductivity of rice roots is caused by the existence of apoplastic barriers in the outer root parts (exodermis and sclerenchymatous (fibre) tissue) and by a strongly developed endodermis rather than by the existence of aerenchyma. According to the composite transport model of the root, the ability to adapt to higher transpirational demands from the shoot should be limited for rice because there were minimal changes in root Lp(r) depending on whether hydrostatic or osmotic forces were acting. It is concluded that this may be one of the reasons why rice suffers from water shortage in the shoot even in flooded fields.

We have studied the initial stages of oxidation of the hydrogen-terminated Si(111) and (100) surfaces stored in air, using infrared spectroscopy in the multiple internal reflection geometry. We investigate the effect of surface roughness and humidity of air on the oxidation of the hydrogen-terminated Si surfaces. We suggest that surface roughness on a microscopic scale does not significantly affect the oxidation of the hydrogen-terminated Si surface and the oxidation occurs on the entire surface. It is demonstrated that water is predominantly involved in the oxidation of the surface Si—H bond, and that the surface Si—H bond is quite inert to the oxygen molecule.

We have investigated the oxidation of hydrogen-terminated Si(111) and (100) surfaces stored in air, using synchrotron radiation photoemission spectroscopy and infrared absorption spectroscopy in the multiple internal reflection geometry. We demonstrate that water present in air is predominantly involved in the oxidation of surface Si–H bonds, and that native oxide starts to grow when the surface hydrogen coverage is decreased. In order to explain the latter phenomenon, we propose a kinetic model of oxidation which considers the manner in which native oxide formation preferentially occurs on those portions of the surface where the Si–H bonds are oxidized. We suggest that the oxidation of surface Si–H bonds, the rate of which is strongly dependent on the humidity of air, is a rate-limiting step in the native oxide formation on hydrogen-terminated Si surfaces.

In this study we have attempted to quantify the thermal and photoperiodical responses of rice (Oryza sativa L.) flowering time QTLs jointly by a 'date-of-planting' field experiment of a mapping population, and a 'phenological model' analysis that separately parameterizes the two responses, based on daily temperature, daily photoperiod and flowering date. For this purpose, the 'three-stage Beta model', which parameterizes the sensitivity to temperature (parameter alpha), the sensitivity to photoperiod (parameter beta), and earliness under optimal conditions (10 h photoperiod at 30 degrees C) (parameter G), was applied to 'Nipponbare' x 'Kasalath' backcross inbred lines that were transplanted on five dates. QTLs for the beta value were detected in the four known flowering time QTL (Hd1, Hd2, Hd6 and Hd8) regions, while QTLs for the G value were detected only in the Hd1 and Hd2 regions. This result was consistent with previous reports on near-isogenic lines (NILs) of Hd1, Hd2 and Hd6, where these loci were involved in photoperiod sensitivity, and where Hd1 and Hd2 conferred altered flowering under both 10 and 14 h photoperiods, while Hd6 action was only affected by the 14 h photoperiod. Hd8 was shown to control photoperiod sensitivity for the first time. Interestingly, Hd1 and Hd2 were associated with a QTL for the alpha value, which might support the previous hypothesis that the process of photoinduction depends on temperature. These results demonstrate that our approach can effectively quantify environmental responses of flowering time QTLs without controlled environments or NILs.

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